WO2025080903A1

WO2025080903A1 - Diode-pumped solid state laser system for i-line applications

Info

Publication number: WO2025080903A1
Application number: PCT/US2024/050864
Authority: WO
Inventors: Alan Petersen; Thomas Sosnowski
Original assignee: Newport Corp USA
Current assignee: Newport Corp USA
Priority date: 2023-10-12
Filing date: 2024-10-11
Publication date: 2025-04-17
Anticipated expiration: 2026-04-12
Also published as: TW202533471A

Abstract

The present application discloses a diode-pumped solid state laser system for use in I-line applications and includes a laser cavity defined by a first mirror and a second mirror, a pump source providing a pump signal, a gain crystal to output an intracavity signal having a wavelength of 1050 nm and 1155 nm in response to the being pumped by the pump signal, a second harmonic crystal configured to output a second harmonic of the intracavity signal, a third harmonic crystal configured to output a third harmonic of the intracavity signal and the second harmonic signal, and an output coupler to output the third harmonic signal having a wavelength from 350 nm to 385 nm.

Description

DIODE-PUMPED SOLID STATE LASER SYSTEM FOR I-LINE APPLICATIONS

BACKGROUND

[0001] Presently, certain semiconductor manufacturing processes utilize high power mercury discharge lamps as light sources. Typically, these high-powered mercury discharge lamps emit optical radiation at a wavelength of about 365 nm. While these lamps have proven useful in the past, a number of shortcomings have been identified. For example, high- powered mercury discharge lamps have limited efficiency and lifetime. Repairing and/or replacing these lamps may be a time consuming and tedious process and disposal of the devices and products which include mercury presents an environmental risk. As such, production of semiconductor devices at facilities utilizing high-powered mercury discharge lamps maybe periodically halted to repair and/or replace these lamps.

[0002] In light of the foregoing, there is an ongoing need for a laser based light source with higher reliability and lower cost of ownership while emulating the spectral and temporal characteristics have a high-powered mercury discharge lamps.

SUMMARY

[0003] The present application is directed to various embodiments of a diode-pumped solid state laser system for I-line applications. More specifically, the embodiments of the laser devices disclosed herein are configured to output at least one laser signal having a wavelength from about 350 nm to about 385 nm and having an optical power of 1 W to 100 W or more.

[0004] In one specific embodiment, the present application discloses a diode-pumped solid state laser system for I-line applications which includes at least one laser cavity formed from a first mirror and a second mirror. At least one pump source is configured to direct at least one pump signal into the laser cavity. One or more gain crystals within the laser cavity are pumped by the pump source and output at least one signal having a wavelength from about 1050 nm to about 1155 nm or more. A second harmonic crystal positioned within the laser cavity outputs at least one second harmonic signal in response to be irradiated by the intracavity signal. The intracavity signal and second harmonic signal is directed into a third harmonic crystal which output a third harmonic signal having a wavelength of about 350 nm to about 385 nm in response. An output coupler may be positioned within the laser cavity and configured to output the third harmonic signal to thereby creating an output signal.

[0005] In another embodiment, the present application discloses another embodiment of a diode-pumped solid state laser system for I-line applications. More specifically, the laser system includes a first laser cavity formed by a first mirror and a second mirror. At least one pump source may be configured to output at least one pump signal having a wavelength from about 780 nm to about 990 nm. The pump beam may be introduced into the first laser cavity via at least one of the first mirror and/or the second mirror. At least one gain crystal may be positioned within the first laser cavity. The gain crystal may be configured to generate at least one intracavity signal when pumped by the pump signal from the pump source. In one embodiment, the at least one intracavity signal having a wavelength between 1050 nm and 1155 nm although any the intracavity signal may have any desired wavelength. The second laser cavity is in communication with the first laser cavity and configured to receive at least a portion of the intracavity signal therein. A second harmonic crystal may be positioned within the second laser cavity and may be configured to output at least one second harmonic signal of the intracavity signal. As such, in one embodiment, the second harmonic signal has a wavelength from 510 nm to 590 nm. In addition, at least one third harmonic crystal may be positioned within the second laser cavity and configured to output at least one third harmonic signal of the intracavity signal and the second harmonic signal. In one embodiment, the third harmonic signal has a wavelength from 350 nm to 385nm. At least one output coupler may be positioned within the second laser cavity and may be configured to direct the third harmonic signal from the second laser cavity to form at least one output signal.

