Optical device

Abstract

An optical device (300) which comprises a carrier substrate (303) having good thermal conductivity, an optical element chip (302) including an optical element disposed on the carrier substrate (303), a temperature control element (305) for changing the temperature of the carrier substrate (303), optical systems (310, 311) which optimize an optical input or an optical output and are positioned on the optical input and / or the optical output of the optical element, and one or more optical fibers (309, 312) which are optically coupled to the optical systems (310, 311), wherein the temperature control element (305) has an upper substrate (306) bonded to the carrier substrate (303), and lc>lp and wc>wp, if the length of the carrier substrate (303) in the longitudinal direction of the carrier substrate (303) is lc, the length of the upper substrate (306) in said direction is lp, the thickness of the carrier substrate (303) is wc, and the thickness of the upper substrate (306) is wp. This configuration makes it possible to reduce carrier substrate (303) warpage caused by temperature changes.

Description

Optical device

[0001] The present disclosure relates to an optical device, and more particularly to an optical device including: an optical element chip comprising an optical element having a semiconductor laser or an optical parametric amplification function; a carrier substrate made of a material with high thermal conductivity, on the upper surface of which the optical element chip is disposed; and a temperature control element.

[0002] In an optical device on which an optical element such as an optical circuit mounting a semiconductor laser or a waveguide having a periodically poled inversion structure is mounted, temperature control is performed on the carrier substrate on which the optical element is mounted, and a temperature control element such as a Peltier element is used for this temperature control. In particular, a periodically poled lithium niobate (hereinafter referred to as "PPLN") waveguide device that realizes a broadband wavelength conversion element exhibits temperature-sensitive behavior, so a carrier substrate with high thermal conductivity is used to uniformly transfer heat to the entire optical element chip on which the PPLN waveguide is formed. The temperature control element is also used as a member for supporting the chip substrate, and the upper surface member of the temperature control element is bonded to the carrier substrate of the chip of the optical device (Patent Document 1).

[0003] FIG. 1 shows, as an example of an optical device having a temperature control function, a mounting structure of an optical device including a PPLN waveguide as an optical element. The optical device 100 includes: an optical assembly 104 composed of an optical element chip 102 and a carrier substrate 103; a temperature control element 105; an input-side optical system 110 that optimizes and couples light from an input-side optical fiber 109 to the light input side of the optical element chip 102; and an output-side optical system 111 that optimizes and couples light from the output side of the optical element chip 102 to an output-side optical fiber 112.

[0004] In FIG. 1, the input-side optical system 110 and the output-side optical system 111 are depicted as a single lens, but any optical system that optimizes optical coupling between the optical input / output unit of the optical element chip and the corresponding optical fiber may be configured with a plurality of lenses, or an optical system other than lenses may be used. Each member constituting the optical device is housed in a case 101.

[0005] Note that when the optical device 100 is used for difference frequency generation and parametric amplification, the input-side optical fiber 109 is composed of two fibers for pump light and signal light, and the input-side optical system 110 is also composed of two sets of lens optical systems corresponding to the respective optical fibers. Similarly, on the output side, the output-side optical fiber 112 is composed of two fibers for signal light and idler light, and the output-side optical system 111 is also composed of two sets of lens optical systems corresponding to the respective optical fibers.

[0006] The temperature control element 105 of the optical device 100 in FIG. 1 is a Peltier element, and the Peltier element is composed of an upper substrate 106 that is a member constituting the upper surface thereof, a lower substrate 107 that constitutes the lower surface thereof, and a Seebeck element 108. The upper substrate 106 is adhesively bonded to a carrier substrate 103 having an optical element chip on the upper surface thereof. The lower substrate 107 is fixed to the bottom surface of the case 101. Accordingly, the optical assembly 104 is supported at the center by the Peltier element 105.

[0007] FIG. 2 is a schematic diagram showing a bonding shape between the carrier substrate 103 of the optical device 100 in FIG. 1 and the upper substrate which is a member constituting the upper surface of the temperature control element 105. FIG. 2(a) shows the state of the bonding shape of the carrier substrate 103 and the upper substrate 106 when thermal stress at the interface between the carrier substrate 103 and the upper substrate of the Peltier element 105 is zero. At this time, no warpage occurs in the carrier substrate 103 and the upper substrate 106.

