Optical Devices

Abstract

A first core (102) of this optical device constitutes an optical waveguide having a nonlinear optical effect and having a super mode by the first core (102) and a second core (103), and the respective refractive indexes and cross-sectional shapes of the first core (102) and the second core (103), and the positional relationship between the first core (102) and the second core (103) in a cross section perpendicular to a waveguide direction are in a state in which the super mode has desired dispersion.

Description

[Technical Field]

[0001] The present invention relates to an optical device including an optical waveguide. [Background technology]

[0002] In recent years, there has been remarkable progress in optical integrated device technology using micro-optical waveguides. For example, in the technological field known as silicon photonics, the integration of optical communication devices has progressed, and high-performance optical integrated devices including active devices such as laser light sources, photodetectors, and modulators in addition to passive devices such as optical splitters and wavelength filters have been put into practical use.

[0003] Furthermore, by taking advantage of the strong optical confinement of the minute optical waveguides that make up optical integrated circuits and actively utilizing nonlinear optical effects, it is possible to realize high-performance elements such as frequency comb light sources, supercontinuum light sources, wavelength conversion elements, phase-sensitive amplifier elements, and quantum entangled photon pair sources.In addition to the optical communications applications that are currently in commercial use, it is expected that the range of applications for optical integrated devices will be further expanded.

[0004] In particular, in recent years, devices using SiN optical waveguides as nonlinear optical waveguides have been widely proposed, taking into account their integration with silicon photonics devices. For example, to realize frequency comb light sources, SiN optical waveguides are used in microring resonators, and they are designed to control wavelength dispersion, particularly anomalous dispersion, in order to utilize the above-mentioned nonlinear optical effect. For example, as described in Non-Patent Document 1, structural dispersion has been imparted to obtain desired dispersion characteristics by appropriately designing the shape of the optical waveguide core, or by incorporating a multilayer cladding structure into a rib-type core structure, as described in Non-Patent Document 2. Furthermore, as described in Non-Patent Document 3, a double-ring structure has been used to adjust the propagation length and obtain appropriate mode coupling between even and odd modes, thereby achieving desired dispersion characteristics. [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] X. Xue et al., "Kerr combs from normal and anomalous dispersion silicon nitride microresonators", Proceedings of SPIE, vol. 10090, 2017. [Non-patent document 2] JM Chavez Boggio et al., "Dispersion engineered silicon nitride waveguides by geometrical and refractive-index optimization", Journal of the Optical Society of America B, vol. 31, no. 11, pp. 2846-2857, 2014. [Non-patent document 3] S. Kim et al., "Dispersion engineering and frequency comb generation in thin silicon nitride concentric microresonators", Nature Communications, vol. 8, Article number: 372, 2017. [Non-patent document 4] WD Sacher et al., "Multilayer Silicon Nitride-on-Silicon Integrated Photonic Platforms and Devices", Journal of Lightwave Technology, vol. 33, no. 4, pp. 901-910, 2015. [Non-patent document 5] H. Nishi et al., "Integration of Eight-Channel Directly Modulated Membrane-Laser Array and SiN AWG Multiplexer on Si", Journal of Lightwave Technology, vol. 37, no. 2, pp. 266-273, 2019. Summary of the Invention [Problem to be solved by the invention]

[0006] However, the conventional technology has the following problems.

[0007] For example, Non-Patent Document 1 mentions that anomalous dispersion can be obtained by increasing the core height (thickness) to 0.75 μm or more. Such a core height is larger than the upper limit of 600 nm of the core height of single-mode SiN optical waveguides generally provided by optical device foundries, as mentioned in Non-Patent Document 4. For reference, Figure 12 shows the chromatic dispersion of the SiN optical waveguide with a 600 × 1000 nm core shown in Non-Patent Document 4. It can be seen that normal dispersion (D<0) is observed at wavelengths of 1500 nm to 1600 nm.

[0008] In this case, when integrating a nonlinear optical waveguide, if other SiN optical waveguides on an optical integrated device are to be formed in the same layer as the nonlinear optical waveguide, the core height must be adjusted to match the nonlinear optical waveguide. Other passive devices such as splitters and wavelength filters must be designed to match the nonlinear optical waveguide, which poses a major problem.