[0006] Other features and advantages of the embodiments of the diode-pumped solid state laser system for I-line applications as disclosed herein will become apparent from a consideration of the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The drawings disclose illustrative embodiments and are not intended to set forth all embodiments of the diode-pumped solid state laser system for I-line applications. Details that may be apparent or unnecessary may be omitted to save space or for more effective illustration. Conversely, some embodiments may be practices without all the detailed disclosed with regard to specific embodiments. When the same reference numbers appear in different drawings, the reference numbers refer to same or similar components or steps. The novel aspects of the diode-pumped solid state laser system for I-line applications as disclosed herein will become more apparent by consideration of the following figures, wherein:

[0008] Figure 1 shows a schematic diagram of an embodiment of a diode-pumped solid state laser system for I-line applications having a single laser cavity formed by a first mirror and a second mirror;

[0009] Figure 2 shows a schematic diagram of an embodiment of a wavelength selective optical system for use in place of an end mirror in a laser cavity such as in Figure 1;

[0010] Figure 3 shows a schematic diagram of an embodiment of a diode-pumped solid state laser system for I-line applications having a Raman crystal positioned within a single laser cavity formed by a first mirror and a second mirror; and

[0011] Figure 4 shows a schematic diagram of an embodiment of a diode-pumped solid state laser system for I-line applications having a first laser cavity and a second laser cavity.

DETAILED DESCRIPTION

[0012] Exemplary embodiments are described below with reference to the accompanying drawings. Unless otherwise expressly stated in the drawings the sizes, positions, etc., of components, features, elements, etc., as well as any distances therebetween, are not necessarily to scale, and may be disproportionate and/or exaggerated for clarity.

[0013] The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting. As used herein, the singular forms “a,” “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It should be recognized that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. Unless otherwise specified, a range of values, when recited, includes both the upper and lower limits of the range, as well as any sub-ranges therebetween. Unless indicated otherwise, terms such as “first,” “second,” etc., are only used to distinguish one element from another. For example, one node could be termed a “first mirror” and similarly, another node could be termed a “second mirror”, or vice versa. [0014] Unless indicated otherwise, the term “about,” “thereabout,” etc., 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.

[0015] Many of the embodiments described in the following description share common components, device, and/or elements. Like named components and elements refer to like named elements throughout. For example, all the embodiments described in the following detailed description include at least one gain crystal, at least one Q switch, at least one harmonic generator. Thus, the same or similar named components or features may be described with reference to other drawings even if they are neither mentioned nor described in the corresponding drawing. Also, even elements that are not denoted by reference numbers may be described with reference to other drawings.

[0016] Many different forms and embodiments are possible without deviating from the spirit and teachings of this disclosure and so this disclosure should not be construed as limited to the example embodiments set forth herein. Rather, these example embodiments are provided so that this disclosure will be thorough and complete, and will convey the scope of the disclosure to those skilled in the art.

[0017] The present application is directed to various embodiments of a diode-pumped solid state laser system capable of producing at least optical signal having a wavelength emulating the Lline of optical radiation. More specifically, the various solid state laser systems disclosed herein may be configured to output at least one output signal having a power of from about 1 W to about 100 W or more within a wavelength range from about 350 nm to about 385 nm. In in specific embodiment, the various solid state laser systems disclosed herein maybe configured to output at least one output signal having a power of from about 5 W to about 30W or more within a wavelength range from about 363 nm to about 367 nm. Those skilled in the art will appreciate that the various diode pumped solid- state laser systems disclosed herein may be configured to output at least one optical signal at any desired output power within any desired wavelength range.

[0018] Figure 1 shows an embodiment of a diode pumped solid-state laser system. As shown, the laser system 10 includes at least one laser cavity 12 defined by at least two (2) mirrors or similar reflectors. In the illustrated embodiment, the laser cavity 12 includes a first mirror 14, a second mirror 16, and at least one input coupling mirror 18, although those skilled in the art will appreciate any number of mirrors may be used within the laser cavity 12. Further, in the illustrated embodiment the first mirror 14 comprises a curved mirror. Optionally, the first mirror 14 may comprise a planar mirror. In addition, any of the mirrors 14, 16, 18, may comprise planar mirrors or curved mirrors. The first mirror 14, second mirror 16, and/or the input coupler mirror 18 may include wavelength selective coatings applied thereto. For example, in one embodiment, the first mirror 14 may be configured to be highly reflective at wavelength of about 1089 nm and 544.5 nm, and highly transmissive at other wavelengths (i.e. 1064 nm). Similarly, the second mirror 16 may be highly reflective at 1089 nm and highly transmissive at other wavelengths (i.e. 1064 nm), while the input coupler mirror 18 is highly reflective at 1089 nm and highly transmissive at other wavelengths (i.e. 879 nm).

