JP2614365B2 - Polarization-independent waveguide optical device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the elimination of polarization dependence of a waveguide type optical device used for construction of an optical communication system, fabrication of an optical information processing apparatus, and the like.

[0002]

2. Description of the Related Art In the field of optical communication and optical information processing, optical devices have conventionally been bulk component types formed by combining microlenses, prisms, interference film filters, and the like.
A fiber type using an optical fiber has been used. However, since both require optical axis adjustment and assembly accuracy on the order of microns, productivity is poor and cost reduction is difficult. In addition, since a lens, a fiber, or the like is used as an element component, there is a limit to miniaturization of the device. In contrast, the waveguide type using an optical waveguide fabricated on a flat substrate by photolithography microfabrication technology is a bulk component type or fiber type in terms of mass productivity, miniaturization, integration, and reproducibility. It is superior to the mold and is considered to become the mainstream of optical devices in the future. This is analogous to the advancement of vacuum tubes to ICs (integrated circuits) in the field of electronic devices.

FIG. 10 shows an optical multiplexer / demultiplexer using a Mach-Zehnder interferometer as an example of a conventional waveguide type optical device. This device is a first device fabricated on a silicon substrate 50.
Input waveguide 51 and second input waveguide 52, first directional coupler 53, second directional coupler 54, first optical path 5
5, a second optical path 56, a first output waveguide 57, and a second output waveguide 58. As the waveguide material, quartz glass produced by a flame deposition method is used. The first and second optical paths differ in length by ΔL. The directional coupler is half the full coupling length, and the input light from the first input waveguide is equally split into a first optical path and a second optical path. Light from the first optical path and the second optical path reach the outlets of the first and second output waveguides after being mixed by the second directional coupler. FIG. 11A shows the wavelength characteristics of the output. The output from the first output waveguide (first output) and the output from the second output waveguide (second output) change sinusoidally with respect to the wavelength. For example, wavelength λ ₁ ,
When _two- wave multiplexed light of λ ₂ is input, light of λ ₁ can be extracted from the first output and light of λ ₂ can be extracted from the second output. That is, it has a wavelength demultiplexing function. When the output side and the input side are inverted due to the reciprocity of light, a wavelength multiplexing function of extracting two waves having different wavelengths from one output is obtained.

In the Mach-Zehnder interferometer using the directional coupler shown in FIG. 10, when the optical path length difference becomes an integral multiple of the wavelength (light propagates from the first input to the second output), a cross state occurs. become. The wavelength at that time is λ ₀ . Previous λ ₂
Is also one of the plurality of λ ₀ . λ ₀ is the following (1)
Given by the formula. λ ₀ = n _c ΔL / m

[0005] where n _c is the effective refractive index in the first and second waveguides, m is a positive integer number that represents the order of interference. In such a device using light interference, the optical path length difference ΔL is an important parameter that determines λ ₀ , which is the center wavelength of the transmission wavelength range, and its accuracy must be several tenths or less of the wavelength. In this regard, in the waveguide type optical device, since the fabrication size of the waveguide is determined by the accuracy of the photolithography process, it is much superior to a bulk component type or fiber type which requires assembly.

[0006]

However, FIG.
When a device of No. 0 was manufactured and measured, there was a problem that there was polarization dependence. FIG. 11B shows the measurement result of the wavelength dependence of the second output of the Mach-Zehnder interferometer of FIG. The center wavelength λ _{0 is} shifted between the horizontal polarization (TE) and the vertical polarization (TM), and the multiplexing / demultiplexing function is affected by the polarization. This is because the effective refractive index n _c of the waveguide is different between TE and TM, that is, the waveguide has birefringence. Quartz glass is originally optically isotropic and does not have birefringence.However, in a quartz-based waveguide fabricated on a silicon substrate, the compressive stress in the horizontal direction from the silicon substrate is applied to the quartz glass, which causes the birefringence. Produces refraction.

