WO2022053434A1

WO2022053434A1 - Optical apparatus and method

Info

Publication number: WO2022053434A1
Application number: PCT/EP2021/074508
Authority: WO
Inventors: Nicholas D Psaila; Richard Laming
Original assignee: Optoscribe Ltd
Current assignee: Optoscribe Ltd
Priority date: 2020-09-11
Filing date: 2021-09-06
Publication date: 2022-03-17
Anticipated expiration: 2023-03-11

Abstract

Optical apparatus (2) comprises: • a body (4) comprising material; • a plurality of optical elements (6a, 6b) formed of the material of the body (4); and • a plurality of alignment holes (8a, 8b) formed in the material of the body (4), • wherein: • the alignment holes (8a, 8b) comprise fibre or other waveguide alignment holes aligned with one or more of the optical elements, and/or the alignment holes (8a, 8b) comprise alignment holes configured to receive mechanical elements for fixing and/or aligning the body to at least one further body.

Description

OPTICAL APPARATUS AND METHOD

Field

The present invention relates to optical apparatus and methods of manufacture of such optical apparatus, for example optical apparatus for routing, transmitting, receiving or manipulating optical signals using an array of optical elements.

Background

Fibre arrays are commonly used in a wide range of fibre optic applications, and many of these additionally involve the combination of a fibre array (e.g. 1 D or 2D array) with a microlens array. Typically the fibre array and lens array need to be carefully aligned and bonded to one another with sub-micron alignment accuracy, which can be a complex and time-consuming task. The fibre array and lens array may, for example, be provided or produced separately, and correct operation of the resulting combination will depend on the alignment and bonding of the fibre array and lens array being performed correctly and accurately.

Summary

In a first aspect there is provided an optical apparatus comprising: a body comprising material; a plurality of optical elements formed of the material of the body; and a plurality of alignment holes formed in the material of the body, wherein the alignment holes comprise fibre or other waveguide alignment holes aligned with one or more of the optical elements, and/or the alignment holes comprise alignment holes configured to receive mechanical elements for fixing and/or aligning the body to at least one further body.

The optical elements may comprise refractive, diffractive and/or reflective optical elements and/or metalenses.

Formation of the optical elements and/or the alignment holes may comprise laser modification of the material and/or laser ablation. The forming of the optical elements and the alignment holes may comprise removing laser-modified material following the laser modification.

The laser modification of the material and/or the laser ablation may comprise a laser processing procedure that comprises holding the body in position using a sample stage and providing relative movement between a laser beam and the sample stage. Laser modification of material and/or laser ablation for formation of both the optical elements and the alignment holes may be performed during the same laser processing procedure.

The laser modification of material for formation of both the optical elements and the alignment holes may be performed without moving or removing the body with respect to or from the sample stage.

The sample stage may comprise any suitable mechanical arrangement for holding the sample in a desired position, for example a desired position with respect to the sample stage and/or a laser source, and/or for providing relative movement with respect to a laser beam produced by the or a laser source, for example in accordance with known laser processing techniques. The sample stage may comprise a planar structure to which the sample is attached.

The body may comprise a monolithic block of the material and the plurality of optical elements, and/or the alignment holes, may be formed in or of the material of the monolithic block.

The plurality of optical elements may comprise an array of optical elements, optionally a 1 D or 2D array of optical elements.

The array may comprise a regular array of optical elements, with periodic spacing between the optical elements.

There may be non-periodic spacing between at least some of the optical elements.

The optical elements may be arranged to provide at least one of: a) a collimator array, optionally for optical switching applications; b) an expanded mode interface, optionally for a multi-channel fibre-optic connector; c) a phased array, optionally for LiDAR or free-space optical communication; d) aligned optics, optionally for optoelectronic applications, for example a transceiver or laser array.

The plurality of optical elements may comprise a plurality of lenses.

At least some of the lenses may comprise spherical lenses; and/or at least some of the lenses may comprise aspherical lenses.

At least one of the optical elements may be tilted with respect to a surface of the body.

The tilted optical element(s) may comprise an aspherical lens(es).

For the alignment hole(s) aligned with the tilted lens(es), an end face of the alignment hole may be tilted with respect to a longitudinal axis of the alignment hole.

The optical elements may be recessed below a surface of the material.

For at least some of the alignment holes, an end face of the alignment hole may be perpendicular to a longitudinal axis of the alignment hole; and/or for at least some of the alignment holes, an end face of the alignment hole may be tilted with respect to a longitudinal axis of the alignment hole.

An end face of the alignment hole may comprise the corresponding optical element. The end face of the alignment hole may comprise material, for example material of the monolithic block, that is aligned with the optical element, for example such that light passes from the end face through said material to the optical element.

At least some of the alignment holes may have different diameters to at least some other of the alignment holes, thereby optionally to accommodate different sizes of optical fibres or waveguide devices. The body may further include at least one channel connected to one or more of the alignment holes.

The at least one channel may be arranged to provide for insertion, for example flow, of adhesive or other filling or other material and/or to provide flow of etchant.

A surface of the at least one channel, or a recess in a surface of the at least one channel, may provide an end face of at least one of the alignment holes.

The depth of the or each recess and/or other dimensions of the or each recess may be selected so as to provide for uniform etching during fabrication and/or uniform filling or other distribution of adhesive during assembly of the apparatus and fibre(s) or other waveguide(s), when the etchant or adhesive is flowed in or otherwise inserted via the channel(s). The depth of the recess may for example be in a range of 5 pm to 250 pm. The diameter of the recess may for example be in a range of 50 pm to 250 pm

The channel or, each of a plurality of the channels, may be connected to a respective plurality of the alignment holes.

The channel(s) may extend from one side of the body to another side of the body. The channel(s) may pass through the body. The channels may be at an angle, for example perpendicular to or at least non-parallel to, the alignment holes. The channels may have a cross-sectional area in a range 10 pm² to 10 mm². The channels may have a length in a range 10 pm to 10 mm.

Formation of the alignment holes and/or optical elements may further comprise passing etchant through the channel(s) to etch regions modified by the laser modification of material.

For at least one of the alignment holes, said at least one of the alignment holes may extend from a surface of the body, and an associated one of the channels connected to said at least one of the alignment holes may extend to another surface of the body, optionally an opposite surface of the body.

Said another surface may be a surface on which the optical elements are present. For at least one of the alignment holes, said at least one of the alignment holes may extend from a surface of the body, and an associated one of the channels connected to said at least one of the alignment holes may extend to the same surface of the body.

The alignment holes may comprise alignment holes configured to receive mechanical elements for fixing and/or aligning the body to at least one further body.

The alignment holes may comprise alignment holes configured to receive mechanical elements to form a stacked structure with a plurality of further bodies or devices.

The at least one further body may comprise an array of further optical elements, and the alignment holes may be arranged to provide a desired alignment between the plurality of optical elements and the array of further optical elements.

The array of further optical elements may comprise an array of emitters and/or receivers and/or light-emitting diodes (LEDs) and/or edge emitter lasers and/or VCSELS and/or comprises at least one photonic integrated circuit.