[0008] FIG. 2(b) shows a changed state of the bonding shape between the carrier substrate 103 and the upper substrate 106 when the temperature is changed by the Peltier element 105. The carrier substrate 103 and the upper substrate 106 are formed of different materials. Therefore, when the temperature is changed from the state where thermal stress at the interface is zero, thermal stress is generated at the interface due to the difference in coefficient of thermal expansion and Young's modulus of the respective members, and warpage occurs in the bonded shape.

[0009] In conventional optical devices, where a carrier substrate and a component forming the upper surface of a temperature control element are bonded together, changing the temperature using the temperature control element causes warping of the carrier substrate, resulting in displacement of the longitudinal end of the carrier substrate (in this example, the z-axis direction, which is the direction of light propagation). As a result, the input and output waveguides of the optical element chip 102 placed on the carrier substrate are also displaced, leading to optical axis misalignment and a problem that worsens the coupling efficiency with the input / output optical system.

[0010] In particular, when the optical element is a PPLN waveguide, the length of the carrier substrate in the longitudinal direction (the z-axis direction, which is the direction of light propagation) in Figure 1 is longer for the PPLN chip than for the Peltier element substrate, so the effect of optical axis misalignment becomes more pronounced.

[0011] International Publication No. 2021 / 214897

[0012] S. Timoshenko, "Analysis of Bi-Metal Thermostats," J. Opt. Soc. Am. Vol. 11, pp. 233-255 (1925)https: / / ebinadk.com / tech / ceramic-kiban / Takushi Kazama et al., "Over-30-dB gain and 1-dB noise figure phase-sensitive amplification using a pump-combiner-integrated fiber I / O PPLN module," Opt. Express vol. 29, pp. 28824-28834 (2021)A. Aratake et al., “Highly Reliable Silica-LiNbO3 Hybrid Modulator Using Heterogeneous Material Integration Technology," IEICE TRANSACTIONS on Electronics Vol.E103-C pp.353-361 (2020)S. Shimizu et al. al., "L- and U-Band WDM Transmission Over 6 THz Using PPLN-Based Optical Parametric Amplification and Wavelength-Band Conversion," J. Lightwave Technol., vol. 42, pp. 1347-1355 (2024)https: / / www.thorlabs.co.jp / _sd.cfm?fileName=QTN049881-S01.pdf&partNumber=DFB1550

[0013] This disclosure aims to solve the above problem by reducing the influence of displacement of the optical input / output section of an optical element chip due to warping of the carrier substrate that occurs when the temperature is changed by a temperature control element, that is, by providing an optical device equipped with a carrier structure that reduces warping of the carrier substrate due to temperature changes.

[0014] One embodiment of the present disclosure includes a thermally conductive carrier substrate, an optical element chip including an optical element disposed on the carrier substrate, a temperature control element for changing the temperature of the carrier substrate, an optical system for optimizing the optical input or output disposed on at least one of the optical input and optical output of the optical element, and one or more optical fibers optically coupled to the optical system, wherein the temperature control element has an upper substrate bonded to the carrier substrate, and the length of the carrier substrate is l in the longitudinal direction of the carrier substrate. c The length of the upper board is l p The thickness of the carrier substrate is w c The thickness of the upper substrate is w p When that happens, l c >l p And lol c >w p It is an optical device.

[0015] This configuration makes it possible to reduce warping of the carrier substrate due to temperature changes.