Generally, the birefringence of a waveguide results from the optical anisotropy of the waveguide material, the asymmetry of the core shape, and the like. Various techniques for removing the birefringence of the waveguide have been researched and developed, but at present there is no definitive solution. For this reason, various waveguide-type optical devices such as a waveguide-type optical multiplexer / demultiplexer using the above-mentioned Mach-Zehnder interferometer, such as an intensity modulator and a ring resonator, have characteristics that their characteristics have polarization dependence. Had a problem.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to solve the problem of polarization dependence, and to provide a more practical waveguide type optical device.

[0009]

As described above, since the birefringence of the channel waveguide depends on the material and the shape used, it is difficult to remove the birefringence after the channel waveguide is manufactured.
Therefore, the present invention proposes a new optical circuit configuration for eliminating the polarization dependence of the waveguide type optical device without removing the birefringence. A feature of the present invention is that a polarization rotator is arranged in the middle of the waveguide, so that all wavelength components in the operating range are provided.
Converts horizontally polarized light into vertically polarized light and vertically polarized light into horizontally polarized light, and equalizes the optical path length in the device for both horizontally polarized and vertically polarized input signal light components. I do.

[0010]

The operation of the present invention will be described as applied to a waveguide type optical multiplexer / demultiplexer using the Mach-Zehnder interferometer of FIG. 10 as an example. When the above-described polarization rotator is disposed at an intermediate point between the first optical path and the second optical path ,
Since the TE input light of the wavelength component changes to TM light on the way, and the TM input light changes to TE light on the way, the phase rotation amount of the light is the same for the input lights of both polarizations. There is no change in the operation of the interferometer for either polarization.
That is, the polarization dependence on the incident signal light is eliminated. As described above, the present invention provides the entire operation range in the middle of the waveguide.
The feature is that the polarization of all wavelength components is exchanged, and the optical path length can be made equal for both TE and TM inputs. The application of this function is not limited to the Mach-Zehnder interferometer, but can be applied to various optical waveguide circuits such as a ring resonator, an array waveguide diffraction grating, and a directional coupler.

[0011]

FIG. 1 shows a first embodiment of the present invention, in which a Mach-Zehnder interferometer composed of two single-mode waveguides formed on a silicon substrate 1 having a thickness of 750 μm is used. This is a waveguide type optical multiplexer / demultiplexer. The waveguide is a quartz-based waveguide manufactured by a flame deposition method and reactive ion etching. The cross section has a structure in which a core having a size of 7 μm × 7 μm is buried almost in the center of a 50 μm thick cladding glass film deposited on a silicon substrate. The relative refractive index difference between the cladding and the core is 0.75%. The previous two waveguides include a first input 2, a second input 3, a first directional coupler 4, a second directional coupler 5, a first optical path 6, and a second optical path 7. , A first output 8 and a second output 9. The first and second directional couplers have a branching ratio of 50%. The first and second optical paths differ in length by ΔL. A groove 1 having a width of 90 μm and a depth of 300 μm is formed on a straight line passing through the intermediate point between the first optical path and the second optical path.
0 is dug. Either etching or machining with a dicing saw or the like may be used to form the grooves. In the groove, a 85 μm thick Y-cut quartz plate 1 cut so that the optical main axis forms an angle of 45 ° with the substrate
1 (polarization rotator) is embedded. For fixing the quartz plate, an ultraviolet curable resin having the same refractive index as that of the waveguide is used so as to suppress the reflection of light generated at the end of the waveguide. The quartz plate acts as a λ / 2 plate, and rotates the polarization plane by 90 degrees so that the 1.55 μm wavelength TE light propagated through the first and second optical paths becomes TM light, and the TM light becomes TE light. Let it.
An optical fiber is connected to the first input (not shown).
When an optical fiber is connected to the second input, only the first output and the second output are interchanged in the following description, and the operation of the waveguide type optical multiplexer / demultiplexer is not affected. The signal light from the first input is equally divided in power by the first directional coupler, propagates independently through the first and second optical paths, and rejoins at the second directional coupler. Retrieved from the first and second outputs.