[0019] Referring again to Figure 1, at least one gain media crystal 30 may be positioned within the laser cavity 12. The one embodiment, the gain media crystal 30 maybe configured to receive at least one pump signal 52 from at least one pump source 50 via the input coupling mirror 18 and output at least one intracavity signal having at wavelength from about 1050 nm to about 1155 nm. Any variety of pump sources 50 may be used. For example, the pump signal 52 may have a wavelength from about 780 nm to about 990 nm, although those skilled in the art will appreciate that any wavelength may be used as a pump signal wavelength. In one embodiment, the gain media crystal 30 is configured to output at least one intracavity signal having a wavelength of about 1095+/- 7nm when pumped with a pump signal 52 having a wavelength of about 879nm. Any variety of materials may be used to form the gain media crystal 30 including, without limitations, Nd:LuVO4, Nd:YALO, Nd:YSO, and Yb:GSO, Ytterbium-doped materials, although alternative materials may be used in the laser system 10 with suitable pump wavelengths (i.e. wavelengths within the range of about 1020 nm to about 1155 nm).

[0020] As shown in Figure 1, at least one Q switch device or similar attenuator 32 may be positioned within the laser cavity 12. The Q switch device 32 may be configured to receive the intracavity signal 54 from the gain media crystal 30. The Q switch device 32 may be configured to modify the intracavity signal 54 to have a desired characteristic (i.e. pulsed operation (cavity on/off), pulse width, etc.). Thereafter, the intracavity signal 54 is reflected by the second mirror 16 back through the Q switch device 32 and gain media crystal 30 and is reflected by the input coupling mirror 18 to the first mirror 14. As stated above, the second mirror 16 may be configured to transmit any wavelengths other than 1089 nm therethrough. Similarly, the input coupling mirror 18 may be configured to be highly reflective of the intracavity signal 54 while transmitting all other wavelengths therethrough.

[0021] Referring again to Figure 1, at least one third harmonic generating crystal 42 (hereinafter T 42) and at least one second harmonic generating crystal 40 (hereinafter S 40) may be positioned within the laser cavity 12 and configured to receive at least a portion of the intracavity signal 54. In one embodiment the S 40 is manufactured from LBO. Optionally, the S 40 may be manufactured from any variety of materials including, without limitations, BBO, LBO, BIBO, KTP, CLBO, YCOB. In the illustrated embodiment, the T 42 is manufactured from LBO also utilizing sum-frequency generation to obtain a third harmonic of the intracavity signal 54. Like the S 40, the T 42 may be manufactured from any variety of materials including, without limitations, BBO, LBO, BIBO, CLBO, YCOB.

[0022] As shown in Figure 1, the intracavity signal 54 traverses through T 42 and is incident on the S 40 which outputs a portion of the intracavity signal 54 and a second harmonic signal 56 (having a wavelength of about 544.5 nm) of the intracavity signal 54. Both the intracavity signal 54 and second harmonic signal 56 are reflected by the first mirror 14. The first mirror 14 may be configured to be highly reflective at 544.5 nm and 1089 nm and highly transmissive at other wavelengths (e.g. 1064 nm). The reflected signal is redirected back through the S 40, which again converts more of the intracavity signal 54 to a second harmonic signal 56. The intracavity signal 54 and second harmonic signal 56 are incident on the T 42 which, in response to the intracavity signal 54 second harmonic signal 56, outputs a third harmonic signal 62 having a wavelength of about 363 nm via sum frequency mixing or similar frequency generation mechanisms. At least one wavelength selective mirror or output coupler 60 may be used to reflect and extract the output signal 62 from the laser cavity 12. For example, the output coupler 60 may comprise a dichroic mirror configured to be highly reflective at a wavelength of about 363 nm and highly transmissive at all other wavelengths. In addition to reflecting the output signal 62 the output coupler 60 may be configured to suppress gain of selected wavelengths such as 1040 nm, 1064 nm, or other undesired wavelengths generated within the laser cavity 12. At least one optional optical element or device 63 may be positioned within the laser cavity 12. For example, the optional optical element 63 may be used to suppress gain of selected wavelengths such as 1040 nm, 1064 nm, or other undesired wavelengths generated within the laser cavity 12. [0023] The laser system shown in Figure 1 comprises one embodiment of the diode- pumped solid-state diode pumped solid-state laser system configured to output at least one output signal having a wavelength of about 365 nm. While the illustrated embodiment of the laser system 10 shows a folded laser cavity those skilled in the art will appreciate that the laser cavity 12 need not form a folded cavity and may be formed in any known laser cavity configuration and architecture. Further, various modifications to the elements forming the laser system 10 may be considered. For example, Figure 2 shows an embodiment of a wavelength selective optical system 80 (hereinafter WSOS 80) which may be used to replace at least one mirror of the laser system 10 shown in Figure 1. For example, the WSOS 80 may replace the second mirror 16. Optionally, the WSOS 80 may replace the first mirror 14. As shown, the WSOS 80 includes at least one waveplate 84. In one embodiment the waveplate 84 may operate as a waveplate at 1089 nm and a X/2 waveplate at 1064 nm waveplate or similar component configured to vary the polarization of the 1064 nm signal and 1089 nm signal in the intracavity signal 54. The input signal 82 corresponding to the intracavity signal 54 from the Q switch device 32 (See Figure 1) traverses through the waveplate 84 and is incident on at least one polarization beamsplitter or similar device 88 configured to distinguish between the 1064 nm signal and the 1089 nm signal of the intracavity signal 54 (See Figure 1). In the illustrated embodiment, the beamsplitter 88 is positioned at a high angle of incidence relative to the incoming input signal 82 thereby transmitting the 1064 nm signal 92 and reflecting 1089 nm signal. At least one reflector 90 may be used to reflect the 1089 nm signal back through the WSOS 80 and into the laser cavity 12 (See Figure 1) while the 1064 nm signal 92 is extracted from the laser cavity 12.

