Polarization-insensitive micro-ring resonator

Abstract

According to the polarization-insensitive micro-ring resonator provided by the invention, the bus waveguide and the runway annular waveguide based on the SION waveguide are designed into the micro-ring resonator, the micro-ring resonator is simple in structural design, and the section shape of the SION waveguide is controlled to be square, so that the effective refractive index of a TE mode is close to that of a TM mode; due to the fact that the bus waveguide and the runway annular waveguide are coupled in the straight waveguide area, the optical coupling coefficient of the coupling area is the same as the effective refractive index of the waveguides, especially at the O wave band (1260-1360 nm), the excellent polarization insensitive characteristic is achieved at the position with the center wavelength being 1310 nm, and therefore the micro-ring resonator has the resonance wavelength polarization insensitive characteristic. Therefore, the micro-ring resonator has a good coupling area polarization insensitive characteristic, and the micro-ring resonator designed based on the above structure has low insertion loss, so that the application of the micro-ring resonator in the fields of filters, wavelength division multiplexing systems, optical sensors and the like with high polarization insensitive requirements is expanded.

Description

Technical Field

[0001] The invention relates to the field of integrated optoelectronic devices, and in particular to a polarization-insensitive microring resonator. Background Art

[0002] As one of the most important devices in integrated optoelectronic chips, microring resonator has the advantages of small size, high integration and high detection sensitivity. It is widely used in modulators, filters, sensors, optical switches, nonlinear optics and other fields.

[0003] The main structure of the microring resonator is the coupler and the ring waveguide, especially the microring resonator based on traditional SOI materials. Its waveguide coupling under single-mode conditions has a very obvious birefringence effect, showing polarization-related characteristics, and its transmission loss is high, which is not conducive to the needs of practical applications such as polarization-insensitive dense wavelength division multiplexers.

[0004] Polarization-insensitive microring resonators in the prior art are all prepared based on SOI materials, and a special structural design is used to achieve polarization independence in the coupling zone and independence of the resonance wavelength. For example, an MMI structure can be used instead of a traditional directional coupler to achieve polarization independence in the coupling zone, but the polarization-independent spectral range of the coupling zone is narrow, and the MMI structure will introduce additional insertion loss. A cross silicon waveguide structure can also be used to achieve polarization insensitivity of the microring resonator, but experiments have shown that it can only achieve the characteristics of resonance wavelength independence, and the coupling zone is still polarization-dependent. Some people also introduce gratings in the straight waveguide coupling region to achieve polarization insensitivity of the microring resonator, but the presence of the grating will introduce additional insertion loss, and the actual design structure is relatively complex.

[0005] Therefore, it becomes a challenge to ensure that the coupling region polarization and resonant wavelength are both insensitive while making the microring resonator have smaller insertion loss and simpler structure. Summary of the invention

[0006] In view of the above-mentioned shortcomings of the prior art, an object of the present invention is to provide a polarization-insensitive microring resonator to solve the problem in the prior art that polarization insensitivity of the coupling region and resonance wavelength insensitivity must be achieved by introducing additional insertion loss and complex structural design.

[0007] To achieve the above objectives and other related objectives, the present invention provides a polarization-insensitive microring resonator, the microring resonator comprising:

[0008] A racetrack annular waveguide, comprising a first curved waveguide, a first straight waveguide, a second curved waveguide and a second straight waveguide, wherein the first curved waveguide and the second curved waveguide have the same bending radius, the first straight waveguide and the second straight waveguide are parallel to each other and have the same length; two ends of the first curved waveguide are respectively connected to one end of the first straight waveguide and the second straight waveguide, and two ends of the second curved waveguide are respectively connected to the other end of the first straight waveguide and the second straight waveguide, thereby forming a centrally symmetrical waveguide structure;

[0009] A first bus waveguide, wherein two ends of the first bus waveguide are respectively provided with an input end and a through end of an optical signal, the first bus waveguide is composed of a third straight waveguide and two third curved waveguides, and the third straight waveguide is arranged on the same side as the first straight waveguide and there is a first gap to form a first coupling region;

[0010] a second bus waveguide, wherein one end of the second bus waveguide is provided with an output end of an optical signal, the second bus waveguide is composed of a fourth straight waveguide and two fourth curved waveguides, and the fourth straight waveguide is provided on the same side as the second straight waveguide and there is a second gap to form a second coupling region;

[0011] The optical signal enters the first bus waveguide through the input end, and is divided into two beams of light through the coupling effect of the first coupling region. The light that does not meet the resonance condition is directly output from the through end of the first bus waveguide, and the light that meets the resonance condition is coupled into the racetrack ring waveguide, coupled to the second bus waveguide from the second coupling region and output from the output end of the second bus waveguide.