In the case of this embodiment, unlike the case of FIG.
Since the polarizations are switched on the way, λ ₀ is modified as follows. When the input is TE, λ ₀ = (nc _(TE) ΔL / 2 + nc _(TM) ΔL / 2) / m (2) When the input is TM, λ ₀ = (nc _(TM) ΔL / 2 + nc _{( TE)} ΔL / 2 ) / m (3) Obviously, the values of both formulas match, indicating that the center wavelength λ ₀ does not depend on the polarization.

FIG. 2 is a graph showing the characteristics of the optical multiplexer / demultiplexer of this embodiment. In measuring the characteristics, assuming an actual communication system, the input signal light contains all polarizations.
ED was used. The horizontal axis represents the wavelength of the signal light, and the vertical axis represents the loss amount of light extracted from the second output. For comparison, the characteristics of the conventional optical multiplexer / demultiplexer having polarization dependency shown in FIG. 10 are indicated by broken lines. The solid line is the case of the present embodiment. In the conventional case, since λ ₀ differs depending on the polarization, there are two peaks, and the power of the incident signal light is also TE
And TM, the loss at the peak wavelength was 3 dB. On the other hand, in the present invention, the above two peaks coincide with each other, and the polarization dependence is eliminated.
Accordingly, the pass band width is narrower than in the conventional case. The loss is 4dB, but the cause is
Since the / 2 plate has been inserted, the loss can be reduced to 0 dB in principle by reducing the loss due to the groove. The method will be described later with reference to FIG.

FIG. 3 shows a second embodiment, in which the present invention is applied to a waveguide ring resonator. Silicon substrate 1
2, an input waveguide 13, a ring waveguide 14, and an output waveguide 15 are arranged. The input waveguide and the ring waveguide are a first directional coupler 16, and the output waveguide and the ring waveguide are a second directional coupler. They are connected by a directional coupler 17. The dimensions, manufacturing conditions, propagation characteristics, and the like of the waveguide are the same as in the first embodiment. In addition, a waveguide type λ / 2 plate 19 (polarization rotator) using the stress release groove 18 is formed at two places in the ring waveguide. The details are shown in FIG. 9, and the function is to exchange the TE mode and the TM mode. It should be noted that the shape of the ring waveguide is not limited to a circle, but may be closed in a ring shape. At this time, the positions of the two waveguide λ / 2 plates divide the length of the ring waveguide into two equal parts. The location can be anywhere as long as it is a location.

Light incident from the input fiber 20 enters the ring waveguide from the first directional coupler, and only the resonance wavelength determined by the length L (resonance length) of one circumference of the ring waveguide is in the second directionality. The light is guided to the output waveguide through the coupler and extracted from the output fiber 21. FIG. 4 shows the output characteristic (a) of the present embodiment and the conventional output characteristic (b) without the polarization rotator when the intensity of the input light is 1, and the horizontal axis represents the wavelength,
The vertical axis is the optical output (transmittance when the input is 1).
The resonance wavelength λ _O of the ring resonator can be determined by the length of one circumference (effective resonance length) n _C L in consideration of the effective refractive index of the waveguide. The effective resonance length in the case of this embodiment is the same for both TE and TM inputs.

N _C L = n _{C (TE)} · L / 2 + n _{C (TM)} · L / 2 (4), and the resonance wavelength λ ₀ is λ ₀ = n _C L where the order is m (integer). / M. Therefore, the characteristic shows the characteristic of an ideal ring resonator as shown in FIG. On the other hand, in the conventional type (b) having polarization dependence, since the effective resonance length differs depending on the polarization, λ ₀ (TE) = n _{C (TE)} L / m (5 ) Λ ₀ (TM) = n _{C (TM)} L / m (6) Moreover, the power of the input light is T
The output is 0.5 at the maximum because it is distributed to two modes, E and TM.

As described above, according to the present invention, it is possible to easily eliminate the polarization dependence of the waveguide type ring resonator by manufacturing the waveguide type λ / 2 plate at two locations. Become. The position of the waveguide type λ / 2 plate is not limited to the position shown in the drawing, but may be any position as long as the circumference of the ring waveguide is bisected. In particular, it should be noted that if the antenna is disposed at the intermediate point of the directional coupler, the polarization dependence of the directional coupler can be eliminated, so that the characteristics can be further improved. In the present embodiment, the waveguide type λ / 2 plate is formed at two places, but the present invention is not limited to this, and it is apparent that the same effect can be obtained if the number is even. It is. In the case of an odd number such as 1 or 3, the resonance length is doubled while the effect of eliminating the polarization dependency is maintained.
In other words, it is noted that the length of the ring waveguide can be reduced to half, and the size can be reduced.

