WO2025096732A1

WO2025096732A1 - Arsenic-rich, selenium-based chalcogenide glasses with ultra-low concentrations of dopant for injection molding

Info

Publication number: WO2025096732A1
Application number: PCT/US2024/053824
Authority: WO
Inventors: Jason Allen BROWN; George Paul Lindberg
Original assignee: Corning Inc
Current assignee: Corning Inc
Priority date: 2023-11-02
Filing date: 2024-10-31
Publication date: 2025-05-08
Anticipated expiration: 2026-05-02

Abstract

A precision optical element is disclosed in one or more embodiments. The precision optical element comprises a glass body. The glass body comprises a chalcogenide glass that is substantially similar to a reference chalcogenide glass in terms of chemistry and certain properties. The reference chalcogenide glass is a binary glass in the arsenic-selenium glassy system. The chalcogenide glass comprises arsenic, selenium, and a dopant configured to prevent shear thickening when the glass body is formed via hot-melt processing. The reference chalcogenide glass corresponds to the chalcogenide glass with the dopant removed and with the arsenic and the selenium stoichiometrically rebalanced without the dopant. The reference chalcogenide glass exhibits shear thickening when the glass body is formed with the reference chalcogenide glass via the same hot-melt processing.

Description

ARSENIC-RICH, SELENIUM-BASED CHALCOGENIDE GLASSES WITH ULTRALOW CONCENTRATIONS OF DOPANT FOR INJECTION MOLDING

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority under 35 U.S.C. § 119 of U.S. Provisional Application No. 63/547,049 filed November 2, 2023, the content of which is incorporated herein by reference in its entirety.

FIELD

[0002] The present disclosure relates to precision optical components and their manufacture using chalcogenide glasses. In particular, the present disclosure relates to arsenic- rich, selenium-based chalcogenide glasses that include ultra-low concentrations of dopants to enable manufacture of precision optical components from such glasses via hot-melt processing techniques.

BACKGROUND

[0003] Chalcogenide glasses are non-oxide glasses that include one or more of the chalcogen elements (e.g., Group VIA elements, CAS nomenclature) sulfur (S), selenium (Se), and tellurium (Te) and one or more metals and/or semi-metals (e.g., metalloids). Chalcogenide glasses transmit primarily in the infrared (IR) wavelength region of the electromagnetic spectrum with the electronic band edge red-shifting as the base chalcogen shifts from sulfur to selenium and from selenium to tellurium. Sulfur-based glasses appear red and have band edge cutoffs in the 600 nm range whereas tellurium-based glasses have cutoffs in the micron range. The IR transmission of chalcogenide glasses is relatively high from the band edge to the phonon (vibrational) edge, which begins around 8 pm in sulfur-based glasses. Chalcogenide glasses with heavier elements have relatively high IR transmission to almost 20 pm. Chalcogenide glasses with oxygen impurities in the ppm ranges may have reduced transmission in the 11-14 pm region, which is often where these glasses have the most utility. Chalcogenide glasses can be used to make optical elements, such as lenses, for various applications. For example, chalcogenide glass lenses are commonly used for long-wave infrared (LWIR) applications that require IR transmission in the 7-14 pm region. Such LWIR applications include military, hunting, automotive, marine, and medical applications that require sensing in the 7-14 pm region. [0004] A common chalcogenide glass used in the manufacture of lenses for LWIR applications is a binary glass comprising arsenic and selenium in a ratio of 40:60 or As4oSeeo (e.g., As2Se3). This glass is commercially available under various trade names, including IRG26 (Schott), IG6 (Vitron), Classic-6 (RPO), and BD6 (LightPath). The As4oSeeo glass has excellent IR transmission (e.g., > 80%, internal transmission at 2 mm) from about 800 nm to 14 pm compared to other commercially-available materials for LWIR applications. For example, other commercially-available LWIR materials with arsenic and selenium often include large amounts of germanium (e.g., > 10%, atomic percent), which can cause increased IR absorption at 12.5 pm. This IR absorption inhibits ideal IR transmission when using these other LWIR materials.

[0005] Despite the desirable IR transmission of the As4oSeeo glass, the costs associated with its processing can be problematic. One issue is that the constituent elements of arsenic and selenium and the purity of these and other metals/metalloids needed to synthesize quality chalcogenide glass can make the glass expensive (e.g., $0.80 - $1.50 per gram). Another issue is that the processing of the synthesized glass to form lenses or other optical components can exacerbate the above-noted material cost issue. After the glass is synthesized, the lens forming process typically includes machining the boule into near net shapes for either traditional lens forming methods or for precision glass molding methods. In either case, material utilization is about 30-50%. Thus, approximately 50-70% of the glass material is wasted by these existing processes.

[0006] One option to improve material utilization could be to form the As4oSeeo glass into desired optical components, such as lenses, by using traditional hot-melt processing techniques, such as inj ection molding and extrusion. However, the As4oSeeo glass is known to shear thicken. While a reliable and good glass former, the As4oSeeo glass has the same stoichiometry as the As2$e3 crystal, which will form under shear stress. The crystallization of a material with a corresponding increase in viscosity as a result of shear stress is hereinafter referred to as shear- induced crystallization and/or shear thickening. FIG. 5 is a plot of viscosity (P) versus temperature (°C) acquired using a parallel plate rheometer to apply a shear rate to the As4oSeeo glass at different temperatures. The parallel plate rheometer was configured to apply a constant shear rate of 10 rad/s to molten As4oSeeo glass disposed between opposed plates configured with a 1.2 mm gap. As shown in FIG. 5, the As4oSeeo glass exhibits shear thickening as a result of crystallization of the material at a temperature of about 353 °C and at a shear rate of 10 rad/s. In particular, there is a sharp increase in shear viscosity beginning at 353 °C (point A on the plot line) until complete crystallization and stoppage of the parallel plate rheometer at 351 °C. While the As4oSeeo glass does not appear to exhibit shear thickening at the 10 rad/s shear rate at temperatures above 353 °C, this shear rate is relatively low, and it is expected that there will exists a region within an injection molding system where the conditions for this shear thickening/crystallization will be met.

[0007] Some chalcogenide glasses are known to exhibit shear thinning when certain elements are present in the glass. However, when trying to adjust a target or reference chalcogenide glass that exhibits shear thickening to, instead, not exhibit such shear thickening and/or exhibit shear thinning under shear stress (e.g., high shear rates associated with hot-melt processing), the inclusion of these certain elements in the amounts previously reported can cause undesirable changes to the certain optical and mechanical properties of the resulting glass. Consequently, it would be advantageous to identify a dopant that can be added to a reference chalcogenide glass, such as the As4oSeeo glass, in ultra-low concentrations so as to prevent shear thickening while substantially preserving the properties of the reference chalcogenide glass. It would be further advantageous to synthesize the doped chalcogenide glass in a manner that substantially preserves the chemistry, such as the primary metal/metalloid to chalcogen ratio (e.g., the As:Se ratio for the As4oSeeo glass) and/or the chalcogen concentration (e.g., Se concentration for the As4oSeeo glass), as close as possible to the target chalcogenide glass. It would be further advantageous to synthesize the doped chalcogenide glass in a manner that reduces impurities, such as carbon particles, which reduce the IR transmission of the chalcogenide glass.

SUMMARY

[0008] According to aspect (1), a precision optical element is provided. The precision optical element comprises: a glass body comprising a chalcogenide glass that is substantially similar to a reference chalcogenide glass in the binary arsenic-selenium glassy system, the chalcogenide glass comprising arsenic, selenium, and a dopant configured to prevent shear thickening when the glass body is formed via hot-melt processing, wherein the reference chalcogenide glass corresponds to the chalcogenide glass with the dopant removed and with the arsenic and the selenium stoichiometrically rebalanced without the dopant, and wherein the reference chalcogenide glass exhibits shear thickening when the glass body is formed with the reference chalcogenide glass via the same hot-melt processing. [0009] According to aspect (2), the precision optical element of aspect (1) is provided, wherein the chalcogenide glass has a refractive index at a wavelength of 4.5 pm that is within ± 0.02 of a refractive index of the reference chalcogenide glass at the same wavelength.

[0010] According to aspect (3), the precision optical element of aspect (2) is provided, wherein the refractive index of the chalcogenide glass is within ± 0.0075 of the refractive index of the reference chalcogenide glass.

[0011] According to aspect (4), the precision optical element of aspect (2) is provided, wherein the refractive index of the chalcogenide glass is within ± 0.005 of the refractive index of the reference chalcogenide glass.

[0012] According to aspect (5), the precision optical element of aspect (1) is provided, wherein the chalcogenide glass has a refractive index at a wavelength of 4.5 pm that is within 0.35% of a refractive index of the reference chalcogenide glass at the same wavelength.

[0013] According to aspect (6), the precision optical element of aspect (5) is provided, wherein the refractive index of the chalcogenide glass is within 0.25% of the refractive index of the reference chalcogenide glass.

[0014] According to aspect (7), the precision optical element of any one of aspects (2) to

(6) is provided, wherein the refractive index of the reference chalcogenide glass is about 2.7928.

