Wavelength conversion device

Abstract

A wavelength conversion device is provided. A wavelength conversion device according to one aspect of the present disclosure is provided with: a wavelength conversion crystal that converts the wavelength of incident light and emits emitted light; a holder that holds the wavelength conversion crystal on an optical path of the incident light; a unit in which the wavelength conversion crystal and the holder are accommodated, the unit having a first introduction port for supplying a purge gas to the inside and a first discharge port for discharging the purge gas from the inside; a first cylindrical member in which the optical path of the incident light passes through the internal space thereof, the first cylindrical member being disposed so as to be separated from the wavelength conversion crystal; and a first partition wall that is disposed between the first introduction port and the first discharge port and that holds the first cylindrical member.

Description

Technical Field

[0001] This disclosure relates to wavelength conversion devices. Background Technology

[0002] In recent years, with the miniaturization and high integration of semiconductor integrated circuits, there has been a demand for higher resolution in semiconductor exposure equipment. Therefore, efforts are underway to shorten the wavelength of light emitted from the exposure light source. For example, as gas laser devices for exposure, KrF excimer lasers using lasers with an output wavelength of approximately 248 nm and ArF excimer lasers using lasers with an output wavelength of approximately 193 nm are being developed.

[0003] The spectral linewidth of the naturally oscillating light from KrF and ArF excimer lasers is as wide as 350 pm to 400 pm. Therefore, if the projection lens is made of a material that allows ultraviolet light, such as that from KrF and ArF lasers, to pass through, chromatic aberration may sometimes occur. As a result, the resolution may be reduced. Therefore, it is necessary to narrow the spectral linewidth of the laser output from the gas laser device to a level where chromatic aberration can be ignored. Thus, in order to narrow the spectral linewidth, the laser resonator of a gas laser device sometimes includes a line-narrowing module (LNM) containing narrowing elements (etalon, grating, etc.). Hereinafter, gas laser devices with narrowed spectral linewidths will be referred to as narrow-bandgap gas laser devices.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2015-155933

[0007] Patent Document 2: Japanese Patent Application Publication No. 3-263017

[0008] Patent Document 3: Japanese Patent Application Publication No. 11-288012 Summary of the Invention

[0009] One aspect of the wavelength conversion device disclosed herein includes: a wavelength conversion crystal that converts the wavelength of incident light to emit outgoing light; a support that holds the wavelength conversion crystal in the optical path of the incident light; a unit that internally houses the wavelength conversion crystal and the support, having a first inlet for supplying purge gas internally and a first outlet for discharging purge gas internally; a first cylindrical member through which the optical path of the incident light passes, and the first cylindrical member is disposed separately from the wavelength conversion crystal; and a first partition wall disposed between the first inlet and the first outlet to hold the first cylindrical member. Attached Figure Description

[0010] The following description, by way of example only, refers to the accompanying drawings to illustrate several embodiments of this disclosure.

[0011] Figure 1 This is a diagram that roughly illustrates the structure of the laser system of the comparative example.

[0012] Figure 2 This is a cross-sectional view that roughly shows the structure of the wavelength conversion device of the comparative example.

[0013] Figure 3 This is a cross-sectional view that schematically shows the structure of the wavelength conversion device according to the embodiment.

[0014] Figure 4 It means along Figure 3 A cross-sectional view of the section of line AA.

[0015] Figure 5 It means along Figure 3 A sectional view of the BB line.

[0016] Figure 6 This is a cross-sectional view showing an example where a gap is provided between the third partition wall and the support.

[0017] Figure 7 This is a cross-sectional view that schematically shows the structure of the wavelength conversion device of the first modified example.

[0018] Figure 8 This is a cross-sectional view that schematically shows the structure of the wavelength conversion device of the second variation.

[0019] Figure 9 This is a cross-sectional view that schematically shows the structure of the wavelength conversion device in the third variation.

[0020] Figure 10 This is a cross-sectional view that schematically shows the structure of the wavelength conversion device in the fourth variation.

[0021] Figure 11 This is a cross-sectional view that schematically shows the structure of the wavelength conversion device in the fifth variation. Detailed Implementation

[0022] <Content>

[0023] 1. Comparative Example

[0024] 1.1 Solid-state laser system

[0025] 1.1.1 Structure

[0026] 1.1.2 Actions

[0027] 1.2 Wavelength Conversion Device

[0028] 1.3 Research Topic

[0029] 2. Implementation Method

[0030] 2.1 Structure

[0031] 2.2 Actions

[0032] 2.3 Effects

[0033] 2.4 Variations of Wavelength Conversion Devices

[0034] 2.4.1 First Variation Example

[0035] 2.4.2 Second variation example

[0036] 2.4.3 Third variation example

[0037] 2.4.4 Fourth Variation Example

[0038] 2.4.5 Fifth Variation

[0039] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. The embodiments described below represent several examples of the present disclosure and do not limit the content of the present disclosure. In addition, the structures and operations described in the embodiments are not necessarily all necessary for the structures and operations of the present disclosure. Furthermore, the same reference numerals are used to refer to the same constituent elements, and repeated descriptions are omitted.