[0016] Figure 1 is a diagram showing the schematic configuration of a conventional optical device mounting structure. Figure 2 is a schematic diagram showing the bonded shape of the carrier substrate and upper substrate of the optical device in Figure 1, where Figure 2(a) shows the state when the thermal stress at the interface between the carrier substrate and the upper substrate is zero, and Figure 2(b) shows the state when the temperature is changed. Figure 3 is a diagram of an optical device according to an embodiment of the present disclosure, where Figure 3(a) is a cross-sectional view showing the schematic configuration of the mounting structure of the optical device, and Figure 3(b) is a top view of the optical assembly. Figure 4 is a diagram illustrating the concept for applying the deformation amount calculation formula of Non-Patent Document 1 to the bonded structure of the carrier substrate and upper substrate of the optical device according to an embodiment of the present disclosure. Figure 4(a) is a schematic diagram of the bonded shape of the carrier substrate and upper substrate, Figure 4(b) is a schematic diagram of the bonded shape of the carrier substrate and upper substrate for calculation, and Figure 4(c) shows the displacement δ from the center of the upper substrate to the edge of the upper substrate. Figure 5 shows the displacement δ from the center to the end face of the bonded structure of the carrier substrate and the upper substrate, and the displacement Δy and Δθ from the center to the end face of the carrier substrate, which is the optical element chip end. Figure 6 shows the calculation results of the change in the amount of change at the end of the carrier substrate due to temperature change for Examples 1 to 3 of this embodiment. Figure 7 shows the calculation results of the change in the amount of change at the end of the carrier substrate due to temperature change for examples of this embodiment, with Figure 7(a) showing the calculation results for Examples 4 to 6 and Figure 7(b) showing the calculation results for Examples 7 to 9. Figure 8 is a table showing the Young's modulus and thermal expansion coefficient of the example materials. Figures 9(a) to (c) show the cross-sectional shape of the carrier substrate as viewed from the longitudinal end face.

[0017] Embodiments of this disclosure will be described in detail below with reference to the drawings. The following description is illustrative, and embodiments with modified configurations are possible without departing from the gist of this disclosure. Identical or similar reference numerals indicate identical or similar elements, and repeated descriptions may be omitted. Numerical values ​​in the following description are illustrative, and other numerical values ​​may be used in carrying out this disclosure without departing from the gist of this disclosure.

[0018] In the following explanation, we will use an optical element with a parametric optical amplification function as an example of an optical element placed on a carrier substrate. However, any optical element requiring temperature control can be mounted on the carrier substrate; for example, an integrated circuit type silicon photonic optical element with a semiconductor laser mounted on it may be used. Furthermore, while we will use a Peltier element as an example of a temperature control element in the following explanation, a heater or the like may be used as a heat source element.

[0019] Figure 3 shows an optical device 300 on which an optical element chip 302 having an optical element with an optical parametric amplification function is mounted, as a specific example of this embodiment. Figure 3(a) is a cross-sectional view showing a schematic configuration of the mounting structure of the optical device 300 according to a specific example of this embodiment, and Figure 3(b) is a top view of the optical assembly. The optical device 300 shown in Figure 3 is housed in a case 301, similar to the prior art.

[0020] The optical device 300 has a mounting structure similar to the conventional optical device 100 shown in Figure 1. The optical device 300 comprises an optical assembly 304 consisting of an optical element chip 302 on which an optical element having an optical parametric amplification function is formed and a carrier substrate 303, a Peltier element 305 which is a temperature control element, an input-side optical system 310 which optimizes and couples light from the input-side optical fiber 309 to the input side of the optical element, and an output-side optical system 311 which optimizes and couples light from the output side of the optical element to the output-side optical fiber 312.

[0021] Furthermore, in cases where the optical element is a silicon photonic optical circuit that implements a semiconductor laser, the input-side optical system 310 or the output-side optical system 311 may be provided by only one of them.

[0022] In Figure 3, the input optical system 310 and the output optical system 311 are depicted as a single lens. However, any optical system that optically couples each waveguide of an optical element with a corresponding optical waveguide may consist of multiple lenses, or optical systems other than lenses may be used. When the optical device 300 is used for difference frequency generation and parametric amplification, the input optical fiber 309 consists of two fibers, one for excitation light and one for signal light, and the input optical system 310 also consists of two sets of lens optical systems corresponding to each optical fiber. Similarly, on the output side, the output optical fiber 312 consists of two fibers, one for signal light and one for idler light, and the output optical system 311 also consists of two sets of lens optical systems corresponding to each optical fiber.

[0023] The temperature control element 305 is a Peltier element and consists of an upper substrate 306, a lower substrate 307, and a Seebeck element 308, which are components that make up its upper surface. The upper substrate 306 is bonded to the lower surface of the carrier substrate 303. The lower substrate 307 is fixed to the bottom surface of the case 301. The lower substrate 307 may be directly fixed to the bottom surface of the case 301, or it may be fixed to the bottom surface of the case 301 via a component fixed to the bottom surface of the case 301. In this way, the optical device 300 is fixed to the bottom surface of the case, with the optical assembly 304 supported in the center by the Peltier element 305. In addition to a Peltier element, a heat source element such as a heater can be used as the temperature control element. When a heater is used as the temperature control element, the case component that makes up the upper surface of the heater is bonded to the carrier substrate as the upper substrate.

