WO2023276053A1

WO2023276053A1 - Optical device

Info

Publication number: WO2023276053A1
Application number: PCT/JP2021/024783
Authority: WO
Inventors: 英隆西; 慎治松尾
Original assignee: 日本電信電話株式会社
Priority date: 2021-06-30
Filing date: 2021-06-30
Publication date: 2023-01-05
Also published as: JPWO2023276053A1

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

optical device

The present invention relates to an optical device having an optical waveguide.

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

Furthermore, by taking advantage of the strong optical confinement of the micro-optical waveguides that make up optical integrated circuits and actively utilizing nonlinear optical effects, for example, frequency comb light sources, supercontinuum light sources, wavelength conversion elements, phase-sensitive amplifier elements, High-performance devices such as quantum entangled photon pair sources can be realized, and further expansion of the application area of optical integrated devices is expected in addition to the currently commercialized optical communication applications.

Especially in recent years, devices using optical waveguides made of SiN as nonlinear optical waveguides have been widely proposed in consideration of integration with silicon photonics devices. For example, in order to realize a frequency comb light source, a SiN optical waveguide is used in a micro-ring resonator and is designed to have wavelength dispersion control, especially anomalous dispersion, in order to utilize the nonlinear optical effect described above. For example, desired dispersion characteristics can be obtained by appropriately designing the shape of the optical waveguide core as described in Non-Patent Document 1, or by providing a rib-type core structure with a multi-layer clad structure as described in Non-Patent Document 2. Structural dispersion was given so that Further, as described in Non-Patent Document 3, a double ring structure is used to adjust the propagation length to obtain appropriate mode coupling between even and odd modes, thereby realizing desired dispersion characteristics.

However, the conventional technology had the following problems.

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 large compared to the 600 nm upper limit of the core height of single-mode SiN optical waveguides commonly provided by optical device foundries, for example, as mentioned in Non-Patent Document 4. For reference, FIG. 12 shows the chromatic dispersion of the SiN optical waveguide having a 600×1000 nm core shown in Non-Patent Document 4. In FIG. It can be seen that normal dispersion (D<0) is obtained at wavelengths of 1500 nm to 1600 nm.

In this case, when integrating a nonlinear optical waveguide, if another SiN optical waveguide on the optical integrated device is formed in the same layer as the nonlinear optical waveguide, a core height that matches the nonlinear optical waveguide is required. Other passive devices, such as splitters and wavelength filters, have been a big problem as they have to be designed for nonlinear optical waveguides.

In addition, increasing the core height itself had various problems. For example, in order to form a high core, a deeper etching process is required, so the core side surface tends to be roughened. If the side surface of the core becomes rough, there is a serious problem that the roughening tends to scatter light and increase the propagation loss.

Also, for example, if the core height increases, the core layer will be deposited thicker when forming the core layer by, for example, the CVD method.

Furthermore, in order to make such a nonlinear optical waveguide and a general passive device have different core heights in the same layer, a process to partially reduce the core height is required, making the manufacturing process redundant. That was the big problem.

In Non-Patent Document 2, as one approach to obtain desired dispersion characteristics other than increasing the core height, which has such problems, a rib-type SiN core is combined with a multi-cladding structure. However, this technology also has the problem that it is not a structure that can be easily manufactured and provided by an optical device foundry, and that a redesign that is optimized for such an optical waveguide structure is required to configure a passive device. rice field.

In addition, as another approach, as described in Non-Patent Document 3, a technique of forming a double ring structure using a thin SiN core has been proposed. However, as described above, this technique requires proper mode coupling between even and odd modes by adjusting the propagation length, and has the problem of a narrow operating band.

As described above, conventional optical device foundries have good single-mode properties, low loss properties, ease of design and manufacture, and good integration with other optical elements (for example, laser light sources, photodetectors, and passive optical waveguide elements). There is a problem that there is no optical device with a low introduction barrier in the field.

The present invention has been made to solve the above problems, and has a single-mode property, low loss property, ease of design and manufacture, good integration with other optical elements, and an optical device. The purpose is to provide an optical device with a low introduction barrier in the device foundry.

An optical device according to the present invention includes a first core having a nonlinear optical effect formed on a lower clad layer, a second core formed on the lower clad layer, and a first core on the lower clad layer. and an upper clad layer formed covering the second core, the first core and the second core constitute an optical waveguide having a super mode, and the refractive index and cross section of each of the first core and the second core The shape and the positional relationship between the first core and the second core in the cross section perpendicular to the waveguide direction are such that the supermode has the desired dispersion.