[0040] 1. Comparative Example

[0041] First, the comparative examples of this disclosure will be explained. The comparative examples of this disclosure are those known only to the applicant and are not publicly known examples that the applicant himself acknowledges.

[0042] 1.1 Solid-state laser system

[0043] 1.1.1 Structure

[0044] Figure 1 The structure of the comparative example solid-state laser system 1 is shown in general. 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. Solid-state laser system 10 outputs a pulsed laser PL with a wavelength of approximately 193.4 nm.

[0045] 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, or continuous wave) and outputs a CW laser with a wavelength of approximately 1553 nm. The solid-state amplifier 21 is a semiconductor optical amplifier (SOA) that amplifies the CW laser output from the semiconductor laser 20 and outputs it as the signal laser Ls. The signal laser Ls output from the signal laser device 2 is incident on the amplification system 4.

[0046] 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 in a single longitudinal mode (CW) 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, which amplifies the CW laser light output from the semiconductor laser 30.

[0047] The LBO crystal 32 is positioned after the solid-state amplifier 31 and converts a portion of the wavelength of the pulsed laser with a wavelength of approximately 1030 nm output from the solid-state amplifier 31 into a second harmonic with a wavelength of approximately 515 nm before outputting it. The remaining portion of the pulsed laser with a wavelength of approximately 1030 nm output from the solid-state amplifier 31 is not converted in wavelength and passes through the LBO crystal 32.

[0048] Dichroic mirror 33 is positioned after LBO crystal 32 to highly reflect the pulsed laser with a wavelength of approximately 1030 nm that has passed through LBO crystal 32, thus ensuring high transmission of the second harmonic output from LBO crystal 32. The pulsed laser highly reflected by dichroic mirror 33 is used as pump laser Lp and incident on amplification system 4.

[0049] Amplification system 4 includes an optical parametric amplifier (OPA). For example, the OPA contains periodically polarized lithium niobate (PPLN) crystal and periodically polarized potassium titanium phosphate (PPKTP) crystal. The OPA uses a pump laser Lp to pulse amplify the signal laser Ls, which is then output as the first pulse laser L1.

[0050] Wavelength conversion system 5 includes CLBO (CsLiB6O) 10 Crystal 50, dichroic mirror 51, CLBO crystal 52, and CLBO crystal 53. CLBO crystal 50, CLBO crystal 52, and CLBO crystal 53 are examples of "wavelength conversion crystals" of the present disclosure.

[0051] The signal laser Ls, which has been pulse-amplified by the amplification system 4, is incident on the wavelength conversion system 5 as the first pulse laser L1. The second harmonic of the laser through the dichroic mirror 33 of the pump laser device 3 is incident on the wavelength conversion system 5 as the second pulse laser L2.

[0052] The CLBO crystal 50 is positioned in the optical path of the second pulse laser L2, converting the wavelength of the incident second pulse laser L2 into a fourth harmonic with a wavelength of approximately 258 nm and outputting it.

[0053] Dichroic mirror 51 is positioned after the CLBO crystal 50 to ensure high transmission of the fourth harmonic pulsed laser output from the CLBO crystal 50. Additionally, the first pulsed laser L1 output from the amplification system 4 is incident on dichroic mirror 51. Dichroic mirror 51 is configured to highly reflect the first pulsed laser L1, so that the first pulsed laser L1 and the fourth harmonic pulsed laser are coaxially incident on the CLBO crystal 52.

[0054] CLBO crystals 52 and 53 are connected in series in the stage after the dichroic mirror 51. By performing sum-frequency generation, they generate and output a pulsed laser PL with a wavelength of approximately 193.4 nm.

[0055] The solid-state laser control unit 6 is composed of a processor and is connected to the signal laser device 2, the pump laser device 3, and the wavelength conversion system 5. An external laser control unit 60 is connected to the solid-state laser control unit 6.

[0056] 1.1.2 Actions

[0057] Next, the operation of the comparative example solid-state laser system 1 will be explained. First, the solid-state laser control unit 6 operates the pump laser device 3 according to the 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 with a wavelength of approximately 1030 nm. Next, the solid-state laser control unit 6 pulses the CW laser by controlling the solid-state amplifier 31.

[0058] As a result, a pulsed laser with a wavelength of approximately 1030 nm is output from the solid-state amplifier 31 and incident on the LBO crystal 32. Part of the pulsed laser is converted into a second harmonic by the LBO crystal 32, while the other part passes through the LBO crystal 32. The second harmonic is highly transmitted through the dichroic mirror 33 and becomes the second pulsed laser L2, which is then incident on the wavelength conversion system 5. The pulsed laser that has passed through the LBO crystal 32 is highly reflected by the dichroic mirror 33 and becomes the pump laser Lp, which is then incident on the amplification system 4.