[0024] Figure 3 shows another embodiment of a diode pumped solid-state laser system. Like the previous embodiment, the laser system 110 includes at least one laser cavity 112 defined by at least two (2) mirrors or similar reflectors. The laser cavity 112 includes a first mirror 114, a second mirror 116, and at least one input coupling mirror 118, although any number of mirrors may be used within the laser cavity 112. Any of the mirrors 114, 116, 118, may comprise planar mirrors or curved mirrors. The first mirror 114, second mirror 116, and/or the input coupler mirror 118 may include wavelength selective coatings applied thereto. In one embodiment, the first mirror 114 may be configured to be highly reflective at wavelength of about 1064 nm, 544.5 nm, and any Raman wavelength generated by the Raman crystal within the laser cavity 112 (hereinafter Stokes shifted wavelengths - for example 1176 nm). For example, if an 890cm'¹ Raman mode of an intracavity Raman crystal is employed the Stokes shifted wavelength would be about 1176 nm. As such, the first mirror 114 would be configured to be highly reflective at wavelength of about 1064 nm, 532 nm, and 1176 nm. Further, the first mirror 114 may be highly transmissive at wavelengths other than 1064 nm, 544.4 nm, and the Stokes shifted wavelengths. Similarly, the second mirror 116 may be highly reflective at 1064 nm and any Stokes shifted wavelengths generated by the Raman crystal within the laser cavity 112 while being highly transmissive at wavelengths other than 1064 nm and the Stokes shifted wavelengths. The input coupler mirror 118 is highly reflective at 1064 nm and any Stokes shifted wavelength and may be highly transmissive at all other wavelengths (i.e. pump wavelength such as about 879 nm to about 990 nm). Further, Figure 3 shows a folded laser cavity 112. Those skilled in the art will appreciate that the laser cavity 112 may be formed in any variety of configurations and need not be a folded cavity.

[0025] Referring again to Figure 3, at least one gain media crystal 130 may be positioned within the laser cavity 112. Like the previous embodiment, the gain media crystal 130 may be configured to receive at least one pump signal 152 from at least one pump source 150 via the input coupling mirror 118. Like the previous embodiment, the pump signal 152 may have a wavelength from about 780 nm to about 990 nm, although any wavelength may be used. In one embodiment, the gain media crystal 130 is configured to output at least one optical signal having a wavelength of about 1064 nm (+/- 7 nm) when pumped with a pump signal 152 having a wavelength of about 879 nm. Any variety of materials may be used to form the gain media crystal 130 including, without limitations, Nd:YVO4, Nd:YALO, Nd:YSO and Yb:GSO, although alternative materials may be used in the laser system 110.

