Wavelength Converter

Abstract

This embodiment is a wavelength converter, and the wavelength converter includes: a nonlinear optical crystal; a guide light source that provides guide light traveling in a first direction within the nonlinear optical crystal so that a thermal waveguide penetrating the nonlinear optical crystal is formed; a signal light source that provides signal light of a first wavelength λ1 traveling in a second direction opposite to the first direction through the thermal waveguide; and a pump light source that provides pump light of a second wavelength λ2 traveling in the second direction through the thermal waveguide, and output light including wavelength components corresponding to the sum of the energies of the first wavelength λ1 and the second wavelength λ2 is provided from the thermal waveguide.

Description

[Technical Field]

[0001] The present disclosure relates generally to wavelength converters. [Background technology]

[0002] Lasers are used in a wide variety of applications in modern society, from pointing, writing, and measuring distances in presentations to cosmetic applications, cutting metals, and welding. Lasers emit light with a single wavelength (single frequency), and the wavelength of a laser is affected by the material properties of the gain medium and cavity that form the laser. Summary of the Invention [Problem to be solved by the invention]

[0003] Research is ongoing into technologies that use nonlinear optical crystals to convert laser wavelengths. Conventional technologies are limited to providing light of a single wavelength to a nonlinear optical crystal and outputting light of a single predetermined wavelength, and are unable to change the wavelength of the output light over a wide range.

[0004] One of the problems to be solved by this embodiment is to overcome the drawbacks of the conventional technology, and to provide a wavelength converter that can control the wavelength of output light within a desired range. [Means for solving the problem]

[0005] The wavelength converter of this embodiment includes: a nonlinear optical crystal; a guide light source that provides guide light traveling in a first direction within the nonlinear optical crystal so that a thermal waveguide is formed through the nonlinear optical crystal; a signal light source that provides signal light of a first wavelength λ1 traveling in a second direction opposite to the first direction through the thermal waveguide; and a pump light source that provides pump light of a second wavelength λ2 traveling in the second direction through the thermal waveguide, and output light having a wavelength component corresponding to the sum of the energies of the first wavelength λ1 and the second wavelength λ2 is output from the thermal waveguide.

[0006] The wavelength converter according to this embodiment includes: a nonlinear optical crystal; a guide light source that provides guide light traveling in a first direction within the nonlinear optical crystal so that a thermal waveguide is formed through the nonlinear optical crystal; a signal light source that provides signal light of a first wavelength λ1 traveling in the first direction through the thermal waveguide; and a pump light source that provides pump light of a second wavelength λ2 traveling in the first direction through the thermal waveguide, and output light including a wavelength component corresponding to the sum of the energies of the first wavelength λ1 and the second wavelength λ2 is output from the thermal waveguide.

[0007] According to one aspect of this embodiment, the nonlinear optical crystal is a PPLN crystal, and the wavelength of the guide light is 532 nm.

[0008] According to one aspect of this embodiment, the nonlinear optical crystal has different periods depending on the position of the nonlinear optical crystal, and the wavelength of the output light corresponds to the period formed in the thermal waveguide.

[0009] According to one aspect of this embodiment, the nonlinear optical crystal includes any one of a KTP-series material such as PKTP, a KDP-series material, an ADP-series material, a BBO-series material, a KTA-series material, a GaSe-series material, a GaAs-series material, and a GAP-series material.

[0010] According to one aspect of this embodiment, the wavelength of the nonlinear optical crystal guided light made of the KTP-series material is 532 nm, the wavelength of the nonlinear optical crystal guided light made of the KDP-series material is 1.3 um, the wavelength of the nonlinear optical crystal guided light made of the ADP-series material is 1.08 um, the wavelength of the nonlinear optical crystal guided light made of the BBO-series material is 2.5 um, the wavelength of the nonlinear optical crystal guided light made of the KTA-series material is 5 um, and the wavelength of the nonlinear optical crystal guided light made of the GaSe-series material is 0.65 um.

[0011] According to one aspect of this embodiment, the wavelength converter further includes a position adjustment unit that controls the position of the nonlinear optical crystal, and the wavelength of the output light varies depending on the position of the nonlinear optical crystal controlled by the position adjustment unit.