FIG. 5 shows a third embodiment of the present invention, which is applied to an optical multiplexer / demultiplexer using an arrayed waveguide type diffraction grating. On a silicon substrate 22, an input waveguide 23, a first
The slab waveguide 24, array waveguide 25, second slab waveguide 27, and a plurality of output waveguides 28 are sequentially connected. The material, dimensions, characteristics, etc. of the waveguide are the same as in the first embodiment. Each of the two slab waveguides has a sector shape with the end of the input waveguide or the output waveguide at the center of curvature. The array waveguide 25 is composed of a plurality of channel waveguides 26 having different lengths by ΔL. A groove 29 is formed, into which a λ / 2 plate 30 (polarization rotator) is inserted. The dimensions and characteristics of the groove 29 and the λ / 2 plate 30 are the same as in the first embodiment. Although the λ / 2 plate 30 needs to be arranged at the midpoint of each channel waveguide 26, the array waveguide 25 is designed symmetrically so that the midpoint of each channel waveguide 26 is aligned on a straight line. The groove 29 is formed as one continuous straight line. At this time, the λ / 2 plate 30 is provided with all the channel waveguides 2 constituting the array waveguide 25.
One having a length across 6 is sufficient. Depending on the design, it may not be symmetrical, but at that time, since the grooves 29 are not on one straight line, it is necessary to insert as many λ / 2 plates 30 as the number of the channel waveguides 26, and the amount of work increases, so that it is less preferable. Absent.

The effect of eliminating the polarization dependency when the present invention is applied to an arrayed waveguide diffraction grating is the same as that of the Mach-Zehnder interferometer of the first embodiment. FIG. 6 is a graph showing the wavelength characteristic of the loss of the optical multiplexer / demultiplexer of FIG. The solid line shows the case of the arrayed waveguide grating in which the polarization dependency is eliminated by the method of the present invention, and the broken line shows the case of the conventional arrayed waveguide grating having polarization dependency. In the conventional type, since the TE component and the TM component of the incident light have different n _C , two peaks are generated. Further, since the input power is distributed to two components, TE and TM, the loss of the transmission wavelength is 3
dB. On the other hand, in the case of the present invention, the polarization dependence has been eliminated, and the above two peaks coincide. Accordingly, the pass band width is narrower than in the conventional case. The loss is 4 dB, but the reason is that
Since the plate has been inserted, the loss can be reduced to 0 dB in principle by reducing the loss in the groove.
The method will be described later with reference to FIG.

FIG. 7 shows a fourth embodiment in which the present invention is applied to a directional coupler. On the silicon substrate 31, a first input waveguide 32, a second input waveguide 33, a directional coupler 34, a first output waveguide 35, and a second output waveguide 36 are formed. A groove 37 is formed at an intermediate point of the coupler, and a quartz λ / 2 plate 38 (polarization rotator) is inserted therein. The dimensions and characteristics of the waveguide, groove, and λ / 2 plate used in this embodiment are the same as those in the first embodiment. The length L of the directional coupler at half the full coupling length, as the de-Bas chair has been designed to operate as a 3dB coupler (branching ratio of 1: 1), the present invention is not limited to this Instead, the present invention can be applied to directional couplers having various branching ratios.