As described above, according to the present invention, an optical waveguide having a super mode is formed by the first core and the second core, and the refractive index, cross-sectional shape, and waveguide of each of the first core and the second core are Since the positional relationship between the first core and the second core in the cross section perpendicular to the direction is set to a state in which the super mode has the desired dispersion, single mode property, low loss, ease of design and manufacture, and other optical It is possible to provide an optical device with good integration with elements and a low introduction barrier in the optical device foundry.

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

An optical device according to an embodiment of the present invention will be described below.

[Embodiment 1]
First, an optical device according to Embodiment 1 of the present invention will be described with reference to FIG. This optical device comprises a lower clad layer 101 , a first core 102 , a second core 103 and an upper clad layer 104 . First core 102 and second core 103 are formed on lower clad layer 101 . Upper clad layer 104 is formed on lower clad layer 101 to cover first core 102 and second core 103 . In this example, the first core 102 is arranged above the second core 103 when viewed from the lower clad layer 101 side.

Here, first, the first core 102 has a nonlinear optical effect. Also, the first core 102 and the second core 103 constitute an optical waveguide having a super mode. Furthermore, the refractive index and cross-sectional shape of each 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 the cross section perpendicular to the waveguide direction are such that the super mode has the desired dispersion. It is considered to be in a state of having For example, even if each of the optical waveguide by the first core 102 and the optical waveguide by the second core 103 has normal dispersion, the first core 102 and the second core are arranged such that the above-described super mode has anomalous dispersion. 103 are set in cross-sectional shape and positional relationship.

　Super mode dispersion design is possible by two-dimensional cross-sectional mode calculation, and does not require a complicated design like Non-Patent Document 4, which considers mode coupling in the propagation direction. Therefore, according to the optical device according to the first embodiment, the operating band can be designed with a high degree of freedom.

Also, the core height of the first core 102 is set to a height that matches another optical device that is optically connected to the optical waveguide by the first core 102 . Similarly, the core height of the second core 103 is set to match other optical devices optically connected to the optical waveguide by the second core 103 . Therefore, it is easy to integrate these other optical devices with the optical device according to the first embodiment.

For example, the first core 102 can be made of SiN, and the second core 103 can be made of InP. The first core 102 can 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 can have a cross-sectional shape perpendicular to the waveguide direction with a width of 300 nm and a core height of 350 nm. Also, the distance (gap) between the first core 102 and the second core 103 in the thickness direction can be set to 300 nm. Also, the distance (offset) between the center of the first core 102 and the center of the second core 103 in the planar direction of the lower clad layer 101 within the plane perpendicular to the waveguide direction can be set to 0 nm. Note that FIG. 1 shows an example in which the center of the first core 102 and the center of the second core 103 are shifted and the offset is not zero.

Also, the lower clad layer 101 and the upper clad layer 104 can be made of silicon oxide. For example, the lower clad layer 101 can be made of silicon oxide formed by thermally oxidizing the surface of a silicon substrate. Also, the upper cladding layer 104 can be composed of a SiO ₂ film deposited by a known CVD method.

FIG. 2 shows the electromagnetic field distribution of the light propagation mode in the first core 102 and the second core 103 calculated under the conditions described above. FIG. 2A 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, (b) of FIG. 2 is a high-order TE mode, in which light is strongly confined in the first core 102, and at the same time, the second core 103 also has an electromagnetic field distribution, resulting in a super mode. I know there is. In the mode shown in FIG. 2(b), the light confinement factor to the first core 102 is 73%.

FIG. 3(a) shows second-order chromatic dispersion (D ₂ ) in the lowest-order TE mode. It is a normal dispersion optical waveguide having a negative value of D ₂ over the entire wavelength range of 1500 nm to 1600 nm, and is poorly used as a nonlinear optical waveguide as it is. For reference, D ₂ of the single SiN optical waveguide shown in FIG. 12 is shown in FIG. 3(c). Next, FIG. 3B shows the chromatic dispersion of the high-order TE mode described above. It can be seen that D ₂ can be anomalous dispersion having a positive value in the entire wavelength range of 1500 nm to 1600 nm.

Further, _FIG . 4 shows the relationship between the change in gap and D2. As shown in FIG. 4, the gap can realize anomalous dispersion in a wide range of 200 nm to 500 nm, and a large manufacturing margin can be obtained.