[0024] Figure 3(b) shows a schematic configuration of the optical assembly 304 shown in Figure 3(a) as viewed from above. As shown in Figure 3(b), the optical assembly 304 has an optical element chip 302 formed on the upper surface of the carrier substrate 303. An optical element having an optical parametric amplification function is formed on the optical element chip 302.

[0025] An optical element having an optical parametric amplification function is made of, for example, a nonlinear optical medium, said nonlinear optical medium being LiNbO₃, LiTaO₃, LiNb (x) Ta (1-x) O₃ (0≦x≦1), or may contain at least one selected from the group consisting of Mg, Zn, Sc, and In as an additive. Further, the optical element having an optical parametric amplification function may have an optical waveguide structure, for example, a waveguide with a periodically poled inversion structure, specifically a PPLN waveguide or the like.

[0026] A temperature measuring element 313 for measuring the temperature of the optical element chip is mounted on the carrier substrate 303 or the optical element chip 302. The Peltier element 305 is controlled in accordance with the temperature detected by the temperature measuring element 313, whereby the temperature of the optical element chip can be accurately controlled. As the temperature measuring element 313, a known temperature measuring element such as a thermistor can be used.

[0027] In this example, an example in which the temperature measuring element 313 is mounted on the upper surface of the carrier substrate 303 is shown, but the temperature measuring element 313 may be mounted at any position other than the upper surface as long as the temperature of the optical element chip 302 can be detected, or may be mounted on the optical element chip 302. Further, in cases such as detection by an infrared sensor or the like, it may be mounted on a member other than the optical assembly 304.

[0028] An optical element made of a nonlinear optical medium and having an optical parametric amplification function exhibits temperature-sensitive behavior, so it is desirable that the optical element is placed on a carrier substrate with good thermal conductivity in order to uniformly transfer heat to the entire optical element chip. Therefore, the carrier substrate is formed of a material with high thermal conductivity.

[0029] As described above, when the temperature is changed by the Peltier element, thermal stress is generated at the interface between the carrier substrate 303 and the upper substrate 306, which is a member constituting the upper surface of the Peltier element, thereby causing warpage. This warpage changes depending on the magnitude of temperature change from a state where there is no thermal stress at the interface. Note that the state without thermal stress refers to the temperature state when the carrier substrate 303 and the upper substrate 306 are bonded and fixed together.

[0030] The magnitude of this warping due to temperature changes can be investigated by following the concept of the bimetallic effect. Therefore, the magnitude of warping can be calculated by applying the calculation of deformation amount due to the bimetallic effect disclosed in Non-Patent Document 1.

[0031] Figure 4 is a diagram illustrating the concept for applying the deformation amount calculation formula of Non-Patent Document 1 to the bonded structure of the carrier substrate 303 and the upper substrate 306 of the optical device 300 according to the embodiment of this disclosure.

[0032] Figure 4(a) is a schematic diagram of the bonded shape of the carrier substrate and the upper substrate of the optical device 300. As shown in Figure 4(a), the length of the carrier substrate 303 in the longitudinal direction (z-axis direction in the figure) is l c The length of the upper substrate 306 in the same direction is l p And the thickness of the carrier substrate 303 is w c The thickness of the upper substrate 306 is w p Let's assume that.

[0033] In the optical device 300, the longitudinal length l of the carrier substrate p This is also the length between the optical input and output terminals of the optical element chip. Therefore, the longitudinal direction of the carrier substrate coincides with the direction of light propagation of the optical element chip.

[0034] Furthermore, the Young's modulus of the upper substrate is E p , the coefficient of thermal expansion is α p The Young's modulus of the carrier substrate is E c , the coefficient of thermal expansion is α c Let's assume the following. Let T be the temperature of the carrier substrate and the upper substrate, and T0 be the temperature of the carrier substrate and the upper substrate when the thermal stress is zero (no warping).

[0035] Furthermore, since warping occurs only in the area where the carrier substrate and the upper substrate are bonded together, the calculation of the amount of warping can be performed assuming that the dimensions are the same except for the thickness of the carrier substrate and the upper substrate, as shown in Figure 4(b).