The material of the body may comprise glass.

The holes may have any suitable cross-sectional shape, for example but not limited to being circular. For example, the holes, or one or more of the holes, may have a crosssection that is irregular or regular in shape, for example circular, oval, triangular, or any suitable polygonal shape. The holes may be empty or wholly or partially filled. The holes may be cylindrical or have any other suitable three-dimensional shape. The holes may have a cross-sectional area or other dimension that varies in a longitudinal direction, for example that tapers and/or varies in stepped fashion.

The holes may comprise channels, which may also be referred to as passages, for example channels through which the fibre or other waveguide can be inserted and/or extend. The channels may be closed passages, for example closed (e.g. surrounded by material in all directions) other than an entrance aperture and/or the channel(s) for flow of etchant, adhesive or other substance. Alternatively, the channels may be open on at least one side, for example in the form of trenches or grooves on the surface of the body. The alignment hole channels may be straight or curved or have any other desired arrangement.

Optionally, each alignment hole, or at least one of the alignment holes, extends along an at least partially curved path.

Optionally, the opening and the end of each hole, or at least one of the holes, are offset relative to one another.

Optionally, the opening defines a first axis normal to the surface of the body, the end defines a second axis normal to the end, and the first and second axes are parallel, but offset, relative to one another.

Optionally, each hole, or at least one of the holes, has a clear aperture defined as a difference between a diameter of the hole and the offset.

Optionally, the clear aperture is less than or equal to a minimum diameter of the corresponding optical fiber.

Optionally, the opening and the end of each hole, or at least one of the holes, are aligned with one another.

Optionally, the opening defines a first axis normal to the surface of the body, the end defines a second axis normal to the end, and the first and second axes are co-axial.

Optionally, the at least partially curved path defines a maximum deviation from a straight line path.

Optionally, each hole, or at least one of the holes, has a clear aperture defined as a difference between a diameter of the hole and the maximum deviation.

Optionally, the apparatus comprises: a plurality of fiber alignment features defined in the material of the body in a surface of each hole, or at least one of the holes, wherein each fiber alignment feature has a known spatial relationship relative to the corresponding hole, and wherein the plurality of fiber alignment features define a position of the corresponding optical fiber relative to the corresponding hole.

Optionally, each fiber alignment feature comprises a protrusion which protrudes from a surface of the corresponding hole.

Optionally, each fiber alignment feature comprises a recess which is defined in a surface of the corresponding hole.

Optionally, each hole, or at least one of the holes, extends into the body and two or more of the fiber alignment features are located at different axial positions defined relative to a longitudinal axis along which the corresponding hole extends.

Optionally, two or more of the fiber alignment features are located at different circumferential positions defined relative to a longitudinal axis along which the corresponding hole extends.

Optionally, two or more of the fiber alignment features are located at the same axial position but different circumferential positions defined relative to a longitudinal axis along which the corresponding hole extends.

Optionally, two or more of the fiber alignment features are located at the same circumferential position but different axial positions defined relative to a longitudinal axis along which the corresponding hole extends.

Optionally, the body comprises a monolithic block of the material and the one or more fiber alignment structures are formed in the material of the monolithic block.

Optionally, each optical element, or one or more of the optical elements, comprises a further optical fiber. Optionally, each optical element comprises an optical source. Optionally, each optical element comprises an optical detector. In a further aspect, which may be provided independently, there is provided a method of forming an optical apparatus comprising laser processing a body comprising material for formation of a plurality of optical elements of the material of the body and a plurality of alignment holes in the material of the body, wherein the alignment holes comprise fibre or other waveguide alignment holes aligned with one or more of the optical elements, and/or the alignment holes comprise alignment holes configured to receive mechanical elements for fixing and/or aligning the body to at least one further body.

The method may comprise forming the optical elements and the alignment holes by at least one of: a) laser modification of the material followed by removing laser-modified material following the laser modification; b) laser ablation.

The laser modification of the material and/or laser ablation may comprise a laser processing procedure that comprises holding the body in position using a sample stage and providing relative movement between a laser beam and the sample stage. Laser modification of material and/or laser ablation for formation of both the optical elements and the alignment holes may be performed during the same laser processing procedure.

The laser modification of material for formation of both the optical elements and the alignment holes may be performed without removing the body from the sample stage.

The method may comprise subsequently applying etchant to the material.

The method may comprise subsequently inserting fibres or other waveguides into at least some of the alignment holes.

The method may comprise applying adhesive to adhere fibres or other waveguides in, or to surfaces of, the alignment holes. The method may comprise inserting at least one mechanical element into at least one of the alignment holes, for example to fix and/or align the body to at least one further body. In a further aspect, which may be provided independently, there is provided an optical system comprising: optical apparatus comprising: a body comprising material; a plurality of optical elements formed of the material of the body; and a plurality of alignment holes formed in the material of the body, the alignment holes comprise alignment holes configured to receive mechanical elements for fixing and/or aligning the body to at least one further body; and the optical system further comprises: fibres or other waveguides inserted into at least some of the alignment holes and aligned with the optical elements; and/or at least one mechanical element inserted in at least one of the alignment holes for fixing and/or aligning the body to at least one further body.

The optical system may comprise at least one further optical apparatus, the at least one further optical apparatus optionally being as claimed or described herein, wherein the optical apparatus and the at least one further optical apparatus may form a stacked structure and are fixed and/or aligned by said at least one mechanical element.

In a further aspect, which may be provided independently, there is provided a monolithic glass device comprised of mechanical passive alignment features such as fibre alignment channels along with an array of microlenses to collimate or focus the light emitted or received by the fibres.

By producing fibre alignment arrays using laser based micromachining techniques, for example laser ablation and/or laser processing followed by material removal, and combining this with microlenses made using the same process in the same substrate, a monolithic piece can be produced which can significantly simplify the manufacturing of lens-coupled fibre arrays.

Features in one aspect may be provided as features in any other aspect. For example, any one of apparatus, method or system features may be provided as any one or more other of apparatus, method or system features.

Brief description of the drawings Embodiments of the invention are now described, by way of non-limiting examples, and are illustrated in the following figures, in which:-

Figure 1 is a schematic illustration of an optical apparatus according to an embodiment; Figure 2 is a schematic illustration of an optical apparatus according to a further embodiment, which includes angled channels;

Figure 3 is a schematic illustration of an optical apparatus according to a further embodiment, which included angled channel end faces;

Figures 4 to 6 are schematic illustrations of optical apparatus according to further embodiments, which include additional channels for example for etchant access and/or adhesive flow;

Figure 7 is a schematic illustration of an optical apparatus according to a further embodiment;

Figures 8a and 8b are schematic illustration of an optical apparatus according to a further embodiment, in the form of a connector insert with microlenses;

Figure 9 is a schematic illustration of an optical apparatus according to a further embodiment, which forms part of a stackable, aligned microlens array;

Figure 10 is a schematic illustration of a laser system for forming optical structures and alignment holes in material of a body; and

FIG. 11 A is a schematic end view of an assembly including an optical fiber positioning apparatus and an optical fiber;

FIG. 11 B is a cross-section on XX of the assembly of FIG. 11 A;

FIG. 11C is a schematic end view of the optical fiber positioning apparatus of FIG. 11A;

FIG. 11 D is a cross-section on XX of the optical fiber positioning apparatus of FIG. 11 C; FIG. 12A is a schematic end view of an assembly including an optical fiber positioning apparatus and a plurality of optical fibers;

FIG. 12B is a cross-section on XX of the assembly of FIG. 12A;

FIG. 13A shows a schematic longitudinal cross-section of an assembly including an optical fiber positioning apparatus and an optical fiber and transverse cross-sections on AA and BB of the assembly; and

FIG. 13B shows a schematic longitudinal cross-section of the optical fiber positioning apparatus of FIG. 13A and transverse cross-sections on AA and BB of the optical fiber positioning apparatus of FIG. 13A.

