Wavelength conversion device

Abstract

To provide a wavelength conversion device which reduces adhesion of contaminants to the surface of a wavelength conversion crystal.SOLUTION: The cell (72) houses the wavelength-converting crystal (80) and the holder (71) therein, and has a first inlet port for supplying a purge gas into the cell (72) and a first outlet port for discharging the purge gas from the cell (72). The first cylindrical member has an inner space through which an optical path of the incident light passes, and an 90a of the first cylindrical member is separated from the wavelength-converting crystal. The first partition 92a is disposed between the first inlet port and the first outlet port and holds the first cylindrical member.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a wavelength conversion device. [Background technology]

[0002] In recent years, semiconductor exposure devices have been required to improve their resolution in response to the miniaturization and high integration of semiconductor integrated circuits. To this end, the wavelength of light emitted from exposure light sources has been shortened. For example, KrF excimer laser devices, which output laser light with a wavelength of approximately 248 nm, and ArF excimer laser devices, which output laser light with a wavelength of approximately 193 nm, are used as gas laser devices for exposure.

[0003] The spectral linewidth of the spontaneously oscillating light from KrF excimer laser devices and ArF excimer laser devices is as wide as 350 to 400 pm. Therefore, if a projection lens is constructed using a material that transmits ultraviolet light, such as KrF and ArF laser light, chromatic aberration may occur. As a result, resolution may decrease. Therefore, it is necessary to narrow the spectral linewidth of the laser light output from the gas laser device to a level where chromatic aberration is negligible. Therefore, a line narrowing module (LNM) containing a line narrowing element (e.g., an etalon or grating) may be installed inside the laser resonator of the gas laser device to narrow the spectral linewidth. Hereinafter, a gas laser device with a narrowed spectral linewidth is referred to as a line narrowing gas laser device. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-155933 [Patent Document 2] Japanese Patent Application Publication No. 3-263017 [Patent Document 3] Summary of Japanese Patent Application Publication No. 11-288012

[0005] A wavelength conversion device according to one aspect of the present disclosure includes a wavelength conversion crystal that converts the wavelength of incident light and emits output light, a holder that holds the wavelength conversion crystal on the optical path of the incident light, a cell that houses the wavelength conversion crystal and the holder and has a first inlet for supplying purge gas to the interior and a first outlet for discharging the purge gas from the interior, a first cylindrical member that is positioned away from the wavelength conversion crystal and through which the optical path of the incident light passes through an internal space, and a first partition that is positioned between the first inlet and the first outlet and holds the first cylindrical member. [Brief explanation of the drawings]

[0006] Some embodiments of the present disclosure will now be described, by way of example only, with reference to the accompanying drawings, in which: [Figure 1] FIG. 1 is a diagram schematically showing the configuration of a laser system according to a comparative example. [Figure 2] FIG. 2 is a cross-sectional view schematically showing the configuration of a wavelength converter according to a comparative example. [Figure 3] FIG. 3 is a cross-sectional view schematically showing the configuration of a wavelength conversion device according to an embodiment. [Figure 4] FIG. 4 is a cross-sectional view taken along the line AA in FIG. [Figure 5] FIG. 5 is a cross-sectional view taken along line BB in FIG. [Figure 6] FIG. 6 is a cross-sectional view showing an example in which a gap is provided between the third partition and the holder. [Figure 7] FIG. 7 is a cross-sectional view schematically showing the configuration of a wavelength conversion device according to a first modified example. [Figure 8] FIG. 8 is a cross-sectional view schematically showing the configuration of a wavelength converter according to a second modified example. [Figure 9] FIG. 9 is a cross-sectional view schematically showing the configuration of a wavelength converter according to a third modified example. [Figure 10] FIG. 10 is a cross-sectional view schematically showing the configuration of a wavelength converter according to a fourth modified example. [Figure 11] FIG. 11 is a cross-sectional view schematically showing the configuration of a wavelength converter according to a fifth modified example. Embodiment

[0007] <Contents> 1. Comparative Example 1.1 Solid-state laser system 1.1.1 Configuration 1.1.2 Operation 1.2 Wavelength conversion device 1.3 Challenges 2. Embodiment 2.1 Configuration 2.2 Operation 2.3 Effects 2.4 Modified Wavelength Converter 2.4.1 First variant 2.4.2 Second variant 2.4.3 Third variant 2.4.4 Fourth Variant 2.4.5 Fifth Variant

[0008] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. The embodiments described below show some examples of the present disclosure and do not limit the content of the present disclosure. Furthermore, not all of the configurations and operations described in the embodiments are necessarily essential as the configurations and operations of the present disclosure. Note that the same components are given the same reference symbols, and redundant explanations will be omitted.

[0009] 1. Comparative Example First, a comparative example of the present disclosure will be described. The comparative example of the present disclosure is a form that the applicant recognizes as being known only by the applicant, and is not a publicly known example that the applicant acknowledges.

[0010] 1.1 Solid-state laser system 1.1.1 Configuration 1 shows a schematic configuration of a solid-state laser system 1 according to a comparative example. The solid-state laser system 1 includes a signal laser device 2, a pump laser device 3, an amplification system 4, a wavelength conversion system 5, and a solid-state laser control unit 6. The solid-state laser system 10 outputs pulsed laser light PL having a wavelength of approximately 193.4 nm.