[0009] Furthermore, increasing the core height itself poses various problems. For example, forming a tall core requires deeper etching, which tends to roughen the core side surfaces. When the core side surfaces become rough, the roughness easily affects the light as light scattering, which causes a major problem of increased propagation loss.

[0010] Furthermore, for example, if the core height increases, the core layer will be deposited thicker when formed by a CVD method or the like, which poses a major manufacturing problem of dealing with increased internal stress in the wafer.

[0011] Furthermore, in order to make such a nonlinear optical waveguide and a general passive device have different core heights while being on the same layer, a process for partially reducing the core height is required, which makes the manufacturing process redundant, which is a major problem.

[0012] As an approach to obtaining the desired dispersion characteristics other than increasing the core height, which has these problems, Non-Patent Document 2 combines a rib-type SiN core with a multi-clad structure. However, this technology also has the problem that the structure is not easily fabricated and provided by optical device foundries, and furthermore, constructing a passive device requires a redesign optimized for this type of optical waveguide structure.

[0013] Another approach proposed is a double-ring structure using a thin SiN core, as described in Non-Patent Document 3. However, as mentioned above, this technique requires adjusting the propagation length to obtain appropriate mode coupling between the even and odd modes, resulting in a narrow operating bandwidth.

[0014] As mentioned above, there has traditionally been a problem in that there are no optical devices that are single-mode, have low loss, are easy to design and manufacture, and have good integration with other optical elements (e.g., laser light sources, photodetectors, and passive optical waveguide elements), and that have low barriers to entry for optical device foundries.

[0015] The present invention has been made to solve the above problems, and aims to provide an optical device that has single-mode characteristics, low loss, is easy to design and manufacture, and has good integration with other optical elements, and has low barriers to introduction in optical device foundries. [Means for solving the problem]

[0016] The optical device according to the present invention comprises a first core having a nonlinear optical effect formed on a lower cladding layer, a second core formed on the lower cladding layer, and an upper cladding layer formed on the lower cladding layer to cover the first and second cores, the first and second cores constituting an optical waveguide having a supermode, and the refractive indexes and cross-sectional shapes of the first and second cores and the positional relationship between the first and second cores in a cross section perpendicular to the waveguiding direction are such that the supermode is formed in a desired manner. wavelength It is considered to be in a state of dispersion. [Effects of the Invention]

[0017] As described above, according to the present invention, an optical waveguide having a supermode is formed using a first core and a second core, and the refractive index and cross-sectional shape of each of the first core and the second core, and the positional relationship between the first core and the second core in a cross section perpendicular to the waveguiding direction are set to a state in which the supermode has a desired dispersion, so that an optical device can be provided that has single-mode properties, low loss, is easy to design and manufacture, and has good integration properties with other optical elements, and has a low barrier to introduction in optical device foundries. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a cross-sectional view showing the configuration of an optical device according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a distribution diagram showing the electromagnetic field distribution of the light propagation mode in the first core 102 and the second core 103. As shown in FIG. [Figure 3] FIG. 3 is a characteristic diagram showing chromatic dispersion (D2) due to the first core 102 and the second core 103. As shown in FIG. [Figure 4] FIG. 4 is a characteristic diagram showing the relationship between the change in the gap between first core 102 and second core 103 and D2. [Figure 5] FIG. 5 is a characteristic diagram showing the relationship between the core width of second core 103 and D2. [Figure 6]FIG. 6 is a characteristic diagram showing the optical confinement factor in first core 102 when second core 103 shown in FIG. 5 has a core width of 400 nm, 300 nm, and 200 nm. [Figure 7] FIG. 7 is a perspective view showing the configuration of an integrated optical device to which the optical device according to the first embodiment is applied. [Figure 8A] FIG. 8A is a distribution diagram showing the propagation mode of light in the output optical waveguide of the membrane laser 201 of the integrated optical device to which the optical device according to the first embodiment is applied. [Figure 8B] FIG. 8B is a distribution diagram showing the propagation mode of light at the tapered tip of InP core 203a of an integrated optical device to which the optical device according to the first embodiment is applied. [Figure 8C] FIG. 8C is a distribution diagram showing the propagation mode of light in the SiN core 204a of the integrated optical device to which the optical device according to the first embodiment is applied. [Figure 8D] FIG. 8D is a distribution diagram showing the propagation mode of light in a nonlinear optical waveguide to which an integrated optical device to which the optical device according to the first embodiment is applied is connected. [Figure 9] FIG. 9 is a cross-sectional view showing the configuration of an optical device according to a second embodiment of the present invention. [Figure 10A] FIG. 10A is a distribution diagram showing the electromagnetic field distribution of the propagation mode of light in first core 102a and second core 103. FIG. [Figure 10B] FIG. 10B is a distribution diagram showing the electromagnetic field distribution of the propagation mode of light in first core 102a in first core 102a and second core 103. As shown in FIG. [Figure 10C] FIG. 10C is a distribution diagram showing the electromagnetic field distribution of the optical propagation mode of first core 102a when only first core 102a is present. [Figure 11] FIG. 11 is a characteristic diagram showing chromatic dispersion (D2) due to the first core 102a and the second core 103. As shown in FIG. [Figure 12] FIG. 12 is a characteristic diagram showing the wavelength dispersion of a SiN optical waveguide having a core with cross-sectional dimensions of 600×1000 nm. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, an optical device according to an embodiment of the present invention will be described.