[0015] According to aspect (8), the precision optical element of any one of aspects (2) to

(7) is provided, wherein the reference chalcogenide glass has the formula As4oSeeo.

[0016] According to aspect (9), the precision optical element of any one of aspects (1) to

(8) is provided, wherein the chalcogenide glass has a 10^{4 0} P temperature of 400 °C or less at a shear rate of approximately 10 sec'¹.

[0017] According to aspect (10), the precision optical element of any one of aspects (1) to (8) is provided, wherein the chalcogenide glass has a 10^{4 0} P temperature of 345 °C or less at a shear rate of approximately 10 sec'¹.

[0018] According to aspect (11), the precision optical element of any one of aspects (1) to (10) is provided, wherein the chalcogenide glass is resistant to shear thickening at shear rates in a range of from about 100 sec'¹ to about 100,000 sec'¹. [0019] According to aspect (12), the precision optical element of any one of aspects (1) to (10) is provided, wherein the chalcogenide glass exhibits shear thinning at a shear rate greater than or equal to about 2,000 sec'¹ at a constant temperature.

[0020] According to aspect (13), the precision optical element of aspect (12) is provided, wherein the constant temperature is in a range of from about 310 °C to about 500 °C.

[0021] According to aspect (14), the precision optical element of any one of aspects (1) to (13) is provided, wherein the chalcogenide glass comprises from about 0.01 at.% to about 2.0 at.% of the dopant.

[0022] According to aspect (15), the precision optical element of any one of aspects (1) to (13) is provided, wherein the chalcogenide glass comprises from about 0.01 at.% to about 1.5 at.% of the dopant.

[0023] According to aspect (16), the precision optical element of any one of aspects (1) to (13) is provided, wherein the chalcogenide glass comprises from about 0.01 at.% to about 1.0 at.% of the dopant.

[0024] According to aspect (17), the precision optical element of any one of aspects (1) to (13) is provided, wherein the chalcogenide glass comprises from about 0.01 at.% to about 0.5 at.% of the dopant.

[0025] According to aspect (18), the precision optical element of any one of aspects (1) to (17) is provided, wherein the dopant is gallium, germanium, indium, antimony, tin, or a combination thereof.

[0026] According to aspect (19), the precision optical element of any one of aspects (1) to (17) is provided, wherein the dopant is gallium, indium, antimony, tin, or a combination thereof.

[0027] According to aspect (20), the precision optical element of any one of aspects (1) to (17) is provided, wherein the dopant is germanium.

[0028] According to aspect (21), the precision optical element of any one of aspects (1) to (17) is provided, wherein the dopant is gallium.

[0029] According to aspect (22), the precision optical element of any one of aspects (1) to (17) is provided, wherein the dopant is indium. [0030] According to aspect (23), the precision optical element of any one of aspects (1) to (17) is provided, wherein the dopant is antimony.

[0031] According to aspect (24), the precision optical element of any one of aspects (1) to (17) is provided, wherein the dopant is tin.

[0032] According to aspect (25), the precision optical element of any one of aspects (1) to (24) is provided, wherein the chalcogenide glass comprises from about 55 at.% to about 65 at.% of the selenium.

[0033] According to aspect (26), the precision optical element of aspect (25) is provided, wherein the chalcogenide glass comprises about 60 at.% of the selenium.

[0034] According to aspect (27), the precision optical element of any one of aspects (1) to (26) is provided, wherein the chalcogenide glass comprises from about 35 at.% to about 45 at.% of the arsenic.

[0035] According to aspect (28), the precision optical element of aspect (27) is provided, wherein the chalcogenide glass comprises from about 38 at.% to about 39.9 at.% of the arsenic.

[0036] According to aspect (29), the precision optical element of any one of aspects (1) to (28) is provided, wherein the chalcogenide glass is substantially free of carbon particles.

[0037] According to aspect (30), a method for forming a precision optical element is provided. The method comprises: hot-melt processing a chalcogenide glass to form the precision optical element, the chalcogenide glass configured to be substantially similar to a reference chalcogenide glass in the binary arsenic-selenium glassy system, the chalcogenide glass comprising arsenic, selenium, and a dopant configured to prevent shear thickening during the hot-melt processing, wherein the reference chalcogenide glass corresponds to the chalcogenide glass with the dopant removed and with the arsenic and the selenium stoichiometrically rebalanced without the dopant, and wherein the reference chalcogenide glass exhibits shear thickening when the precision optical element is formed with the reference chalcogenide glass via the same hot-melt processing.

[0038] According to aspect (31), the method of aspect (30) is provided, wherein the hot- melt processing comprises injection molding.

[0039] According to aspect (32), the method of aspect (30) or aspect (31) is provided, wherein the hot-melt processing comprises injection molding at a temperature of less than 500 °C. [0040] According to aspect (33), the method of any one of aspects (30) to (32) is provided, wherein the chalcogenide glass has a 10^{4 0} P temperature of 500 °C or less during the hot-melt processing.

[0041] According to aspect (34), the method of any one of aspects (30) to (33) is provided, wherein the chalcogenide glass is resistant to shear thickening at shear rates in a range of from about 1,000 sec'¹ to about 10,000 sec'¹.

[0042] According to aspect (35), the method of any one of aspects (30) to (33) is provided, wherein the chalcogenide glass exhibits shear thinning at a shear rate greater than or equal to about 2,000 sec'¹ at a constant temperature.

[0043] According to aspect (36), the method of any one of aspects (30) to (35) is provided, wherein, prior to the hot-melt processing, the chalcogenide glass is synthesized using the ampoule melt technique to heat raw materials within an ampoule according to a heating profile, the heating profile comprising: heating the raw materials to a first temperature and holding the first temperature for a first duration, and heating the raw materials to a second temperature that is greater than the first temperature and holding the second temperature for a second duration that is less than the first duration, the second temperature and the second duration configured to dissolve carbon particles in the raw materials.

[0044] According to aspect (37), the method of aspect (36) is provided, wherein the second temperature is at least 850 °C.

[0045] According to aspect (38), the method of aspect (36) or aspect (37) is provided, wherein the second duration is at least 60 minutes.

[0046] According to aspect (39), the method of any one of aspects (30) to (38) is provided, wherein the chalcogenide glass has a refractive index at a wavelength of 4.5 pm that is within ± 0.01 of a refractive index of the reference chalcogenide glass at the same wavelength.

[0047] According to aspect (40), a method for forming a precision optical element is provided. The method comprises: identifying a reference chalcogenide glass that has one or more desired properties for the precision optical element, but that otherwise exhibits shear thickening if the precision optical element was formed with the reference chalcogenide glass via hot-melt processing, the reference chalcogenide glass configured as a binary glass in the arsenic- selenium glassy system; synthesizing a chalcogenide glass that is substantially similar to the reference chalcogenide glass, the chalcogenide glass comprising arsenic, selenium, and a dopant configured to prevent shear thickening when the precision optical element is formed via the same hot-melt processing, the dopant comprising gallium, germanium, indium, antimony, tin, or a combination thereof, the chalcogenide glass comprising from about 0.5 at.% to about 2.0 at.% of the dopant; and hot-melt processing the chalcogenide glass to form the precision optical element.

[0048] According to aspect (41), the method of aspect 40 is provided, wherein the hot-melt processing comprises injection molding.

BRIEF DESCRIPTION OF THE DRAWINGS

[0049] FIG. 1 is a plot of viscosity (P) versus temperature (°C) for various doped chalcogenide glasses and a reference chalcogenide glass acquired using a parallel plate rheometer;

[0050] FIG. 2 is a plot of viscosity (P) versus shear rate (1/s) for various doped chalcogenide glasses acquired using a capillary rheometer;

[0051] FIG. 3 is a bar chart illustrating refractive index for various doped chalcogenide glasses and a reference chalcogenide glass at a wavelength of 4.5 pm;

[0052] FIG. 4 is a flow chart of a method for forming a precision optical element; and

[0053] FIG. 5 is a plot of viscosity (P) versus temperature (°C) for a reference chalcogenide glass acquired using a parallel plate rheometer.

DETAILED DESCRIPTION

[0054] For the purposes of promoting an understanding of the principles of the disclosure, reference will now be made to the embodiments illustrated in the drawings and described in the following written specification. It is understood that no limitation to the scope of the disclosure is thereby intended. It is further understood that the present disclosure includes any alterations and modifications to the illustrated embodiments and includes further applications of the principles disclosed herein as would normally occur to one skilled in the art to which this disclosure pertains.

[0055] As used herein, the term “and/or,” when used in a list of two or more items, means that any one of the listed items can be employed by itself, or any combination of two or more of the listed items can be employed. For example, if a composition is described as containing components A, B, and/or C, the composition can contain A alone; B alone; C alone; A and B in combination; A and C in combination; B and C in combination; or A, B, and C in combination.

[0056] In this document, relational terms, such as first and second, top and bottom, and the like, are used solely to distinguish one entity or action from another entity or action, without necessarily requiring or implying any actual such relationship or order between such entities or actions.