[0011] The signal laser device 2 includes a semiconductor laser 20 and a solid-state amplifier 21. The semiconductor laser 20 oscillates in a single longitudinal mode (CW) and outputs CW laser light with a wavelength of approximately 1553 nm. The solid-state amplifier 21 is a semiconductor optical amplifier (SOA) that amplifies the CW laser light output from the semiconductor laser 20 and outputs it as signal laser light Ls. The signal laser light Ls output from the signal laser device 2 is incident on an amplification system 4.

[0012] The pump laser device 3 includes a semiconductor laser 30, a solid-state amplifier 31, an LBO (LiB3O5) crystal 32, and a dichroic mirror 33. The semiconductor laser 30 oscillates CW in a single longitudinal mode and outputs CW laser light with a wavelength of approximately 1030 nm. The solid-state amplifier 31 includes a semiconductor optical amplifier, a Yb fiber amplifier, and a Yb:YAG crystal, and pulse-amplifies the CW laser light output from the semiconductor laser 30.

[0013] LBO crystal 32 is disposed downstream of solid-state amplifier 31, and wavelength-converts a portion of the pulsed laser light having a wavelength of approximately 1030 nm output from solid-state amplifier 31 into a second harmonic having a wavelength of approximately 515 nm and outputs the converted light. The remaining portion of the pulsed laser light having a wavelength of approximately 1030 nm output from solid-state amplifier 31 passes through LBO crystal 32 without being wavelength-converted.

[0014] The dichroic mirror 33 is disposed after the LBO crystal 32 and highly reflects the pulsed laser light with a wavelength of approximately 1030 nm that has passed through the LBO crystal 32, and highly transmits the second harmonic wave output from the LBO crystal 32. The pulsed laser light highly reflected by the dichroic mirror 33 enters the amplification system 4 as pump laser light Lp.

[0015] The amplification system 4 includes an optical parametric amplifier (OPA). For example, the OPA includes a periodically poled lithium niobate (PPLN) crystal or a periodically poled potassium titanyl phosphate (PPKTP) crystal. The OPA pulse-amplifies the signal laser light Ls using a pump laser light Lp and outputs the amplified signal laser light Ls as a first pulse laser light L1.

[0016] The wavelength conversion system 5 is a CLBO (CsLiBO 10 The optical system includes a CLBO crystal 50, a dichroic mirror 51, a CLBO crystal 52, and a CLBO crystal 53. The CLBO crystals 50, 52, and 53 are nonlinear optical crystals and are examples of the "wavelength conversion crystal" according to the technique of the present disclosure.

[0017] The signal laser light Ls pulse-amplified by the amplification system 4 enters the wavelength conversion system 5 as the first pulse laser light L1, and the second harmonic that has passed through the dichroic mirror 33 of the pump laser device 3 enters as the second pulse laser light L2.

[0018] The CLBO crystal 50 is disposed on the optical path of the second pulsed laser light L2, and wavelength-converts the incident second pulsed laser light L2 into a fourth harmonic wave with a wavelength of approximately 258 nm and outputs the fourth harmonic wave.

[0019] The dichroic mirror 51 is disposed downstream of the CLBO crystal 50 and has high transmittance for the fourth harmonic pulsed laser beam output from the CLBO crystal 50. The first pulsed laser beam L1 output from the amplification system 4 is incident on the dichroic mirror 51. The dichroic mirror 51 highly reflects the first pulsed laser beam L1 and is disposed so that the first pulsed laser beam L1 and the fourth harmonic pulsed laser beam are incident on the CLBO crystal 52 coaxially.

[0020] The CLBO crystal 52 and the CLBO crystal 53 are arranged in series after the dichroic mirror 51, and each performs sum frequency generation to generate and output pulsed laser light PL having a wavelength of approximately 193.4 nm.

[0021] The solid-state laser control unit 6 is configured by a processor, and is connected to the signal laser device 2, the pump laser device 3, and the wavelength conversion system 5. The solid-state laser control unit 6 is connected to an external laser control unit 60.

[0022] 1.1.2 Operation Next, the operation of the solid-state laser system 1 according to the comparative example will be described. First, the solid-state laser control unit 6 operates the pump laser device 3 in response to an instruction from the laser control unit 60. Specifically, the solid-state laser control unit 6 controls the current value of the semiconductor laser 30 to cause the semiconductor laser 30 to output CW laser light with a wavelength of approximately 1030 nm. Next, the solid-state laser control unit 6 controls the solid-state amplifier 31 to pulse-amplify the CW laser light.

[0023] As a result, pulsed laser light having a wavelength of approximately 1030 nm is output from the solid-state amplifier 31 and enters the LBO crystal 32, part of which is wavelength-converted to a second harmonic by the LBO crystal 32, and the other part is transmitted through the LBO crystal 32. The second harmonic is highly transmitted through the dichroic mirror 33 and enters the wavelength conversion system 5 as second pulsed laser light L2. The pulsed laser light transmitted through the LBO crystal 32 is highly reflected by the dichroic mirror 33 and enters the amplification system 4 as pump laser light Lp.