[0059] Next, the solid-state laser control unit 6 activates 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 oscillate in a CW pattern, outputting a CW laser with a wavelength of approximately 1553 nm. The CW laser output from the semiconductor laser 20 is amplified by the solid-state amplifier 21 and output as the signal laser Ls, which is then incident on the amplification system 4.

[0060] The signal laser Ls incident on the amplification system 4 is pulsed and amplified by the pump laser Lp, and output as the first pulse laser L1 and incident on the wavelength conversion system 5.

[0061] The first pulse laser L1 incident on the wavelength conversion system 5 is highly reflected by the dichroic mirror 51 and then incident on the CLBO crystal 52. In addition, the second pulse laser L2 incident on the wavelength conversion system 5 is wavelength-converted to the fourth harmonic by the CLBO crystal 50, and is highly transmitted through the dichroic mirror 51 and then incident on the CLBO crystal 52.

[0062] A first pulsed laser L1 with a wavelength of approximately 1553 nm and a fourth harmonic with a wavelength of approximately 258 nm are incident on the CLBO crystal 52 to generate a sum frequency, thereby generating a first sum frequency light with a wavelength of approximately 221 nm. A portion of the first pulsed laser L1 passes through the CLBO crystal 52 and is incident on the CLBO crystal 53 coaxially with the first sum frequency.

[0063] A first pulsed laser L1 with a wavelength of approximately 1553 nm and a first sum-frequency light with a wavelength of approximately 221 nm incident on the CLBO crystal 53 generate a sum-frequency light, thereby generating a second sum-frequency light with a wavelength of approximately 193.4 nm. The second sum-frequency light is output from the wavelength conversion system 5 as the aforementioned pulsed laser PL.

[0064] In addition, the pulsed laser PL output from the wavelength conversion system 5 can also be amplified by an excimer amplifier (not shown).

[0065] 1.2 Wavelength Conversion Device

[0066] CLBO crystals 50, 52, and 53 are hygroscopic and are therefore placed inside the unit being purged by the purging gas to create a low-humidity atmosphere. Hereinafter, the device having a unit housing wavelength conversion crystals such as CLBO crystals 50, 52, and 53 will be referred to as a "wavelength conversion device".

[0067] Figure 2The structure of the comparative example wavelength conversion device 70 is shown in schematic. The wavelength conversion device 70 includes a wavelength conversion crystal 80, a support 71 for holding the wavelength conversion crystal 80, and a unit 72 for housing the support 71. In addition, the wavelength conversion crystal 80 is any crystal selected from CLBO crystal 50, CLBO crystal 52, and CLBO crystal 53.

[0068] Unit 72 is, for example, a sealed container made of aluminum or stainless steel (SUS). In this comparative example, unit 72 is cuboid in shape. Support 71 is fixed to the inner bottom surface of unit 72. An adjustment mechanism capable of adjusting the configuration angle of wavelength conversion crystal 80 may also be provided on support 71.

[0069] In unit 72, an incident-side opening 72a is formed in the optical path of the incident light incident on the wavelength conversion crystal 80. Additionally, in unit 72, an exit-side opening 72b is formed in the optical path of the outgoing light emitted from the wavelength conversion crystal 80. The incident-side opening 72a and the exit-side opening 72b are formed at opposite positions, separated by a space between them and the wavelength conversion crystal 80. For example, if the wavelength conversion crystal 80 is a CLBO crystal 50, the incident light is a second pulse laser L2, and the outgoing light is a fourth harmonic laser.

[0070] Additionally, incident light is incident on the incident side end face 80a of the wavelength conversion crystal 80. Outgoing light is emitted from the outgoing side end face 80b of the wavelength conversion crystal 80. Hereinafter, the incident side end face 80a and the outgoing side end face 80b are sometimes simply referred to as the "surface of the wavelength conversion crystal 80".

[0071] 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 sides of a substrate made of calcium fluoride (CaF2) crystal or synthetic quartz with a reflection-suppressing film (not shown). The incident window 73 allows incident light to pass through and enter the wavelength conversion crystal 80. The exit window 74 allows outgoing light emitted from the wavelength conversion crystal 80 to pass through.

[0072] The entrance window 73 is secured to the unit 72 via an O-ring 75a for ensuring airtightness. Specifically, an O-ring 75a is disposed between the entrance window 73 and the unit 72. The entrance window 73 is held by a window bracket 76a, which is secured to the unit 72 by bolts or the like (not shown).

[0073] The exit window 74 is secured to the unit 72 via an O-ring 75b for ensuring airtightness. Specifically, an O-ring 75b is disposed between the exit window 74 and the unit 72. The exit window 74 is held by a window bracket 76b, which is secured to the unit 72 by bolts or the like (not shown).

[0074] O-rings are ring-shaped sealing components with a roughly circular cross-section. For example, O-rings 75a and 75b are resin rings formed from Teflon (a registered trademark), rubber, etc.