Next, FIG. 5 shows the relationship between the core width of the _second core 103 and D2. Note that the gap described above is set to 500 nm. As shown in FIG. 5, when the core width of the second core 103 is 400 nm, normal dispersion is obtained. On the other hand, when the core width of the second core 103 is 300 nm and 200 nm, anomalous dispersion is obtained.

In order to increase the optical confinement in the first core 102 and more efficiently develop the nonlinear optical effect, when designing the above cross-sectional structure, not only the dispersion but also the optical confinement coefficient to the first core 102 should be considered. Designed to be as large as possible.

FIG. 6 shows the optical confinement coefficient in the first core 102 when the core widths of the second core 103 shown in FIG. 5 are 400 nm, 300 nm, and 200 nm. When the core width of the second core 103 is 300 nm, which provides anomalous dispersion, the confinement factor in the first core 102 is about 73% (wavelength 1550 nm). On the other hand, in the case of the second core 103 having a core width of 200 nm, which also provides anomalous dispersion, the confinement factor in the first core 102 decreases to about 67% (wavelength 1550 nm). In this way, the design may be made by comprehensively considering the dispersion and the optical confinement factor.

In the above description, the wavelength band of 1500 nm to 1600 nm has been described, but in a wider wavelength range, suitable materials with low loss as optical waveguide materials are combined, and the first core 102 and the second core 102 of the optical device according to Embodiment 1 are combined. It is clear that designing the structural parameters for core 103 provides the desired dispersion characteristics.

In the above description, the control of D ₂ and the optical confinement factor has been described. It is clear that higher-order dispersion, polarization mode dispersion, etc. can also be appropriately controlled. Further, by periodically changing the structures of the first core 102 and the second core 103 in the light propagation (guiding) direction, conditions such as quasi-phase matching of propagating light can be satisfied, or the light propagation direction can be satisfied. Based on the design theory shown in Non-Patent Document 3, it is possible to obtain the necessary mode coupling conditions.

By the way, the configuration of the optical device according to Embodiment 1 described with reference to FIG. 1 is an example, and can be changed as appropriate in consideration of, for example, manufacturability. For example, the upper clad layer 104 made of silicon oxide may be formed up to the bottom surface of the first core 102 , and the first core 102 may not be covered with the upper clad layer 104 . With such a configuration, for example, it can be applied to an optical sensor that optically detects the presence or absence of some substance above the first core 102, which is particularly important industrially.

Next, an example in which the optical device according to Embodiment 1 is applied to an integrated optical device will be described with reference to FIG. This integrated optical device is a combination of the semiconductor laser light source and the optical device according to the first embodiment.

In FIG. 7, reference numeral 201 is a membrane laser described in Non-Patent Document 4, which is fabricated on a SiO ₂ /Si substrate 202 .

InP cores

203a, 203b, and 203c correspond to the second cores. The InP core 203a serves as an output optical waveguide core of the membrane laser 201, which is also made of an InP-based material. A SiN core 204a is placed over the

InP cores

203a and 203b, and a SiN core 204b is placed over the InP core 203c. The

SiN cores

204a and 204b correspond to the first core.

In the output optical waveguide of the membrane laser 201, the light propagation mode has an electromagnetic field within the InP core 203a as shown in FIG. 8A. The width of the InP core 203a is gradually narrowed in a tapered shape, and the mode is adiabatically converted while the output light from the membrane laser 201 propagates. This is a light propagation mode in which an electromagnetic field mainly exists in the SiN core 204a. The taper tip 205 is butt-coupled with a SiN optical waveguide as used in Patent Document 3, in which the InP core 203a does not exist, and beyond that, a SiN core having a light propagation mode as shown in FIG. 8C 204a for optical wiring.

Next, in order to connect with the nonlinear optical device according to the present invention, the InP core 203b is tapered again at the connection point, and then adiabatically mode-converted to the light propagation mode of the nonlinear optical waveguide shown in FIG. 8D. be done. The mode shown in FIG. 8D is the nonlinear optical waveguide of the optical device according to Embodiment 1 described using FIG.

A ring resonator 206 is fabricated by the SiN core 204a, the ring-shaped InP core 203c, the InP core 203b, and the ring-shaped SiN core 204b, which constitute the nonlinear optical waveguide. The ring resonator 206 is a nonlinear optical waveguide device that takes advantage of the increased light intensity within the resonator.