[0024] Next, the solid-state laser control unit 6 operates the signal laser device 2. Specifically, the solid-state laser control unit 6 controls the current value of the semiconductor laser 20 to cause the semiconductor laser 20 to CW oscillate and output CW laser light with a wavelength of approximately 1553 nm. The CW laser light output from the semiconductor laser 20 is amplified by the solid-state amplifier 21, output as signal laser light Ls, and enters the amplification system 4.

[0025] The signal laser light Ls incident on the amplification system 4 is pulse-amplified by the pump laser light Lp, and is output as a first pulse laser light L1 and incident on the wavelength conversion system 5.

[0026] The first pulsed laser beam L1 incident on the wavelength conversion system 5 is highly reflected by the dichroic mirror 51 and then incident on the CLBO crystal 52. The second pulsed laser beam L2 incident on the wavelength conversion system 5 is wavelength-converted to the fourth harmonic by the CLBO crystal 50, passes through the dichroic mirror 51 with high transmittance, and then incident on the CLBO crystal 52.

[0027] First sum-frequency light with a wavelength of approximately 221 nm is generated by sum-frequency generation of the first pulsed laser light L1 with a wavelength of approximately 1553 nm and the fourth harmonic with a wavelength of approximately 258 nm that are incident on the CLBO crystal 52. A portion of the first pulsed laser light L1 passes through the CLBO crystal 52 and enters the CLBO crystal 53 coaxially with the first sum-frequency light.

[0028] Second sum-frequency light having a wavelength of approximately 193.4 nm is generated by sum-frequency generation between the first pulsed laser beam L1 having a wavelength of approximately 1553 nm and the first sum-frequency light having a wavelength of approximately 221 nm that are incident on the CLBO crystal 53. The second sum-frequency light is output from the wavelength conversion system 5 as the pulsed laser beam PL described above.

[0029] The pulsed laser light PL output from the wavelength conversion system 5 may be amplified by an excimer amplifier (not shown).

[0030] 1.2 Wavelength conversion device Because the CLBO crystals 50, 52, and 53 are deliquescent, they are placed inside cells purged with purge gas to maintain a low-humidity atmosphere. Hereinafter, a device having a cell containing wavelength conversion crystals such as the CLBO crystals 50, 52, and 53 will be referred to as a "wavelength conversion device."

[0031] 2 is a schematic diagram showing the configuration of a wavelength conversion device 70 according to a comparative example. The wavelength conversion device 70 includes a wavelength conversion crystal 80, a holder 71 for holding the wavelength conversion crystal 80, and a cell 72 containing the holder 71. The wavelength conversion crystal 80 is one of the CLBO crystals 50, 52, and 53.

[0032] The cell 72 is a sealed container made of, for example, aluminum or stainless steel (SUS). In this comparative example, the cell 72 has a rectangular parallelepiped shape. The holder 71 is fixed to the inner bottom surface of the cell 72. The holder 71 may be provided with an adjustment mechanism that allows the arrangement angle of the wavelength conversion crystal 80 to be adjusted.

[0033] The cell 72 has an incident-side opening 72a formed on the optical path of the incident light entering the wavelength conversion crystal 80. The cell 72 also has an output-side opening 72b formed on the optical path of the output light emitted from the wavelength conversion crystal 80. The incident-side opening 72a and the output-side opening 72b are formed at positions facing each other with the wavelength conversion crystal 80 interposed therebetween. For example, when the wavelength conversion crystal 80 is a CLBO crystal 50, the incident light is the second pulsed laser light L2 and the output light is the fourth harmonic.

[0034] The incident light is incident on the incident side end face 80a of the wavelength conversion crystal 80. The emitted light is emitted from the emission side end face 80b of the wavelength conversion crystal 80. Hereinafter, the incident side end face 80a and the emission side end face 80b may be simply referred to as "surfaces of the wavelength conversion crystal 80."

[0035] An incident window 73 is provided to cover the incident-side opening 72a. An exit window 74 is provided to cover the exit-side opening 72b. The incident window 73 and the exit window 74 are formed by coating both surfaces of a substrate made of calcium fluoride (CaF2) crystal or synthetic quartz with an anti-reflection film (not shown). The incident window 73 transmits incident light and makes it incident on the wavelength conversion crystal 80. The exit window 74 transmits exit light emitted from the wavelength conversion crystal 80.

[0036] The entrance window 73 is fixed to the cell 72 via an O-ring 75a to ensure airtightness. Specifically, the O-ring 75a is disposed between the entrance window 73 and the cell 72. The entrance window 73 is held by a window holder 76a, and the window holder 76a is fixed to the cell 72 with bolts or the like (not shown).

[0037] The exit window 74 is fixed to the cell 72 via an O-ring 75b to ensure airtightness. Specifically, the O-ring 75b is disposed between the exit window 74 and the cell 72. The exit window 74 is held by a window holder 76b, and the window holder 76b is fixed to the cell 72 with bolts or the like (not shown).