Detailed description Figure 1 is an illustration of an optical apparatus 2 according to an embodiment. The apparatus comprises a body in the form of a monolithic block of material 4 in which is formed a plurality of lenses 6a, 6b, and a plurality of alignment holes 8a, 8b.

In Figure 1 , optical fibres 5a, 5b are shown inserted into the alignment holes 8a, 8b. The alignment holes are aligned with the lenses 6a, 6b and the end faces of the alignment holes are perpendicular to a longitudinal axis of the alignment holes.

The alignment of the alignment holes 8a, 8b and lenses 6a, 6b is such that light, for example light of a desired wavelength, transmitted through the end faces of the alignment holes 8a, 8b in a desired direction, for instance a direction parallel to the longitudinal axes of the alignment holes 8a, 8b, is transmitted to the lenses 6a, 6b.

For instance, when the optical fibres 5a, 5b are inserted into the alignment holes to a desired position, for example with end faces of the fibres abutting or adjacent to the end faces of the alignment holes, light emitted by the optical fibres propagates to the lenses 5a, 5b. Optical axes of the lenses are aligned with the alignment holes in some embodiments. In the embodiment of Figure 1 , the end faces of the alignment holes are perpendicular to a longitudinal axis of the alignment holes.

The light can be of any desired wavelength and may for example be visible light.

The embodiment of figure 1 includes lenses 6a, 6b but in alternative embodiments, any suitable refractive, diffractive or reflective optical elements or metalenses may be provided instead of as well as lenses. For example, mirrors may be provided instead of lenses. The lenses 6a, 6b are spherical lenses but any other suitable type of lenses can be provided in other embodiments. Either concave, convex or any other suitable shape of lens may be used in various embodiments. Any suitable lens properties may be provided, for example focal lengths in a range 10 pm to 10mm, diameter in a range 10 pm to 10mm.

Although only two lenses 6a, 6b are shown in Figure 1 , any desired number of lenses or other optical elements and/or corresponding alignment holes may be formed of the material of the body, for example the monolithic block of material 4. The optical elements and the alignment holes can be provided in any suitable arrangement.

For example, in some embodiments the optical elements are formed in an array, optionally a 1 D or 2D array. The array may comprise a regular array, with periodic spacing between the optical elements, or may comprise a non-regular array with nonperiodic spacing between at least some of the optical elements.

Although optical fibres are shown in Figure 1 any other suitable type of waveguide device may inserted into the alignment holes, for example in order to transmit or receive light to from the lenses or other optical elements with which the alignment holes are aligned.

Although light is transmitted from the optical fibres or other waveguide devices to the lenses or other optical elements in the embodiment of Figure 1 , in other embodiments or modes of operation light may be transmitted from the optical elements to the optical fibres or other waveguide devices.

In the embodiment of Figure 1 , the alignment holes have a constant diameter along their length, but in some embodiments the diameter of the alignment holes vary, for example taper, with position in a longitudinal direction. In some embodiments, a flared opening to each alignment hole is provided, which can assist in guiding insertion of fibre or other waveguide device. Any suitable length and diameter of the alignment holes can be provided, for example a diameter in a range 50 pm to 500 pm, for instance 81 pm or 126 pm, and a length in a range 0.25 mm to 5 mm.

It is a feature of the embodiment of Figure 1 that the lenses 6a, 6b and the alignment holes 8a, 8b are formed by laser modification of the material, with laser modified material being removed following the laser modification (e.g. laser-induced selective etching) although in variants or alternative embodiments laser ablation may be used as well as or instead of such laser modification/etching or other subsequent selective removal. In particular, in the embodiment of Figure 1 , the material 4 is glass and the lenses 6a, 6b are made of the glass 4 using laser assisted wet chemical etching. Glass wafers or other body of any suitable material are irradiated with a focussed ultrashort pulsed laser to induce regions of enhanced chemical etch rate. The glass or other material is then placed in an etch solution (e.g. KOH or HF based) and the regions which have been irradiated etch preferentially with respect to the surrounding material. After etching, the microlens surfaces are post-processed to improve the surface quality, which can consist of a CO2 laser polishing process, a flame polishing process or a chemical smoothing process.

The alignment holes 8a, 8b are also formed in the glass using the laser assisted wet chemical etching process, and the alignment holes 8a, 8b and the lenses 6a, 6b are formed using the same laser processing procedure. For example, the laser modification of the material may comprise a laser processing procedure that comprises holding the body in position using a sample stage and providing relative movement between a laser beam and the sample stage, with laser modification of material for formation of both the optical elements and the alignment holes is performed during the same laser processing procedure. The laser modification of material for formation of both the optical elements and the alignment holes can be performed without moving or removing the body with respect to or from the sample stage.

By forming both the lenses or other optical elements and the alignment holes during the same laser processing procedure, desired positioning and alignment of the optical elements and the alignment holes can be provided in a particularly efficient manner, and the use of the alignment holes in turn enables straightforward and accurate alignment of the optical fibres or other waveguide devices with lenses or other optical elements, lenses or other optical elements, by insertion of the optical fibres or other waveguide devices into the alignment holes.

The accurate positioning and formation of the lenses or other optical elements, and the alignment holes, that can be provided by the laser processing procedure, and the removal of the need for subsequent, separate alignment procedures can also enable a wide variety of arrangements or properties of lenses or other optical elements and/or associated alignment holes to be provided without increase in complexity associated with alignment procedures.

For example, due to the flexibility of the laser manufacturing process, arrays with differing fibre alignment holes can be accommodated e.g. smaller and larger holes for different fibre (or other waveguide) diameters or types. Other mechanical alignment features for passive alignment with other components can also be provided if desired. In alternative embodiments, the laser processing can comprise laser ablation as well as or instead of laser modification of material properties followed by etching, or any other suitable laser processing technique. In some such embodiments, the glass body or other material may be maintained in the same position on a sample stage or similar structure whilst the laser ablation to produce both optical elements and alignment holes is performed. Any suitable known laser ablation technique may be used.

Further properties and arrangements of lenses or other optical elements, and associated alignment holes, according to further embodiments are discussed in relation to Figures 2 to 7.