[0026] As shown in Figure 3, at least one Q switch device or similar attenuator 132 may be positioned within the laser cavity 112 and configured to receive the intracavity signal 154 from the gain media crystal 130. The Q switch device 132 may be configured to modify the intracavity signal 154 to have a desired characteristic (i.e. pulse operation (cavity on/off), pulse width, etc.). Thereafter, the intracavity signal 154 having a wavelength of about 1064 nm is reflected by the second mirror 116 back through the Q switch device 132 and gain media crystal 130 and is reflected by the input coupling mirror 118 to the first mirror 114. As stated above, the second mirror 116 may be configured to transmit any wavelengths other than 1089 nm therethrough. Similarly, the input coupling mirror 118 may be configured to be highly reflective of the intracavity signal 154 having a wavelength of about 1064 nm (and any Stokes shifted wavelength) while transmitting all other wavelengths therethrough. [0027] Referring again to Figure 3, third harmonic generating crystal 142 (hereinafter T 142) and at least one second harmonic generating crystal 140 (hereinafter S 140) may be positioned within the laser cavity 112 and configured to receive at least a portion of the intracavity signal 154. In one embodiment the S 140 is manufactured from LBO. Optionally, the S 140 may be manufactured from any variety of materials including, without limitations, BBO, LBO, BIBO, KTP, CLBO, YCOB. In the illustrated embodiment, the T 142 is manufactured from LBO also utilizing sum-frequency generation to obtain a third harmonic of the intracavity signal 154. Like the S 140, the T 142 may be manufactured from any variety of materials including, without limitations, BBO, LBO, BIBO, CLBO, YCOB.

[0028] As shown in Figure 3, the intracavity signal 154 traverses through T 142 and is incident on the S 140 which outputs a portion of the intracavity signal 154 and a second harmonic signal 156 (e.g. about 532 nm) of the intracavity signal 154. Both the intracavity signal 154 and second harmonic signal 156 are reflected by the first mirror 114. The first mirror 114 may be configured to be highly reflective at 1064 nm, 532 nm, and any Stokes- shifted wavelength generated by the Raman crystal within the laser cavity 112 and highly transmissive at all other wavelengths. The reflected signals are redirected back through the S 140, which again converts more of the intracavity signal 154 to a composite signal comprising various ratios of the fundamental wavelength (1064 nm) and the Stokes wavelength (1176nm). The intracavity signals 154 and composite signal are incident on the T 142 which outputs a third harmonic signal 180 having a wavelength of about 363 nm via sum frequency mixing or similar mechanisms. At least one wavelength selective mirror or output coupler 160 may be used to reflect and extract the output signal 180 from the laser cavity 112. For example, the output coupler 160 may comprise a dichroic mirror configured to be highly reflective at a wavelength of about 363 nm and highly transmissive at all other wavelengths.

[0029] In contrast to the laser system 10 shown in Figure 1, the laser system 110 shown in Figure 3 may include at least one Raman crystal 144 positioned within the laser cavity 112 and be configured to utilize Stokes shifts and mixing combinations to produce an output signal having a desired optical characteristics (i.e. wavelength, power, etc.). In one embodiment, the Raman crystal 144 is manufactured from YVCh. In another embodiment, the Raman crystal 144 is manufactured from KGW, although those skilled in the art will appreciate that any variety of materials know in the art may be used to form the Raman crystal 144. Optionally, lithium niobate, KTP, RTP and similar materials may be used to manufacture the Raman crystal. The shift in third harmonic wavelength from 354.7nm to the about 365+/-2nm implies an energy difference of 645-945 wavenumbers (cm-1), which represents the total energy that may go into the intracavity Raman material per UV output photon. This net energy difference may be accomplished via generation of one, two or three Raman phonons utilizing appropriate Raman modes in a variety of materials. For instance, using the fundamental wavelength of 1064nm and YVCh as the Raman material, appropriate intracavity mixing of Raman wavelengths involving generation of one, two or three Raman phonons can result in generation of output at 366.3, 364.5 or 364.8nm, respectively. To accomplish this, the laser cavity 112 should be resonant at the fundamental and/or desired Stokes wavelengths.

[0030] During use, the Raman crystal 144 receives a portion of the intracavity signal 154 and generates a Stokes shifted wavelength, For example, in one embodiment the Stokes shifted wavelength is about 1176 nm, although those skilled in the art will appreciate that any variety of Raman crystals and lengths could be used to generated any variety of Raman wavelengths. The Raman wavelength signal traverses through the laser cavity 112 as part of the intracavity signal 154. As such, the first, second, and input coupling mirrors 114, 116, and 118 are configured to be highly reflective at both 1064 nm and the Stokes shifted wavelength generated by the Raman crystal within the laser cavity 112. Intracavity mixing of the 1064 nm signal and the Stokes shifted wavelength may be used to generate the second harmonic signal 156 and, ultimately, the third harmonic output signal 180. Various mixing configurations may be used to tailor the output wavelength as desired. For example, two (2) photons of 1064nm and one (1) photon of the Stokes shifted signal will produce an output signal 180 having a wavelength of about 366.2 nm. In contrast, the combination of one (1) photon of 1064 nm and two (2) photons of the Stoked shifted signal will produce an output signal 180 having a wavelength of about 364.5 nm. In yet another combination, generating the output signal 180 from the Stokes shifted signal will produce a signal having a wavelength of 364.8 nm. Of course, those skilled in the art will appreciate any variety of other combinations are contemplated.