[0038] The O-ring is an annular sealing member having a substantially circular cross section. For example, the O-rings 75a and 75b are resin rings made of Teflon (registered trademark), rubber, or the like.

[0039] The cell 72 is also formed with an inlet 77 for introducing a purge gas G into the cell 72 and an outlet 78 for discharging the purge gas G to the outside of the cell 72. For example, the inlet 77 is disposed on the light incident side of the wavelength conversion crystal 80, and the outlet 78 is disposed on the light emitting side of the wavelength conversion crystal 80. The purge gas is a gas such as N2, CO2, Ar, O2, or CDA (Clean dry air).

[0040] A gas inlet pipe 77a is connected to the inlet 77 for introducing a purge gas G supplied from a gas supply source 79a such as a cylinder. A gas outlet pipe 78a is connected to the outlet 78 for discharging the purge gas G by an exhaust device 79b such as a pump. Note that the end of the gas outlet pipe 78a may be an open end and not connected to the exhaust device 79b.

[0041] 1.3 Challenges The present applicant has found that in the wavelength conversion device 70 according to the comparative example, contaminants presumably originating from the O-rings 75a and 75b adhere to the surface of the wavelength conversion crystal 80. Specifically, contaminants such as fluorides and hydrocarbons adhere to the surface of the wavelength conversion crystal 80. This reduces the power of the light emitted from the wavelength conversion crystal 80 and degrades the profile of the emitted light, thereby deteriorating the wavelength conversion efficiency of the downstream wavelength conversion crystal. When the wavelength conversion crystal 80 is contaminated in this way, the light utilization efficiency decreases, and the wavelength conversion crystal 80 needs to be replaced. Since the wavelength conversion crystal 80 is expensive, frequent replacement is not desirable.

[0042] Therefore, an object of the present disclosure is to reduce adhesion of contaminants to the surface of the wavelength conversion crystal 80.

[0043] 2. Embodiment 2.1 Configuration The solid-state laser system 1 according to the embodiment of the present disclosure has the same configuration as the solid-state laser system 1 according to the comparative example, except that the configuration of the wavelength conversion device 70 is different.

[0044] Fig. 3 shows a schematic configuration of a wavelength converter 70 according to an embodiment. Fig. 4 shows a cross section taken along line AA in Fig. 3. Fig. 5 shows a cross section taken along line BB in Fig. 3.

[0045] In this embodiment, a first cylindrical member 90a, a second cylindrical member 90b, a first partition 92a, a second partition 92b, and a third partition 93 are provided inside the cell 72. The first cylindrical member 90a and the first partition 92a are arranged on the light incident side of the wavelength conversion crystal 80. The second cylindrical member 90b and the second partition 92b are arranged on the light exit side of the wavelength conversion crystal 80.

[0046] The first cylindrical member 90a and the second cylindrical member 90b are each a rectangular tube or a cylindrical member. In this embodiment, the first cylindrical member 90a and the second cylindrical member 90b are each a rectangular tube with a square cross section.

[0047] The first cylindrical member 90a is arranged so that the optical path of incident light entering the wavelength conversion crystal 80 passes through the internal space 91a of the first cylindrical member 90a, and the end of the first cylindrical member 90a is spaced a predetermined distance from the incident-side end face 80a of the wavelength conversion crystal 80. The second cylindrical member 90b is arranged so that the optical path of output light exiting the wavelength conversion crystal 80 passes through the internal space 91b of the second cylindrical member 90b, and the end of the second cylindrical member 90b is spaced a predetermined distance from the output-side end face 80b of the wavelength conversion crystal 80.

[0048] The first partition wall 92a holds the first cylindrical member 90a and is connected to the inner wall of the cell 72. Specifically, as shown in Fig. 4, the first partition wall 92a is connected to the outer periphery of the first cylindrical member 90a and is a wall that separates the space outside the first cylindrical member 90a within the cell 72. In this embodiment, the first partition wall 92a is connected to the end of the first cylindrical member 90a opposite to the wavelength conversion crystal 80.

[0049] Similarly, the second partition wall 92b holds the second cylindrical member 90b and is connected to the inner wall of the cell 72. Specifically, the second partition wall 92b is connected to the outer periphery of the second cylindrical member 90b and is a wall that separates the space outside the second cylindrical member 90b within the cell 72. In this embodiment, the second partition wall 92b is connected to the end of the second cylindrical member 90b opposite to the wavelength conversion crystal 80.

[0050] The third partition 93 is a wall that separates the space on the light incident side and the space on the light emitting side of the wavelength conversion crystal 80 within the cell 72. Specifically, as shown in FIG. 5 , the third partition 93 is connected between the outer periphery of the holder 71 and the inner wall of the cell 72.

[0051] When the holder 71 is provided with the above-mentioned adjustment mechanism, a gap S may be provided between the third partition wall 93 and the holder 71 as shown in FIG. 6 to allow movement by the adjustment mechanism.

[0052] In addition, in this embodiment, the cell 72 is provided with a first inlet 94a, a second inlet 94b, a first outlet 95a, and a second outlet 95b, instead of the inlet 77 and outlet 78 of the comparative example.