[0057] As used herein, the term “about” means that amounts, sizes, formulations, parameters, and other quantities and characteristics are not and need not be exact, but may be approximate and/or larger or smaller, as desired, reflecting tolerances, conversion factors, rounding off, measurement error and the like, and other factors known to those of skill in the art. When the term “about” is used in describing a value or an end-point of a range, the disclosure should be understood to include the specific value or end-point referred to. Whether or not a numerical value or end-point of a range in the specification recites “about,” the numerical value or end-point of a range is intended to include two embodiments: one modified by “about,” and one not modified by “about.” It will be further understood that the end-points of each of the ranges are significant both in relation to the other end-point, and independently of the other end-point.

[0058] Concentrations, amounts, and other numerical data may be expressed or presented herein in a range format. It is to be understood that such a range format is used merely for convenience and brevity and thus should be interpreted flexibly to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range was explicitly recited. As an illustration, a numerical range of “about 1 to about 5” should be interpreted to include not only the explicitly recited values of about 1 to about 5, but also to include individual values and sub-ranges within the indicated range. Thus, included in this numerical range are individual values such as 2, 3, and 4, the sub ranges such as from 1-3, from 2-4, from 3-5, etc., as well as 1, 2, 3, 4, and 5 individually. The same principle applies to ranges reciting only one numerical value as a minimum or maximum. Furthermore, such an interpretation should apply regardless of the breadth of the range or the characteristics being described by the range.

[0059] The terms “substantial,” “substantially,” and variations thereof as used herein, unless defined elsewhere in association with specific terms or phrases, are intended to note that a described feature is equal or approximately equal to a value or description. For example, a “substantially planar” surface is intended to denote a surface that is planar or approximately planar. Moreover, “substantially” is intended to denote that two values are equal or approximately equal. In some embodiments, “substantially” may denote values within about 10% of each other, such as within about 5% of each other, or within about 2% of each other.

[0060] Directional terms as used herein — for example up, down, right, left, front, back, top, bottom, above, below, and the like — are made only with reference to the figures as drawn and are not intended to imply absolute orientation.

[0061] As used herein the terms "the," "a," or "an," mean "at least one," and should not be limited to "only one" unless explicitly indicated to the contrary. Thus, for example, reference to "a component" includes embodiments having two or more such components unless the context clearly indicates otherwise.

[0062] As used herein, the term “chalcogenide glass” means a non-oxide glass that includes one or more of the chalcogen elements sulfur (S), selenium (Se), and tellurium (Te) and one or more metals and/or semi-metals (e.g., metalloids). Chalcogenide glasses generally transmit electromagnetic radiation (light) in the 500-20,000 nm (0.5-20 pm) range of the infrared (IR) spectrum.

[0063] As used herein, the terms “atomic percentage,” “atomic percent,” and similar shortened versions (e.g., “at.%,” “atom%,” “atomic%,” “atomic-%,” or the like) when used in connection with a particular element or component in a composition denotes the molar relationship between the element and any other elements or components in the composition for which an atomic percentage is expressed. In other words, the value given for a particular element represents the percent of atoms of that element present in a composition relative to 100 percent for the total number of atoms in the composition. Similarly, the values given for different elements also indicate the molar ratio of these different elements. For example, if a composition comprises 2 atomic percent of component X and 5 atomic percent of component Y, the components X and Y are present in the composition at a molar ratio of 2:5. The components X and Y are present in this molar ratio regardless of whether the composition comprises additional components.

[0064] As used herein, the terms “hot-melt processing,” “hot-melt processes,” or the like refer to any process that involves heating the chalcogenide glass above its glass transition temperature (Tg) and applying pressure to the (molten) chalcogenide glass to form it into a glass article of interest. Examples of hot-melt processing include injection molding, extrusion, and transfer molding.

[0065] As used herein, the terms “10,000 poise temperature,” “10,000 P temperature,” “IO⁴⁰ P temperature,” or the like refer to a temperature at which glass has a viscosity of 10,000 P. The IO⁴⁰ P temperature is an approximate estimate of the temperature at which a glass can be worked according to the processes disclosed herein. The 10^{4 0} P temperature varies with the materials in the glass and can be determined using techniques known in the art. In embodiments, the chalcogenide glasses disclosed herein have IO⁴⁰ P temperatures of 500 °C or less, or preferably of 400 °C or less, which enables these glasses to be injection molded using equipment typically configured for hot-melt processing of polymer materials.

[0066] As used herein, the term “shear rate” refers to the rate at which a progressive shearing deformation is applied to a material. As used herein, a high shear rate refers to 1,000- 10,000 sec'¹. In embodiments, the chalcogenide glass disclosed herein is resistant to crystallization when subjected to high shear rates.

[0067] As used herein, the term “crystallization” refers to the formation of crystals or solid phases where the constituents of a material are arranged in a highly ordered microscopic structure. As used herein, the term “shear thickening” and “shear-induced crystallization” refer to the crystallization of a (fluid) material whose viscosity increases when the material is under (increasing) shear stress. As used herein, the term “shear thinning” refers to the behavior of a (fluid) material whose viscosity decreases when the material is under (increasing) shear stress. Shear thickening and shear thinning can exist under a constant temperature. In embodiments, crystallization is undesirable in the chalcogenide glass and methods disclosed herein. In embodiments, the chalcogenide glass disclosed herein is resistant to shear thickening during processing, particularly hot-melt processing during which the chalcogenide glass (e.g., molten chalcogenide glass) can be subjected to shear rates in a range of from about 1,000 sec'¹ to about 10,000 sec'¹ at temperatures common for such hot-melt processing (e.g., .from about 250 °C to about 500 °C or higher).

[0068] As used herein, the term “glass transition temperature” (T_g) of a material refers to the temperature at which glass transition occurs in an amorphous material. At temperatures below T_g, the material exists in a solid state whereas, at temperatures above T_g, the material exists in a molten state. T_g is lower than the melting temperature of a material in its crystalline state if a crystalline state exists for the material. [0069] As used herein, the “refractive index” (n) of a material is a number that describes how light propagates through that material. The refractive index is defined by the equation n = c/v, where c is the speed of light in a vacuum and v is the speed of light as it propagates through the material. A thermal property related to the refractive index is the temperature coefficient of refractive index or “thermal change” (e.g., dn/dT). This thermal property describes the degree to which the refractive index of the material changes in response to changes in temperature within relevant temperature ranges. In embodiments, the chalcogenide glass disclosed herein has a high refractive index and low thermal change, similar to the As4oSeeo glass.

[0070] As used herein, the terms “infrared” (IR), “IR radiation,” or the like refer to the portion of the electromagnetic spectrum that covers wavelengths in a range of from about 750 nm to about 1 mm. A material that has “IR transparency” allows photons with wavelengths in that range (or a portion of that range) to pass therethrough.

[0071] The present disclosure relates to precision optical components and their manufacture using chalcogenide glasses. In particular, the present disclosure relates to arsenic- rich, selenium-based chalcogenide glasses that include ultra-low concentrations of dopants to enable manufacture of precision optical components from such glasses via hot-melt processing techniques.

[0072] In embodiments, a precision optical element includes a glass body that is formed from (e.g., comprises) the doped, arsenic-rich, selenium-based chalcogenide glass of the present disclosure. The glass body is configured to define the structure of the precision optical element. In embodiments, the glass body (as formed via hot-melt processing) has one or more surfaces that are smooth (e.g., surface roughness < 10 nm Ra), have simple or complex profiles (e.g., concave, convex, and/or true prismatic profiles), and/or have exacting surface features in the micron (e.g., < 500 pm) to sub-micron dimensional range, as needed for image forming or transmission applications. In embodiments, the precision optical element can be a lens, a microlens, an array of microlenses, a prism, a coupler, a sensor, a diffraction grating, a surface relief diffuser, a Fresnel lens, an optical fiber, or a precision optical device that incorporates multiple optical elements. In an exemplary embodiment, the precision optical element.

[0073] The doped, arsenic-rich, selenium-based chalcogenide glass of the present disclosure is substantially similar to a reference chalcogenide glass. The doped, arsenic-rich, selenium-based chalcogenide glass of the present disclosure is (interchangeably) referred to as “the chalcogenide glass” for simplicity and to distinguish it from the reference chalcogenide glass. The chalcogenide glass is substantially similar to the reference chalcogenide glass in terms of chemistry and certain optical and mechanical properties, such refractive index, thermal change (dn/dT), and coefficient of thermal expansion (CTE). In embodiments, the reference chalcogenide glass is a binary glass in the arsenic-selenium glassy system. In other words, the reference chalcogenide glass consists only of arsenic and selenium arranged (e.g., bonded, associated, etc.) in an amorphous (e.g., non-crystalline) state. In an exemplary embodiment, the reference chalcogenide glass is an arsenic-rich, selenium-based chalcogenide glass, such as As4oSeeo.