[0036] Therefore, by applying the calculation formula for the displacement between the center and the end of the bimetallic structure in Non-Patent Document 1, if the displacement of the carrier substrate from the center of the upper substrate to the end of the upper substrate is denoted as δ as shown in Figure 4(c), then δ can be expressed by the following formula (1).

[0037]

[0038] Here, Δα = α c -α p , ΔT=T−T0, m=w c / w p、 n = E c / E p That is the case.

[0039] The longitudinal length of the carrier substrate of the optical device 300 shown in Figure 3. c In practice, when the optical element is a PLNN optical waveguide with optical parametric amplification capabilities, the length of wc is set to be the same as the length of the optical waveguide, so wc is set to be longer than wp.

[0040] Therefore, as shown in Figure 5, the displacement Δy from the center to the edge of the carrier substrate, which is the edge of the optical element chip, is larger than the displacement δ from the center to the edge of the bonded structure of the carrier substrate and the upper substrate.

[0041] The deformation of the carrier substrate actually has curvature, but it is a small displacement, so if we approximate it with a straight line, the relationship between δ and Δy can be expressed by the following equation (2), as is clear from Figure 5.

[0042]

[0043] Furthermore, the carrier curvature angle Δθ shown in Figure 5 can be expressed by the following equation (3).

[0044]

[0045] Therefore, the amount of displacement of the carrier substrate within a predetermined temperature range can be determined by the following equation (4).

[0046]

[0047] As shown in the environmental testing standards of table 4 of Non-Patent Literature 4, the permissible optical fluctuation loss in environmental testing is 1.0 dB (20%) or less. In the optical device 300 shown in Figure 5, the carrier substrate is displaced symmetrically at both the optical input and output ends (see Figure 5), so the change in each input and output side is permissible up to half of 1.0 dB (20%), which is 0.5 dB (10%), and the optical loss change must be less than this.

[0048] In an optical device 300 equipped with an optical element having an optical parametric amplification function, it is assumed that the temperature of the optical element chip will be changed by a temperature control element (see Patent Document 1, Non-Patent Document 5, etc.). Optical elements such as semiconductor lasers are also used with varying temperatures. The practical operating range of these optical elements is, for example, 10°C above and below 25°C, as shown in the Specifications table of Non-Patent Document 6. Thus, optical devices are typically used with temperatures varied within a range of about 10°C.

[0049] Based on the above considerations, we found that by setting the material, thickness, and longitudinal length of the carrier substrate and upper substrate in an optical device that satisfies the following equation (5), it is possible to suppress the optical loss fluctuations due to the displacement of the carrier substrate caused by temperature changes to a predetermined value within the allowable range, thereby realizing a mounting structure that does not affect optical coupling.

[0050]

[0051] Here, T min The lowest temperature is T max is the highest temperature, d fiber This is the diameter of the core of the input optical fiber 309 or the output optical fiber 312.

[0052] When the optical device is mounted, the optical axis of the optical optical system is aligned with the optical element waveguides of the optical element chip of the optical assembly 304 and the optical fiber. Therefore, in this embodiment, it is not a problem if the temperature at the time of mounting the optical assembly 304 is different from the temperature of the carrier substrate and the upper substrate when there is no thermal stress. However, if the carrier substrate 303 and the upper substrate 306 are bonded with a thermosetting adhesive, using an adhesive that cures at a temperature close to the expected operating temperature will allow the carrier substrate to be used without warping or with minimal warping. Therefore, in the optical device of this embodiment, an optical assembly may be used in which the carrier substrate 303 and the upper substrate 306 are bonded with a thermosetting adhesive that cures at a temperature close to the expected operating temperature.

[0053] Figure 6 shows the results of calculating the change in the edge of the carrier substrate due to temperature change using equation (4) for an example of the optical device 300 shown as an example of the optical device according to this embodiment. In all of the embodiments according to this embodiment, the carrier substrate 303 is made of copper and the upper substrate 306 is made of alumina.

[0054] Therefore, the Young's modulus Ec and thermal expansion coefficient αc of the carrier substrate are as shown in the table in Figure 8, respectively, E c = 35.0 × 10 10 Pa, α c = 6.5 × 10 -6 It will be set to K.