[0053] A gas introduction pipe 96a is connected to the first inlet 94a, and a gas supply source similar to the gas supply source 79a is connected to the gas introduction pipe 96a. A gas introduction pipe 96b is connected to the second inlet 94b, and a gas supply source similar to the gas supply source 79a is connected to the gas introduction pipe 96b. A common gas supply source may be connected to the gas introduction pipes 96a and 96b.

[0054] A gas exhaust pipe 97a is connected to the first exhaust port 95a, and an exhaust device similar to the exhaust device 79b described above is connected to the gas exhaust pipe 97a. A gas exhaust pipe 97b is connected to the second exhaust port 95b, and an exhaust device similar to the exhaust device 79b described above is connected to the gas exhaust pipe 97a. A common exhaust device may be connected to the gas exhaust pipe 97a and the gas exhaust pipe 97b. Furthermore, each end of the gas exhaust pipe 97a and the gas exhaust pipe 97b may be open and not connected to an exhaust device.

[0055] The first inlet 94a and the first outlet 95a are arranged on the light incident side of the wavelength conversion crystal 80. The second inlet 94b and the second outlet 95b are arranged on the light exit side of the wavelength conversion crystal 80.

[0056] Furthermore, the first inlet 94a is disposed at a position closer to the wavelength conversion crystal 80 than the first outlet 95a. That is, the first outlet 95a is disposed on the light incident side than the first inlet 94a. The second inlet 94b is disposed at a position closer to the wavelength conversion crystal 80 than the second outlet 95b. That is, the second outlet 95b is disposed on the light exit side than the second inlet 94b.

[0057] The first partition wall 92a is disposed between the first inlet 94a and the first outlet 95a. As a result, the purge gas G introduced into the cell 72 from the first inlet 94a passes through the internal space 91a of the first cylindrical member 90a and heads toward the first outlet 95a. The second partition wall 92b is disposed between the second inlet 94b and the second outlet 95b. As a result, the purge gas G introduced into the cell 72 from the second inlet 94b passes through the internal space 91b of the second cylindrical member 90b and heads toward the second outlet 95b.

[0058] Other configurations of the wavelength converter 70 according to this embodiment are the same as those of the comparative example.

[0059] 2.2 Operation The operation of the solid-state laser system 1 according to this embodiment is the same as that of the comparative example, except for the function of the wavelength converter 70. The function of the wavelength converter 70 will be described below.

[0060] In this embodiment, the purge gas G introduced into the cell 72 from the first inlet 94a passes between the end of the first cylindrical member 90a and the end of the wavelength conversion crystal 80, and flows along the incident-side end surface 80a of the wavelength conversion crystal 80. The purge gas G then passes through the internal space 91a of the first cylindrical member 90a from the wavelength conversion crystal 80 side to the incident window 73 side, and heads toward the first outlet 95a. Therefore, contaminants generated from the O-ring 75a near the incident window 73 are discharged together with the purge gas G from the first outlet 95a.

[0061] In this embodiment, the purge gas G introduced into the cell 72 from the second inlet 94b passes between the end of the second cylindrical member 90b and the end of the wavelength conversion crystal 80, and flows along the output end surface 80b of the wavelength conversion crystal 80. The purge gas G then passes through the internal space 91b of the second cylindrical member 90b from the wavelength conversion crystal 80 side to the output window 74 side, and heads toward the second outlet 95b. Therefore, contaminants generated from the O-ring 75b near the output window 74 are discharged together with the purge gas G from the second outlet 95b.

[0062] In this embodiment, the third partition 93 is provided to separate the space on the light incident side and the space on the light exit side within the cell 72, so that the flow rate of the purge gas G can be made different between the light incident side and the light exit side. For example, the flow rate on the light exit side, where exiting light having a shorter wavelength than the incident light is emitted, may be made higher than the flow rate on the light incident side.

[0063] 2.3 Effects In this embodiment, the purge gas G flows in a direction away from the surface of the wavelength conversion crystal 80, thereby preventing contaminants from reaching the surface of the wavelength conversion crystal 80. This reduces the adhesion of contaminants to the surface of the wavelength conversion crystal 80. As a result, a decrease in the power of the light emitted from the wavelength conversion crystal 80 and deterioration of the profile are suppressed, thereby improving the life of the wavelength conversion crystal 80 and eliminating the need for frequent replacement of the wavelength conversion crystal 80.

[0064] 2.4 Modified Wavelength Converter Various modifications of the wavelength converter 70 according to the above embodiment will be described below.

[0065] 2.4.1 First variant 7 is a schematic diagram showing the configuration of a wavelength converter 70 according to a first modified example. The wavelength converter 70 according to this modified example differs from the wavelength converter 70 according to the above embodiment only in the connection positions of the first partition 92a to the first cylindrical member 90a and the second partition 92b to the second cylindrical member 90b.

[0066] In the above embodiment, the first partition 92a is connected to the end of the first cylindrical member 90a opposite to the wavelength conversion crystal 80, but in this modification, the first partition 92a is connected to the end of the first cylindrical member 90a facing the wavelength conversion crystal 80. Similarly, in the above embodiment, the second partition 92b is connected to the end of the second cylindrical member 90b opposite to the wavelength conversion crystal 80, but in this modification, the second partition 92b is connected to the end of the second cylindrical member 90b facing the wavelength conversion crystal 80.