[0074] In embodiments, the chalcogenide glass is “substantially similar” to the reference chalcogenide glass in terms of chemistry in that the chalcogenide glass comprises selenium as the only chalcogen element and arsenic as the only metal or metalloid element in concentrations above about 2.0 atomic percent (i.e., the primary metal/metalloid element). In embodiments, the chalcogenide glass is “substantially similar” to the reference chalcogenide glass in terms of chemistry in that chalcogenide glass has a target molar ratio of arsenic and selenium that is approximately the same as the molar ratio of arsenic and selenium in the reference chalcogenide glass. In embodiments, the chalcogenide glass is “substantially similar” to the reference chalcogenide glass in terms of chemistry in that chalcogenide glass has a target concentration of selenium that is approximately the same as the concentration of selenium in the reference chalcogenide glass.

[0075] The chalcogenide glass further comprises a dopant configured to prevent shear thickening when the glass body is formed from the chalcogenide glass via hot-melt processing. In contrast, the reference chalcogenide glass exhibits shear thickening, such as described above with reference to FIG. 5, when subjected to the same hot-melt processing (as described throughout this disclosure). Thus, in terms of chemistry, the reference chalcogenide glass corresponds to the chalcogenide glass with the dopant removed and with the arsenic and the selenium (stoichiometrically) rebalanced without the dopant. As used herein, the phrase “same hot-melt processing” can refer to broadly to the same kind of hot-melt processing such as extrusion or injection molding. The phrase “same hot-melt processing” can further refer to not only the same kind of hot-melt processing (e.g., extrusion or injection molding), but also the same conditions under which the hot-melt processing takes place, such as with respect to the various temperature zones, pressures, volumes, times, and similar processing parameters associated with hot-melt processing. [0076] It has been unexpectedly discovered that ultra-low concentrations (e.g., < 2.0 at.%) of certain dopants can stabilize the reference glass against shear thickening, which can occur during hot-melt processing. In embodiments, the chalcogenide glass of the present disclosure comprises from about 0.01 at.% to about 2.0 at.% of the dopant, from about 0.02 at.% to about 2.0 at.% of the dopant, from about 0.05 at.% to about 2.0 at.% of the dopant, from about 0.01 at.% to about 1.5 at.% of the dopant, from about 0.02 at.% to about 1.5 at.% of the dopant, from about 0.1 at.% to about 2.0 at.% of the dopant, from about 0.1 at.% to about 1.5 at.% of the dopant, from about 0.1 at.% to about 1.0 at.% of the dopant, from about 0.1 at.% to about 0.5 at.% of the dopant, from about 0.2 at.% to about 1.8 at.% of the dopant, from about 0.3 at.% to about 1.6 at.% of the dopant, from about 0.4 at.% to about 1.4 at.% of the dopant, from about 0.5 at.% to about 1.2 at.% of the dopant, from about 0.6 at.% to about 1.0 at.% of the dopant, from about 0.15 at.% to about 2.0 at.% of the dopant, from about 0.25 at.% to about 2.0 at.% of the dopant, from about 0.35 at.% to about 2.0 at.% of the dopant, from about 0.45 at.% to about 2.0 at.% of the dopant, or from about 0.55 at.% to about 2.0 at.% of the dopant, and also comprising all sub-ranges and sub-values between these range endpoints.

[0077] In some embodiments, the dopant is gallium, germanium, indium, antimony, tin, or a combination thereof. In other embodiments, the dopant is gallium, indium, antimony, tin, or a combination thereof (i.e., the chalcogenide glass does not include germanium). In embodiments in which the dopant is gallium, indium, antimony, tin, or a combination thereof, the arresting of shear thickening is surprising since glass formability is expected to be hindered by the addition of these dopants. For example, tin and antimony are known to decrease glass formability as reported in Borisova, Z. U., Chapter 1, Section 5 “Influence of Delocalization of the Chemical Bonds on the Ability of Chalcogenide Alloys to Form Glasses,” Glassy Semiconductors, Springer, New York, NY (1981), pages 5-35. Moreover, the arresting of shear thickening by antimony is further surprising since antimony bonds to selenium in the same fashion as arsenic bonds to selenium in As4oSeeo (e.g., As2Ses) and As4oSeeo is known to shear thicken.

[0078] In some embodiments, the dopant is one of gallium, germanium, indium, antimony, and tin. In other words, the dopant is only gallium, only germanium, only indium, only antimony, or only tin. In other embodiments, the dopant is one of gallium, indium, antimony, and tin (i.e., the chalcogenide glass does not include germanium). In other words, the dopant is only gallium, only indium, only antimony, or only tin. In some embodiments, the dopant is two or more of gallium, germanium, indium, antimony, and tin. In other embodiments, the dopant is two or more of gallium, indium, antimony, and tin (i.e., the chalcogenide glass does not include germanium). In embodiments in which the chalcogenide glass comprises two or more of the dopants, the dopants collectively have the ultra-low concentrations indicated above. For example, if the dopant comprises both gallium and antimony, the chalcogenide glass can include gallium and antimony in amounts collectively ranging from about 0.01 at.% to about 2.0 at.%, such as from about 0.05 at.% to about 2.0 at.% or from about 0.1 at.% to about 2.0 at.%.

[0079] In embodiments, the chalcogenide glass comprises at least about 50 at.% Se, at least about 51 at.% Se, at least about 52 at.% Se, at least about 53 at.% Se, at least about 54 at.% Se, at least about 55 at.% Se, at least about 56 at.% Se, at least about 57 at.% Se, at least about 58 at.% Se, at least about 59 at.% Se, or at least about 60 at.% Se. In embodiments, the chalcogenide glass comprises at most about 70 at.% Se, at most about 69 at.% Se, at most about 68 at.% Se, at most about 67 at.% Se, at most about 66 at.% Se, at most about 65 at.% Se, at most about 64 at.% Se, at most about 63 at.% Se, at most about 62 at.% Se, at most about 61 at.% Se, or at most about 60 at.% Se. In embodiments, the chalcogenide glass comprises from about 50 at.% to about 70 at.% Se, from about 51 at.% to about 69 at.% Se, from about 52 at.% to about 68 at.% Se, from about 53 at.% to about 67 at.% Se, from about 54 at.% to about 66 at.% Se, from about 55 at.% to about 65 at.% Se, from about 56 at.% to about 64 at.% Se, from about 57 at.% to about 63 at.% Se, from about 58 at.% to about 62 at.% Se, or from about 59 at.% to about 61 at.% Se. In embodiments, the chalcogenide glass comprises about 60 at.% Se. In embodiments, the amount of Se in the chalcogenide glass comprises all sub-ranges and subvalues between the range endpoints listed in this paragraph. The chalcogenide glass with any of these amounts of Se can be referred to as “Se-based” or “Se-based chalcogenide glass.”

[0080] In embodiments, the chalcogenide glass comprises at least about 30 at.% As, at least about 31 at.% As, at least about 32 at.% As, at least about 33 at.% As, at least about 34 at.% As, at least about 35 at.% As, at least about 36 at.% As, at least about 37 at.% As, at least about 38 at.% As, at least about 39 at.% As, or at least about 40 at.% As. In embodiments, the chalcogenide glass comprises at most about 50 at.% As, at most about 49 at.% As, at most about 48 at.% As, at most about 47 at.% As, at most about 46 at.% As, at most about 45 at.% As, at most about 44 at.% As, at most about 43 at.% As, at most about 42 at.% As, at most about 41 at.% As, or at most about 40 at.% As. In embodiments, the chalcogenide glass comprises from about 30 at.% to about 50 at.% As, from about 31 at.% to about 49 at.% As, from about 32 at.% to about 48 at.% As, from about 33 at.% to about 47 at.% As, from about 34 at.% to about 46 at.% As, from about 35 at.% to about 45 at.% As, from about 36 at.% to about 44 at.% As, from about 37 at.% to about 43 at.% As, from about 38 at.% to about 42 at.% As, or from about 39 at.% to about 41 at.% As. In embodiments, the chalcogenide glass comprises about 40 at.% As. In embodiments, the amount of As in the chalcogenide glass comprises all sub-ranges and sub-values between the range endpoints listed in this paragraph. The chalcogenide glass with any of these amounts of As can be referred to as “As-rich” or “As- rich chalcogenide glass.”

[0081] In embodiments, the chalcogenide glass has a ratio of arsenic and selenium (e.g., As:Se ratio) that is approximately the same as the As:Se ratio in the reference chalcogenide glass. It should be appreciated that while the number of arsenic atoms and the number of selenium atoms in the chalcogenide glass may differ compared to the numbers of the same atoms in the reference chalcogenide glass, the ratio of the arsenic atoms and the selenium atoms in the chalcogenide glass is approximately the same as the ratio of the arsenic atoms and the selenium atoms in the reference chalcogenide glass. As an example, if the reference chalcogenide glass is As4oSeeo, the As:Se ratio in its simplest, most-reduced ratio of elements is 2:3. The chalcogenide glass will have the same As:Se ratio even though the number of atoms of each element may differ compared to the reference chalcogenide glass. To illustrate this point in the following paragraph, the As:Se ratios for the chalcogenide glass include the molecular ratio (number of atoms of each element) and the empirical ratio (the simplest, most- reduced ratio of elements) listed parenthetically for each molecular ratio.