[0020] [Embodiment 1] First, an optical device according to a first embodiment of the present invention will be described with reference to Fig. 1. This optical device includes a lower cladding layer 101, a first core 102, a second core 103, and an upper cladding layer 104. The first core 102 and the second core 103 are formed on the lower cladding layer 101. The upper cladding layer 104 is formed on the lower cladding layer 101 to cover the first core 102 and the second core 103. In this example, the first core 102 is located above the second core 103 when viewed from the lower cladding layer 101 side.

[0021] Here, first, the first core 102 has a nonlinear optical effect. The first core 102 and the second core 103 form an optical waveguide having a supermode. Furthermore, the refractive indexes and cross-sectional shapes of the first core 102 and the second core 103, and the positional relationship between the first core 102 and the second core 103 in a cross section perpendicular to the waveguiding direction are set so that the supermode has a desired dispersion. For example, even if the optical waveguide formed by the first core 102 and the optical waveguide formed by the second core 103 each have normal dispersion, the cross-sectional shapes and positional relationship of the first core 102 and the second core 103 are set so that the above-mentioned supermode has anomalous dispersion.

[0022] The dispersion design of the supermode can be achieved by two-dimensional cross-sectional mode calculation, and does not require a complicated design that takes into account mode coupling in the propagation direction, as in Non-Patent Document 4. Therefore, the optical device according to the first embodiment provides a high degree of freedom in designing the operating band.

[0023] Furthermore, the core height of the first core 102 is set to a height that matches other optical devices that are optically connected to the optical waveguide formed by the first core 102. Similarly, the core height of the second core 103 is set to a height that matches other optical devices that are optically connected to the optical waveguide formed by the second core 103. Therefore, these other optical devices can be easily integrated with the optical device according to the first embodiment.

[0024] The first core 102 may be made of, for example, SiN, and the second core 103 may be made of InP. The first core 102 may have a cross-sectional shape perpendicular to the waveguide direction with a width of 1000 nm and a core height of 600 nm. The second core 103 may have a cross-sectional shape perpendicular to the waveguide direction with a width of 300 nm and a core height of 350 nm. The gap between the first core 102 and the second core 103 in the thickness direction may be 300 nm. The offset between the centers of the first core 102 and the second core 103 in the planar direction of the lower cladding layer 101 in a plane perpendicular to the waveguide direction may be 0 nm. Note that FIG. 1 shows an example in which the centers of the first core 102 and the second core 103 are misaligned, resulting in a non-zero offset.

[0025] The lower cladding layer 101 and the upper cladding layer 104 can be made of silicon oxide. For example, the lower cladding layer 101 can be made of silicon oxide formed by thermally oxidizing the surface of a silicon substrate. The upper cladding layer 104 can be made of an SiO2 film deposited by a known CVD method.