The effective refractive indices of two propagation modes (even mode and odd mode) in the directional coupler are ne and n _e , respectively.
and n _o, depending on the polarization (TE), attach a subscript of (TM). Even and odd modes are excited at the left end of the directional coupler by the light propagating from the first input waveguide. Since the polarization planes are exchanged on the way, the difference between the optical path lengths of the even mode and the odd mode is as follows. For the TE input, ( _{ne (TE)} L / 2 + _{ne (TM)} L / 2)-(no _(TE) L / 2 + no _(TM) L / 2) (7) For the TM input, ( _{Ne (TM)} L / 2 + _{ne (TE)} L / 2)-(no _(TM) L / 2 + no _(TE) L / 2) (8), and the values of the two coincide. Therefore, the branching ratio has no polarization dependence. The length L of the directional coupler is given by Equation 7 and 8
Since the value of the equation is set to be 1/4 of the wavelength, one-to-one distributed power is extracted from the first and second output waveguides. Of course, the present invention has a branching ratio of 1
It is clear that the invention is not limited to one-to-one but can be applied to various branching ratios.

Of the above four embodiments, the Mach-Zehnder interferometer, the array waveguide diffraction grating, the directional coupler have a λ / 2 plate inserted in a groove as a polarization rotator, and the ring resonator has a stress release groove. The used waveguide type λ / 2 plate is used. Which of the polarization rotators is used depends on which of the precision and the loss of the polarization rotation angle is prioritized. In the case of a ring resonator, if the loss is large, the finesse becomes small and the resonance itself deteriorates, so the waveguide type λ / 2 having a small loss was used. Of course, the effect of the present invention is effective regardless of which polarization rotator is used for any waveguide type optical device.

In the first, third and fourth embodiments, since the inserted λ / 2 plate does not have a waveguide structure,
The beam is divergent and loss occurs. Ideally, it is desirable to form a core having a high refractive index at a desired position on the λ / 2 plate to form a waveguide structure. However, when inserting the λ / 2 plate into the groove, it is necessary to accurately align the core of the waveguide with the core of the λ / 2 plate. As a simple method of reducing loss,
The method shown in FIG. 8 is useful.

First, it is desirable to increase the width of the waveguide near the groove. If the width of the waveguide is increased, the spread angle of the beam in the horizontal direction is reduced, and the loss can be suppressed.
It is preferable to insert a tapered waveguide 41 at the connection portion between the waveguide 40 having a normal width and the wide waveguide 42 near the groove to suppress the mode conversion loss that occurs when the waveguide width changes. The same can be said for the vertical direction. It is preferable that the thickness of the waveguide film is made larger than the thickness of the waveguide film at 40, and the thickness of the tapered waveguide in the middle is gradually changed. However,
If the manufacturing process is complicated, all the waveguides must be 42
May be set. At this time, the waveguide is multi-mode in the thickness direction, but in a waveguide fabricated on a flat substrate, since light bends only in the horizontal direction, the probability that a higher-order mode in the thickness direction occurs during propagation is low, Low modal noise. However, it should be noted that when light is input from the input fiber to the waveguide, it is necessary to perform strict alignment in the thickness direction and take care not to excite higher-order modes.

Second, when the curved waveguide 39 exists near the groove, the groove and the curved waveguide should not be directly joined.
It is desirable to insert a straight waveguide between them. This is because, if light enters the quartz plate 44 without a waveguide structure while the wavefront is inclined in the curved waveguide, the traveling direction of the light is shifted and loss occurs. Therefore, if a straight waveguide is arranged between the curved waveguide and the quartz plate, the inclination of the wavefront is gradually recovered when propagating through the straight waveguide, and the loss can be reduced.

Thirdly, when used in an optical communication system in which reflected return light from the λ / 2 plate becomes a problem, the angle between the groove 43 and the waveguide 42 is slightly inclined from 90 degrees, and It is desirable that return light is not guided. Furthermore, it is obvious that the same effect can be obtained even if the groove is dug slightly inclining, not perpendicularly to the substrate.

It should be noted that a combination of the above-described formation of the waveguide structure in the λ / 2 plate and the method shown in FIG. 8 can further reduce the loss. Further, in the above-mentioned embodiment, a Y-cut quartz plate is used as the λ / 2 plate. This is because quartz is practical as a wave plate and its refractive index is close to that of quartz glass which is a waveguide material. This is because the loss due to reflection can be reduced, and the present invention is not limited to this. For example, use of various birefringent materials such as crystals such as magnesium fluoride, polymer films, and liquid crystals Can be. It is desirable that a non-reflective coating be applied to the surface so as to match the refractive index of the waveguide. Also, λ / 2
As the thickness of the plate, a thicker plate having a higher order can be used, but it is preferable to use a thinner plate as thin as possible in consideration of the above-mentioned beam spread.