[0082] In embodiments, the chalcogenide glass has an As:Se ratio of about 39.20:58.80 (2:3), an As:Se ratio of about 39.24:58.86 (2:3), an As:Se ratio of about 39.28:58.92 (2:3), an As:Se ratio of about 39.32:58.98 (2:3), an As:Se ratio of about 39.36:59.04 (2:3), an As:Se ratio of about 39.40:59.10 (2:3), an As:Se ratio of about 39.44:59.16 (2:3), an As:Se ratio of about 39.48:59.22 (2:3), an As:Se ratio of about 39.52:59.28 (2:3), an As:Se ratio of about

39.56:59.34 (2:3), an As:Se ratio of about 39.60:59.40 (2:3), an As:Se ratio of about

39.64:59.46 (2:3), an As:Se ratio of about 39.68:59.52 (2:3), an As:Se ratio of about

39.72:59.58 (2:3), an As:Se ratio of about 39.76:59.64 (2:3), an As:Se ratio of about

39.80:59.70 (2:3), an As:Se ratio of about 39.84:59.76 (2:3), an As:Se ratio of about

39.88:59.82 (2:3), an As:Se ratio of about 39.92:59.88 (2:3), or an As:Se ratio of about

39.96:59.94 (2:3).

[0083] In embodiments in which the dopant (M) is antimony (Sb), gallium (Ga), indium (In), or combinations thereof, the concentration of arsenic (As) in the chalcogenide glass can have a relationship to the amount of dopant (M) in the chalcogenide glass such as represented by the formula M_xAs_y-x, where M is Sb, Ga, and/or In, where 0.01 < x < 2.0, and where y = 40 when the reference chalcogenide glass is As4oSeeo. This relationship can exist because arsenic, antimony, gallium, and indium are all in the same coordination, i.e., they are all 3 -coordinated. As such, in embodiments, the chalcogenide glass comprises from about 38 at.% to about 39.9 at.% As, from about 38.1 at.% to about 39.8 at.% As, from about 38.2 at.% to about 39.7 at.% As, from about 38.3 at.% to about 39.6 at.% As, from about 38.4 at.% to about 39.5 at.% As, from about 38.5 at.% to about 39.4 at.% As, from about 38.6 at.% to about 39.3 at.% As, from about 38.7 at.% to about 39.2 at.% As, from about 38.8 at.% to about 39.1 at.% As, or from about 38.9 at.% to about 39 at.% As. In embodiments, the amount of As in the chalcogenide glass comprises all sub-ranges and sub-values between the range endpoints listed in this paragraph.

[0084] In embodiments, the chalcogenide glass has a IO^{4 0} P temperature of about 400 °C or less, about 390 °C or less, about 380 °C or less, about 370 °C or less, about 360 °C or less, about 350 °C or less, about 345 °C or less, about 344 °C or less, about 343 °C or less, about 342 °C or less, or about 341 °C or less. In embodiments, the chalcogenide glass has a IO^{4 0} P temperature in a range of from about 310 °C to about 500 °C, from about 315 °C to about 450 °C, from about 320 °C to about 400 °C, from about 320 °C to about 350 °C, or from about 320 °C to about 340 °C. In embodiments, the chalcogenide glass has a viscosity of 100,000 P or less at a temperature of about 340 °C or more, about 335 °C or more, about 330 °C or more, about 325 °C or more, about 320 °C or more, about 315 °C or more, about 310 °C or more, about 305 °C or more, about 300 °C or more, about 295 °C or more, about 290 °C or more, or about 285 °C or more. In the embodiments described in this paragraph, viscosities at temperatures of about 330 °C and above are associated with a shear rate of approximately 10 sec'¹ whereas viscosities at temperatures below about 330 °C are associated with a shear rate of approximately 1 sec'¹.

[0085] In embodiments, the chalcogenide glass is resistant to shear thickening at shear rates in a range of from about 100 sec'¹ to about 100,000 sec'¹, from about 200 sec'¹ to about 90,000 sec'¹, from about 300 sec'¹ to about 80,000 sec'¹, from about 400 sec'¹ to about 70,000 sec'¹, from about 500 sec'¹ to about 60,000 sec'¹, from about 600 sec'¹ to about 50,000 sec'¹, from about 700 sec'¹ to about 40,000 sec'¹, from about 800 sec'¹ to about 30,000 sec'¹, from about 900 sec'¹ to about 20,000 sec'¹, from about 1,000 sec'¹ to about 10,000 sec'¹, from about 100 sec'¹ to about 1,000 sec'¹, from about 100 sec'¹ to about 800 sec'¹, from about 100 sec'¹ to about 600 sec'¹, from about 100 sec'¹ to about 400 sec'¹, from about 20,000 sec'¹ to about 100,000 sec'¹, from about 40,000 sec'¹ to about 100,000 sec'¹, from about 60,000 sec'¹ to about 100,000 sec'¹, or from about 80,000 sec'¹ to about 100,000 sec'¹, and comprising all sub-ranges and subvalues between these range endpoints.

[0086] In embodiments, the chalcogenide glass exhibits shear thinning at a shear rate of greater than or equal to about 2,000 sec'¹, greater than or equal to about 2,100 sec'¹, greater than or equal to about 2,200 sec'¹, greater than or equal to about 2,300 sec'¹, greater than or equal to about 2,400 sec'¹, greater than or equal to about 2,500 sec'¹, greater than or equal to about 2,600 sec'¹, greater than or equal to about 2,700 sec'¹, greater than or equal to about 2,800 sec'¹, greater than or equal to about 2,900 sec'¹, greater than or equal to about 3,000 sec'¹, greater than or equal to about 3,250 sec'¹, greater than or equal to about 3,500 sec'¹, greater than or equal to about 3,750 sec'¹, or greater than or equal to about 4,000 sec'¹. In embodiments, the chalcogenide glass has not reached the infinite shear viscosity plateau at a shear rate of about 100,000 sec-1. In the embodiments described in this paragraph, the presence (or absence) of shear thinning and the shear rates are associated with a constant temperature. In embodiments, the constant temperature corresponds to the IO⁴⁰ P temperature of the chalcogenide glass. In embodiments, the constant temperature is in a range of from about 310 °C to about 500 °C, from about 315 °C to about 450 °C, from about 320 °C to about 400 °C, from about 320 °C to about 350 °C, or from about 320 °C to about 340 °C.

[0087] The chalcogenide glass is substantially similar to the reference glass in terms of certain optical and mechanical properties, such refractive index, thermal change (dn/dT), and coefficient of thermal expansion (CTE). In embodiments, the chalcogenide glass is substantially similar to the reference glass in terms of refractive index in that the refractive index of the chalcogenide glass at the wavelength of 4.5 pm is within 0.5% of the refractive index of the reference chalcogenide glass at the same wavelength. In embodiments, the refractive index of the chalcogenide glass at a wavelength of 4.5 pm is within 0.45%, within 0.4%, within 0.35%, within 0.3%, within 0.25%, within 0.2%, within 0.15%, within 0.1%, within 0.05%, within 0.04%, within 0.03%, within 0.02%, or within 0.01% of the refractive index of the reference chalcogenide glass at the same wavelength.

[0088] In embodiments, the chalcogenide glass is substantially similar to the reference glass in terms of refractive index in that the chalcogenide glass has a refractive index at a wavelength of 4.5 pm that is within ± 0.025 of a refractive index of the reference chalcogenide glass at the same wavelength. In embodiments, the refractive index of the chalcogenide glass at a wavelength of 4.5 gm is within ± 0.02, within ± 0.015, within ± 0.01, within ± 0.0095, within ± 0.009, within ± 0.0085, within ± 0.008, within ± 0.0075, within ± 0.007, within ± 0.0065, within ± 0.006, within ± 0.0055, within ± 0.005, within ± 0.0045, within ± 0.004, within ± 0.0035, within ± 0.003, within ± 0.0025, within ± 0.002, within ± 0.0015, within ± 0.001, or within ± 0.0005 of the refractive index of the reference chalcogenide glass at the same wavelength.

[0089] In embodiments, the reference chalcogenide glass has the formula As4oSeeo with a refractive index of 2.7928 at a wavelength of 4.5 gm. In such embodiments, the chalcogenide glass has a refractive index at a wavelength of 4.5 gm in a range of from about 2.7728 to about 2.8128, from about 2.7778 to about 2.8078, from about 2.7828 to about 2.8028, from about 2.7833 to about 2.8023, from about 2.7838 to about 2.8018, from about 2.7843 to about 2.8013, from about 2.7848 to about 2.8008, from about 2.7853 to about 2.8003, from about 2.7858 to about 2.7998, from about 2.7863 to about 2.7993, from about 2.7868 to about 2.7988, from about 2.7873 to about 2.7983, from about 2.7878 to about 2.7978, from about 2.7883 to about 2.7973, from about 2.7888 to about 2.7968, from about 2.7893 to about 2.7963, from about 2.7898 to about 2.7958, from about 2.7903 to about 2.7953, from about 2.7908 to about 2.7948, from about 2.7913 to about 2.7943, from about 2.7918 to about 2.7938, or from about 2.7923 to about 2.7933, and comprising all sub-ranges and sub-values between these range endpoints.