[0026] The electromagnetic field distribution of the light propagation mode in the first core 102 and the second core 103 calculated under each of the conditions described above is shown in Figure 2. (a) in Figure 2 is the lowest-order TE mode, and it can be seen that light is strongly confined within the second core 103. On the other hand, (b) in Figure 2 is a higher-order TE mode, and it can be seen that light is strongly confined in the first core 102, and at the same time, it is a supermode in which an electromagnetic field distribution also exists in the second core 103. In the mode shown in (b) in Figure 2, the light confinement factor in the first core 102 is 73%.

[0027] Figure 3(a) shows the second-order chromatic dispersion (D2) in the lowest-order TE mode. It is a normal dispersion optical waveguide with a negative D2 value over the entire wavelength range from 1500 nm to 1600 nm, which makes it unsuitable for use as a nonlinear optical waveguide. For reference, Figure 3(c) shows D2 for the SiN optical waveguide alone, as shown in Figure 12. Next, Figure 3(b) shows the chromatic dispersion of the higher-order TE mode mentioned above. It can be seen that it is possible to achieve anomalous dispersion with a positive D2 value over the entire wavelength range from 1500 nm to 1600 nm.

[0028] Furthermore, the relationship between the change in gap and D2 is shown in Figure 4. As shown in Figure 4, it is clear that anomalous dispersion can be achieved over a wide gap range of 200 nm to 500 nm, providing a large manufacturing margin.

[0029] Next, the relationship between the core width of the second core 103 and D2 is shown in Figure 5. The gap described above is set to 500 nm. As shown in Figure 5, when the core width of the second core 103 is set to 400 nm, normal dispersion is obtained. On the other hand, when the core width of the second core 103 is set to 300 nm or 200 nm, anomalous dispersion is obtained.

[0030] In order to increase the optical confinement within the first core 102 and more efficiently realize the nonlinear optical effect, when designing the above cross-sectional structure, it is necessary to design it so that not only the dispersion but also the optical confinement coefficient in the first core 102 is as large as possible.

[0031] Figure 6 shows the optical confinement factor within first core 102 for each of the core widths of second core 103 shown in Figure 5: 400 nm, 300 nm, and 200 nm. When second core 103 has a core width of 300 nm, which provides anomalous dispersion, the confinement factor within first core 102 is approximately 73% (wavelength 1550 nm). On the other hand, when second core 103 has a core width of 200 nm, which also provides anomalous dispersion, the confinement factor within first core 102 drops to approximately 67% (wavelength 1550 nm). In this way, it is sufficient to design by taking dispersion and optical confinement factor into consideration in an integrated manner.

[0032] Although the above description has been given with respect to the wavelength band of 1500 nm to 1600 nm, it is clear that desired dispersion characteristics can be obtained over a wider wavelength range by combining appropriate materials with low loss as optical waveguide materials and designing the structural parameters for the first core 102 and second core 103 of the optical device according to embodiment 1.

[0033] Although the above has described the control of D2 and the optical confinement factor, it is clear that in the optical device according to the first embodiment, for example, higher-order dispersion and polarization mode dispersion can also be appropriately controlled by appropriately designing the materials and dimensional parameters of the first core 102 and the second core 103. Furthermore, by periodically changing the structures of the first core 102 and the second core 103 in the light propagation (waveguide) direction, it is possible to satisfy conditions such as quasi-phase matching of the propagating light, or to obtain the required mode coupling conditions in the light propagation direction based on the design theory shown in Non-Patent Document 3.

[0034] 1 is merely an example, and can be modified as appropriate, taking into consideration, for example, manufacturability. For example, the upper cladding layer 104 made of silicon oxide can be formed up to the bottom surface of the first core 102, and the first core 102 can be configured not to be covered by the upper cladding layer 104. With such a configuration, for example, it can be applied to an optical sensor that optically detects the presence or absence of a substance above the first core 102, which is particularly important in industry.

[0035] Next, an example in which the optical device according to the first embodiment is applied to an integrated optical device will be described with reference to Fig. 7. This integrated optical device is a combination of a semiconductor laser light source and the optical device according to the first embodiment.