[0055] Similarly, the Young's modulus Ep and thermal expansion coefficient αp of the upper substrate are, respectively, E p = 12.98 × 10 10 Pa, α p = 16.5 × 10 -6 It will be set to K.

[0056] Figure 6 shows Example 1 (the length of the carrier substrate in the longitudinal direction of the carrier substrate l c = 45 mm, length l of the upper substrate p = 15 mm, m = w, which is the ratio of the thickness of the carrier substrate to the upper substrate. c / w p= 17.5) and Example 2 (Length of the carrier substrate in the longitudinal direction of the carrier substrate l c = 45 mm, length l of the upper substrate p = 10 mm, m = 17.5 (the ratio of the thickness of the carrier substrate to the upper substrate), and Example 3 (the length of the carrier substrate in the longitudinal direction of the carrier substrate l c = 45 mm, length l of the upper substrate p = 15 mm, m = w, which is the ratio of the thickness of the carrier substrate to the upper substrate. c / w p This shows the results of calculating the displacement of the substrate edge in response to temperature changes (=20.0).

[0057] Note that the dashed line in Figure 6 represents the case where the misalignment of the input / output fiber in the 1550 nm band relative to the center is 10% of the optical fiber core diameter of 10 μm, i.e., 1 μm.

[0058] Comparing Example 1 and Example 2, the length l of the upper substrate p It can be seen that a shorter length suppresses substrate fluctuations in response to temperature changes. Similarly, comparing Example 1 and Example 3, it can be seen that a larger ratio m, which is the ratio of the thickness of the carrier substrate to the thickness of the upper substrate, suppresses substrate fluctuations in response to temperature changes.

[0059] Furthermore, in Example 1, a temperature change of 10°C resulted in a positional displacement of more than 10%. In contrast, in Example 2, the displacement remained within 10% with a temperature change of 10°C.

[0060] Figure 7 shows the length l of the carrier substrate in each embodiment of Figure 6. p The following shows the same calculation results for an embodiment where the conditions were set the same except that the values ​​were changed to 35 mm and 15 mm, respectively.

[0061] Figure 7(a) shows Example 4 (the length of the carrier substrate in the longitudinal direction of the carrier substrate l c = 35 mm, length l of the upper substrate p = 15 mm, m = w, which is the ratio of the thickness of the carrier substrate to the upper substrate. c / w p = 17.5) and Example 5 (Length of the carrier substrate in the longitudinal direction of the carrier substrate l c = 35 mm, length l of the upper substratep = 10 mm, m = 17.5 (the ratio of the thickness of the carrier substrate to the upper substrate), and Example 6 (the length of the carrier substrate in the longitudinal direction of the carrier substrate l c = 35 mm, length l of the upper substrate p = 15 mm, m = w, which is the ratio of the thickness of the carrier substrate to the upper substrate. c / w p This shows the results of calculating the displacement of the substrate edge in response to temperature changes (=20.0).

[0062] Then, in Figure 7(b), Example 7 (the length of the carrier substrate in the longitudinal direction of the carrier substrate l c = 25 mm, length l of the upper substrate p = 15 mm, m = w, which is the ratio of the thickness of the carrier substrate to the upper substrate. c / w p = 17.5) and Example 8 (Length of the carrier substrate in the longitudinal direction of the carrier substrate l c = 25 mm, length l of the upper substrate p = 10 mm, m = 17.5 (the ratio of the thickness of the carrier substrate to the upper substrate), and Example 9 (the length of the carrier substrate in the longitudinal direction of the carrier substrate l c = 25 mm, length l of the upper substrate p = 15 mm, m = w, which is the ratio of the thickness of the carrier substrate to the upper substrate. c / w p This shows the results of calculating the displacement of the substrate edge in response to temperature changes (=20.0).

[0063] Comparing these embodiments, the longitudinal length l of the carrier substrate c It can be understood that the shorter the interval, the more effectively the amount of positional displacement due to temperature changes can be suppressed.

[0064] According to the studies based on the embodiments shown in Figures 6 and 7, the length l of the carrier substrate in the longitudinal direction of the carrier substrate c , length l of the upper substrate p Both should ideally be short, and the thickness of the carrier substrate is also important. c And the thickness of the upper circuit board lol p The ratio is m = w c / w p A larger size is preferable.