[0012] According to one aspect of this embodiment, the output light output from the thermal waveguide includes a wavelength corresponding to the difference in energy between the first wavelength λ1 and the second wavelength λ2.

[0013] According to one aspect of the present embodiment, the wavelength converter further includes a guide optical system that adjusts a spot size of the beam of the guide light provided by the guide light source, a signal optical system that adjusts a spot size of the beam of the signal light provided by the signal light source, and a pump optical system that adjusts a spot size of the beam of the pump light provided by the pump light source.

[0014] According to one aspect of the present embodiment, the wavelength converter further includes an optical system that adjusts spot sizes of the guide light, the pump light, and the signal light.

[0015] According to one aspect of this embodiment, the spot size of the guide light beam, the spot size of the signal light beam, and the spot size of the pump light are adjusted to be the same as each other. [Effects of the Invention]

[0016] According to this embodiment, a wavelength converter capable of controlling the wavelength of output light over a wide wavelength range is provided. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a diagram illustrating an overview of a wavelength converter according to one embodiment;

[0018] [Figure 2] 10 is a diagram illustrating an outline of a wavelength converter according to another embodiment;

[0019] [Figure 3] 10 is a diagram illustrating an outline of a wavelength converter according to another embodiment;

[0020] [Figure 4] 10 is a diagram illustrating an outline of a wavelength converter according to another embodiment;

[0021] [Figure 5] 1 is a diagram illustrating an outline of a nonlinear optical crystal.

[0022] [Figure 6] 1 is a diagram illustrating wavelengths that can be generated in a PPLN nonlinear optical crystal.

[0023] [Figure 7] 1 is a diagram illustrating wavelengths generated depending on the conditions of an OP-GaAs nonlinear optical crystal.

[0024] [Figure 8] 10 is a graph showing the efficiency of a nonlinear optical crystal formed of PPLN in a state where a thermal waveguide is not formed and in a state where a thermal waveguide is formed.

[0025] [Figure 9] 1 is a diagram showing the results of measuring the increase in conversion efficiency due to wavelength tunability in a nonlinear optical crystal formed from PPLN. DETAILED DESCRIPTION OF THE INVENTION

[0026] Hereinafter, this embodiment will be described with reference to the accompanying drawings. Figures 1 and 2 are diagrams illustrating an overview of a wavelength converter 10 according to this embodiment. Referring to Figures 1 and 2, the wavelength converter 10 according to this embodiment includes a nonlinear optical crystal 100, a guide light source 210 that outputs guide light so that a thermal waveguide is formed in an optical path passing through the nonlinear optical crystal 100, a signal light source 220 that provides signal light of a first wavelength λ1 through the thermal waveguide (110, see Figure 5), and a pump light source 230 that provides pump light of a second wavelength λ2 through the thermal waveguide (110, see Figure 5). Output light O having a wavelength corresponding to the sum of the energies of the first wavelength λ1 and the second wavelength λ2 is output from the thermal waveguide (110, see Figure 5).

[0027] 1, the guide light source 210 can provide the guide light GL in the same direction as the signal light SL and the pump light PL travel in the optical path. In the embodiment illustrated in FIG. 1, the guide light GL, the signal light SL, and the pump light PL are provided to the nonlinear optical crystal 100 through a single first optical system 510. However, as in the embodiment illustrated in FIG. 2, the guide light GL provided by the guide light source 210 can be provided to the nonlinear optical crystal 100 through a guide optical system 510g, the signal light SL provided by the signal light source 220 can be provided to the nonlinear optical crystal 100 through a signal optical system 510s, and the pump light PL provided by the pump light source 230 can be provided to the nonlinear optical crystal 100 through a pump optical system 510g.

[0028] 3, the guide light source 210 can provide the guide light GL in the direction opposite to the direction in which the signal light SL and the pump light PL travel within the optical path. As in the embodiment illustrated in FIG. 4, the signal light SL provided by the signal light source 220 can be provided to the nonlinear optical crystal 100 through a signal optical system 510s, and the pump light PL provided by the pump light source 230 can be provided to the nonlinear optical crystal 100 through a pump optical system 510g. In an embodiment not shown, the guide light provided by the guide light source can be provided to the nonlinear optical crystal 100 through a guide optical system.