A waveguide type phase plate (JP-A-63-147114) used as an example of the second polarization rotator will be described. FIGS. 9A and 9B are a sectional view of a waveguide and a plan view showing a configuration of the waveguide type phase plate. A cladding glass 46 is deposited on a silicon substrate 45, and a core 47 is embedded therein. The cladding glass near the core is removed by etching, and a stress release groove 48 is formed. The length of the stress release groove is designed such that the difference between the optical path lengths of two orthogonally polarized waves is の of the wavelength, that is, the λ / 2 plate operates. The position and size of the stress relief groove are designed so that the optical main axis 49 forms an angle of 22.5 degrees with the substrate perpendicular near the waveguide core. To convert TE and TM, that is, to rotate the plane of polarization by 90 degrees, the main axis must be inclined at 45 degrees. However, in the quartz-based waveguide used in this embodiment, since this cannot be realized due to the stress, the half of 22. 5 degrees. For this reason, since the polarization plane can be rotated only 45 degrees with one release groove, as shown in FIG.
It is designed to be turned 0 degrees. Of course, it can be realized in one stage depending on the material system used for the waveguide.

This polarization rotator can be applied to all of the first to fourth embodiments, and has the following two advantages. First,
The etching step for forming the stress release groove can be the same as the etching step for patterning the core of the waveguide, so that the manufacturing cost can be reduced. Second, the waveguides in the polarization rotator are continuous and identical to the other waveguides, and there is no loss at the connection.

As described above, the present invention relates to a Mach-Zehnder interferometer,
Ring resonator array waveguide diffraction grating has been described four embodiments applied to the directional coupler, the present invention is not limited thereto, various waveguide type optical de Bas y <br / > It can be applied to the solution of the polarization dependence of In particular, it would be useful for a Mach-Zehnder interferometer type intensity modulator on a lithium niobate substrate, which had a problem with strong polarization dependence. In the embodiment of the present invention,
Quartz glass on a silicon wafer is used as the waveguide material because quartz glass is the most practical material, and the present invention is not limited to this. However, it is apparent that the same polarization dependency eliminating effect can be obtained. In the present embodiment, the Mach-Zehnder interferometer on the silicon substrate 1, the ring resonator on the silicon substrate 12, the arrayed waveguide diffraction grating on the silicon substrate 22, and the directional coupler on the silicon substrate 31, Although the polarization rotators are provided, they may all be provided on the same silicon substrate.

Since the present invention is characterized in that the polarization is exchanged at the midpoint of the waveguide and the phase shift due to the polarization is canceled, the birefringence values of the first half and the second half of the waveguide with respect to the midpoint are determined. Must be equal. The birefringence of a quartz-based waveguide fabricated on a silicon substrate is due to compressive stress from the substrate, and concentric birefringence values may vary within the wafer. With this in mind,
Note that it is necessary to determine the layout of the waveguide so that the position where the polarization rotator is arranged is the center of symmetry of the birefringence distribution (for example, the center of the wafer). When a crystal such as lithium niobate is used as a waveguide, the birefringence distribution is not as high as that of a quartz-based waveguide on a silicon substrate. It is desirable to lay out so that the rotator is arranged.

[0032]

As described above, according to the present invention,
The operating range is controlled by the polarization rotator installed in the middle of the waveguide.
Replace the TE and TM modes for all wavelength components, it is possible to easily produce various waveguide type optical de Bas chair without polarization dependence. Polarization dependent waveguide type optical de Bas chair are dependent on the birefringence of the waveguide, conventionally,
Efforts have been made to remove birefringence to eliminate polarization dependence. However, the birefringence is also an inherent property of the waveguide material, and its removal requires a complicated process, so it has been difficult to say that it is a practical method. On the other hand, unlike the conventional method, the method of the present invention does not eliminate birefringence, but rather exchanges polarization for all wavelength components in the operating range and cancels polarization dependence. such a method, the basic principles can be applied to all of the guided optical de bus chair. Moreover, it can be manufactured by a very easy method such as digging a groove and inserting a λ / 2 plate, or digging a stress release groove, and the manufacturing cost is extremely low.