[0065] Typically, the size of a Peltier element is often determined by standards, and if the optical element has a waveguide structure with a parametric optical amplification function, the length of the carrier substrate in the optical propagation direction (longitudinal length) must also be above a certain length from the perspective of the optical element's performance.

[0066] As can be seen from this example, in typical optical devices, the length l of the upper substrate p Carrier substrate l c The value will be set to be larger. c >l p In that case, it is necessary to adjust m to set the positional deviation within the temperature range used to within the allowable value.

[0067] Therefore, as a structure to suppress displacement of the substrate due to temperature changes, w c >w p That's all you need to do.

[0068] In the above study, we used the case where the carrier substrate is copper and the upper substrate is alumina as an example, but these substrate materials may be other.

[0069] The carrier substrate can be any material with good thermal conductivity and easy processing, such as copper, iron, aluminum, or alloys thereof. The upper substrate can be alumina, zirconia, aluminum nitride, etc. (Non-Patent Literature 2).

[0070] Figure 8 is a table showing the Young's modulus and thermal expansion coefficient of these materials as examples. By using these values ​​to determine the conditions that satisfy equation (5), it is possible to realize optical devices that, even when using these materials, have a positional displacement due to temperature changes below the allowable value, similar to the examples described above.

[0071] Furthermore, in the above embodiment, an example was shown in which the cross-sectional shape viewed from the longitudinal (Z-axis direction) end face of the carrier substrate is a commonly used rectangular shape. However, as illustrated in Figures 9(a) to (c), by making the cross-sectional shape viewed from the longitudinal end face of the carrier substrate an H-shape or a U-shape, warping can be further suppressed compared to a carrier substrate of the same thickness and longitudinal length but with a normal shape.

[0072] This allows us to provide an optical device equipped with a carrier structure that reduces warping of the carrier substrate due to temperature changes.

[0073] 300... Optical device 301... Case 302... Optical element chip 303... Carrier substrate 304... Optical assembly 305... Temperature control element, Peltier element 306... Upper substrate 307... Lower substrate 308... Seebeck element 309... Input optical fiber 310... Input optical system 311... Output optical system 312... Output optical fiber 313... Temperature measuring element

Claims

1. The device comprises a carrier substrate with good thermal conductivity, an optical element chip including an optical element disposed on the carrier substrate, a temperature control element for changing the temperature of the carrier substrate, an optical system for optimizing the optical input or output disposed on at least one of the optical input side and optical output side of the optical element, and one or more optical fibers optically coupled to the optical system, wherein the temperature control element has an upper substrate bonded to the carrier substrate, and the length of the carrier substrate in the longitudinal direction of the carrier substrate is l c The length of the upper substrate is l p The thickness of the carrier substrate is w c The thickness of the upper substrate is w p When that happens, l c >l p And lol c >w p It is an optical device.

2. where E is the Young's modulus of the upper substrate p , α is the coefficient of thermal expansion p , E is the Young's modulus of the carrier substrate c , α is the coefficient of thermal expansion c , where T is the temperature of the carrier substrate and the upper substrate, and T0 is the temperature of the carrier substrate and the upper substrate when thermal stress is zero (there is no warpage), a displacement Δy(T) of a longitudinal end caused by a temperature change of the carrier substrate is defined by the following mathematical formula 1, d is a core diameter of the optical fiber fiber , T is the lowest temperature in an operating temperature range of the optical device min , and T is the highest temperature max , the optical device according to claim 1, wherein the following mathematical formula 2 is satisfied. (Mathematical formula 1) where Δα=α c -α p , ΔT=T-T0, m=w c / w p、 n=E c / E p . (Mathematical formula 2) 3. The optical device according to claim 1, further comprising a temperature measuring element for measuring the temperature of the optical element chip.

4. The optical device according to claim 1, characterized in that the optical element has an optical parametric amplification function.

5. The optical element having the optical parametric amplification function is made of a nonlinear optical medium, and the nonlinear optical medium is LiNbO3, LiTaO3, LiNb (x) Ta (1-x) The optical device according to claim 4, characterized in that it contains O3 (0 ≤ x ≤ 1), or at least one selected from the group consisting of Mg, Zn, Sc, and In as an additive.

6. The optical device according to claim 4, characterized in that the optical element having the optical parametric amplification function has an optical waveguide structure.

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