[0012] Optionally, the waveguides in the first bus waveguide, the second bus waveguide and the racetrack ring waveguide have a thickness of 1 μm to 1.5 μm and a width of 1 μm to 1.5 μm.

[0013] Optionally, the waveguide thickness and the waveguide width in the first bus waveguide, the second bus waveguide and the racetrack ring waveguide are of equal size.

[0014] Optionally, the length of the first coupling region is 20 μm to 50 μm, and the length of the second coupling region is 20 μm to 50 μm and is equal to the length of the first coupling region.

[0015] Optionally, the length of the first coupling region is 25 μm, and the length of the second coupling region is 25 μm.

[0016] Optionally, the width of the first gap is 1 μm to 2 μm, and the width of the second gap is 1 μm to 2 μm and is equal to the width of the first gap.

[0017] Optionally, the length of the racetrack ring waveguide is 2000 μm to 2100 μm.

[0018] Optionally, the first bus waveguide, the second bus waveguide and the racetrack ring waveguide are all single-mode waveguides.

[0019] Optionally, the effective refractive index of the first straight waveguide is the same as that of the third straight waveguide, and the effective refractive index of the second straight waveguide is the same as that of the fourth straight waveguide.

[0020] Optionally, the materials of the waveguides in the first bus waveguide, the second bus waveguide and the racetrack ring waveguide are independently selected from SION coated with a buried oxide layer on an insulator.

[0021] As described above, the polarization-insensitive microring resonator of the present invention has the following beneficial effects: the bus waveguide and the racetrack ring waveguide based on the SION waveguide are designed into a microring resonator, and the structural design is simple. By controlling the cross-sectional shape of the SION waveguide to be a square, the effective refractive index of the TE mode is made close to the effective refractive index of the TM mode, so that the microring resonator has the polarization-insensitive characteristic of the resonance wavelength, and because the bus waveguide and the racetrack ring waveguide are coupled in the straight waveguide region and the optical coupling coefficient of the coupling region is the same as the effective refractive index of the waveguide, the microring resonator has a good polarization-insensitive characteristic of the coupling region, especially in the O band (1260nm~1360nm), especially at the center wavelength of 1310nm, a very excellent polarization-insensitive characteristic is achieved, and it has a lower insertion loss, thereby expanding the application of the microring resonator in the fields of filters, wavelength division multiplexing systems and optical sensors with high polarization insensitivity requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Shown is a schematic cross-sectional structural diagram of a microring resonator in an embodiment of the present invention.

[0023] Figure 2 Shown is a schematic diagram of a top view of the structure of a microring resonator in an embodiment of the present invention.

[0024] Figure 3 Schematic diagram showing the variation of the effective refractive index of the microring resonator in TE and TM modes with the waveguide width in an embodiment of the present invention

[0025] Figure 4 Shown is a transmission spectrum diagram of the microring resonator in the embodiment of the present invention in TE and TM modes.

[0026] Figure 5 Display as Figure 4 A local enlarged view of AA′ in FIG.

[0027] Component number description

[0028] 101. first curved waveguide; 102. first straight waveguide; 103. second curved waveguide; 104. second straight waveguide; 105. third curved waveguide; 1051. input end of optical signal; 1052. through end; 106. third straight waveguide; 1061. first gap; 107. fourth curved waveguide; 1071. output end of optical signal; 1072. second gap; 108. fourth straight waveguide; 109. first coupling region; 110. second coupling region; 111. silicon substrate; 112. silicon dioxide oxide buried layer; 113. SION waveguide. DETAILED DESCRIPTION

[0029] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0030] For example, when describing the embodiments of the present invention in detail, for the sake of convenience, the schematic diagrams showing the device structure will not be partially enlarged according to the general scale, and the schematic diagrams are only examples, which should not limit the scope of protection of the present invention. In addition, in actual production, the three-dimensional dimensions of length, width and depth should be included.

[0031] For convenience of description, spatially relative terms such as "under", "below", "below", "below", "above", "on", etc. may be used herein to describe the relationship of one element or feature shown in the drawings to other elements or features. It will be understood that these spatially relative terms are intended to encompass other orientations of the device in use or operation in addition to the orientation depicted in the drawings.

[0032] In the context of the present application, a structure in which a first feature is described as being "above" a second feature may include embodiments in which the first and second features are in direct contact, and may also include embodiments in which additional features are formed between the first and second features, such that the first and second features may not be in direct contact.