In the embodiment of Figure 2, alignment holes 28 and lenses 26 are formed in a body comprising a block of material 24 using the or a laser processing procedure. The alignment holes 28 are in the form of angled fibre channels and the lenses 26 are aspheric lenses. The lenses are also tilted with respect to the body, in this case with respect to the surface of the body on which they are formed. Although only a single lens 26 and corresponding single alignment hole 28 is shown in Figure 2, an array of the lenses 26 and alignment holes 28 is provided in the embodiment.

In the embodiment of Figure 2, angled fibre channels with aspheric lens surfaces and tilted lenses are provided. By angling the fibre alignment channel and creating an appropriate aspheric lens surface, a low back reflection array can be achieved. In applications where low back reflections are important, other configurations can be provided in further embodiments which also allow suppression of back reflection.

Figure 3 is a schematic illustration of part of an optical apparatus according to an embodiment, which also uses angling to reduce back reflection. In this embodiment, alignment holes 38 and lenses 36 are formed in a body comprising a block of material 34 using the or a laser processing procedure. The lenses 36 are spherical lenses, and the holes 38 are in the form of straight channels perpendicular to the surface on which the lenses 36 are provided and aligned with the lenses 36. In this embodiment, the endfaces of the channels 38 are angled with respect to the walls/longitudinal axis of the channels and/or with respect to a line joining the centre of the end-face with the centre of the corresponding lens 36. The end faces may be inclined at any suitable angle with respect to the walls/longitudinal axis to reduce back reflection, for instance any angle in a range 1 degree to 45 degrees, for example 8 degrees.

An optical adhesive with suitable refractive index for the wavelengths of light of interest is used in the embodiment of Figure 3 to attach fibres or other waveguide devices within the holes 38. The angling of the end faces of the alignment holes 38 can provide a low back reflection array.

Although only a single lens 36 and corresponding single alignment hole 38 is shown in Figure 2, an array of the lenses 36 and alignment holes 38 is provided in the embodiment.

As well as providing aligned fibre or other waveguide alignment holes, and associated lenses or other optical elements, certain embodiments included additional structures formed in the body, for example using laser processing. For example, in some embodiments modifications to structure are made to enable adhesive flow and/or venting, and/or to aid etch formation of structures.

An example of one such embodiment is shown in Figure 4, which is a variant of the embodiment of Figure 1 in which channel(s) 40 for enhanced etchant access during processing and for subsequent adhesive flow during assembly (e.g. insertion of fibres or other waveguide devices into the holes 8a, 8b and application of adhesive to fix them in place). For example, etchant and, subsequently, excess adhesive can escape or at least flow away from the holes 8a, 8b via the channel(s) 40.

In the embodiment of Figure 4, a single channel 40 can connect multiple alignment holes, for example at least alignment holes 8a, 8b. In alternative embodiments, a plurality of channels can be provided each connected to one, or a respective plurality, of the alignment holes, for example adjacent fibre channels. A plane may effectively be formed at the end faces of the fibre channels by a surface of the channel 40. The or each channel 40 may, for example, exit the body at a side face.

In the embodiment of Figure 4, a surface of the channel(s) 40 provides an end face of at least one of the alignment hole(s) 8a. By providing that the surface of the channel(s) provides an end face of the alignment hole(s), if adhesive, etchant or other substance is flowed in through the channel(s) and/or hole(s) it can be ensured that the adhesive, etchant or other substance is present at or near the end face, or intended end face, of the alignment hole. For example, in the case of adhesive it can be ensured that there is good adhesive bonding between the end face of the alignment hole and the fibre, whilst also allowing adhesive or other substance to escape and/or overflow via the channel. In the case of etchant, the it can be ensured that the etchant interacts with all areas that are intended to be etched, for example all areas that have been laser treated.

In variants of the embodiment of Figure 4, the surface of the channel may include a recess and the end face of the channel may be a surface of the recess. A recess according to one such variant is indicated in Figure 4 by a dotted line. In such variants, the depth of the recess and/or other dimensions of the recess may be selected so as to provide for uniform etching during fabrication and/or uniform filling or other distribution of adhesive during assembly of the apparatus and fibre(s), when the etchant or adhesive is flowed in or otherwise inserted via the channel 40 or hole 8a. The depth of the recess may for example be in a range of 5 pm to 250 pm. The diameter of the recess may for example be in a range of 50 pm to 250 pm.

The presence of a small recess as in the embodiment of Figure 4 can, for example, assist with positioning of a fibre when inserted through the hole and into the recess, whilst still allowing for good distribution of the adhesive, etchant or other substance during manufacture and/or assembly. In some embodiments, if the recess is too deep then the adhesive, etchant or other substance may not extend to a desired depth or with desired homogeneity into the recess, for example it may not fill, or fill jointly with the fibre, or pass through the entirety of, the recess.

A further embodiment is illustrated in Figure 5, and is a variant of the embodiment of Figure 1 in which vent hole(s) 50 are provided which connect to the alignment hole 8a. As well as allowing etchant access, the vent hole(s) can also be used for insertion of adhesive to adhere the fibre 5a or other waveguide device in the alignment hole 8a.

A further embodiment is illustrated in Figure 6, and is a variant of the embodiment of Figure 1 in which vent hole(s) 60 are provided which connect to the alignment hole 8a. As well as allowing etchant access, the vent hole(s) 60 can also be used for insertion of adhesive to adhere the fibre 5a or other waveguide device in the alignment hole 8a. The embodiment of Figure 6 is similar to that of Figure 5, except that the vent hole(s) 60 connect the hole 8a to the surface on which the lens 6a or other optical device is provided rather than providing an additional path between the alignment hole 8a and the surface in which the alignment hole is formed.

Although, for clarity, only a single lens 6a and corresponding alignment hole 8a is shown in Figures 4 to 6, an array of the lenses and alignment holes is provided in the embodiments of Figures 4 to 6.

In the embodiments of Figures 1 to 6 the lenses or other optical elements are recessed below a surface of the material of the body, which can provide for a robust structure. The recess would generally not be filled but in some embodiments may be filled with an appropriate material e.g. epoxy, if required. Additional optical functionality, e.g. crosstalk suppression, may be provided in some embodiments by introducing a light absorbing layer at the sides of the recesses containing the lenses or other optical elements.

As well as or instead of alignment holes that can be used to align optical fibre or other waveguides with lenses or other optical elements, in some embodiments the apparatus includes alignment hole(s) that can be used to receive mechanical elements, for instance pins, for fixing and/or aligning the body to at least one further body. The alignment holes for receiving fixing/aligning elements can be formed using the same laser processing procedure as used to form the optical elements and waveguide alignment holes, for example a single laser processing procedure performed without removing the body from the sample stage, thus providing an efficient way to ensure correct positioning of the various alignment holes and optical elements.

An embodiment that includes alignment holes for fixing/alignment elements is illustrated schematically in Figure 7. The apparatus 70 of Figure 7 includes a body 74 in which is formed alignment holes 78 (one shown by way of example) for receiving optical fibres 75 (one shown by way of example) and that align with an array of optical elements 76.