[0029] 5 is a diagram illustrating an outline of a nonlinear optical crystal 100. Referring to FIGS. 1 to 5, the nonlinear optical crystal 100 has a fanout optical crystal structure. As illustrated in FIG. 5, the nonlinear optical crystal 100 has a crystal arrangement period that varies depending on the position. As illustrated, the crystal arrangement period at one position of the nonlinear optical crystal 100 may be T1, and the crystal arrangement period at another position may be T2.

[0030] In one embodiment, the nonlinear optical crystal may be a PPLN (periodically poled lithium niobate) series material. In another embodiment, the nonlinear optical crystal may be any one of a KTP series material such as PPKTP, a KDP series material, an ADP series material, a BBO series material, a KTA series material, a GaSe series material, a GaAs series material, and a GAP series material.

[0031] The guide light source 210 provides guide light GL to the nonlinear optical crystal 100 to form a thermal waveguide 110 in the nonlinear optical crystal 100. Generally, a waveguide can be formed by contacting materials having different refractive indices. However, if a waveguide is formed by contacting the nonlinear optical crystal 100 with a separate material having a different refractive index, the output light is limited to a single wavelength.

[0032] When the guide light GL is provided to the nonlinear optical crystal 100 as in this embodiment, the energy of the guide light GL is absorbed by the nonlinear optical crystal 100. The absorption of the energy by the nonlinear optical crystal 100 changes the refractive index around the optical path, and due to the changed refractive index, a waveguide is formed around the optical path, similar to when materials having different refractive indices are in contact with each other, and this is called a thermal waveguide (110).

[0033] As an example, the wavelength of the guide light GL may vary depending on the material properties of the nonlinear optical crystal 100. For example, if the nonlinear optical crystal 100 is PPLN, the guide light GL may be light in the green band, and may have a wavelength of, for example, 532 nm.

[0034] Figure 6 is a diagram illustrating wavelengths that can be generated in a PPLN nonlinear optical crystal. Referring to Figure 6, when the wavelength of pump light is set to 1064 nm and incident on the nonlinear optical crystal 100, it can be seen that two wavelength bands of light, signal light shown in gray and idler light shown in black, are generated. The vertical lines indicate the conditions under which the signal and idler can be generated simultaneously. Therefore, it can be seen that the wavelength generated varies depending on the polling period of the nonlinear crystal, which is shown on the horizontal axis.

[0035] Figure 7 shows the wavelength generated depending on the conditions of an OP-GaAs nonlinear optical crystal. Referring to Figure 7, in the case of OP-GaAs, as in PPLN, different signal idlers are generated depending on the wavelength of the pump light (light gray and dark gray are the results when tuning the pump using crystals with different periods). Therefore, in the case of an OP-GaAs nonlinear optical crystal, it is possible to control the wavelength of the output light by controlling the period of the optical crystal where the thermal waveguide is formed.

[0036] As an example, the wavelength of the signal light SL provided by the signal light source 220 and input to the thermal waveguide 110 and the wavelength of the pump light PL provided by the pump light source 230 and input to the thermal waveguide 110 may differ depending on the properties of the material constituting the nonlinear optical crystal 100. For example, if the nonlinear optical crystal 100 is made of PPLN, the wavelength of the signal light SL may be 1550 nm and the wavelength of the pump light PL may be 1064 nm.

[0037] The wavelength of the guide light may vary depending on the material constituting the nonlinear optical crystal. For example, LN-based materials such as PPLN and KTP-based materials such as PPKTP can use light with a wavelength of 532 nm as the guide light. KDP-based materials can use light with a wavelength of 1.3 μm, ADP-based materials can use light with a wavelength of 1.08 μm, BBO-based materials can use light with a wavelength of 2.5 μm, ZGP-based materials can use light with a wavelength of 1.9 μm, KTA-based materials can use light with a wavelength of 5 μm, and GaSe-based materials can use light with a wavelength of 0.65 μm. In other words, a wavelength band with high absorption irradiated by a material constituting a nonlinear optical crystal can be used as the guide light.