[0036] In Figure 7, reference numeral 201 denotes the membrane laser described in Non-Patent Document 4, which is fabricated on an SiO2 / Si substrate 202. Reference numerals 203a, 203b, and 203c denote InP cores, which correspond to the second core. The InP core 203a serves as the output optical waveguide core of the membrane laser 201, which is also fabricated from an InP-based material. A SiN core 204a is provided above the InP cores 203a and 203b, and a SiN core 204b is provided above the InP core 203c. The SiN cores 204a and 204b correspond to the first core.

[0037] In the output optical waveguide of the membrane laser 201, the propagation mode of light is such that an electromagnetic field exists in the InP core 203a as shown in Fig. 8A. The width of the InP core 203a is gradually tapered, and the output light from the membrane laser 201 undergoes adiabatic mode conversion as it propagates, and at the tapered tip 205 of the InP core 203a, the propagation mode of light is such that an electromagnetic field exists mainly in the SiN core 204a as shown in Fig. 8B. The tapered tip 205 is butt-coupled with a SiN optical waveguide that does not have an InP core 203a, such as that used in Patent Document 3, and its tip is connected to an optical waveguide made of the SiN core 204a having an optical propagation mode as shown in Fig. 8C, for optical wiring.

[0038] Next, in order to connect to the nonlinear optical device according to the present invention, the InP core 203b is again arranged in a tapered shape at the connection point, and then the mode is adiabatically converted to the optical propagation mode of the nonlinear optical waveguide shown in Fig. 8D. The mode shown in Fig. 8D is the nonlinear optical waveguide of the optical device according to the first embodiment described with reference to Fig. 1.

[0039] The nonlinear optical waveguide is made up of SiN core 204a, ring-shaped InP core 203c, InP core 203b, and ring-shaped SiN core 204b, which form ring resonator 206. Ring resonator 206 is a nonlinear optical waveguide device that utilizes the increased optical intensity within the resonator.

[0040] After this, the light is adiabatically mode-converted again via the tapered InP core 203b and connected to the SiN optical waveguide at the output destination. Here, the SiN optical waveguide may be a general-purpose optical waveguide as shown in Non-Patent Document 3, and not only optical wiring but also various passive devices can be integrated. For example, a wavelength filter for cutting the pump light from the membrane laser 201, a low-loss fiber coupling device, a spatial light emission device, etc. can be integrated.

[0041] Here, by making the InP cores 203a, 203b, and 203c the same thickness in the output optical waveguide portion and the nonlinear optical waveguide portion of the membrane laser 201, they can be easily formed in the same layer by the manufacturing method shown in Non-Patent Document 5. Moreover, after manufacturing the above-mentioned InP core, the SiN cores 204a and 204b can be formed into a layer thickness that becomes a designed gap by depositing SiO2 by the CVD method and performing CMP polishing, and then further formed in the same layer by the manufacturing method shown in Non-Patent Document 5.

[0042] By using the integrated optical device shown in FIG. 7, for example, the oscillation wavelength of the membrane laser 201 is swept from the short wavelength side to the long wavelength side across the resonance wavelength of the ring resonator 206, and the χ (3) After a nonlinear process, frequency comb light is obtained from the output SiN optical waveguide, realizing an integrated frequency comb light source that integrates a pump laser and a nonlinear microcavity.

[0043] Although only membrane lasers have been described here, it is also possible to integrate other membrane devices, such as a phase shifter for generating solitons in a nonlinear microresonator, or a heater structure for wavelength tuning of a ring resonator, as a membrane device.

[0044] [Embodiment 2] Next, an optical device according to a second embodiment of the present invention will be described with reference to Fig. 9. This optical device includes a lower cladding layer 101, a first core 102a, a second core 103, and an upper cladding layer 104. The first core 102a and the second core 103 are formed on the lower cladding layer 101. The upper cladding layer 104 is formed on the lower cladding layer 101 to cover the first core 102a and the second core 103. In this example, the second core 103 is located above the first core 102a when viewed from the lower cladding layer 101 side.