[0033] See also Figures 1 to 5 It should be noted that the illustrations provided in this embodiment are only used to illustrate the basic concept of the present invention in a schematic manner, and therefore the illustrations only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0034] Embodiment 1:

[0035] Figure 1 1 is a schematic diagram of the cross-sectional structure of the polarization-insensitive microring resonator of the present invention. Among them, the materials of the waveguides in the first bus waveguide, the second bus waveguide and the racetrack ring waveguide are independently selected from SION coated by an oxide buried layer on an insulator, from bottom to top, respectively, a silicon substrate 111, a silicon dioxide oxide buried layer 112 and a SION waveguide 113 coated in the silicon dioxide oxide buried layer 112. In order to reduce the mode crosstalk and polarization-related loss in the waveguide and reduce the process difficulty, the shape of the SION waveguide 113 is designed to be a square waveguide, that is, the thickness and width of all waveguides in this embodiment have the same size.

[0036] like Figure 2As shown, it is a schematic diagram of the top view of the polarization-insensitive microring resonator, and the microring resonator is composed of a racetrack ring waveguide, a first bus waveguide and a second bus waveguide. The racetrack ring waveguide includes a first curved waveguide 101, a first straight waveguide 102, a second curved waveguide 103 and a second straight waveguide 104. In order to prepare a compact microring resonator device, the total length of the racetrack ring waveguide is 2000μm to 2100μm, for example, it can be 2000μm, 2025μm, 2055μm, 2085μm or 2100μm, and the first curved waveguide 101 and the second curved waveguide 103 are set to have the same bending radius, and the first curved waveguide 101 The first straight waveguide 102 and the second straight waveguide 104 are both U-shaped waveguides, the first straight waveguide 102 and the second straight waveguide 104 are symmetrical strip straight waveguide structures, and the first straight waveguide 102 and the second straight waveguide 104 are equal in length and arranged in parallel with each other. In order to prepare a compact microring resonator device, considering the process reasons comprehensively, the spacing between the first straight waveguide 102 and the second straight waveguide 104 can be set according to actual needs, the two ends of the first curved waveguide 101 are respectively connected to one end of the first straight waveguide 102 and the second straight waveguide 104, and the second curved waveguide The two ends of the first straight waveguide 103 are respectively connected to the other ends of the first straight waveguide 102 and the second straight waveguide 104, thereby forming a centrally symmetrical waveguide structure; the first bus waveguide, the two ends of the first bus waveguide are respectively provided with an input end 1051 and a straight-through end 1052 of the optical signal, the first bus waveguide is composed of a third straight waveguide 106 and two third curved waveguides 105, wherein the third straight waveguide 106 is located between the two third curved waveguides 105 and are sequentially connected to each other, and the input end 1051 of the optical signal is located at one of the third curved waveguides. One end of the waveguide 105, the through end 1052 is located at one end of another third curved waveguide 105, the first bus waveguide is located on one side of the first straight waveguide 102 so that a first coupling region 109 is formed between the third straight waveguide 106 and the first straight waveguide 102, the length of the first coupling region 109 is 20 μm to 50 μm, for example, 20 μm, 30 μm, 40 μm or 50 μm, which is not limited here, and there is a first gap 1061 between the third straight waveguide 106 and the first straight waveguide 102;A second bus waveguide, one end of which is provided with an output end 1071 of an optical signal, the second bus waveguide is composed of a fourth straight waveguide 108 and two fourth curved waveguides 107, wherein the fourth straight waveguide 108 is located between the two fourth curved waveguides 107 and connected to each other in sequence, the output end 1071 of the optical signal is located at one end of one of the fourth curved waveguides 107 and is located on the same side as the input end 1051 of the optical signal, the second bus waveguide is located on one side of the second straight waveguide 104 so that a second coupling region 110 is formed between the fourth straight waveguide 108 and the second straight waveguide 104, the length of the second coupling region 110 is 20 μm to 50 μm and is equal to the length of the first coupling region 109, for example, it can be 20 μm, 30 μm, 40 μm or 50 μm, which is not limited here, and there is a second gap 1072 between the fourth straight waveguide 108 and the second straight waveguide 104. ;

[0037] As an example, the waveguides in the first bus waveguide, the second bus waveguide and the racetrack ring waveguide have a thickness of 1 μm to 1.5 μm and a width of 1 μm to 1.5 μm.