[0031] Figure 4 shows yet another embodiment of a diode pumped solid-state laser system. The laser system 210 includes multiple laser cavities formed by at least four (4) mirrors or similar reflectors. The first laser cavity 212a is formed by a first mirror 214, a second mirror 216, at least one input coupling mirror 218, while the second laser cavity 212b is formed from the first mirror 214 and the fourth mirror 220, although any number of mirrors may be used within the laser cavities 212a, 212b. Any of the mirrors 214, 216, 218, and/or 220 may comprise planar mirrors or curved mirrors, consistent with conventional optical cavity design principles. Further any of the mirrors 214, 216, 218, and/or 220 may include wavelength selective coatings applied thereto. For example, in one embodiment, the first mirror 214 may be configured to be highly reflective at wavelengths of about 1094 nm and 1064nm and highly transmissive at all other wavelengths. The second mirror 216 may be highly reflective at 1064 nm, while the input coupler mirror 118 is highly reflective at 1064nm and highly transmissive at all other wavelengths (i.e. 879 nm). The fourth mirror 220 may be highly reflective at 1094 nm and 547 nm and highly transmissive at other wavelengths.

[0032] Referring again to Figure 4, at least one gain media crystal 230 positioned within the first laser cavity 212a. Like the previous embodiment, the gain media crystal 230 maybe configured to receive at least one pump signal 262 from at least one pump source 260 via the input coupling mirror 218. The pump signal 262 may have a wavelength from about 780 nm to about 990 nm, although any wavelength may be used. In one embodiment, the gain media crystal 230 is configured to output at least one optical signal having a wavelength of about 1064 nm when pumped with a pump signal 262 having a wavelength of about 879 nm. Any variety of materials may be used to form the gain media crystal 230 including, without limitations, Nd:YVO4, although alternative materials may be used in the laser system 110.

[0033] As shown in Figure 4, like the previous embodiments at least one Q switch device or similar variable attenuator 232 may be positioned within the first laser cavity 212a and configured to receive the intracavity signal 264 from the gain media crystal 230. The intracavity signal 264 having a wavelength of about 1064 nm is reflected by the second mirror 216 back through the Q switch device 232 and gain media crystal 230 and is reflected by the input coupling mirror 218 to the first mirror 214 via at least one waveplate of similar device 234. In one embodiment the waveplate 234 comprises a X/2 1064 nm waveplate. The input coupling mirror 218 may be configured to be highly reflective of the intracavity signal 264 having a wavelength of about 1064 nm while transmitting all other wavelengths therethrough.

[0034] Referring again to Figure 4, at least one Raman crystal 240 may be positioned within the first laser cavity 212a and be configured to utilize a Stokes shift to produce a Raman-shifted signal having a desired optical characteristic (i.e. wavelength, power, polarization, etc.). In one embodiment, the Raman crystal 240 is manufactured from YVO4 and may have a C-cut orientation, although those skilled in the art will appreciate that any orientation of cut may be used. In one embodiment, the Raman-shifted signal comprises a 1094 nm signal having S polarization.

[0035] As shown in Figure 4, the first mirror 214 reflects the intracavity signal 264 and Raman-shifted signal back through the Raman crystal 240 and is incident on at least one polarizing beamsplitter 236 in the second laser cavity 212b. In one embodiment, the polarizing beamsplitter 236 is configured to be highly transmissive at 1064 nm having P polarization and highly reflective at 1094 nm having S polarization. The reflected signal 268 having a wavelength of 1094 nm (S polarization) is directed through at least one second harmonic crystal 254 and at least one third harmonic crystal 252 positioned within the second laser cavity 212b. The second harmonic crystal 254 (hereinafter S 254) and at least one third harmonic crystal (hereinafter T 252) may be configured to receive at least a portion of the reflected signal 268. In one embodiment the S 254 is manufactured from LBO. Optionally, the S 254 may be manufactured from any variety of materials including, without limitations, BBO, LBO, BIBO, KTP, CLBO, YCOB. In the illustrated embodiment, the T 252 is manufactured from LBO also utilizing sum-frequency generation to obtain a third harmonic of the reflected signal 268. Like the S 254, the T 252 may be manufactured from any variety of materials including, without limitations, BBO, LBO, BIBO, CLBO, YCOB.