[0075] Furthermore, unit 72 has an inlet 77 for introducing purge gas G into the interior of unit 72 and an outlet 78 for discharging purge gas G to the exterior of unit 72. For example, inlet 77 is disposed on the light incident side of wavelength conversion crystal 80, and outlet 78 is disposed on the light emitting side of wavelength conversion crystal 80. The purge gas is a gas such as N2, CO2, Ar, O2, or CDA (Cleandry air).

[0076] A gas inlet pipe 77a is connected to the inlet 77 for introducing purge gas G supplied from a gas supply source 79a such as a gas cylinder. A gas outlet pipe 78a is connected to the outlet 78 for discharging the purge gas G using an exhaust device 79b such as a pump. Alternatively, the end of the gas outlet pipe 78a may be left unconnected to the exhaust device 79b and remain open.

[0077] 1.3 Research Topic

[0078] The applicant discovered that in the wavelength conversion device 70 of the comparative example, contaminants presumably originating from the O-rings 75a and 75b adhered to the surface of the wavelength conversion crystal 80. Specifically, contaminants such as fluorides and hydrocarbons adhered to the surface of the wavelength conversion crystal 80. This resulted in a decrease in the power of the emitted light from the wavelength conversion crystal 80, a deterioration in the characteristics of the emitted light, and consequently, a decline in the wavelength conversion efficiency of subsequent wavelength conversion crystals. Thus, if the wavelength conversion crystal 80 is contaminated, the light utilization efficiency decreases, necessitating replacement of the wavelength conversion crystal 80. Since the wavelength conversion crystal 80 is expensive, frequent replacement is not preferable.

[0079] Therefore, the purpose of this disclosure is to reduce the adhesion of contaminants to the surface of the wavelength conversion crystal 80.

[0080] 2. Implementation Method

[0081] 2.1 Structure

[0082] The solid-state laser system 1 of the present disclosure has the same structure as the solid-state laser system 1 of the comparative example, except that the structure of the wavelength conversion device 70 is different.

[0083] Figure 3 The structure of the wavelength conversion device 70 in the embodiment is shown in a schematic diagram. Figure 4 Indicates along Figure 3 The cross section of line AA. Figure 5 Indicates along Figure 3 The cross section of the BB line.

[0084] In this embodiment, a first cylindrical component 90a, a second cylindrical component 90b, a first partition wall 92a, a second partition wall 92b, and a third partition wall 93 are disposed inside the unit 72. The first cylindrical component 90a and the first partition wall 92a are disposed on the light incident side of the wavelength conversion crystal 80. The second cylindrical component 90b and the second partition wall 92b are disposed on the light emitting side of the wavelength conversion crystal 80.

[0085] The first cylindrical component 90a and the second cylindrical component 90b are respectively square or cylindrical. In this embodiment, the first cylindrical component 90a and the second cylindrical component 90b are square tubes with a quadrilateral cross-section.

[0086] The first cylindrical member 90a is configured such that the optical path of the incident light incident on the wavelength conversion crystal 80 passes through the internal space 91a of the first cylindrical member 90a, and its end is separated from the incident side end face 80a of the wavelength conversion crystal 80 by a predetermined interval. The second cylindrical member 90b is configured such that the optical path of the outgoing light emitted to the wavelength conversion crystal 80 passes through the internal space 91b of the second cylindrical member 90b, and its end is separated from the outgoing side end face 80b of the wavelength conversion crystal 80 by a predetermined interval.

[0087] The first partition wall 92a retains the first cylindrical member 90a and is connected to the inner wall of the unit 72. Specifically, as Figure 4 As shown, the first partition wall 92a is a wall that connects to the outer periphery of the first cylindrical member 90a and divides the space outside the first cylindrical member 90a within the unit 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.

[0088] Similarly, the second partition wall 92b holds the second cylindrical member 90b and is connected to the inner wall of the unit 72. Specifically, the second partition wall 92b is a wall that connects to the outer periphery of the second cylindrical member 90b and divides the space outside the second cylindrical member 90b within the unit 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.

[0089] The third partition wall 93 is the wall that defines the space on the light-incident side and the light-outceasing side of the wavelength conversion crystal 80 within unit 72. Specifically, as... Figure 5 As shown, the third partition wall 93 is connected between the outer periphery of the bracket 71 and the inner wall of the unit 72.

[0090] Furthermore, when the bracket 71 is equipped with the aforementioned adjustment mechanism, such as Figure 6As shown, a gap S can also be provided between the third partition wall 93 and the bracket 71 to allow movement based on the adjustment mechanism.

[0091] In addition, in this embodiment, a first inlet 94a, a second inlet 94b, a first outlet 95a, and a second outlet 95b are provided in unit 72 to replace the inlet 77 and outlet 78 of the comparative example.