[0067] In this modified example, the same functions and effects as those of the above embodiment can be obtained.

[0068] 2.4.2 Second variant 8 is a schematic diagram showing the configuration of a wavelength converter 70 according to a second modification. Similar to the first modification, the wavelength converter 70 according to this modification differs from the wavelength converter 70 according to the above embodiment only in the connection positions of the first partition wall 92a to the first cylindrical member 90a and the second partition wall 92b to the second cylindrical member 90b.

[0069] In this modification, the first partition 92a is connected between the end of the first cylindrical member 90a on the wavelength conversion crystal 80 side and the end on the opposite side from the wavelength conversion crystal 80. The connection position of the first partition 92a to the first cylindrical member 90a may be anywhere between the end on the wavelength conversion crystal 80 side and the end on the opposite side from the wavelength conversion crystal 80.

[0070] Similarly, in this modification, the second partition 92b is connected between the end of the second cylindrical member 90b on the wavelength conversion crystal 80 side and the end on the opposite side from the wavelength conversion crystal 80. The connection position of the second partition 92b to the second cylindrical member 90b may be anywhere between the end on the wavelength conversion crystal 80 side and the end on the opposite side from the wavelength conversion crystal 80.

[0071] In this modified example, the same functions and effects as those of the above embodiment can be obtained.

[0072] 2.4.3 Third variant FIG. 9 schematically illustrates the configuration of a wavelength converter 70 according to a third modification. The wavelength converter 70 according to this modification differs from the wavelength converter 70 according to the above embodiment in that the third partition 93 is not provided. That is, in this modification, the space on the light incident side of the wavelength conversion crystal 80 communicates with the space on the light exit side. Therefore, in this modification, only the first inlet 94a is provided out of the first inlet 94a and the second inlet 94b. That is, in this modification, the second partition 92b is disposed between the first inlet 94a and the second outlet 95b. In this case, it is preferable to dispose the first inlet 94a directly above the wavelength conversion crystal 80, i.e., at the boundary between the space on the light incident side and the space on the light exit side.

[0073] In this modification, the same effects and advantages as those of the above embodiment can be obtained. Furthermore, in this modification, the third partition wall 93 and the second introduction port 94b are not provided, so the configuration of the wavelength converter 70 is simplified and the manufacturing cost is reduced.

[0074] In this modified example, the connection position of the first partition 92a to the first cylindrical member 90a and the connection position of the second partition 92b to the second cylindrical member 90b are the same as in the above embodiment, but they may also be the positions described in the first or second modified example above.

[0075] 2.4.4 Fourth Variant 10 is a schematic diagram showing the configuration of a wavelength converter 70 according to a fourth modified example. The wavelength converter 70 according to this modified example differs from the wavelength converter 70 according to the above embodiment only in the configurations of the first cylindrical member 90a and the second cylindrical member 90b.

[0076] In this modification, the end of the first cylindrical member 90a opposite the wavelength conversion crystal 80 extends closer to the entrance window 73 than the first outlet 95a. Specifically, this end of the first cylindrical member 90a is close to the entrance window 73 and spaced apart from the entrance window 73 and the cell 72. It is preferable that this end of the first cylindrical member 90a extends to the space inside the O-ring 75a. The surface of the entrance window 73 that faces this end of the first cylindrical member 90a is located inside the O-ring 75a. For example, when the first cylindrical member 90a has a cylindrical shape, its outer diameter is smaller than the inner diameter of the O-ring 75a.

[0077] In this modification, the end of the second cylindrical member 90b opposite the wavelength conversion crystal 80 extends closer to the output window 74 than the second outlet 95b. Specifically, this end of the second cylindrical member 90b is close to the output window 74 and spaced apart from the output window 74 and the cell 72. It is preferable that this end of the second cylindrical member 90b extends to the space inside the O-ring 75b. The surface of the output window 74 that faces this end of the second cylindrical member 90b is located inside the O-ring 75b. For example, when the second cylindrical member 90b has a cylindrical shape, its outer diameter is smaller than the inner diameter of the O-ring 75b.

[0078] The first partition wall 92a may be disposed between the first inlet 94a and the first outlet 95a, and the second partition wall 92b may be disposed between the second inlet 94b and the second outlet 95b.

[0079] In this modification, the purge gas G introduced into the cell 72 from the first inlet 94a passes between the end of the first cylindrical member 90a and the end of the wavelength conversion crystal 80, and flows along the incident-side end surface 80a of the wavelength conversion crystal 80. The purge gas G then passes through the internal space 91a of the first cylindrical member 90a from the wavelength conversion crystal 80 side to the incident window 73 side, and hits the surface of the incident window 73. The purge gas G that hits the surface of the incident window 73 forms a flow toward the outer periphery of the incident window 73 and passes through gaps between the first cylindrical member 90a and the incident window 73 and the cell 72 toward the first outlet 95a. Therefore, even if contaminants are generated from the O-ring 75a near the incident window 73, the contaminants are discharged together with the purge gas G from the first outlet 95a.