[0038] However, the materials constituting the nonlinear optical crystal 100 and the wavelengths of the signal light SL and pump light PL are not strictly defined, and effects similar to those disclosed herein can be obtained even when light of other wavelengths is used with the exemplified materials. Therefore, the materials constituting the optical crystal 100 and the wavelengths of the signal light SL and pump light PL are merely examples and are not intended to define the scope of the present invention.

[0039] Wavelength converter 10 includes a position adjuster 300 that adjusts the position of nonlinear optical crystal 100 relative to the optical path. In the illustrated embodiment, position adjuster 300 includes a mounting stage 310 on which nonlinear optical crystal 100 is mounted and positioned, a rod 320 that moves the mounting stage to change the position of the mounting stage, and a driver 330 that drives rod 320. In one embodiment, driver 330 may be a precision-controlled motor that can precisely control rod 320.

[0040] By moving the rod 320 using the driving unit 330, the position of the optical path passing through the nonlinear optical crystal 100 placed on the mounting table 310 can be changed, and therefore the position of the thermal waveguide 110 formed in the nonlinear optical crystal 100 can also be changed.

[0041] The operation of the wavelength converter 10 of this embodiment will be described in detail below with reference to the accompanying drawings. Referring to FIG. 1, a guide light source 210 provides a guide light GL. The light provided by the guide light is reflected by reflecting members M1 and M2 and provided to the nonlinear optical crystal 100 through the first optical system 510. As described above, the light provided to the nonlinear optical crystal 100 is absorbed by the nonlinear optical crystal 100, causing a change in the refractive index and forming the thermal waveguide 110.

[0042] The signal light SL provided by the signal light source 220 passes through the reflecting members M3 and M2 and is provided to the first optical system 510. Also, the pump light PL provided by the pump light source 230 is reflected by the reflecting members M4 and M3 and is provided to the first optical system 510. Also, as in the embodiment illustrated in Fig. 2, the guide light GL provided by the guide light source 210 can be provided to the nonlinear optical crystal 100 through the guide optical system 510g, the signal light SL provided by the signal light source 220 can be provided to the nonlinear optical crystal 100 through the signal optical system 510s, and the pump light PL provided by the pump light source 230 can be provided to the nonlinear optical crystal 100 through the pump optical system 510g.

[0043] As an example, the reflecting member M1 may be formed of a mirror or a dichroic mirror that can reflect light of the wavelength of the guide light GL, the reflecting member M2 may be a dichroic mirror that reflects light of the wavelength of the guide light GL but transmits the signal light SL and the pump light PL, the reflecting member M4 may be formed of a mirror or a dichroic mirror that can reflect light of the wavelength of the pump light PL, and the reflecting member M3 may be a dichroic mirror that transmits light of the wavelength of the signal light SL but reflects light of the wavelength of the pump light PL.

[0044] The first optical system 510 receives the guide light GL, the signal light SL, and the pump light PL and provides them to the nonlinear optical crystal 100. In one embodiment, the first optical system 510 adjusts the beam spot sizes of the guide light GL, the signal light SL, and the pump light PL input to the nonlinear optical crystal 100 to be the same, and provides them to the nonlinear optical crystal 100.

[0045] The signal light SL and the pump light PL form wavelength-converted output light while propagating along the thermal waveguide 110. Since the conversion efficiency of the light that exits the thermal waveguide 110 and propagates within the nonlinear optical crystal 100 decreases, the first optical system 510 controls the spot size of the signal light SL and the pump light PL to be the same as the spot size of the guide light GL that forms the thermal waveguide 110.

[0046] The signal light SL and the pump light PL incident on the thermal waveguide 110 formed in the nonlinear optical crystal 100 form output light O having a wavelength corresponding to the sum of their respective energies and / or output light O having a wavelength corresponding to the difference between their respective energies. The output light O, the signal light SL, and the pump light PL are provided to the second optical system 520 and the first filter 610. The first filter 610 can selectively transmit light in a wavelength band corresponding to the output light O.

[0047] 3, a guide light source 210 provides a guide light GL. The light provided by the guide light is transmitted through a reflecting member M5 and provided to the nonlinear optical crystal 100 via a second filter 620. As an example, the second filter 620 may be a filter that transmits the guide light GL and the output light O but blocks the signal light SL and the pump light PL.