[0092] A gas inlet pipe 96a is connected to the first inlet port 94a, and a gas supply source identical to the aforementioned gas supply source 79a is connected to the gas inlet pipe 96a. A gas inlet pipe 96b is connected to the second inlet port 94b, and a gas supply source identical to the aforementioned gas supply source 79a is connected to the gas inlet pipe 96b. Alternatively, a common gas supply source can be connected to both the gas inlet pipes 96a and 96b.

[0093] A gas exhaust pipe 97a is connected to the first outlet 95a, and an exhaust device identical to the aforementioned exhaust device 79b is connected to the gas exhaust pipe 97a. A gas exhaust pipe 97b is connected to the second outlet 95b, and an exhaust device identical to the aforementioned exhaust device 79b is connected to the gas exhaust pipe 97b. Alternatively, a common exhaust device may be connected to both gas exhaust pipes 97a and 97b. Furthermore, the ends of both gas exhaust pipes 97a and 97b may be open and not connected to any exhaust device.

[0094] The first inlet 94a and the first outlet 95a are disposed on the light incident side of the wavelength conversion crystal 80. The second inlet 94b and the second outlet 95b are disposed on the light emitting side of the wavelength conversion crystal 80.

[0095] Furthermore, the first inlet 94a is positioned closer to the wavelength conversion crystal 80 than the first outlet 95a. That is, the first outlet 95a is positioned closer to the light incident side than the first inlet 94a. The second inlet 94b is positioned closer to the wavelength conversion crystal 80 than the second outlet 95b. That is, the second outlet 95b is positioned closer to the light emitting side than the second inlet 94b.

[0096] A first partition wall 92a is disposed between the first inlet 94a and the first outlet 95a. Thus, the purge gas G introduced into the unit 72 from the first inlet 94a passes through the internal space 91a of the first cylindrical member 90a and faces towards the first outlet 95a. A second partition wall 92b is disposed between the second inlet 94b and the second outlet 95b. Thus, the purge gas G introduced into the unit 72 from the second inlet 94b passes through the internal space 91b of the second cylindrical member 90b and faces towards the second outlet 95b.

[0097] The wavelength conversion device 70 of this embodiment has the same other structure as the comparative example.

[0098] 2.2 Actions

[0099] The operation of the solid-state laser system 1 in this embodiment is the same as that in the comparative example, except that the function of the wavelength conversion device 70 is different. The function of the wavelength conversion device 70 will be explained below.

[0100] In this embodiment, the purge gas G introduced into the unit 72 from the first inlet 94a flows between the end of the first cylindrical member 90a and the end of the wavelength conversion crystal 80, along the incident side end face 80a of the wavelength conversion crystal 80. Then, the purge gas G flows from the wavelength conversion crystal 80 side through the internal space 91a of the first cylindrical member 90a toward the incident window 73 side, toward the first outlet 95a. Therefore, contaminants generated near the incident window 73 from the O-ring 75a are discharged from the first outlet 95a along with the purge gas G.

[0101] In this embodiment, the purge gas G introduced into the unit 72 from the second inlet 94b flows between the end of the second cylindrical member 90b and the end of the wavelength conversion crystal 80, along the emission side end face 80b of the wavelength conversion crystal 80. Then, the purge gas G flows from the wavelength conversion crystal 80 side through the internal space 91b of the second cylindrical member 90b toward the emission window 74 side, toward the second outlet 95b. Therefore, contaminants generated near the emission window 74 from the O-ring 75b are discharged from the second outlet 95b along with the purge gas G.

[0102] Furthermore, in this embodiment, a third partition wall 93 is provided within the demarcation unit 72 to separate the space on the light incident side and the space on the light emitting side, thus enabling the flow rate of the purge gas G to differ between the light incident side and the light emitting side. For example, the flow rate of the emitted light with a shorter wavelength than the incident light can be made greater on the light emitting side than on the light incident side.

[0103] 2.3 Effects

[0104] In this embodiment, the purge gas G flows away from the surface of the wavelength conversion crystal 80, thus suppressing contaminants from reaching the surface of the wavelength conversion crystal 80. Consequently, the adhesion of contaminants to the surface of the wavelength conversion crystal 80 is reduced. As a result, the reduction in the power of the emitted light from the wavelength conversion crystal 80 and the degradation of its characteristics are suppressed, thus increasing the lifespan of the wavelength conversion crystal 80 and eliminating the need for frequent replacements.

[0105] 2.4 Variations of Wavelength Conversion Devices

[0106] Hereinafter, various modifications of the wavelength conversion device 70 of the above-described embodiment will be described.

[0107] 2.4.1 First Variation Example

[0108] Figure 7 The structure of the wavelength conversion device 70 in the first modified example is shown in general. The only difference between the wavelength conversion device 70 in this modified example and the wavelength conversion device 70 in the above embodiment is the connection position between the first partition wall 92a and the first cylindrical member 90a and the connection position between the second partition wall 92b and the second cylindrical member 90b.