[0038] Specifically, in this embodiment, in order to make the microring resonator meet the requirements of polarization insensitivity of the resonance wavelength, the waveguide thickness of the first bus waveguide, the second bus waveguide and the racetrack ring waveguide is 1 μm to 1.5 μm, for example, the waveguide thickness is 1 μm, 1.2 μm or 1.5 μm, and the width is 1 μm to 1.5 μm, for example, the waveguide width is 1 μm, 1.2 μm or 1.5 μm, such as Figure 3 As shown, when the waveguide thickness and the waveguide width are 1.2 μm, the effective refractive index of the waveguide in the TE mode and the TM mode is equal, so that the microring resonator has the polarization-insensitive characteristic of the resonance wavelength.

[0039] As an example, the first bus waveguide, the second bus waveguide and the racetrack ring waveguide are all single mode waveguides.

[0040] Specifically, the optical signal enters the first bus waveguide from the optical signal input end 1051, the light meeting the resonance wavelength enters the racetrack ring waveguide in the third straight waveguide 106 in a gap coupling manner, and the light not meeting the resonance wavelength is output through the through end 1052 of the third waveguide. In this embodiment, Figure 3As shown, since the waveguide thickness and waveguide width of the first bus waveguide, the second bus waveguide and the racetrack ring waveguide are 1.5μm at most, the optical signal will not excite high-order modes during transmission, and since the first bus waveguide, the second bus waveguide and the racetrack ring waveguide are all single-mode waveguides, only the fundamental mode is coupled into the racetrack ring waveguide, and no high-order modes exist. On this basis, since the racetrack ring waveguide will not excite high-order modes for the fundamental mode, there are no high-order modes coupled into the racetrack ring waveguide and the losses caused by them.

[0041] As an example, the width of the first gap 1061 is 1 μm to 2 μm, and the width of the second gap 1072 is 1 μm to 2 μm and is equal to the width of the first gap 1061 .

[0042] Specifically, during the transmission of the optical signal in the first coupling region 109 and the second coupling region 110, the change in the distance between the first gap 1061 between the third straight waveguide 106 and the first straight waveguide 102 and the second gap 1072 between the fourth straight waveguide 108 and the second straight waveguide 104 will excite the radiation mode in the waveguide, thereby causing an increase in the loss in the racetrack ring waveguide. In order to avoid this problem, in this embodiment, the width of the first gap 1061 is 1μm to 2μm, the width of the second gap 1072 is 1μm to 2μm and is equal to the width of the first gap 1061, and since the effective refractive index of the first straight waveguide 102 is the same as that of the third straight waveguide 106, and the effective refractive index of the second straight waveguide 104 is the same as that of the fourth straight waveguide 108, the effective refractive index of the TE mode and the TM mode of the waveguide is finally made equal, and the optical signal enters the first bus waveguide through the input end 1051 of the optical signal. , the light is divided into two beams through the coupling effect of the first coupling region 109. The light that does not meet the resonance condition is directly output from the through end 1052 of the first bus waveguide, and the light that meets the resonance condition is coupled into the racetrack ring waveguide, coupled to the second bus waveguide from the second coupling region 110 and output from the output end 1071 of the optical signal of the second bus waveguide, thereby reducing the loss of the optical signal in the racetrack ring waveguide and improving the transmission efficiency of the optical signal, so that the microring resonator has the polarization-insensitive characteristics of the resonance wavelength and the polarization-insensitive characteristics of the coupling region.

[0043] Embodiment 2:

[0044] The present embodiment provides a polarization-insensitive microring resonator, whose structure is basically the same as that of the first embodiment, except that: the length of the first coupling region 109 is 25 μm, the length of the second coupling region 110 is 25 μm, and the size of the first gap 1061 between the third straight waveguide 106 and the first straight waveguide 102 is 1.5 μm, and the size of the second gap 1072 between the fourth straight waveguide 108 and the second straight waveguide 104 is 1.5 μm.

[0045] The polarization-insensitive microring resonator in the embodiment of the present invention is simulated under the input of transverse magnetic wave (TM) and transverse electric wave (TE) mode light sources to obtain its transmission spectrum, as shown in FIG. Figure 4 and Figure 5 As shown, it is a transmission spectrum diagram of the first bus waveguide through end 1052 under transverse magnetic wave (TM) and transverse electric wave (TE) mode light sources. It can be seen from the figure that the microring resonator in the embodiment of the present invention has achieved very excellent polarization-insensitive characteristics in the O band (1260nm~1360nm), especially at the center wavelength of 1310nm, and has a low insertion loss. The coupling efficiency in the TE mode is 0.0985416, and the coupling efficiency in the TM mode is 0.0944215, respectively, and the difference between the two is only 0.004, so it can be concluded that the microring resonator in this embodiment has the characteristic of polarization insensitivity in the coupling zone.