[0036] As shown in Figure 4, the reflected signal 268 traverses through T 252 and is incident on the S 254 which outputs a portion of the reflected signal 268 and a second harmonic signal 270 (having a wavelength of about 547 nm) of the reflected signal 268. Both the reflected signal 268 and second harmonic signal 270 are reflected by the fourth mirror 220. The fourth mirror 220 may be configured to be highly reflective at 547 nm and 1094 nm and highly transmissive at all other wavelengths (e.g. 1165 nm). The reflected signal 268 is redirected back through the S 254, which again converts more of the reflected signal 268 to a second harmonic signal 270. The reflected signal 268 and second harmonic signal 270 are incident on the T 252 which, in response to the second harmonic signal 270, outputs a third harmonic signal 272 having a wavelength of about 364.8 nm via sum frequency mixing or similar mechanisms. At least one wavelength selective mirror 250 positioned within the second laser cavity 212b may be used to reflect and extract the third harmonic signal 272 from the second laser cavity 212b. For example, the wavelength selective mirror 250 may comprise a dichroic mirror configured to be highly reflective at a wavelength of about 364.8 nm and highly transmissive at all other wavelengths. As such, the laser system shown in Figure 4 includes two (2) resonant laser cavities, each cavity resonant at different wavelengths. More specifically, the first laser cavity 212a is resonant at 1064 nm while the second resonant cavity 212b is resonant at 1094 nm.

[0037] Further, those skilled in the art will appreciate that any variety of materials known in the art may be used to form the Raman crystal shown in Figures 3 and 4. In additional, any variety of crystal cuts may be used to form the Raman crystal. Further, any variety of materials may be used to form the Raman crystal, including, without limitations, lithium niobate, KTP, RTP, YVO4, KGW and similar materials may be used to manufacture the Raman crystal. The shift in third harmonic wavelength from 354.7nm to 365+/-2nm implies an energy difference of 645-945 wavenumbers (cm-1). This is total energy which may go into the intracavity Raman material per UV output photon. Intracavity mixing involving three, two or one appropriate Raman shifts can thus provide total energy shift in the required range and output at 364.8, 364.5 or 366.3nm, respectively. Further, the laser cavities shown in Figures 3 and 4 may be resonant at both the fundamental and Stokes wavelengths. Optionally, the entire optical cavity 212 shown in Figure 3 and/or the laser cavities 212a, 212b shown in Figure 4 can be resonant and low loss (high Q) at both the fundamental and Raman wavelengths which can present difficulties in broadband optical coating design. The configuration shown in Figure 4 forms coupled resonant cavities for fundamental 1064nm and 1094nm (259cm- 1 Raman shifted) wavelengths. The two cavities, share only a high reflector, Raman crystal and high AOI polarizer. The 364.8nm third harmonic of the resonant Raman-shifted wavelength is generated by S and T crystals within in the second cavity formed by mirrors 214 and 220.

[0038] The embodiments disclosed herein are illustrative of the principles of the invention. Other modifications may be employed which are within the scope of the invention. Accordingly, the devices disclosed in the present application are not limited to that precisely as shown and described herein.

Claims

1. A diode-pumped solid state laser system for I-line applications, comprising: at least one laser cavity formed from a first mirror and at least a second mirror; at least one pump source configured to output at least one pump signal having a wavelength from 780 nm to about 990 nm; at least one gain crystal positioned within the at least one laser cavity and configured to generate at least one intracavity signal when pumped by the at least one pump source, the at least one intracavity signal having a wavelength between 1050 nm and 1155 nm; at least one second harmonic crystal positioned within the at least one laser cavity and configured to output at least one second harmonic signal of the at least one intracavity signal, the at least one second harmonic signal having a wavelength from 510 nm to 590 nm; at least one third harmonic crystal to positioned within the at least one laser cavity and configured to output at least one third harmonic signal of the at least one intracavity signal and the at least one second harmonic signal, the at least one third harmonic signal having a wavelength from 350 nm to 385 nm; and at least one output coupler positioned within the at least one laser cavity and configured to direct the at least one third harmonic signal from the at least one laser cavity to form at least one output signal having an output wavelength from 350 nm to 385 nm.

2. The diode-pumped solid state laser system of claim 1 further comprising at least one variable attenuator positioned within the at least one laser cavity.

3. The diode-pumped solid state laser system of claim 2 wherein the at least one variable attenuator comprises a Q-switch.