[0109] In the above embodiment, the first partition wall 92a is connected to the end of the first cylindrical member 90a opposite to the wavelength conversion crystal 80. However, in this modified example, the first partition wall 92a is connected to the end of the first cylindrical member 90a on the wavelength conversion crystal 80 side. Similarly, in the above embodiment, the second partition wall 92b is connected to the end of the second cylindrical member 90b opposite to the wavelength conversion crystal 80. However, in this modified example, the second partition wall 92b is connected to the end of the second cylindrical member 90b on the wavelength conversion crystal 80 side.

[0110] The same function and effect as the above-described embodiments can be obtained in this modified example.

[0111] 2.4.2 Second variation example

[0112] Figure 8 The structure of the wavelength conversion device 70 in the second modification is shown in general. The wavelength conversion device 70 in this modification is the same as that in the first modification, except that the connection position between the first partition wall 92a and the first cylindrical member 90a and the connection position between the second partition wall 92b and the second cylindrical member 90b are different from those in the wavelength conversion device 70 of the above embodiment.

[0113] In this modified example, the first partition wall 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 of the wavelength conversion crystal 80. Furthermore, the connection position between the first partition wall 92a and the first cylindrical member 90a can be any position between the end on the wavelength conversion crystal 80 side and the end on the opposite side of the wavelength conversion crystal 80.

[0114] Similarly, in this modified example, the second partition wall 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 of the wavelength conversion crystal 80. Furthermore, the connection position between the second partition wall 92b and the second cylindrical member 90b can be any position between the end on the wavelength conversion crystal 80 side and the end on the opposite side of the wavelength conversion crystal 80.

[0115] The same function and effect as the above-described embodiments can be obtained in this modified example.

[0116] 2.4.3 Third variation example

[0117] Figure 9 The structure of the wavelength conversion device 70 in the third modification is shown in general. The wavelength conversion device 70 in this modification differs from the wavelength conversion device 70 of the above-described embodiment in that it does not have a third partition wall 93. That is, in this modification, the space on the light-incident side of the wavelength conversion crystal 80 is connected to the space on the light-outceasing side. Therefore, in this modification, only the first inlet 94a of the first inlet 94a and the second inlet 94b is provided. That is, in this modification, the second partition wall 92b is disposed between the first inlet 94a and the second outlet 95b. In this case, the first inlet 94a is preferably disposed 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-outceasing side.

[0118] The same function and effect as the above-described embodiment can be obtained in this modified example. In addition, in this modified example, the third partition wall 93 and the second inlet 94b are not provided, thus simplifying the structure of the wavelength conversion device 70 and reducing manufacturing costs.

[0119] It should be noted that in this modified example, the connection position between the first partition wall 92a and the first cylindrical component 90a and the connection position between the second partition wall 92b and the second cylindrical component 90b are set to the same position as in the above-described embodiment, but they can also be set to the positions described in the first or second modified example above.

[0120] 2.4.4 Fourth Variation Example

[0121] Figure 10 The structure of the wavelength conversion device 70 in the fourth modification is shown in general. The wavelength conversion device 70 of this modification differs from the wavelength conversion device 70 of the above embodiment only in the structure of the first cylindrical member 90a and the second cylindrical member 90b.

[0122] In this modified example, the end of the first cylindrical member 90a opposite to the wavelength conversion crystal 80 extends further toward the incident window 73 than the first outlet 95a. Specifically, this end of the first cylindrical member 90a is close to the incident window 73 and separate from the incident window 73 and the unit 72. Preferably, this end of the first cylindrical member 90a extends into the space inside the O-ring 75a. The surface of the incident window 73 opposite to this end of the first cylindrical member 90a is located inside the O-ring 75a. For example, if the first cylindrical member 90a is cylindrical, its outer diameter is smaller than the inner diameter of the O-ring 75a.

[0123] In this modified example, the end of the second cylindrical member 90b opposite to the wavelength conversion crystal 80 extends further towards the emission window 74 than the second outlet 95b. Specifically, this end of the second cylindrical member 90b is close to the emission window 74 and separate from the emission window 74 and the unit 72. Preferably, this end of the second cylindrical member 90b extends into the space inside the O-ring 75b. The surface of the emission window 74 opposite this end of the second cylindrical member 90b is located inside the O-ring 75b. For example, if the second cylindrical member 90b is cylindrical, its outer diameter is smaller than the inner diameter of the O-ring 75b.

[0124] The first partition wall 92a only needs to be disposed between the first inlet 94a and the first outlet 95a. The second partition wall 92b only needs to be disposed between the second inlet 94b and the second outlet 95b.