[0045] In the second embodiment, the first core 102a has a nonlinear optical effect. The first core 102a and the second core 103 form an optical waveguide having a supermode. In this example, the first core 102a is rib-shaped.

[0046] Also in the second embodiment, the refractive index and cross-sectional shape of each of first core 102a and second core 103, and the positional relationship between first core 102a and second core 103 in a cross section perpendicular to the waveguiding direction are set so that the supermode has a desired dispersion. For example, even if the optical waveguide formed by first core 102a and the optical waveguide formed by second core 103 each have normal dispersion, the cross-sectional shapes and positional relationship of first core 102a and second core 103 are set so that the above-mentioned supermode has anomalous dispersion.

[0047] Furthermore, the core height of first core 102a is set to a height that matches other optical devices that are optically connected to the optical waveguide formed by first core 102a. Similarly, the core height of second core 103 is set to a height that matches other optical devices that are optically connected to the optical waveguide formed by second core 103. Therefore, these other optical devices can be easily integrated with the optical device according to the second embodiment.

[0048] The first core 102a may be made of, for example, LiNbO3, and the second core 103 may be made of InP. The first core 102a may have a slab thickness of 100 nm, a cross section perpendicular to the waveguide direction having a width of 1000 nm, and a total height including the slab of 200 nm. The second core 103 may have a cross section perpendicular to the waveguide direction having a width of 300 nm and a core height of 350 nm.

[0049] The distance (gap) between the first core 102a and the second core 103 in the thickness direction can be set to 300 nm. The distance (offset) between the center of the first core 102a and the center of the second core 103 in the planar direction of the lower cladding layer 101 in a plane perpendicular to the waveguiding direction can be set to 0 nm. Note that Fig. 9 shows an example in which the centers of the first core 102a and the second core 103 are misaligned, resulting in an offset that is not 0.

[0050] The electromagnetic field distributions of the light propagation modes calculated under each of the conditions described above are shown in Figures 10A, 10B, and 10C. Figure 10A shows the lowest-order TE mode, and it can be seen that light is strongly confined within the second core 103. On the other hand, Figure 10B shows a higher-order TE mode, and it can be seen that light is strongly confined within the first core 102a, and at the same time, it forms a supermode in which an electromagnetic field distribution also exists in the second core 103. In the mode shown in Figure 10B, the optical confinement factor to the first core 102a is 43%. For reference, Figure 10C also shows the electromagnetic field distribution of the lowest-order TE mode when only the first core 102a exists.

[0051] The electromagnetic field distribution of the light propagation mode calculated for such an optical waveguide structure is shown in Figure 10. Figure 10A shows the lowest-order TE mode, and it can be seen that light is strongly confined within the second core 103. On the other hand, Figure 10B shows a higher-order TE mode, and it can be seen that light is strongly confined within the first core 102a, and at the same time, it forms a supermode in which the electromagnetic field distribution also exists in the second core 103.

[0052] In the mode of Fig. 10B, the optical confinement factor to the LiNbO3 core is 43%. For reference, the electromagnetic field distribution of the lowest order TE mode when only the LiNbO3 core exists is also shown in 10-3.

[0053] FIG. 11(a) shows D2 of the lowest-order TE mode (FIG. 10A). This shows a normal dispersion optical waveguide in which D2 has a negative value over the entire wavelength range from 1500 nm to 1600 nm, making it unsuitable for use as a nonlinear optical waveguide in this state. FIG. 11(c) shows D2 of the lowest-order TE mode in the case of only the first core 102a shown in FIG. 10C. Similar to FIG. 11(a), this shows a normal dispersion optical waveguide in which D2 has a negative value over the entire wavelength range from 1500 nm to 1600 nm, making it unsuitable for use as a nonlinear optical waveguide in this state.

[0054] On the other hand, it can be seen that the chromatic dispersion of the high-order TE mode shown in FIG. 10B can be anomalous dispersion in which D2 has a positive value over the entire wavelength range from 1500 nm to 1600 nm, as shown in FIG. 11(b).