[0080] In this modification, the purge gas G introduced into the cell 72 from the second inlet 94b passes between the end of the second cylindrical member 90b and the end of the wavelength conversion crystal 80, and flows along the output end surface 80b of the wavelength conversion crystal 80. The purge gas G then passes through the internal space 91b of the second cylindrical member 90b from the wavelength conversion crystal 80 side to the output window 74 side, and hits the surface of the output window 74. The purge gas G that hits the surface of the output window 74 forms a flow toward the outer periphery of the output window 74, passes through gaps between the second cylindrical member 90b and the output window 74 and the cell 72, and heads toward the second outlet 95b. Therefore, contaminants generated from the O-ring 75b near the output window 74 are discharged from the second outlet 95b together with the purge gas G.

[0081] This modification also provides the same effects and advantages as the above-described embodiment. Furthermore, in this modification, clean purge gas G continues to flow over the surfaces of the entrance window 73 and the exit window 74, making it difficult for contaminants generated by the O-rings 75 a and 75 b to reach the surfaces, thereby suppressing adhesion of contaminants. This prevents a decrease in the light transmittance of the entrance window 73 and the exit window 74.

[0082] As explained in the third modification, the wavelength converter 70 according to this modification does not necessarily have to be provided with the third partition wall 93 and the second introduction port 94b. In this case, it is preferable to place the first introduction port 94a directly above the wavelength conversion crystal 80, that is, at the boundary between the space on the light incident side and the space on the light exit side.

[0083] 2.4.5 Fifth Variant 11 is a schematic diagram showing the configuration of a wavelength converter 70 according to a fifth modified example. The wavelength converter 70 according to this modified example differs from the wavelength converter 70 according to the above embodiment in the configuration of the cell 72.

[0084] In this modification, the cell 72 is not provided with an entrance window 73 or an exit window 74. Therefore, the cell 72 is not provided with O-rings 75a, 75b and window holders 76a, 76b. In this modification, the cell 72 is cylindrical and has openings at both the light entrance side end and the light exit side end. In this modification, the opening on the entrance side of the cell 72 is a first exhaust port 95a, and the opening on the exit side of the cell 72 is a second exhaust port 95b. In this modification, gas exhaust pipes 97a, 97b are not provided.

[0085] The configurations of the first cylindrical member 90a, the second cylindrical member 90b, the first partition wall 92a, the second partition wall 92b, and the third partition wall 93 according to this modification are the same as those in the above embodiment.

[0086] Therefore, in this modification, the first outlet 95a is arranged on the optical path of the incident light that enters the wavelength conversion crystal 80, and the second outlet 95b is arranged on the optical path of the output light that is output from the wavelength conversion crystal 80. Also, in this modification, the opening of the first cylindrical member 90a on the opposite side to the wavelength conversion crystal 80 is included in the first outlet 95a, and the opening of the second cylindrical member 90b on the opposite side to the wavelength conversion crystal 80 is included in the second outlet 95b.

[0087] In this modification, the purge gas G introduced into the cell 72 from the first inlet 94a passes between the end of the first cylindrical member 90a and the end of the wavelength conversion crystal 80, and flows along the incident-side end surface 80a of the wavelength conversion crystal 80. Thereafter, the purge gas G flows through the internal space 91a of the first cylindrical member 90a in the opposite direction to the wavelength conversion crystal 80, and is discharged from the first outlet 95a.

[0088] In this modification, the purge gas G introduced into the cell 72 from the second inlet 94b passes between the end of the second cylindrical member 90b and the end of the wavelength conversion crystal 80, and flows along the output end surface 80b of the wavelength conversion crystal 80. Thereafter, the purge gas G flows through the internal space 91b of the second cylindrical member 90b in the opposite direction to the wavelength conversion crystal 80, and is discharged from the second outlet 95b.

[0089] In this modification, the cell 72 is not provided with the O-rings 75a and 75b, and therefore contaminants resulting from the O-rings 75a and 75b do not adhere to the surface of the wavelength conversion crystal 80. Furthermore, in this modification, the cell 72 is not sealed, but the purge gas G flows in a direction away from the surface of the wavelength conversion crystal 80, which prevents moisture and impurities from reaching the surface of the wavelength conversion crystal 80, and the area around the wavelength conversion crystal 80 is maintained at a low humidity.

[0090] In addition, in this modification, the cell 72 is not provided with an entrance window 73 and an exit window 74, so there is no decrease in light transmittance due to deterioration of the entrance window 73 and the exit window 74. In addition, in this modification, the expensive entrance window 73 and the exit window 74 are not necessary, so the configuration of the wavelength converter 70 is simplified and the manufacturing cost is reduced.

[0091] As explained in the third modification, the wavelength converter 70 according to this modification does not necessarily have to be provided with the third partition wall 93 and the second introduction port 94b. In this case, it is preferable to place the first introduction port 94a directly above the wavelength conversion crystal 80, that is, at the boundary between the space on the light incident side and the space on the light exit side.