The apparatus 70 is an optical connector and includes a flange 71 for connector mating and alignment holes 77 for receipt of pins, for example MT connector pins or any other known or standard connector pins, that can be used to connect the apparatus 70 to a body of a further apparatus or structure. The body 74 is a monolithic piece of glass. The alignment holes 78 are simple blind holes and the optical elements 76 in this embodiment provide an expanded mode interface, although they can be used for any other purpose or to provide any other optical characteristics in alternative embodiments.

A further embodiment is illustrated in schematic perspective and side-on views in Figures 8A and 8B. The apparatus of Figures 8A and 8B is a connector insert with microlenses 86 and MT or other connector pin holes 87. In this embodiment, alignment holes for receiving optical fibres or other waveguides are not provided. The apparatus of Figures 8A and 8B enables assembly to existing connector ferrules, for example, to enable expanded mode capability.

Another embodiment is illustrated in Figure 9, in which two devices 90, 100 are provided each formed using laser processing of a block of glass or other suitable material to produce arrays of microlenses or other optical elements 96a, 96b and 106 and to produce alignment holes 98, 108 through which pins 110 or other connection or alignment features can be inserted in order to connect and/or align the devices 90, 100. Thus, stackable passive aligned microlens (or other optical element) arrays can be provided with laser machined passive alignment features to allow easily assembled stacks. The alignment holes in this embodiment enable alignment of the optical elements 96a, 96b with the optical elements 106 and with an array of emitters/receivers 112 provided on substrate 114.

The alignment holes 77, 98, 108 are shown as closed holes surrounded by the material on all sides in lateral directions. In some embodiments, alignment holes may be at least partially open on one or more sides, for example if they are positioned at the edge of the body. Alignment holes may have any suitable shape, and are not limited to being circular only.

Embodiments have been described in which the holes comprise straight channels through which the fibre or other waveguide can pass. In alternative embodiments, the holes may comprise alignment channels for fibres and/or waveguides that are curved or have any other desired shape. Some such embodiments are illustrated schematically in Figures 11 to 13.

Figures 11A and 11 B are schematic face-on and side views with a fibre inserted, and Figures 11C and 11 D are schematic face-on and side views without a fibre inserted. Referring to FIGS. 11A and 11 B there is shown an assembly generally designated 1201. The assembly 1201 includes an apparatus 1202 and an optical fiber 1204, wherein the apparatus 1202 is configured for positioning the optical fiber 1204 relative to the apparatus 1202.

As shown in FIGS. 11C and 11 D, the apparatus 1202 includes a body 1206 formed from a glass material and having first and second surfaces 1212 and 1216 respectively. The apparatus 1202 includes an optical element in the form of a lens 1270 defined in the second surface 1216 of the body 1206, and an alignment hole 1208 in the form of a passage defined in the body 1206, wherein the hole 1208 extends from an opening 1210 at the first surface 1212 of the body 1206 to an end 1214 which is located adjacent to the lens 1270, and wherein the hole 1208 is configured to accommodate the optical fiber 1204 allowing for the tolerances associated with the manufacturing of the optical fiber 1204. The hole 1208 extends along a path which is at least partially curved and which extends from the opening 1210 to the end 1214 of the hole 1208. As shown most clearly in FIG. 11 D, the opening 1210 and the end 1214 of the hole 1208 are offset relative to one another by a distance d. Moreover, a difference between a diameter 0_a of the hole 1208 and the offset d is less than or equal to a minimum diameter O^ of the corresponding optical fiber 1204. In other words, the hole 1208 defines a “clear aperture” which is less than or equal to the minimum diameter 0_f of the corresponding optical fiber 1204. Consequently, as the optical fiber 1204 is inserted into the hole 1208, a cylindrical outer surface of the optical fiber 1204 is forced into contact with a wall of the hole 1208 causing the optical fiber 1204 to flex to a limited degree and inducing one or more bends in the optical fiber 1204 until an end of the optical fiber 1204 abuts the end 1214 of the hole 1208 with the cylindrical outer surface of the optical fiber 1204 in contact with the wall of the hole 1208 in a region adjacent to the opening 1210 and in a region adjacent the end 1214 of the hole 1208 as shown in FIG. 11 B. It should be understood that, although the optical fiber 1204 is shown in FIG. 11 B as having a curvature which is greater than a curvature of the hole 1208, in reality, the resilience of the optical fiber 1204 means that the optical fiber 1204 adopts a path through the hole 1208 such that the curvature of the optical fiber 1204 is less than the curvature of the hole 1208 with the cylindrical outer surface of the optical fiber 1204 remaining in contact with the wall of the hole 1208 in a region adjacent to the opening 1210 and with the cylindrical outer surface of the optical fiber 1204 remaining in contact with the wall of the hole 1208 in a region adjacent to the end 1214 of the hole 1208. Moreover, although the optical fiber 1204 is shown in FIG. 11 B as extending through the opening 1210 with an axis of the optical fiber 1204 normal to the surface 1212 of the body 1206, the axis of the optical fiber 1204 may be inclined at a small but predictable angle relative to a normal to the surface 1212 of the body 1206, depending on the relative dimensions of the optical fiber 1204 and the hole 1208 and depending on the flexibility of the optical fiber 1204. Similarly, although the optical fiber 1204 is shown in FIG. 11 B with an axis of the optical fiber 1204 normal to the end 1214 of the hole 1208, the axis of the optical fiber 1204 may be inclined at a small but predictable angle relative to a normal to the end 1214 of the hole 1208, depending on the relative dimensions of the optical fiber 1204 and the hole 1208 and depending on the flexibility of the optical fiber 1204. Regardless of whether or not the axis of the optical fiber 1204 is inclined at a small but predictable angle relative to a normal to the surface 1212 of the body 1206 and/or regardless of whether or not the axis of the optical fiber 1204 is inclined at a small but predictable angle relative to a normal to the end 1214 of the hole 1208 the optical fiber 1204 is positioned at a more predictable position relative to the end 1214 of the hole 1208 and therefore also at a more predictable position relative to the lens 1270. Consequently, the apparatus 1202 may facilitate more accurate positioning of the optical fiber 1204 relative to the apparatus 1202 as a whole and, in particular, relative to the lens 1270 for more efficient optical coupling between the optical fiber 1204 and the lens 1270. In the embodiment, and some alternative embodiments, the optical fiber 304 may have a minimum diameter 0_f of around 125 .m, the curved portion of the passage 308 may be defined over a longitudinal distance in the range of a few tens of .m up to 1 mm e.g. of the order of 100 .m, and the offset d may be in the range of 1 - 10 .m, 4 to 6 .m, or substantially equal to 5 .m. This may result in positional accuracies of the optical fiber 304 in the regions adjacent to the opening 310 and end face 314 of the order of ±1 .m or better.