[0090] The reference chalcogenide glass with the formula As4oSeeo has different refractive indices at different wavelengths. In an exemplary embodiment, at a temperature of about 22 °C, the As4oSeeo glass has a refractive index of 2.9316 at a wavelength of 1.0 pm, a refractive index of 2.8460 at a wavelength of 1.5 pm, a refractive index of 2.8197 at a wavelength of 2.0 gm, a refractive index of 2.8015 at a wavelength of 3.0 gm, a refractive index of 2.7947 at a wavelength of 4.0 gm, a refractive index of 2.7909 at a wavelength of 5.0 gm, a refractive index of 2.7882 at a wavelength of 6.0 gm, a refractive index of 2.7857 at a wavelength of 7.0 gm, a refractive index of 2.7833 at a wavelength of 8.0 gm, a refractive index of 2.7808 at a wavelength of 9.0 gm, a refractive index of 2.7781 at a wavelength of 10.0 gm, a refractive index of 2.7753 at a wavelength of 11.0 gm, and a refractive index of 2.7722 at a wavelength of 12.0 gm. These refractive index values have a tolerance of ± 0.001 at a wavelength of 10 gm.

[0091] In further embodiments in which the reference chalcogenide glass has the formula As4oSeeo, the chalcogenide glass has a refractive index at a wavelength of 4.5 gm in a range of from about 2.7638 to about 2.8038, from about 2.7688 to about 2.7988, from about 2.7738 to about 2.7938, from about 2.7743 to about 2.7933, from about 2.7748 to about 2.7928, from about 2.7753 to about 2.7923, from about 2.7758 to about 2.7918, from about 2.7763 to about 2.7913, from about 2.7768 to about 2.7908, from about 2.7773 to about 2.7903, from about 2.7778 to about 2.7898, from about 2.7783 to about 2.7893, from about 2.7788 to about 2.7888, from about 2.7793 to about 2.7883, from about 2.7798 to about 2.7878, from about 2.7803 to about 2.7873, from about 2.7808 to about 2.7868, from about 2.7813 to about 2.7863, from about 2.7818 to about 2.7858, from about 2.7823 to about 2.7853, from about 2.7828 to about 2.7848, or from about 2.7833 to about 2.7843, and comprising all sub-ranges and sub-values between these range endpoints.

[0092] In embodiments, the chalcogenide glass is substantially similar to the reference glass in terms of temperature coefficient of refractive index or “thermal change” (e.g., dn/dT) in that the thermal of the chalcogenide glass at a wavelength of 10.6 pm is within 1.5% of the thermal change of the reference chalcogenide glass at the same wavelength. In embodiments, the thermal change ex of the chalcogenide glass at the wavelength of 10.6 pm is within 1.0%, within 0.95%, within 0.9%, within 0.85%, within 0.8%, within 0.75%, within 0.7%, within 0.65%, within 0.6%, within 0.55%, within 0.5%, within 0.45%, within 0.4%, within 0.35%, within 0.3%, within 0.25%, within 0.2%, within 0.15%, or within 0.1% of the thermal change of the reference chalcogenide glass at the same wavelength.

[0093] In embodiments, the chalcogenide glass is substantially similar to the reference glass in terms of coefficient of thermal expansion (CTE) in that the CTE of the chalcogenide glass over a temperature range of 20-100 °C is within 1.5% of the CTE of the reference chalcogenide glass over the same temperature range. In embodiments, the CTE of the chalcogenide glass over a temperature range of 20-100 °C is within 1.0%, within 0.95%, within 0.9%, within 0.85%, within 0.8%, within 0.75%, within 0.7%, within 0.65%, within 0.6%, within 0.55%, within 0.5%, within 0.45%, within 0.4%, within 0.35%, within 0.3%, within 0.25%, within 0.2%, within 0.15%, or within 0.1% of the CTE of the reference chalcogenide glass over the same temperature range.

[0094] FIG. 4 is a flow chart of a method 400 for forming a precision optical element. In embodiments, the method comprises identifying a reference chalcogenide glass that has one or more desired properties for the precision optical element, but that otherwise exhibits shear thickening if the precision optical element was formed with the reference chalcogenide glass via hot-melt processing, such as via injection molding (block 402). In embodiments, the reference chalcogenide glass is a binary glass in the arsenic-selenium glassy system. In an exemplary embodiment, the reference chalcogenide glass is an arsenic-rich, selenium-based chalcogenide glass, such as As4oSeeo. In embodiments, the desired properties of the reference chalcogenide glass include one or more of refractive index, thermal change (dn/dT), coefficient of thermal expansion (CTE), and other optical and mechanical properties.

[0095] After the reference chalcogenide glass is identified (block 402), the method comprises synthesizing a chalcogenide glass that is substantially similar to the reference chalcogenide glass, the chalcogenide glass comprising arsenic, selenium, and a dopant configured to prevent shear thickening when the precision optical element is formed via the hot-melt processing (block 404). The chalcogenide glass is substantially similar to the reference chalcogenide glass in terms of chemistry and the desired properties (e.g., refractive index, thermal change, coefficient of thermal expansion) as described throughout this disclosure. The concentrations of the arsenic, the selenium, and the dopant in the chalcogenide glass are described throughout this disclosure. In particular, the chalcogenide glass comprises the dopant in ultra-low concentrations so as to prevent shear thickening during the hot-melt processing while substantially preserving the desired properties of the reference chalcogenide glass.

[0096] In embodiments, synthesizing the chalcogenide glass comprises selecting a dopant from gallium, germanium, indium, antimony, tin, or a combination thereof; or from gallium, indium, antimony, tin, or a combination thereof (i.e., the chalcogenide glass does not include germanium); or from gallium, germanium, indium, antimony, or tin (i.e., the chalcogenide glass includes only one of the listed dopants); or from gallium, indium, antimony, or tin (i.e., the chalcogenide glass includes only one of the listed dopants and that one dopant is not germanium); or from two or more of gallium, germanium, indium, antimony, and tin; or from two or more of gallium, indium, antimony, and tin (i.e., the chalcogenide glass does not include germanium). The dopant is configured to prevent shear thickening when the precision optical element is formed with the chalcogenide glass via the hot-melt processing.

[0097] In embodiments, the chalcogenide glass can be synthesized from raw (starting) materials in a batch process via the ampoule melt technique. The raw materials, which comprise target elements, such as a chalcogen (e.g., selenium), a metal/metalloid (e.g., arsenic), and a dopant, arranged in predetermined ratios configured to achieve the desired composition of the chalcogen glass after synthesis, are deposited into a quartz ampoule. The ampoule is vacuum sealed using a flame sealing process and then loaded into a single zone rocking furnace. The rocking furnace is configured to react the target elements at high temperature so as to form a boule of glass with the desired composition of the chalcogen glass. The glass is continuously rocked while it is heated in the rocking furnace according to a heating profile. [0098] In an exemplary embodiment, the heating profile comprises heating the raw materials to a first temperature and holding the first temperature for a first duration. The heating profile further comprises, after holding the first temperature for the first duration, heating the raw materials to a second temperature that is greater than the first temperature and holding the second temperature for a second duration that is less than the first duration. It has been discovered that certain raw materials, such as arsenic, when used in the amounts needed to synthesize the chalcogenide glass of the present disclosure, can form carbon and/or carbon particles in the chalcogenide glass when insufficient temperatures and/or durations are used during synthesis thereof. Such carbon and/or carbon particles can alter the expected properties of the chalcogenide glass.

[0099] In embodiments, the second temperature and the second duration are configured to dissolve the carbon and/or carbon particles in the raw materials during synthesis of the chalcogenide glass. In embodiments, the second temperature is at least 850 °C, at least 855 °C, at least 860 °C, at least 865 °C, at least 870 °C, at least 875 °C, at least 900 °C, at least 925 °C, at least 950 °C, at least 975 °C, at least 1,000 °C, at least 1,025 °C, or greater than 1,025 °C. In embodiments, the second duration is at least 60 minutes, at least 70 minutes, at least 80 minutes, at least 90 minutes, at least 100 minutes, at least 110 minutes, or at least 120 minutes.

[0100] In embodiments, the first temperature is at least 600 °C, at least 610 °C, at least 620 °C, at least 630 °C, at least 640 °C, at least 650 °C, at least 675 °C, at least 700 °C, at least 725 °C, at least 750 °C, at least 775 °C, or at least 800 °C. In embodiments, the first duration is at least 2 hours, at least 3 hours, at least 4 hours, or greater than or equal to 5 hours. The heating profile further comprises, after holding the second temperature for the second duration, cooling the melt to a third temperature (e.g., 400 °C) for a third duration (e.g., 30 minutes). The rocking of the furnace is then stopped for a fourth duration (e.g., 30 minutes). The ampoule is then quenched until a boule of the chalcogenide glass therein pulls away from the ampoule. The chalcogenide glass is then placed in a furnace configured to maintain an annealing temperature.