After that, the mode is adiabatically converted again through the taper of the InP core 203b, and is connected to the SiN optical waveguide of the output destination. Here, the SiN optical waveguide may be a general-purpose optical waveguide as disclosed 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 pump light from the membrane laser 201, a low-loss fiber coupling device, a spatial light radiation device, etc. can be integrated.

Here, the

InP cores

203a, 203b, and 203c are made to have the same thickness in the output optical waveguide portion of the membrane laser 201 and in the nonlinear optical waveguide portion by a manufacturing method as shown in Non-Patent Document 5. They can be easily formed in the same layer. In addition, the

SiN cores

204a and 204b are made to have a layer thickness that becomes the designed gap by depositing SiO ₂ by CVD method and performing CMP polishing after producing the InP core described above. They may be formed in the same layer by such a manufacturing method.

With the integrated optical device shown in FIG. 7, for example, by sweeping the oscillation wavelength of the membrane laser 201 from the short wavelength side to the long wavelength side across the resonance wavelength of the ring resonator 206, the inside of the

SiN cores

204a and 204b Through the χ ⁽³⁾ nonlinear process, frequency comb light is obtained from the output SiN optical waveguide. That is, an integrated comb light source in which a pump laser and a nonlinear microresonator are integrated can be realized.

Although only membrane lasers are described here, other membrane devices such as phase shifters for generating solitons in nonlinear microcavities and heater structures for wavelength tuning of ring cavities are integrated as membrane devices. It is also possible to

[Embodiment 2]
Next, an optical device according to Embodiment 2 of the present invention will be described with reference to FIG. This optical device comprises a lower clad layer 101 , a first core 102 a , a second core 103 and an upper clad layer 104 . First core 102 a and second core 103 are formed on lower clad layer 101 . Upper clad layer 104 is formed on lower clad layer 101 to cover first core 102 a and second core 103 . In this example, when viewed from the lower clad layer 101 side, the second core 103 is arranged above the first core 102a.

In Embodiment 2, the first core 102a has a nonlinear optical effect. Also, the first core 102a and the second core 103 constitute an optical waveguide having a super mode. In this example, the first core 102a is rib-shaped.

Also in the second embodiment, the refractive index, the cross-sectional shape, and the positional relationship between the first core 102a and the second core 103 in the cross section perpendicular to the waveguide direction of each of the first core 102a and the second core 103 are , the supermode is assumed to have the desired dispersion. For example, even if each of the optical waveguide by the first core 102a and the optical waveguide by the second core 103 has normal dispersion, the first core 102a and the second core may 103 are set in cross-sectional shape and positional relationship.

Also, the core height of the first core 102a is set to a height that matches another optical device that is optically connected to the optical waveguide by the first core 102a. Similarly, the core height of the second core 103 is set to match other optical devices optically connected to the optical waveguide by the second core 103 . Therefore, it is easy to integrate these other optical devices with the optical device according to the second embodiment.

The first core 102a can be made of, for example, LiNbO ₃ and the second core 103 can be made of InP. The first core 102a can have a slab thickness of 100 nm, a width of 1000 nm in a cross-sectional shape perpendicular to the waveguide direction, and a total height including the slab of 200 nm. The second core 103 can have a cross-sectional shape perpendicular to the waveguide direction with a width of 300 nm and a core height of 350 nm.

Also, the distance (gap) between the first core 102a and the second core 103 in the thickness direction can be set to 300 nm. Also, 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 clad layer 101 within the plane perpendicular to the waveguide direction can be set to 0 nm. Note that FIG. 9 shows an example in which the center of the first core 102a and the center of the second core 103 are deviated, and the offset is not zero.

The electromagnetic field distributions of the light propagation modes calculated under the above conditions are shown in FIGS. 10A, 10B, and 10C. FIG. 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, FIG. 10B shows a higher-order TE mode, in which light is strongly confined in the first core 102a and, at the same time, the second core 103 also has an electromagnetic field distribution. . Note that the light confinement factor to the first core 102a in the mode of FIG. 10B is 43%. For reference, FIG. 10C also shows the electromagnetic field distribution of the lowest-order TE mode when only the first core 102a exists.

Fig. 10 shows the electromagnetic field distribution of the light propagation mode calculated for such an optical waveguide structure. FIG. 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, FIG. 10B shows a higher-order TE mode, in which light is strongly confined in the first core 102a, and at the same time, the second core 103 is also in a super mode in which an electromagnetic field distribution exists. I understand.

Note that the light confinement factor to the LiNbO ₃ core in the mode of FIG. 10B is 43%. For reference, 10-3 also shows the electromagnetic field distribution of the lowest-order TE mode when only the LiNbO ₃ core exists.