[0048] As described above, light provided to the nonlinear optical crystal 100 is absorbed by the nonlinear optical crystal 100, changing the refractive index and forming the thermal waveguide 110. In the embodiment illustrated in Fig. 2, the guide light GL propagates in the opposite direction to the direction in which the signal light SL and the pump light PL travel in the nonlinear optical crystal 100, forming the thermal waveguide 110. The guide light GL passes through the nonlinear optical crystal 100 but cannot pass through the reflecting member M2.

[0049] The signal light SL provided by the signal light source 220 passes through the reflecting members M3 and M2 and is provided to the first optical system 510. In addition, the pump light PL provided by the pump light source 230 is reflected by the reflecting members M4 and M3 and is provided to the first optical system 510.

[0050] The first optical system 510 receives the signal light SL and the pump light PL and provides them to the nonlinear optical crystal 100. In one embodiment, the first optical system 510 adjusts the beam spot sizes of the signal light SL and the pump light PL input to the nonlinear optical crystal 100 to be the same and provides them to the nonlinear optical crystal 100.

[0051] 4, the signal light SL provided by the signal light source 220 can be provided to the nonlinear optical crystal 100 through the signal optical system 510s, and the pump light PL provided by the pump light source 230 can be provided to the nonlinear optical crystal 100 through the pump optical system 510g. In an embodiment not shown, the guide light provided by the guide light source can be provided to the nonlinear optical crystal 100 through the guide optical system.

[0052] The signal light SL and the pump light PL form wavelength-converted output light O while propagating along the thermal waveguide 110. As described above, the conversion efficiency of the light that exits the thermal waveguide 110 and propagates within the nonlinear optical crystal 100 decreases, so the first optical system 510 controls the spot size of the signal light SL and the pump light PL to be the same as the spot size of the guide light GL that forms the thermal waveguide 110.

[0053] The signal light SL and the pump light PL incident on the thermal waveguide 110 formed in the nonlinear optical crystal 100 form output light O having a wavelength corresponding to the sum of their respective energies or output light O having a wavelength corresponding to the difference between their respective energies, and the output light O, the signal light SL, and the pump light PL are provided to the third optical system 530 and the second filter 620. The second filter 620 can selectively transmit light in a wavelength band corresponding to the output light O.

[0054] As shown, the guide light GL is provided to the nonlinear optical crystal 100 after passing through the reflecting member M5 and the second filter 620, and the signal light SL, the pump light PL, and the output light O output from the nonlinear optical crystal 100 are passed through the third optical system 530 and the second filter 620, reflected by the reflecting member M5, and then output. Therefore, the reflecting member M5 and the second filter 620 may be implemented as a dichroic mirror and an optical filter implemented to have corresponding reflection and transmission characteristics.

[0055] 5 to 7, a process of generating output light from signal light SL and pump light PL propagating through thermal waveguide 110 formed in nonlinear optical crystal 100 will be described. Referring to Fig. 5, nonlinear optical crystal 100 has a fanout optical crystal structure. Therefore, the period in which the crystals are arranged varies depending on the position in nonlinear optical crystal 100, and the period in which the crystals are arranged at one position in nonlinear optical crystal 100 may be T1, and the period in which the crystals are arranged at another position in nonlinear optical crystal 100 may be T2.

[0056] As an example, the wavelength of the output light O formed from the pump light PL and signal light SL propagating through the thermal waveguide 110 formed in the portion where the crystals are arranged at a period T1 is different from the wavelength of the output light O formed from the pump light PL and signal light SL propagating through the thermal waveguide 110 formed in the portion where the crystals are arranged at a period T2.

[0057] Therefore, by adjusting the position of the mounting table 310 so that the thermal waveguide 110 through which light propagates is formed in the desired portion within the nonlinear optical crystal 100, the position adjustment unit 300 can control the output of light having the desired wavelength.