[0055] As described above, the fact that anomalous dispersion can be obtained even with the first core 102a having a thin core thickness has an excellent effect, particularly in reducing propagation loss, and is particularly effective in increasing the Q value of the optical resonator. For example, in a material that is difficult to process, such as LiNbO3, the smaller the core height can be made, the smaller the effect of scattering loss caused by rough processing of the core sidewalls can be, so being able to make a thin core has an excellent effect.

[0056] Although the wavelength band of 1500 nm to 1600 nm has been described above, it is clear that desired dispersion characteristics can be obtained over a wider wavelength range by combining appropriate low-loss materials as optical waveguide materials and designing the structural parameters of the first core 102 a and the second core 103 of the optical device according to the second embodiment. It is also clear that not only D2 and the optical confinement factor but also, for example, higher-order dispersion and polarization mode dispersion can be appropriately controlled. Furthermore, by periodically changing the structure of the first core 102 a and the second core 103 in the light propagation direction, it is possible to satisfy conditions such as quasi-phase matching of the propagating light, or to obtain the mode coupling conditions required in the light propagation direction based on the design theory shown in Non-Patent Document 2.

[0057] The configuration of the optical device according to the second embodiment described with reference to Fig. 9 is one example, and can be modified as appropriate, taking into consideration, for example, manufacturability. For example, the upper clad layer 104 made of silicon oxide can extend up to the bottom surface of the second core 103, and the second core 103 can be configured not to be covered by the upper clad layer 104. Such a structure can be applied to an optical sensor that optically detects the presence or absence of a substance above the second core 103, which is particularly important industrially.

[0058] By the way, the LiNbO3 constituting the first core 102a has a χ (3) In addition to nonlinearity, χ (2) Therefore, the optical device according to the second embodiment can be used in a wide range of applications, such as in a SiN device. (3) In addition to the nonlinear process, χ (3) This provides the excellent effect of making it possible to utilize nonlinear processes. Furthermore, while nonlinear optical devices realized using existing LiNbO3 optical waveguides do not integrate pumping light sources, the use of the optical device according to the second embodiment provides the excellent effect of making it possible to integrate pumping light sources as well. For example, when configuring an integrated comb light source with a semiconductor laser light source as described with reference to FIG. 7, this can also be realized by appropriately adjusting the arrangement of the first core and the second core.

[0059] As described above, according to the present invention, an optical waveguide having a supermode is formed using a first core and a second core, and the refractive index, cross-sectional shape, and positional relationship between the first core and the second core in a cross section perpendicular to the waveguiding direction of each of the first core and the second core are set to a state in which the supermode has a desired dispersion. This makes it possible to provide an optical device that has single-mode properties, low loss, is easy to design and manufacture, and has good integration with other optical elements, and has a low barrier to introduction in optical device foundries.

[0060] It should be noted that the present invention is not limited to the embodiments described above, and it is clear that many modifications and combinations can be made by a person having ordinary knowledge in the art within the technical concept of the present invention. [Explanation of symbols]

[0061] 101...lower clad layer, 102...first core, 103...second core, 104...upper clad layer.

Claims

1. a first core having a nonlinear optical effect formed on the lower cladding layer; a second core formed on the lower clad layer; an upper clad layer formed on the lower clad layer to cover the first core and the second core; Equipped with the first core and the second core constitute an optical waveguide having a supermode; the refractive index and cross-sectional shape of each of the first core and the second core, and the positional relationship between the first core and the second core in a cross section perpendicular to a waveguiding direction are such that the supermode has a desired chromatic dispersion, The first core and the second core are formed to be spaced apart from each other, the first core is made of SiN or LiNbO 3 ; the second core is made of InP, The lower cladding layer and the upper cladding layer are made of silicon oxide. are An optical device characterized by:

2. 2. The optical device according to claim 1, a core height of the first core is set to a height that matches with another optical device optically connected to the optical waveguide formed by the first core; a core height of the second core is set to a height that matches with another optical device optically connected to the optical waveguide formed by the second core; the first core comprises a ring-shaped core, the second core comprises a ring-shaped core, The first core, the ring-shaped core of the first core, the second core, and the ring-shaped core of the second core form a ring resonator. An optical device characterized by:

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