[0033] In a practical optical communication system, since it is difficult to keep the polarization of the transmission line constant, the optical de Bas chair is a necessary condition not influenced by polarization. According to the present invention, it is possible to provide a low cost can be mass-produced a polarization-independent waveguide-type optical de bus y <br/> scan, significant effect in building an optical communication system Can be expected.

[Brief description of the drawings]

FIG. 1 is a diagram showing a waveguide type optical multiplexer / demultiplexer using a Mach-Zehnder interferometer according to the present invention.

FIG. 2 is a graph showing the demultiplexing characteristics of the waveguide type optical multiplexer / demultiplexer shown in FIG.

FIG. 3 is a diagram showing a waveguide ring resonator according to the present invention.

FIG. 4 is a graph showing characteristics of the waveguide ring resonator of FIG.

FIG. 5 is a diagram showing a waveguide type optical multiplexer / demultiplexer using an array waveguide diffraction grating according to the present invention.

FIG. 6 is a graph showing a demultiplexing characteristic of the waveguide type optical multiplexer / demultiplexer shown in FIG. 3;

FIG. 7 is a diagram showing a waveguide type directional coupler according to the present invention.

FIG. 8 is a detailed view of a first polarization rotator according to the present invention.

FIG. 9 is a detailed view of a second polarization rotator according to the present invention.

FIG. 10 is a diagram showing a waveguide type optical multiplexer / demultiplexer using a conventional Mach-Zehnder interferometer.

11 is a graph showing characteristics of the waveguide type optical multiplexer / demultiplexer shown in FIG. It is.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Silicon substrate 2 1st input waveguide 3 2nd input waveguide 4 1st directional coupler 5 2nd directional coupler 6 1st optical path 7 2nd optical path 8 1st output waveguide Reference Signs List 9 second output waveguide 10 groove 11 quartz plate 12 silicon substrate 13 input waveguide 14 ring waveguide 15 output waveguide 16 first directional coupler 17 second directional coupler 18 stress release groove 19 waveguide Type λ / 2 plate 20 Input fiber 21 Output fiber 22 Silicon substrate 23 Input waveguide 24 First slab waveguide 25 Array waveguide 26 Channel waveguide 27 Second slab waveguide 28 Output waveguide 29 Groove 30 Quartz plate 31 Silicon substrate 32 First input waveguide 33 Second input waveguide 34 Directional coupler 35 First output waveguide 36 Second output waveguide 37 Groove 38 Quartz plate 39 Curved waveguide Reference Signs List 40 first linear waveguide 41 taper waveguide 42 second linear waveguide 43 groove 44 quartz plate 45 silicon substrate 46 cladding glass 47 core 48 stress release groove 49 optical main axis 50 silicon substrate 51 first input waveguide 52 second input waveguide 53 first directional coupler 54 second directional coupler 55 first optical path 56 second optical path 57 first output waveguide 58 second output waveguide

Claims (3)

(57) [Claims] 1. A waveguide type optical device comprising one or two or more birefringent waveguides fabricated on a substrate , wherein all wavelength components within the operating range are controlled.
A polarization rotator that converts horizontal polarization to vertical polarization and vertical polarization to horizontal polarization so that the optical path length for horizontal polarization input light and the optical path length for vertical polarization input light are equal.
A polarization independent waveguide type optical device, wherein one or two or more waveguides are provided in the middle of the waveguide. 2. A waveguide according to claim 1, wherein said polarization rotator has an angle perpendicular to or close to said waveguide, and is formed in a groove dug so as to traverse said waveguide. 2. The polarization-independent waveguide optical device according to claim 1, wherein the optical device is a λ / 2 plate installed at an angle. 3. The polarization-independent waveguide according to claim 1, wherein the polarization rotator is a waveguide type λ / 2 plate having a stress release groove formed near the waveguide. Type optical device.