[0101] After the glass the chalcogenide glass is synthesized (block 404), the chalcogenide glass is removed from the ampoule and then broken into pieces, ground, and sieved to a selected size range suitable for use in an injection molding system (block 406). In embodiments, the resulting chalcogenide glass material is powder or granules. In some embodiments, fine and oversized particles (i.e., particles not suitable for use in the injection molding system) can be recycled to subsequent preparations. In embodiments, typical (sieved) particle sizes can be in the approximate range of 0.1 to 10 mm, from 0.1 to 4 mm, from 0.5 to 4 mm, or from 1 to 2 mm.

[0102] In embodiments, the particles of the chalcogenide glass of the present disclosure can be charged to the injection molding system at a temperature sufficient for the chalcogenide glass to be a fluid, e.g., at or below the 10^{4 0} P temperature (block 408).

[0103] In embodiments, the chalcogenide glass disclosed herein can be injection molded by the “ram” process or the “screw” process (block 410). In the ram process, each stroke of a plunger pushes unmelted material into a heated cylinder, which in turn forces molten material at the front of the cylinder out through the nozzle and into a mold with one or more cavities configured in the shape of the precision optical element. In the screw process, unmelted granular material is conveyed forward, through a heated cylinder, by the rotation of an augertype element. The material is converted to a viscous melt by the action of friction and heat conducted from the cylinder. The molten material, in front of the screw, is injected into a mold by a separate plunger/ram or by the screw itself. Similar to the mold in the ram process, the mold in the screw process has one or more cavities configured in the shape of the precision optical element. In an exemplary embodiment, a screw-type injection molding system is preferred to a ram -type injection molding system due to the better mixing and process consistency of the screw process.

[0104] In embodiments, the injection molding system is typically operated at a maximum temperature of 500 °C or, preferably, at a maximum temperature of 400 °C to form the precision optical element from the chalcogenide glass. At these temperatures, the chalcogenide glass has a IO⁴⁰ P temperature of 400 °C or less and is resistant to shear thickening when processed at high shear rates (e.g., 1,000-10,000 sec'¹) at its IO^{4 0} P temperature.

[0105] The precision optical element formed from the chalcogenide glass associated with the method disclosed herein is configured to have properties (e.g., optical and mechanical properties) that are substantially similar to the properties of the reference chalcogenide glass associated with the method. In embodiments, hot-melt processing (e.g., injection molding) the chalcogenide glass to form the precision optical element, such as a lens, can achieve a material utilization of 90% or greater compared to existing methods of forming such elements from chalcogenide glasses that cannot be injection molded, such as the As4oSeeo glass. [0106] EXAMPLES

[0107] The following examples are put forth so as to provide those of ordinary skill in the art with a complete disclosure and description of how the compounds, compositions, and methods described and claimed herein are made and evaluated. The examples are intended to be purely exemplary and are not intended to limit the scope of what the inventors regard as their invention. Efforts have been made to ensure accuracy with respect to numbers (e.g., amounts, temperature, etc.) but some errors and deviations should be accounted for. Unless indicated otherwise, elemental portions are by atomic percent, temperature is in °C or is at ambient temperature, and pressure is at or near atmospheric. Numerous variations and combinations of reaction conditions (e.g., component concentrations, desired solvents, solvent mixtures, temperatures, pressures, and other reaction ranges and conditions) can be used to optimize the product purity and yield obtained from the described process. Only reasonable and routine experimentation will be required to optimize such process conditions.

[0108] Example 1: Method of Making Glass Compositions

[0109] Table 1 lists various doped, arsenic-rich, selenium-based chalcogenide glass samples made in accordance with the principles of this disclosure. The chalcogenide glass samples are identified in Table 1 and elsewhere throughout the Examples as “Sample 1” or “SI,” “Sample 2” or “S2,” and so on. The chalcogenide glass samples were configured to be substantially similar (e.g., in terms of chemistry and properties) to a reference chalcogenide glass. As described throughout this disclosure, the reference chalcogenide glass has one or more desired properties for a glass body (e.g., a precision optical element), but otherwise exhibits shear thickening if the glass body was formed from the reference chalcogenide glass via hot-melt processing (e.g., injection molding). The reference chalcogenide glass in each of the Examples was As4oSeeo. This reference chalcogenide glass is identified as “Comparative 1” or “Cl” in Table 1 and throughout the Examples. Other reference chalcogenide glasses can be used as long as they meet the definition of a reference glass, as described herein. In reference to the compositions of the glasses described herein and reported in Table 1, all compositions are given in terms of atomic/element percentages. [0110] Table 1. Exemplary Chalcogenide Glass Compositions and Properties

[0111] Table 1 (Continued)

[0112] Table 1 (Continued)

[0113] By way of illustration and not to be construed as limiting, the S4 chalcogenide glass listed in Table 1 was prepared in the following manner, which is representative of the process disclosed herein. The equipment used in the following process is commercially available.

[0114] A mixture, in atomic percent, of 0.50% Ge, 39.40% As, and 60.10% Se was mixed together and placed in a quartz ampoule in an amount sufficient to prepare a 500 g glass boule. The ampoule was then evacuated (e.g., to about 10-4 mm Hg or less) and sealed (e.g., flame sealed). The ampoule was placed into a single zone rocking furnace and then rocked and heated according to the following heating profile. First, the ampoule was heated to a first temperature (e.g., about 650 °C) and held at the first temperature for a first duration (e.g., about 2-12 hours). Next, the ampoule was heated to a second temperature (e.g., about 850 °C) and held at the second temperature for a second duration (e.g., at least about 1 hour). Next, the ampoule was cooled to a third temperature (e.g., about 400 °C) and held at the third temperature for a third duration (e.g., about 30 minutes). [0115] After the ampoule was heated according to the heating profile, the rocking of the furnace is stopped for a fourth duration (e.g., about 30 minutes). The ampoule was then rapidly cooled (i.e., quenched) by immersing the ampoule in a 4,000 mL beaker of room temperature water until the chalcogenide glass delaminated from the ampoule wall. At this point, the ampoule was placed in an annealing furnace and heated to a fifth temperature (e.g., about 144 °C) and held at this fifth temperature for a fifth duration (e.g., about 1 hour). The furnace power was then turned off and the annealing furnace was allowed to naturally cool to room temperature. The ampoule was then removed from the furnace and the boule of the chalcogenide glass was removed from the ampoule. The boule was analyzed, and the chalcogenide glass was found to have a composition of Geo.5As39.7Se 59.9., which is within expectations for lab-scale synthesis of the glass.

[0116] Example 2: Characterization of Properties — Shear Dependence

[0117] In one experiment, the shear dependence of some of the chalcogenide glass samples was measured by parallel plate rheometry. FIG. 1 illustrates viscosity (P) versus temperature (°C) for the SI, S3, S4, S7, S9, and Si l chalcogenide glasses from Table 1. Each of these samples comprises a specific dopant having a specific concentration as shown in Table 1. FIG. 1 also illustrates viscosity (P) versus temperature (°C) for the Cl reference chalcogenide glass (e.g., As4oSeeo). The shear dependence of viscosity for the Cl reference chalcogenide glass alone is also shown in FIG. 5, which is described separately in the background section of this disclosure. Due to limitations of the parallel plate rheometer at higher viscosities, the shear rate was changed from 10 sec'¹ at temperatures of 330 °C or more to 1 sec'¹ at temperatures below 330 °C for the testing illustrated in FIG. 1. As shown in FIG. 1, none of the SI, S3, S4, S7, S9, and SI 1 chalcogenide glasses exhibit shear thickening over the range of temperatures evaluated (e.g., about 270 °C to about 390 °C). In other words, each of the SI, S3, S4, S7, S9, and SI 1 chalcogenide glasses remained in the viscous state below 300 °C. In contrast, the Cl reference chalcogenide glass clearly exhibits shear thickening at a temperature of about 353 °C. The shear dependence of additional chalcogenide glass samples (e.g., S14-S16) was measured by parallel plate rheometry. None of the S14-S16 chalcogenide glasses exhibit shear thickening over the range of temperatures evaluated, as indicated in Table 1.

[0118] In another experiment, the shear dependence of some of the chalcogenide glass samples was measured by capillary rheometry. A capillary rheometer is capable of much higher shear rates than a parallel plate rheometer and is more analogous to the conditions within an injection molding system. FIG. 2 illustrates viscosity (P) versus shear rate (1/s) for the S4, S5, S9, and Si l chalcogenide glasses from Table 1. Each of these samples comprises a specific dopant having a specific concentration as shown in Table 1. The experiment was conducted at constant temperature such that all samples would have a similar starting viscosity of approximately 1000 P. As shown in FIG. 2, each of the S4, S5, S9, and Si l chalcogenide glasses exhibits shear thinning, starting at a shear rate of approximately 2,000 sec'¹. Thus, no shear-induced crystallization was observed in any of these samples.