[0125] In this modified example, the purge gas G introduced into the unit 72 from the first inlet 94a flows along the incident side end face 80a of the wavelength conversion crystal 80 between the end of the first cylindrical member 90a and the end of the wavelength conversion crystal 80. Then, the purge gas G flows from the wavelength conversion crystal 80 side towards the incident window 73 side through the internal space 91a of the first cylindrical member 90a and contacts the surface of the incident window 73. The purge gas G contacting the surface of the incident window 73 forms an airflow towards the outer periphery of the incident window 73, passing through the gap between the first cylindrical member 90a, the incident window 73, and the unit 72, and towards the first outlet 95a. Therefore, even if contaminants are generated near the incident window 73 from the O-ring 75a, the contaminants are discharged from the first outlet 95a along with the purge gas G.

[0126] In this modified example, the purge gas G introduced into the unit 72 from the second inlet 94b flows along the exit side end face 80b of the wavelength conversion crystal 80 between the end of the second cylindrical member 90b and the end of the wavelength conversion crystal 80. Then, the purge gas G flows from the wavelength conversion crystal 80 side towards the exit window 74 side through the internal space 91b of the second cylindrical member 90b and contacts the surface of the exit window 74. The purge gas G contacting the surface of the exit window 74 forms an airflow towards the outer periphery of the exit window 74, passing through the gap between the second cylindrical member 90b, the exit window 74, and the unit 72 towards the second outlet 95b. Therefore, contaminants generated near the exit window 74 from the O-ring 75b are discharged from the second outlet 95b along with the purge gas G.

[0127] In this modified example, the same effects and functions as in the above-described embodiment can be obtained. Furthermore, in this modified example, clean purge gas G continuously flows over the surfaces of the incident window 73 and the exit window 74, respectively. Therefore, contaminants generated from the O-rings 75a and 75b are difficult to reach the surfaces, and contaminant adhesion is suppressed. Thus, the reduction in light transmittance of the incident window 73 and the exit window 74 can be suppressed.

[0128] Furthermore, regarding the wavelength conversion device 70 of this modified example, as described in the third modified example above, the third partition wall 93 and the second inlet 94b may not be provided. In this case, the first inlet 94a is preferably disposed 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 emitting side.

[0129] 2.4.5 Fifth Variation

[0130] Figure 11 The structure of the wavelength conversion device 70 in the fifth modification is shown in general. The structure of the unit 72 of the wavelength conversion device 70 in this modification is different from that of the wavelength conversion device 70 in the above embodiment.

[0131] In this modified example, the entrance window 73 and the exit window 74 are not provided in unit 72. Therefore, O-rings 75a and 75b and window supports 76a and 76b are not provided in unit 72. In this modified example, unit 72 is cylindrical, with openings at both the light entrance and exit ends. In this modified example, the opening on the entrance side of unit 72 is the first outlet 95a, and the opening on the exit side of unit 72 is the second outlet 95b. In this modified example, gas exhaust pipes 97a and 97b are not provided.

[0132] The structures of the first cylindrical component 90a, the second cylindrical component 90b, the first partition wall 92a, the second partition wall 92b, and the third partition wall 93 in this modified example are the same as those in the above-described embodiment.

[0133] Therefore, in this modified example, a first outlet 95a is provided in the optical path of the incident light incident on the wavelength conversion crystal 80, and a second outlet 95b is provided in the optical path of the outgoing light emitted from the wavelength conversion crystal 80. Furthermore, in this modified example, the opening of the first cylindrical member 90a on the side opposite to the wavelength conversion crystal 80 is included in the first outlet 95a, and the opening of the second cylindrical member 90b on the side opposite to the wavelength conversion crystal 80 is included in the second outlet 95b.

[0134] In this modified example, the purge gas G introduced into the unit 72 from the first inlet 94a flows between the end of the first cylindrical member 90a and the end of the wavelength conversion crystal 80, along the incident side end face 80a of the wavelength conversion crystal 80. Then, the purge gas G flows through the internal space 91a of the first cylindrical member 90a to the side opposite to the wavelength conversion crystal 80 and is discharged from the first outlet 95a.

[0135] In this modified example, the purge gas G introduced into the unit 72 from the second inlet 94b flows along the emission side end face 80b of the wavelength conversion crystal 80 between the end of the second cylindrical member 90b and the end of the wavelength conversion crystal 80. Then, the purge gas G flows through the internal space 91b of the second cylindrical member 90b to the side opposite to the wavelength conversion crystal 80 and is discharged from the second outlet 95b.

[0136] In this modified example, since O-rings 75a and 75b are not provided in unit 72, contaminants caused by O-rings 75a and 75b will not adhere to the surface of the wavelength conversion crystal 80. Furthermore, in this modified example, although unit 72 is not sealed, the purging gas G flows away from the surface of the wavelength conversion crystal 80, thus suppressing moisture and impurities from reaching the surface of the wavelength conversion crystal 80, maintaining a low humidity around the wavelength conversion crystal 80.

[0137] Furthermore, in this modified example, since the incident window 73 and the exit window 74 are not provided in unit 72, there is no reduction in light transmittance caused by the deterioration of the incident window 73 and the exit window 74. In addition, in this modified example, the expensive incident window 73 and the exit window 74 are not required, thus simplifying the structure of the wavelength conversion device 70 and reducing manufacturing costs.