4. The diode-pumped solid state laser system of claim 1 wherein the at least one gain crystal is manufactured for at least one material selected from the group consisting of Nd:LuVO₄, Nd:YALO, Nd:YSO and Yb:GSO.

5. The diode-pumped solid state laser system of claim 1 wherein the at least one second harmonic crystal is selected from the group consisting of BBO, LBO, BIBO, KTP, CLBO, and YCOB.

6. The diode-pumped solid state laser system of claim 1 wherein the at least one third harmonic crystal is selected from the group consisting of BBO, LBO, BIBO, CLBO, and YCOB.

7. The diode-pumped solid state laser system of claim 1 wherein the at least one output signal has a power of 1 W to 100 W.

8. The diode-pumped solid state laser system of claim 1 where the at least one laser cavity includes a first laser cavity and at least a second laser cavity.

9. The diode-pumped solid state laser system of claim 1 further comprising at least one Raman crystal positioned within the at least one laser cavity, the at least one Raman crystal configured to utilize Stokes frequency shifts and mixing combinations to produce the at least one output signal.

10. The diode-pumped solid state laser system of claim 9 wherein the at least one Raman crystal is manufactured from at least one material selected from the group consisting of YVCh, KGW, lithium niobate, KTP, and RTP.

11. The diode-pumped solid state laser system of claim 1 wherein the at least one output signal has an output wavelength of 365 nm +/- 2 nm.

12. A diode-pumped solid state laser system for I-line applications, comprising: at least one laser cavity formed from a first mirror and at least a second mirror; at least one pump source configured to output at least one pump signal having a wavelength from about 780 nm to about 990 nm; at least one gain crystal positioned within the at least one laser cavity and configured to generate at least one intracavity signal when pumped by the at least one pump source, the at least one intracavity signal having a wavelength between 1050 nm and 1155 nm; at least one Raman crystal configured to output at least one Raman signal having a wavelength from 1080 nm to 1200 nm when irradiated with the at least one intracavity signal; at least one second harmonic crystal positioned within the at least one laser cavity and configured to output at least one second harmonic signal of at least one of the intracavity signal and the Raman signal, the at least one second harmonic signal having a wavelength from 530 nm to 600 nm; at least one third harmonic crystal to positioned within the at least one laser cavity and configured to output at least one third harmonic signal via frequency summing of the second harmonic signal of at least one of the intracavity signal and the Raman signal, the at least one third harmonic signal having a wavelength from 350 nm to 385 nm; and at least one output coupler positioned within the at least one laser cavity and configured to direct the at least one third harmonic signal from the at least one laser cavity to form at least one output signal having an output wavelength from 350 nm to 385 nm.

13. A diode-pumped solid state laser system of claim 12 wherein the at least one laser cavity further comprises a first laser cavity and a second laser cavity is communication with the first laser cavity and configured to receive at least a portion of the at least one intracavity signal therein.

14. A diode-pumped solid state laser system of claim 12 wherein the at least one Raman signal having a wavelength of 1095 +/- 10 nm.

15. The diode-pumped solid state laser system of claim 12 wherein the at least one output signal has an output wavelength of 365 nm +/- 2 nm.

16. The diode-pumped solid state laser system of claim 12 further comprising at least one variable attenuator positioned within the at least one laser cavity.

17. The diode-pumped solid state laser system of claim 12 wherein the at least one variable attenuator comprises a Q-switch.

18. The diode-pumped solid state laser system of claim 12 wherein the at least one gain crystal is manufactured for at least one material selected from the group consisting of Nd:LuVO₄, Nd:YALO, Nd:YSO and Yb:GSO.

19. The diode-pumped solid state laser system of claim 12 wherein the at least one second harmonic crystal is selected from the group consisting of BBO, LBO, BIBO, KTP, CLBO, and YCOB.

20. The diode-pumped solid state laser system of claim 12 wherein the at least one third harmonic crystal is selected from the group consisting of BBO, LBO, BIBO, CLBO, and YCOB.

21. The diode-pumped solid state laser system of claim 12 wherein the at least one output signal has a power of 1 W to 100 W.

22. The diode-pumped solid state laser system of claim 12 where the at least one laser cavity includes a first laser cavity and at least a second laser cavity.

23. The diode-pumped solid state laser system of claim 12 further comprising at least one Raman crystal positioned within the at least one laser cavity, the at least one Raman crystal configured to utilize Stokes frequency shifts and mixing combinations to produce the at least one output signal.

24. The diode-pumped solid state laser system of claim 12 wherein the at least one Raman crystal is manufactured from at least one material selected from the group consisting of YVO4, KGW, lithium niobate, KTP, and RTP.