FIG. 11(a) shows D ₂ of the lowest-order TE mode (FIG. 10A). It is a normal dispersion optical waveguide having a negative value of D ₂ over the entire wavelength range of 1500 nm to 1600 nm, and is poorly used as a nonlinear optical waveguide as it is. FIG. 11(c) shows D ₂ of the lowest-order TE mode in the case of only the first core 102a shown in FIG. 10C. As in FIG. 11(a), the normal dispersion optical waveguide has a negative value of D ₂ over the entire wavelength range of 1500 nm to 1600 nm, and is poorly used as a nonlinear optical waveguide.

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 D ₂ has a positive value over the entire wavelength range of 1500 nm to 1600 nm, as shown in FIG. 11(b).

As described above, the ability to obtain anomalous dispersion even in the first core 102a having a small core thickness is particularly effective in reducing propagation loss, and is particularly effective in increasing the Q value of an optical resonator. For example, in the case of materials such as LiNbO ₃ that are difficult to process, the smaller the core height, the smaller the effect of scattering loss caused by rough processing of the core side walls.

In the above description, the wavelength band of 1500 nm to 1600 nm has been described, but in a wider wavelength range, suitable materials with low loss as optical waveguide materials are combined, and the first core 102a and the second core 102a of the optical device according to the second embodiment are combined. It is clear that designing the structural parameters for core 103 provides the desired dispersion characteristics. Moreover, it is clear that not only D ₂ and the optical confinement coefficient but also higher-order dispersion, polarization mode dispersion, etc. can be appropriately controlled. In addition, by periodically changing the structure of the first core 102a and the second core 103 in the light propagation direction, conditions such as quasi-phase matching of propagating light can be met, or in the light propagation direction It is also possible to obtain the required mode-coupling conditions based on the design theory presented in 2.

The configuration of the optical device according to Embodiment 2 described with reference to FIG. 9 is an example, and can be changed as appropriate in consideration of, for example, manufacturability. For example, the upper clad layer 104 made of silicon oxide may extend to the bottom surface of the second core 103 , and the second core 103 may not be covered with the upper clad layer 104 . With such a structure, it can be applied to an optical sensor that optically detects the presence or absence of some substance above the second core 103, which is particularly important industrially.

By the way, LiNbO ₃ forming the first core 102a is widely used as a material having χ ⁽²⁾ nonlinearity in addition to χ ⁽³⁾ nonlinearity. Therefore, according to the optical device according to the second embodiment, in addition to the χ ⁽³⁾ nonlinear process that is generally used in SiN and the like, it is possible to utilize the χ ⁽³⁾ nonlinear process, which is an excellent effect. is obtained. In addition, the nonlinear optical device realized by the existing LiNbO ₃ optical waveguide does not have an integrated excitation light source, but the use of the optical device according to the second embodiment makes it possible to integrate the excitation light source. effect is obtained. For example, when configuring an integrated comb light source with a semiconductor laser light source as described with reference to FIG. 7, it can be similarly realized by appropriately adjusting the arrangement of the first core and the second core.

As described above, according to the present invention, an optical waveguide having a super mode is formed by the first core and the second core, and the refractive index, cross-sectional shape, and waveguide of each of the first core and the second core are determined. The positional relationship between the first core and the second core in the cross section perpendicular to the wave direction is set to a state in which the supermode has a desired dispersion. It is possible to provide an optical device that is highly integrated with an optical element and has a low introduction barrier in an optical device foundry.

It should be noted that the present invention is not limited to the embodiments described above, and many modifications and combinations can be implemented by those skilled in the art within the technical concept of the present invention. It is clear.

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

Claims

a first core having a nonlinear optical effect formed on the lower clad layer;
a second core formed on the lower clad layer;
an upper clad layer formed over the lower clad layer and covering the first core and the second core;
An optical waveguide having a super mode is configured by the first core and the second core,
The refractive index of each of the first core and the second core, the cross-sectional shape, and the positional relationship between the first core and the second core in the cross section perpendicular to the waveguide direction are such that the super mode has desired dispersion. An optical device characterized by being in a state of having.
The optical device of claim 1, wherein
An optical device, wherein the core height of the first core is matched with another optical device optically connected to the optical waveguide by the first core.
3. The optical device according to claim 1, wherein
The optical device according to claim 1, wherein the core height of the second core is matched with another optical device optically connected to the optical waveguide by the second core.