Although the assembly 1201 of FIGS. 11A and 11 B is, for clarity, shown with a single optical fiber 1204 and FIGS. 11C and 11 D, for clarity, show a single hole 1208 for accommodating the optical fiber 1204, it should be understood that the apparatus includes a plurality of holes 1208 similar, wherein each hole has an end which is located adjacent to a corresponding optical element such a corresponding lens and wherein each hole is configured to accommodate a corresponding optical fiber. As will be appreciated by one of skill in the art, control of the position of the optical fibers with respect to the lenses may be important. The lenses are generally manufactured with a high tolerance. However, if each optical fiber had a different offset relative to an optical axis of the corresponding lens, then the optical coupling between the different optical fibers and the different lenses would be different. For example, the optical fields resulting from the optical coupling between the different optical fibers and the different lenses would then be different. For instance collimated or focused beams could diverge from one another in undesirable fashion. In the embodiment of Figure 11 , since each of the optical fibers would have a more accurate alignment relative to the corresponding lens as a consequence of using a curved hole like curved hole 1208, then any differences in the optical fields resulting from the optical coupling between the different optical fibers and the different lenses can be minimised.

Referring to FIGS. 12A and 12B there is shown an assembly generally designated 1301. The assembly 1301 includes apparatus 1302 and a plurality of optical fibers 1304, wherein the apparatus 1302 is configured for positioning the optical fibers 1304 relative to the apparatus 1302.

The apparatus 1302 includes a body 1306 formed from a glass material and having first and second surfaces 1312 and 1316 respectively. The apparatus 1302 includes a plurality of optical elements in the form of a plurality of lenses 1370 defined in the second surface 1316 of the body 1306 and a plurality of fiber alignment structures in the form of a plurality of holes 1308 defined in the body 1306, wherein each hole 1308 extends from a corresponding opening 1310 at the first surface 1312 of the body 1306 to a corresponding end 1314 which is which is located adjacent to a corresponding lens 1370, and wherein each hole 1308 is configured to accommodate a corresponding optical fiber 1304. Each hole 1308 extends along a corresponding path which is at least partially curved and which extends from the corresponding opening 1310 to the corresponding end 1314. As shown most clearly in FIG. 12B, the first opening 1310 and the corresponding end 1314 of each hole 1308 are aligned with one another.

As shown in FIG. 12B, each at least partially curved path defines a maximum deviation d from a straight line path. A difference between a diameter 0_a of each hole 1308 and the maximum deviation d is less than or equal to a minimum diameter 0_f of the corresponding optical fiber 1304. In other words, each hole 1308 defines a “clear aperture” which is less than or equal to the minimum diameter 0_f of the corresponding optical fiber 1304. Consequently, as the optical fiber 1304 is inserted into the hole 1308, an outer cylindrical surface of each optical fiber 1304 is forced into contact with a wall of the corresponding hole 1308 causing each optical fiber 1304 to flex to a limited degree and inducing one or more bends in each optical fiber 1304 until each optical fiber 1304 abuts the end 1314 of the corresponding hole 1308 with the cylindrical outer surface of each optical fiber 1304 in contact with the wall of the corresponding hole 1308 in a region adjacent to the corresponding opening 1310 and in a region adjacent to the end 1314 of the hole 1308 as shown in FIG. 12B. It should be understood that although the optical fiber 1304 is shown in FIG. 12B as extending along a straight line, in reality each optical fiber 1304 may extend along a path which is at least partially curved. Moreover, in reality, the resilience of the optical fiber 1304 means that the optical fiber 1304 adopts a path through the corresponding hole 1308 such that the curvature of the optical fiber 1304 is less than the curvature of the corresponding hole 1308 with the cylindrical outer surface of the optical fiber 1304 remaining in contact with the wall of the hole 1308 in the region adjacent to the opening 1310 and with the cylindrical outer surface of the optical fiber 1304 remaining in contact with the wall of the hole 1308 in the region of the end 1314 of the hole 1308. In addition, although the optical fiber 1304 is shown in FIG. 12B as extending through the opening 1310 with an axis of the optical fiber 1304 normal to the surface 1312 of the body 1306, the axis of each optical fiber 1304 may be inclined at a small but predictable angle relative to the normal to the surface 1312 of the body 1306, depending on the relative dimensions of the optical fiber 1304 and the hole 1308, and depending on the flexibility of the optical fiber 1304. Similarly, although the optical fiber 1304 is shown in FIG. 12B with an axis of the optical fiber 1304 normal to the end 1314 of the hole 1308, the axis of the optical fiber 1304 may be inclined at a small but predictable angle relative to the normal to the end 1314 of the hole 1308, depending on the relative dimensions of the optical fiber 1304 and the hole 1308, and depending on the flexibility of the optical fiber 1304. Regardless of whether or not each optical fiber 1304 extends along a path which is at least partially curved, regardless of whether or not an axis of each optical fiber 1304 is inclined at a small angle relative to the normal to the surface 1312 of the body 1306 and regardless of whether or not an axis of each optical fiber 1304 is inclined at a small angle relative to the normal to the end 1314 of each hole 1308 each optical fiber 1304 is positioned at a more predictable position relative to the end 1314 of the corresponding hole 1308 and therefore also at a more predictable position relative to the corresponding lens 1370. Consequently, the apparatus 1302 may facilitate more accurate positioning of the plurality of optical fibers 1304 relative to the apparatus 1302 as whole and, in particular, relative to the plurality of lenses 1370 for more efficient optical coupling between the plurality of optical fibers 1304 and the plurality of lenses 1370. As will be appreciated by one of skill in the art, what matters is control of the position of the optical fibers 1304 with respect to the lenses 1370. The lenses 1370 are generally manufactured with a high tolerance. However, if each optical fiber 1304 had a different offset relative to an optical axis of the corresponding lens 1370, then the optical coupling between the different optical fibers 1304 and the different lenses 1370 would be different. For example, the optical fields resulting from the optical coupling between the different optical fibers 1304 and the different lenses 1370 would then be different. For instance collimated or focused beams could diverge from one another in undesirable fashion Since each of the optical fibers 1304 has a more accurate alignment relative to the corresponding lens 1370 as a consequence of using a curved hole like curved hole 1308, then any differences in the optical fields resulting from the optical coupling between the different optical fibers 1304 and the different lenses 1370 can be minimised.

Referring to FIGS. 13A and 13B there is shown an assembly generally designated 1401 . The assembly 1401 includes apparatus 1402 and an optical fiber 1404, wherein the apparatus 1402 is configured for positioning the optical fiber 1404 relative to the apparatus 1402.

The apparatus 1402 includes a body 1406 formed from a glass material and having first and second surfaces 1412 and 1416 respectively. The apparatus 1402 includes an optical element in the form of a lens 1470 defined in the second surface 1416 of the body 1206, and a fiber alignment structure in the form of a hole 1408 defined in the body 1406, wherein the hole 1408 extends from a corresponding opening 1410 at the first surface 1412 of the body 1406 to an end 1414 which is located adjacent to the lens 1470, and wherein the hole 1408 is configured to accommodate the optical fiber 1404 allowing for the tolerances associated with the manufacturing of the optical fiber 1404.