[0119] Example 3: Characterization of Properties — Refractive Index

[0120] The refractive index (e.g., index of refraction or IOR) at a wavelength of 4.5 pm for the S4, S9, and Si l chalcogenide glasses and the Cl reference chalcogenide glass (e.g., As4oSeeo) was measured via ellipsometry. FIG. 3 is bar chart comparing the results of the measurements. The Si l chalcogenide glass (e.g., +0.5 at.% Sn) was shown to increase the refractive index by about 0.001 compared to the Cl reference chalcogenide glass. The S4 chalcogenide glass (e.g., +0.5 at.% Ge) was shown to decrease the refractive index by about 0.006 compared to the Cl reference chalcogenide glass. The S9 chalcogenide glass (e.g., +0.5 at.% Sb) was shown to increase the refractive index by about 0.009 compared to the Cl reference chalcogenide glass. It is believed that these small changes in refractive index should be acceptable in many optical designs, allowing for the chalcogenide glass of the present disclosure to be a drop-in replacement for designs using the reference chalcogenide glass (e.g., As4oSeeo). Since some dopants will increase the refractive index (e.g., Sb and Sn) and some dopants will decrease the refractive index (e.g., Ge), the chalcogenide glass of the present disclosure can include two or more (mixed) dopants selected such that there is neutral or nearneutral effect of the refractive index when compared to the refractive index of the reference chalcogenide glass.

[0121] While the disclosure has been illustrated and described in detail in the drawings and foregoing description, the same should be considered as illustrative and not restrictive in character. It is understood that only the preferred embodiments have been presented and that all changes, modifications, and further applications that come within the spirit of the disclosure are desired to be protected.

Claims

CLAIMS What is claimed is:

1. A precision optical element, comprising: a glass body comprising a chalcogenide glass that is substantially similar to a reference chalcogenide glass in the binary arsenic-selenium glassy system, the chalcogenide glass comprising arsenic, selenium, and a dopant configured to prevent shear thickening when the glass body is formed via hot-melt processing, wherein the reference chalcogenide glass corresponds to the chalcogenide glass with the dopant removed and with the arsenic and the selenium stoichiometrically rebalanced without the dopant, and wherein the reference chalcogenide glass exhibits shear thickening when the glass body is formed with the reference chalcogenide glass via the same hot-melt processing.

2. The precision optical element of claim 1, wherein the chalcogenide glass has a refractive index at a wavelength of 4.5 pm that is within ± 0.02 of a refractive index of the reference chalcogenide glass at the same wavelength.

3. The precision optical element of claim 2, wherein the refractive index of the chalcogenide glass is within ± 0.0075 of the refractive index of the reference chalcogenide glass.

4. The precision optical element of claim 2, wherein the refractive index of the chalcogenide glass is within ± 0.005 of the refractive index of the reference chalcogenide glass.

5. The precision optical element of claim 1, wherein the chalcogenide glass has a refractive index at a wavelength of 4.5 pm that is within 0.35% of a refractive index of the reference chalcogenide glass at the same wavelength.

6. The precision optical element of claim 5, wherein the refractive index of the chalcogenide glass is within 0.25% of the refractive index of the reference chalcogenide glass.

7. The precision optical element of any one of claims 2-6, wherein the refractive index of the reference chalcogenide glass is about 2.7928.

8. The precision optical element of any one of claims 2-7, wherein the reference chalcogenide glass has the formula As4oSeeo.

9. The precision optical element of any one of claims 1-8, wherein the chalcogenide glass has a IO⁴⁰ P temperature of 400 °C or less at a shear rate of approximately 10 sec'¹.

10. The precision optical element of any one of claims 1-8, wherein the chalcogenide glass has a IO⁴⁰ P temperature of 345 °C or less at a shear rate of approximately 10 sec'¹.

11. The precision optical element of any one of claims 1-10, wherein the chalcogenide glass is resistant to shear thickening at shear rates in a range of from about 100 sec'¹ to about 100,000 sec'¹.

12. The precision optical element of any one of claims 1-10, wherein the chalcogenide glass exhibits shear thinning at a shear rate greater than or equal to about 2,000 sec'¹ at a constant temperature.

13. The precision optical element of claim 12, wherein the constant temperature is in a range of from about 310 °C to about 500 °C.

14. The precision optical element of any one of claims 1-13, wherein the chalcogenide glass comprises from about 0.01 at.% to about 2.0 at.% of the dopant.

15. The precision optical element of any one of claims 1-13, wherein the chalcogenide glass comprises from about 0.01 at.% to about 1.5 at.% of the dopant.

16. The precision optical element of any one of claims 1-13, wherein the chalcogenide glass comprises from about 0.01 at.% to about 1.0 at.% of the dopant.

17. The precision optical element of any one of claims 1-13, wherein the chalcogenide glass comprises from about 0.01 at.% to about 0.5 at.% of the dopant.

18. The precision optical element of any one of claims 1-17, wherein the dopant is gallium, germanium, indium, antimony, tin, or a combination thereof.

19. The precision optical element of any one of claims 1-17, wherein the dopant is gallium, indium, antimony, tin, or a combination thereof.

20. The precision optical element of any one of claims 1-17, wherein the dopant is germanium.

21. The precision optical element of any one of claims 1-17, wherein the dopant is gallium.

22. The precision optical element of any one of claims 1-17, wherein the dopant is indium.

23. The precision optical element of any one of claims 1-17, wherein the dopant is antimony.

24. The precision optical element of any one of claims 1-17, wherein the dopant is tin.

25. The precision optical element of any one of claims 1-24, wherein the chalcogenide glass comprises from about 55 at.% to about 65 at.% of the selenium.

26. The precision optical element of claim 25, wherein the chalcogenide glass comprises about 60 at.% of the selenium.

27. The precision optical element of any one of claims 1-26, wherein the chalcogenide glass comprises from about 35 at.% to about 45 at.% of the arsenic.

28. The precision optical element of claim 27, wherein the chalcogenide glass comprises from about 38 at.% to about 39.9 at.% of the arsenic.

29. The precision optical element of any one of claims 1-28, wherein the chalcogenide glass is substantially free of carbon particles.

30. A method for forming a precision optical element, comprising: hot-melt processing a chalcogenide glass to form the precision optical element, the chalcogenide glass configured to be substantially similar to a reference chalcogenide glass in the binary arsenic-selenium glassy system, the chalcogenide glass comprising arsenic, selenium, and a dopant configured to prevent shear thickening during the hot-melt processing, wherein the reference chalcogenide glass corresponds to the chalcogenide glass with the dopant removed and with the arsenic and the selenium stoichiometrically rebalanced without the dopant, and wherein the reference chalcogenide glass exhibits shear thickening when the precision optical element is formed with the reference chalcogenide glass via the same hot-melt processing.

31. The method of claim 30, wherein the hot-melt processing comprises injection molding.

32. The method of claim 30 or claim 31, wherein the hot-melt processing comprises injection molding at a temperature of less than 500 °C.

33. The method of any one of claims 30-32, wherein the chalcogenide glass has a IO⁴⁰ P temperature of 500 °C or less during the hot-melt processing.

34. The method of any one of claims 30-33, wherein the chalcogenide glass is resistant to shear thickening at shear rates in a range of from about 1,000 sec'¹ to about 10,000 sec'¹.

35. The method of any one of claims 30-33, wherein the chalcogenide glass exhibits shear thinning at a shear rate greater than or equal to about 2,000 sec'¹ at a constant temperature.

36. The method of any one of claims 30-35, wherein, prior to the hot-melt processing, the chalcogenide glass is synthesized using the ampoule melt technique to heat raw materials within an ampoule according to a heating profile, the heating profile comprising: heating the raw materials to a first temperature and holding the first temperature for a first duration, and heating the raw materials to a second temperature that is greater than the first temperature and holding the second temperature for a second duration that is less than the first duration, the second temperature and the second duration configured to dissolve carbon particles in the raw materials.

37. The method of claim 36, wherein the second temperature is at least 850 °C.

38. The method of claim 36 or claim 37, wherein the second duration is at least 60 minutes.

39. The method of any one of claims 30-38, wherein the chalcogenide glass has a refractive index at a wavelength of 4.5 pm that is within ± 0.01 of a refractive index of the reference chalcogenide glass at the same wavelength.

40. A method for forming a precision optical element, comprising: identifying a reference chalcogenide glass that has one or more desired properties for the precision optical element, but that otherwise exhibits shear thickening if the precision optical element was formed with the reference chalcogenide glass via hot-melt processing, the reference chalcogenide glass configured as a binary glass in the arsenic-selenium glassy system; synthesizing a chalcogenide glass that is substantially similar to the reference chalcogenide glass, the chalcogenide glass comprising arsenic, selenium, and a dopant configured to prevent shear thickening when the precision optical element is formed via the same hot-melt processing, the dopant comprising gallium, germanium, indium, antimony, tin, or a combination thereof, the chalcogenide glass comprising from about 0.01 at.% to about 2.0 at.% of the dopant; and hot-melt processing the chalcogenide glass to form the precision optical element.

41. The method of claim 40, wherein the hot-melt processing comprises injection molding.