[0046] In summary, the polarization-insensitive microring resonator of the present invention is designed as a microring resonator based on the bus waveguide and the racetrack ring waveguide of the SION waveguide. The structure design is simple, and the cross-sectional shape of the SION waveguide is controlled to be a square, so that the effective refractive index of the waveguide in the TE mode is close to the effective refractive index in the TM mode, so that the microring resonator has the polarization-insensitive characteristic of the resonance wavelength, and because the bus waveguide and the racetrack ring waveguide are coupled in the straight waveguide region and the optical coupling coefficient of the coupling region is the same as the effective refractive index of the waveguide, the microring resonator has a good polarization-insensitive characteristic of the coupling region, especially at the O band (1260nm~1360nm), especially at the center wavelength of 1310nm, a very excellent polarization-insensitive characteristic is achieved, and it has a low insertion loss, thereby expanding the application of the microring resonator in the fields of filters, wavelength division multiplexing systems and optical sensors with high polarization insensitivity requirements. Therefore, the present invention effectively overcomes various shortcomings in the prior art and has a high industrial utilization value.

[0047] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A polarization-insensitive microring resonator, characterized in that: The microring resonator comprises: A racetrack annular waveguide, comprising a first curved waveguide, a first straight waveguide, a second curved waveguide and a second straight waveguide, wherein the first curved waveguide and the second curved waveguide have the same bending radius, the first straight waveguide and the second straight waveguide are parallel to each other and have the same length; two ends of the first curved waveguide are respectively connected to one end of the first straight waveguide and the second straight waveguide, and two ends of the second curved waveguide are respectively connected to the other end of the first straight waveguide and the second straight waveguide, thereby forming a centrally symmetrical waveguide structure; A first bus waveguide, wherein both ends of the first bus waveguide are respectively provided with an input end and a through end of an optical signal, The first bus waveguide is composed of a third straight waveguide and two third curved waveguides, and the third straight waveguide is arranged on the same side as the first straight waveguide and there is a first gap to form a first coupling region; a second bus waveguide, wherein one end of the second bus waveguide is provided with an output end of an optical signal, the second bus waveguide is composed of a fourth straight waveguide and two fourth curved waveguides, and the fourth straight waveguide is provided on the same side as the second straight waveguide and there is a second gap to form a second coupling region; The optical signal enters the first bus waveguide through the input end, and is divided into two beams of light through the coupling effect of the first coupling region. The light that does not meet the resonance condition is directly output from the through end of the first bus waveguide, and the light that meets the resonance condition is coupled into the racetrack ring waveguide, coupled to the second bus waveguide from the second coupling region and output from the output end of the second bus waveguide.

2. The microring resonator according to claim 1, characterized in that: The waveguides in the first bus waveguide, the second bus waveguide and the racetrack ring waveguide have a thickness of 1 μm to 1.5 μm and a width of 1 μm to 1.5 μm.

3. The microring resonator according to claim 2, characterized in that: The waveguide thickness and the waveguide width in the first bus waveguide, the second bus waveguide and the racetrack ring waveguide have equal sizes.

4. The microring resonator according to claim 1, characterized in that: The length of the first coupling region is 20 μm to 50 μm, and the length of the second coupling region is 20 μm to 50 μm and is equal to the length of the first coupling region.

5. The microring resonator according to claim 1, characterized in that: The length of the first coupling region is 25 μm, and the length of the second coupling region is 25 μm.

6. The microring resonator according to claim 1, characterized in that: The width of the first gap is 1 μm to 2 μm, and the width of the second gap is 1 μm to 2 μm and is equal to the width of the first gap.

7. The microring resonator according to claim 1, characterized in that: The length of the racetrack ring waveguide is 2000 μm to 2100 μm.

8. The microring resonator according to any one of claims 1 to 7, characterized in that: The first bus waveguide, the second bus waveguide and the racetrack ring waveguide are all single-mode waveguides.

9. The microring resonator according to claim 8, characterized in that: The first straight waveguide has the same effective refractive index as the third straight waveguide, and the second straight waveguide has the same effective refractive index as the fourth straight waveguide.

10. The microring resonator according to claim 9, characterized in that: The materials of the waveguides in the first bus waveguide, the second bus waveguide and the racetrack ring waveguide are independently selected from SION coated with a buried oxide layer on an insulator.

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