A plurality of fiber alignment features in the form of a plurality of protrusions 1430 are defined in the material of the body 1406 in a surface or sidewall of the hole 1408. As will be appreciated from the following description, the protrusions 1430 have a known spatial relationship relative to the hole 1408 so that the protrusions 1430 together define a position of the optical fiber 1404 relative to the hole 1408. Specifically, two of the protrusions 1430 are located at a first axial position defined relative to a longitudinal axis 1432 along which the hole 1408 extends as shown in the transverse cross-sections on AA in FIGS. 13A and 13B and two of the protrusions 1430 are located at a second axial position defined relative to the longitudinal axis 1432 as shown in the transverse crosssections on BB in FIGS. 13A and 13B. Moreover, each of the protrusions 1430 at the first axial position are located at different circumferential positions defined relative to the longitudinal axis 1432 as shown in the transverse cross-sections on AA in FIGS. 13A and 13B and each of the protrusions 1430 at the second axial position are located at different circumferential positions defined relative to the longitudinal axis 1432 as shown in the transverse cross-sections on BB in FIGS. 13A and 13B. One of ordinary skill in the art will understand that the optical fiber 1404 has a limited degree of flexibility. Moreover, as a consequence of the arrangement of the protrusions 1430, a cylindrical outer surface of the optical fiber 1404 engages a wall of the hole 1408 in a region adjacent to the opening 1410 and in a region adjacent to the end 1414 of the hole 1408 as shown in FIG. 13A. It should be understood that although the optical fiber 1404 is shown in FIG. 13A as extending through the opening 1410 with an axis of the optical fiber 1404 normal to the surface 1412 of the body 1406, the axis of the optical fiber 1404 may be inclined at a small but predictable angle relative to a normal to the surface 1412 of the body 1406, depending on the relative dimensions of the optical fiber 1404 and the hole 1408, depending on the size and positioning of the protrusions 1430, and depending on the flexibility of the optical fiber 1404. Similarly, although the optical fiber 1404 is shown in FIG. 13A as extending with an axis of the optical fiber 1404 normal to the end 1414 of the hole 1408, the axis of the optical fiber 1404 may be inclined at a small but predictable angle relative to a normal to the end 1414 of the hole 1408, depending on the relative dimensions of the optical fiber 1404 and the hole 1408, depending on the size and positioning of the protrusions 1430, and depending on the flexibility of the optical fiber 1404. Regardless of whether or not the axis of the optical fiber 1404 is inclined at a small angle relative to the normal to the surface 1412 of the body 1406 and regardless of whether or not the axis of the optical fiber 1404 is inclined at a small angle relative to the normal to the end 1414 of the hole 1408, the optical fiber 1404 is positioned at a more predictable position relative to the end 1414 of the hole 1408 and therefore also at a more predictable position relative to the corresponding lens 1470. Consequently, the apparatus 1402 may facilitate more accurate positioning of the optical fiber 1404 relative to the apparatus 1402 as whole and, in particular, relative to the lens 1470 for more efficient optical coupling between the optical fiber 1404 and the lens 1470. Although the assembly 1401 of FIGS. 13A and 13B is shown, for clarity, with a single optical fiber 1404 and the apparatus 1402 of FIGS. 13A and 13B is shown with a single hole 1404 for accommodating the optical fiber 1404, it should be understood that the assembly 1401 of FIGS. 13A and 13B and the apparatus 1402 of FIGS. 13A and 13B, includes a plurality of holes1408 or similar 1408, wherein each hole has an end which is located adjacent to a corresponding optical element such a corresponding lens, and wherein each hole is configured to accommodate a corresponding optical fiber. As will be appreciated by one of skill in the art, control of the position of the optical fibers with respect to the lenses may be important. The lenses are generally manufactured with a high tolerance. However, if each optical fiber had a different offset relative to an optical axis of the corresponding lens, then the optical coupling between the different optical fibers and the different lenses would be different. For example, the optical fields resulting from the optical coupling between the different optical fibers and the different lenses would then be different. For instance collimated or focused beams could diverge from one another in undesirable fashion In such a variant, since each of the optical fibers would have a more accurate alignment relative to the corresponding lens as a consequence of the use of protrusions 1430, then any differences in the optical fields resulting from the optical coupling between the different optical fibers and the different lenses can be minimised.

A curved arrangement for the alignment holes, and/or the presence of alignment structures, such as those shown in Figures 11 to 13 may be provided in variants of any of the embodiments of Figures 1 to 9. In alternative embodiments, any desired curvature of the alignment hole passages may be provided and the curvature is not limited to the specific conditions and parameters discussed in relation to Figures 11 to 13.

Apparatus according to some embodiments can provide, for example, an array of blind fibre alignment holes in a substrate with correspondingly placed microlenses on the opposite facet fabricated in 1 D or 2D arrays with flexible positioning of fibre holes, and manufactured at wafer scale or individual die scale.

Apparatus according to various embodiments can, for example, be standalone to create combinations of lenses e.g. fast axis and slow axis collimators. Apparatus according to various embodiments can, for example, be integrated into active sub-assemblies with arrays of emitters or receivers and/or can be applicable to arrays of discrete emitters e.g. VCSELS, microLEDs, edge emitter lasers, as well as photonic integrated circuits such as Silicon Photonic devices. Apparatus according to embodiments can in some cases be assembled on the wafer scale.

Apparatus according to embodiments can be used for a variety of applications, including but not limited to, optical fibre collimator arrays for optical switching, multichannel fibre optic connectors with expanded mode interfaces, phased arrays for LiDAR and free- space optical communications, passively aligned optics for optoelectronic modules such as transceivers or laser arrays.

Any suitable mechanical elements for connection and/or alignment can be used in embodiments, for example MTP/MPO guide pins with diameters of 700 urn or 550 urn.

Embodiments have been described in which the material of the body is glass. Any suitable material can be used according to embodiments, for example glasses such as silicates, borosilicates, doped or modified silicates, phosphate glasses, doped or modified phosphates, chalcogenide glasses, doped or modified chalcogenides, crystalline materials such lithium niobate, yttrium aluminium garnet and also doped, poled or modified crystals such as periodically poled lithium niobate or Neodymium doped yttrium aluminium garnet, laser or amplifier gain media such as rare earth doped glasses and crystals.

As mentioned above, it is a feature of some embodiments that the optical elements and the alignment holes can formed using laser modification of the material, with laser modified material being removed following the laser modification. Various examples of laser processing techniques according to embodiments, which may be used to produce the optical elements and the alignment holes are described in WO 2008/155548, WO 2011/154701 , WO 2019/166803 and WO 2019/122914 the contents of which are hereby incorporated by reference.

Figure 10 shows a laser system for forming the optical structures and alignment holes in material of a body, for example a bulk sample, according to some embodiments. The laser system comprises a laser 206 that, in this embodiment, has an associated acoustooptic modulator that can modulate a pulse train from the laser 206. The laser in this embodiment has an external compressor stage, for emitting a beam of laser radiation 208 for use in forming optical structures or holes in a radiation sensitive material 210, for example suitable glass or crystal material.

In the embodiment of Figure 1 , the material 210 is carried in a sample space on a stage structure 212 that can be moved under the control of a computer based control unit 214. The control unit also controls operation of the laser 206.