[0058] As an example, the output light may have a wavelength corresponding to the sum of the energies of the pump light PL and the signal light SL. When the material of the nonlinear optical crystal 100 is PPLN, the wavelength of the light output from the nonlinear optical crystal 100 is expressed as follows in Equation 1: O is as follows:

[0059] [Mathematical formula 1]

[0060]

number

[0061] In another embodiment, the output light may have a wavelength corresponding to the difference in energy between the pump light PL and the signal light SL. In this case, when the material of the nonlinear optical crystal 100 is PPLN, the wavelength of the light output from the nonlinear optical crystal 100 can be calculated using the following mathematical formula 2. When the wavelength of the signal light SL is 1550 nm and the wavelength of the pump light PL is 1064 nm, the wavelength λ of the output light is O is as follows:

[0062] [Mathematical formula 2]

[0063]

number

[0064] The output light O thus formed can, for example, output all wavelengths corresponding to the sum component of the energy and the difference component, or can output only a wavelength corresponding to one of the components.

[0065] Therefore, by adjusting the position of the mounting table 310 using the position adjusting unit 300 so that the thermal waveguide 110 through which the light propagates is formed in the desired portion within the nonlinear optical crystal 100, it is possible to control the output of light having a desired wavelength. Furthermore, by precisely adjusting the wavelengths of the pump light PL and the signal light SL and the positions at which they are incident on the nonlinear optical crystal 100, it is possible to obtain the effect of being able to control the wavelength of the output light over a wide range.

[0066]

[0067] Experimental example

[0068] Figure 8 is a graph showing the efficiency of a nonlinear optical crystal formed from PPLN when a thermal waveguide is not formed and when a thermal waveguide is formed. Referring to Figure 8, the lower solid line with low amplitude represents the output light output from the nonlinear crystal when a thermal waveguide is not formed, and the upper solid line with large amplitude represents the magnitude of the output optical signal when a thermal waveguide is created by the guide light. As clearly shown in Figure 9, the magnitude of the output light increases by forming a thermal waveguide, and it can be seen that wavelength-converted output light can be obtained with higher efficiency.

[0069] Figure 9 shows the results of measuring the increase in conversion efficiency due to wavelength tuning of a nonlinear optical crystal formed from PPLN. Referring to Figure 9, when the thermal waveguide is induced, wavelength-converted signals can be seen in a wide wavelength range from 3064 nm to 3393 nm, and the conversion efficiency is approximately double that of signals generated from a nonlinear crystal in a normal state.

[0070]

[0071] Although the present invention has been described with reference to the embodiments shown in the drawings to facilitate understanding of the present invention, these are merely illustrative examples for implementation, and those skilled in the art will recognize that various modifications and equivalent embodiments are possible. Therefore, the true technical scope of the present invention should be determined by the appended claims.

Claims

1. Nonlinear optical crystals; a guide light source that provides guide light traveling in a first direction within the nonlinear optical crystal so that a thermal waveguide penetrating the nonlinear optical crystal is formed; a signal light source that provides signal light of a first wavelength (λ1) traveling through the thermal waveguide in a second direction opposite to the first direction; a pump light source that provides pump light of a second wavelength (λ2) traveling in the second direction through the thermal waveguide; A wavelength converter, wherein output light including a wavelength component corresponding to the sum of the energies of the first wavelength (λ1) and the second wavelength (λ2) is provided from the thermal waveguide.

2. The nonlinear optical crystal is It is a PPLN series material, 2. The wavelength converter of claim 1, wherein the wavelength of the guide light is 532 nm.

3. The nonlinear optical crystal is The nonlinear optical crystal has different periods depending on the position, 2. The wavelength converter of claim 1, wherein the wavelength of the output light corresponds to the period formed in the thermal waveguide.

4. The nonlinear optical crystal is 2. The wavelength converter of claim 1, comprising any one of a KTP-based material such as PKTP, a KDP-based material, an ADP-based material, a BBO-based material, a KTA-based material, a GaSe-based material, a GaAs-based material, and a GAP-based material.

5. 5. The wavelength converter of claim 4, wherein the wavelength of the nonlinear optical crystal guided light made of the KTP-based material is 532 nm, the wavelength of the nonlinear optical crystal guided light made of the KDP-based material is 1.3 μm, the wavelength of the nonlinear optical crystal guided light made of the ADP-based material is 1.08 μm, the wavelength of the nonlinear optical crystal guided light made of the BBO-based material is 2.5 μm, the wavelength of the nonlinear optical crystal guided light made of the KTA-based material is 5 μm, and the wavelength of the nonlinear optical crystal guided light made of the GaSe-based material is 0.65 μm.