[0138] Furthermore, regarding the wavelength conversion device 70 of this modified example, as described in the third modified example above, the third partition wall 93 and the second inlet 94b may not be provided. In this case, the first inlet 94a is preferably disposed 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 emitting side.

[0139] Furthermore, in the above embodiments and their variations, a first component comprising a first cylindrical member 90a, a first partition wall 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 comprising a second cylindrical member 90b, a second partition wall 92b, a second inlet 94b, and a second outlet 95b is provided on the light emitting side of the wavelength conversion crystal 80. It is not necessary to provide both the first and second components; either the first or the second component may be provided.

[0140] The foregoing description is not intended to be limiting but merely illustrative. Therefore, it will be apparent to those skilled in the art that modifications can be made to the embodiments of this disclosure without departing from the appended claims.

[0141] The terms used in this specification and the appended claims should be interpreted as “non-limiting” terms. For example, the terms “comprising” or “including” should be interpreted as “not limited to the parts described as included”. The term “having” should be interpreted as “not limited to the parts described as having”. Furthermore, the phrase “a” recorded in this specification and the appended claims should be interpreted as “at least one” or “one or more”.

[0142] The foregoing description is not limiting but merely illustrative. Therefore, modifications to the embodiments of this disclosure can be made without departing from the claims, as will be apparent to those skilled in the art. Furthermore, combinations and variations of the embodiments of this disclosure will also be apparent to those skilled in the art. Unless otherwise expressly stated, all terms used in this specification and claims should be interpreted as "non-limiting." For example, terms such as "comprising," "having," "possessing," and "complementing" should be interpreted as "not excluding the presence of constituent elements other than those described." Additionally, the modifier "a" should be interpreted as "at least one" or "one or more." Furthermore, terms such as "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," and should also be interpreted as including combinations thereof with content other than "A," "B," and "C."

Claims

1. A wavelength conversion device, wherein, The wavelength conversion device includes: Wavelength conversion crystal, which converts the wavelength of incident light to emit outgoing light; A support that holds the wavelength conversion crystal in the optical path of the incident light; The unit internally houses the wavelength conversion crystal and the support, and has a first inlet for supplying purge gas into the interior and a first outlet for discharging the purge gas from the interior. The first cylindrical component, the optical path of the incident light passes through the internal space of the first cylindrical component, and the first cylindrical component is separately configured from the wavelength conversion crystal; as well as A first partition wall is disposed between the first inlet and the first outlet to hold the first cylindrical component.

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

3. The wavelength conversion device according to claim 1, wherein, The purging gas flows in the internal space of the first cylindrical component in a direction away from the wavelength conversion crystal.

4. The wavelength conversion device according to claim 1, wherein, The unit has a second outlet from which the purge gas is discharged from the interior. The first outlet is configured on the light incident side of the wavelength conversion crystal, and the second outlet is configured on the light emitting side of the wavelength conversion crystal.

5. The wavelength conversion device according to claim 4, wherein, The wavelength conversion device includes: The second cylindrical component has the optical path of the emitted light passing through the internal space of the second cylindrical component, and the second cylindrical component is separately configured from the wavelength conversion crystal; as well as A second partition wall is disposed between the first inlet and the second outlet to hold the second cylindrical component.

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

7. The wavelength conversion device according to claim 5, wherein, The wavelength conversion device includes a third partition wall that defines the space on the light incident side and the space on the light emitting side of the internal wavelength conversion crystal.

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

9. The wavelength conversion device according to claim 7, wherein, The third partition wall is disposed between the outer periphery of the bracket and the inner wall of the unit. A gap is provided between the third partition wall and the support.

10. The wavelength conversion device according to claim 7, wherein, The unit has a second inlet for supplying the purge gas into the interior. The first inlet is disposed in the space on the light incident side, and the second inlet is disposed in the space on the light emitting side. The second partition wall is disposed between the second inlet and the second outlet.

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

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

13. The wavelength conversion device according to claim 5, wherein, The incident window, which is disposed in the optical path of the incident light, and the exit window, which is disposed in the optical path of the exit light, are respectively fixed to the unit through an O-ring.

14. The wavelength conversion device according to claim 13, wherein, The end of the first cylindrical component opposite to the wavelength conversion crystal extends further toward the incident window than the first outlet. The end of the second cylindrical component opposite to the wavelength conversion crystal extends further toward the emission window than the second outlet.

15. The wavelength conversion device according to claim 14, wherein, The end of the first cylindrical component opposite to the wavelength conversion crystal is close to the incident window and separate from the incident window and the unit. The end of the second cylindrical component opposite to the wavelength conversion crystal is close to the emission window and separate from the emission window and the unit.

16. The wavelength conversion device according to claim 5, wherein, The first outlet is configured in the optical path of the incident light, and the second outlet is configured in the optical path of the outgoing light.

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