In operation, the beam 208 is focused vertically down onto the material 210 by a lens system 216. The beam delivery may be mounted to a support structure (not shown) to minimize vibration and thermal movements. The beam reaches a focal point 218 at a point of the material 210. The translation of the sample through the focus results in laser modification of the material at desired positions and to provide desired effects. In alternative embodiments the substrate remains stationary and the laser beam is moved relative to the substrate.

Through tailoring of the laser parameters, for example under control of the control unit 214, such as power, polarization, pulse length, pulse repetition rate, wavelength and/or speed of translation, structures can be created with desired properties.

The laser parameters that are used depend on the material properties of the sample, and on the desired modifications. Examples of suitable laser processing parameters are provided in WO 2008/155548, WO 2011/154701 , WO 2019/166803 and WO 2019/122914 the contents of which are hereby incorporated by reference. In some embodiments, pulse durations from 10 fs to 20 ps, for example 200fs, pulse repetition rates from 1 kHz to 1 GHz, and pulse energies from 10 nJ to 1 mJ may be used, but any other suitable laser processing parameters may be used in accordance with known laser processing techniques.

By performing the laser processing for formation of both the optical elements and the alignment holes during the same laser processing procedure, for example, without removing the material 210 from, or altering its position on, the stage structure, accurate alignment of the optical elements and the alignment holes can be assured in an efficient manner as mentioned above. As mentioned above, the laser processing can comprise laser ablation as well as or instead of laser modification of material properties followed by etching, or any other suitable laser processing technique. Again, in such embodiments, the material 210 may be maintained in the same position on a sample stage or similar structure whilst the laser ablation and/or machining to produce both optical elements and alignment holes is performed. Following laser processing by irradiating the material with a focussed ultrashort pulsed laser to induce regions of enhanced chemical etch rate, the glass is then placed in an etch solution (e.g. KOH or HF based) and the regions which have been irradiated etch preferentially with respect to the surrounding material. After etching, surfaces can be processed to improve the surface quality, which can for example consist of a CO2 laser polishing process, a flame polishing process or a chemical smoothing process, as mentioned above.

It will be understood that the present invention has been described above purely by way of example, and modifications of detail can be made within the scope of the invention.

Each feature disclosed in the description, and (where appropriate) the claims and drawings may be provided independently or in any appropriate combination.

Claims

29 CLAIMS

1 . Optical apparatus comprising: a body comprising material; a plurality of optical elements formed of the material of the body; and a plurality of alignment holes formed in the material of the body, wherein: the alignment holes comprise fibre or other waveguide alignment holes aligned with one or more of the optical elements, and/or the alignment holes comprise alignment holes configured to receive mechanical elements for fixing and/or aligning the body to at least one further body.

2. Apparatus according to claim 1 , wherein the optical elements comprise refractive, diffractive and/or reflective optical elements, and/or metalenses.

3. Apparatus according to claim 1 or 2, wherein formation of the optical elements and/or the alignment holes comprises laser modification of the material and/or laser ablation

4. Apparatus according to claim 3, wherein the laser modification and/or laser ablation of the material comprises a laser processing procedure that comprises holding the body in position using a sample stage and providing relative movement between a laser beam and the sample stage, and wherein laser modification of material and/or laser ablation for formation of both the optical elements and the alignment holes is performed during the same laser processing procedure.

5. Apparatus according to claim 4, wherein the laser modification of material and/or laser ablation for formation of both the optical elements and the alignment holes is performed without removing the body from the sample stage and/or without moving the body relative to the sample stage.

6. Apparatus according to any preceding claim, wherein the body comprises a monolithic block of the material and the plurality of optical elements, and the alignment holes, are formed in or of the material of the monolithic block. 30

7. Apparatus according to any preceding claim , wherein the plurality of optical elements comprises an array of optical elements.

8. Apparatus according to claim 7, wherein the array comprises a regular array of optical elements, with a periodic spacing between the optical elements.

9. Apparatus according to any preceding claim , wherein the optical elements are arranged to provide at least one of: e) a collimator array, optionally for optical switching applications; f) an expanded mode interface, optionally for a multi-channel fibre-optic connector; g) a phased array, optionally for LiDAR or free-space optical communication; h) Aligned optics, optionally for optoelectronic applications, for example a transceiver or laser array.

10. Apparatus according to any preceding claim , wherein the plurality of optical elements comprises a plurality of lenses.

11 . Apparatus according to any preceding claim , wherein at least one of the optical elements is tilted with respect to a surface of the body.

12. Apparatus according to claim 11 , wherein for the alignment hole(s) aligned with the tilted lens(es), an end face of the alignment hole is tilted with respect to a longitudinal axis of the alignment hole.

13. Apparatus according to any preceding claim , wherein: for at least some of the alignment holes, an end face of the alignment hole is perpendicular to a longitudinal axis of the alignment hole; and/or for at least some of the alignment holes, an end face of the alignment hole is tilted with respect to a longitudinal axis of the alignment hole.

14. Apparatus according to any preceding claim , wherein at least some of the alignment holes have different diameters to at least some other of the alignment holes, thereby to accommodate different sizes of optical fibres or waveguide devices.

15. Apparatus according to any preceding claim , wherein the body further includes at least one channel connected to one or more of the alignment holes, and the at least one channel is arranged to provide flow of adhesive or other filling and/or to provide flow of etchant.

16. Apparatus according to claim 15, wherein the channel or, each of a plurality of the channels, is connected to a respective plurality of the alignment holes.

17. Apparatus according to claim 15 or 16, wherein formation of the alignment holes and/or optical elements further comprises passing etchant through the channel(s) to etch regions modified by the laser modification of material.

18. Apparatus according to any preceding claim, wherein the alignment holes comprise alignment holes configured to receive mechanical elements for fixing and/or aligning the body to at least one further body.

19. Apparatus according to claim 18, wherein the at least one further body comprises an array of further optical elements, and the alignment holes are arranged to provide a desired alignment between the plurality of optical elements and the array of further optical elements.

20. Apparatus according to any preceding claim, wherein the body comprises a or the monolithic block of the material, and the plurality of optical elements and the alignment holes are formed in or of the material of the monolithic block; the body further includes at least one channel connected to one or more of the alignment holes, and the at least one channel is arranged to provide flow or other insertion of adhesive or other filling or other material and/or to provide flow or other insertion of etchant; and a surface of the at least one channel, or a recess in a surface of the at least one channel, provides an end face of at least one of the alignment holes.

21. A method of forming an optical apparatus comprising laser processing a body comprising material for formation of a plurality of optical elements of the material of the body and a plurality of alignment holes in the material of the body, wherein: the alignment holes comprise fibre or other waveguide alignment holes aligned with one or more of the optical elements, and/or the alignment holes comprise alignment holes configured to receive mechanical elements for fixing and/or aligning the body to at least one further body.

22. An optical system comprising: optical apparatus according to any of claims 1 to 19; and at least one of: fibres or other waveguides inserted into at least some of the alignment holes and aligned with the optical elements; and/or at least one mechanical element inserted in at least one of the alignment holes for fixing and/or aligning the body to at least one further body.