6. The wavelength converter comprises: Further comprising a position adjusting unit for controlling the position of the nonlinear optical crystal, 4. The wavelength converter according to claim 3, wherein the wavelength of the output light varies depending on the position of the nonlinear optical crystal controlled by the position adjusting unit.

7. In paragraph 1, The output light output from the thermal waveguide is 2. The wavelength converter of claim 1, comprising a wavelength corresponding to a difference in energy between the first wavelength (.lambda.1) and the second wavelength (.lambda.2).

8. In paragraph 1, The wavelength converter comprises: a guide optical system for adjusting a spot size of the beam of the guide light provided by the guide light source; a signal optical system for adjusting a spot size of the beam of the signal light provided by the signal light source; The wavelength converter of claim 1 , further comprising a pump optical system for adjusting a spot size of the pump light provided by the pump light source.

9. In paragraph 1, The wavelength converter comprises: The wavelength converter of claim 1 , further comprising an optical system for adjusting spot sizes of the guide light, the pump light, and the signal light.

10. 10. The wavelength converter according to claim 8, wherein the spot size of the guide light beam, the spot size of the signal light beam, and the spot size of the pump light are adjusted to be identical to each other.

11. Nonlinear optical crystals; a guide light source that provides guide light traveling in a first direction within the nonlinear optical crystal so that a thermal waveguide penetrating the nonlinear optical crystal is formed; a signal light source that provides signal light of a first wavelength (λ1) traveling in the first direction through the thermal waveguide; a pump light source that provides pump light of a second wavelength (λ2) traveling in the first direction through the thermal waveguide; A wavelength converter, wherein output light including a wavelength component corresponding to the sum of the energies of the first wavelength (λ1) and the second wavelength (λ2) is provided from the thermal waveguide.

12. The nonlinear optical crystal is It is a PPLN series material, The wavelength converter of claim 11 , wherein the wavelength of the guide light is 532 nm.

13. The nonlinear optical crystal is The nonlinear optical crystal has different periods depending on the position, 12. The wavelength converter of claim 11, wherein the wavelength of the output light corresponds to the period formed in the thermal waveguide.

14. The nonlinear optical crystal is 12. The wavelength converter of claim 11, comprising any one of a KTP-based material such as PKTP, a KDP-based material, a BDP-based material, a BBO-based material, a KTB-based material, a GaSe-based material, a GaAs-based material, and a GaP-based material.

15. 15. The wavelength converter of claim 14, wherein the wavelength of the nonlinear optical crystal guided light made of the KTP-based material is 532 nm, the wavelength of the nonlinear optical crystal guided light made of the KDP-based material is 1.3 μm, the wavelength of the nonlinear optical crystal guided light made of the BDP-based material is 1.08 μm, the wavelength of the nonlinear optical crystal guided light made of the BBO-based material is 2.5 μm, the wavelength of the nonlinear optical crystal guided light made of the KTB-based material is 5 μm, and the wavelength of the nonlinear optical crystal guided light made of the GaSe-based material is 0.65 μm.

16. The wavelength converter comprises: Further comprising a position adjusting unit for controlling the position of the nonlinear optical crystal, 14. The wavelength converter according to claim 13, wherein the wavelength of the output light varies depending on the position of the nonlinear optical crystal controlled by the position adjusting unit.

17. The output light output from the thermal waveguide is 12. The wavelength converter of claim 11, comprising a wavelength corresponding to a difference in energy between the first wavelength (λ1) and the second wavelength (λ2).

18. The wavelength converter comprises: a guide optical system for adjusting a spot size of the beam of the guide light provided by the guide light source; a signal optical system for adjusting a spot size of the beam of the signal light provided by the signal light source; The wavelength converter of claim 11 , further comprising pump optics for adjusting a spot size of the pump light provided by the pump light source.

19. The wavelength converter comprises: The wavelength converter of claim 11 , further comprising an optical system for adjusting spot sizes of the guide light, the pump light, and the signal light.

20. 20. The wavelength converter according to claim 18, wherein the spot size of the guide light beam, the spot size of the signal light beam, and the spot size of the pump light are adjusted to be identical to each other.

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