[0092] Furthermore, in the above embodiment and each modified example, a first component including a first cylindrical member 90a, a first partition 92a, a first inlet 94a, and a first outlet 95a is provided on the light incident side of the wavelength conversion crystal 80, and a second component including a second cylindrical member 90b, a second partition 92b, a second inlet 94b, and a second outlet 95b is provided on the light exit side of the wavelength conversion crystal 80. It is not necessarily necessary to provide both the first component and the second component, and only one of the first component and the second component may be provided.

[0093] The above description is intended to be illustrative rather than limiting. Thus, it will be apparent to those skilled in the art that modifications can be made to the embodiments of the present disclosure without departing from the scope of the appended claims.

[0094] Terms used throughout this specification and the appended claims should be interpreted as "open-ended" terms. For example, the terms "including" or "including" should be interpreted as "not limited to what is stated as including." The term "having" should be interpreted as "not limited to what is stated as having." Additionally, the modifier "a" or "an" used in this specification and the appended claims should be interpreted as meaning "at least one" or "one or more."

[0095] The above description is intended to be illustrative, not limiting. Accordingly, it will be apparent to those skilled in the art that modifications can be made to the embodiments of the present disclosure without departing from the scope of the claims. It will also be apparent to those skilled in the art that embodiments and variations of the present disclosure can be used in combination. Terms used throughout this specification and claims should be construed as "open-ended" terms unless expressly stated. For example, terms such as "comprise," "have," "comprise," and "equip" should be interpreted as meaning "without excluding the presence of elements other than those listed." The modifier "a" or "an" should be interpreted as meaning "at least one" or "one or more." The term "at least one of A, B, and C" should be interpreted as "A," "B," "C," "A+B," "A+C," "B+C," or "A+B+C," including combinations other than "A," "B," and "C."

Claims

1. a wavelength conversion crystal that converts the wavelength of incident light and outputs output light; a holder that holds the wavelength conversion crystal on an optical path of the incident light; a cell that accommodates the wavelength conversion crystal and the holder therein, and has a first inlet for supplying a purge gas into the cell and a first outlet for discharging the purge gas from the cell; a first cylindrical member, the first cylindrical member having an internal space through which the optical path of the incident light passes, the first cylindrical member being disposed at a distance from the wavelength conversion crystal; a first partition wall that is disposed between the first inlet and the first outlet and that holds the first cylindrical member; A wavelength conversion device comprising:

2. 2. The wavelength conversion device according to claim 1, The first inlet is disposed closer to the wavelength conversion crystal than the first outlet.

3. 2. The wavelength conversion device according to claim 1, The purge gas flows through the internal space of the first cylindrical member in a direction away from the wavelength conversion crystal.

4. 2. The wavelength conversion device according to claim 1, the cell has a second outlet for discharging the purge gas from the interior thereof; The first outlet is disposed on the light input side of the wavelength conversion crystal, and the second outlet is disposed on the light output side of the wavelength conversion crystal.

5. 5. The wavelength conversion device according to claim 4, a second cylindrical member arranged apart from the wavelength conversion crystal, the second cylindrical member having an internal space through which the optical path of the emitted light passes; a second partition wall disposed between the first inlet and the second outlet and holding the second cylindrical member; A wavelength conversion device comprising:

6. 6. The wavelength conversion device according to claim 5, The purge gas flows through the internal space of the second cylindrical member in a direction away from the wavelength conversion crystal.

7. 6. The wavelength conversion device according to claim 5, A third partition wall is provided to define a space on the light incident side and a space on the light emitting side of the wavelength conversion crystal in the interior.

8. 8. The wavelength conversion device according to claim 7, The third partition wall is connected between the outer periphery of the holder and the inner wall of the cell.

9. 8. The wavelength conversion device according to claim 7, the third partition is disposed between an outer periphery of the holder and an inner wall of the cell, A gap is provided between the third partition and the holder.

10. 8. The wavelength conversion device according to claim 7, the cell has a second inlet for supplying the purge gas to the interior thereof, the first introduction port is disposed in the space on the light incident side, and the second introduction port is disposed in the space on the light exit side, The second partition wall is disposed between the second inlet and the second outlet.

11. 11. The wavelength conversion device according to claim 10, The second inlet is disposed closer to the wavelength conversion crystal than the second outlet.

12. 12. The wavelength conversion device according to claim 11, The purge gas flows through the internal space of the second cylindrical member in a direction away from the wavelength conversion crystal.

13. 6. The wavelength conversion device according to claim 5, An incident window disposed on the optical path of the incident light and an exit window disposed on the optical path of the exit light are fixed to the cell via O-rings.

14. 14. The wavelength conversion device according to claim 13, an end of the first cylindrical member opposite to the wavelength conversion crystal extends toward the entrance window beyond the first outlet; The end of the second cylindrical member opposite to the wavelength conversion crystal extends toward the exit window beyond the second outlet.

15. 15. The wavelength conversion device according to claim 14, an end of the first cylindrical member opposite the wavelength conversion crystal is close to the entrance window and is spaced apart from the entrance window and the cell; The end of the second cylindrical member opposite the wavelength conversion crystal is close to the exit window and spaced apart from the exit window and the cell.

16. 6. The wavelength conversion device according to claim 5, The first outlet is disposed on the optical path of the incident light, and the second outlet is disposed on the optical path of the emitted light.

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