CN112596282B - Broadband adjustable splitting ratio polarization rotation beam splitter based on SOI - Google Patents
Broadband adjustable splitting ratio polarization rotation beam splitter based on SOI Download PDFInfo
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- G—PHYSICS
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- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/0147—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on thermo-optic effects
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- G—PHYSICS
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- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
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- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
- G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
- G02B6/126—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind using polarisation effects
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- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/011—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour in optical waveguides, not otherwise provided for in this subclass
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- G—PHYSICS
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- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/0136—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour for the control of polarisation, e.g. state of polarisation [SOP] control, polarisation scrambling, TE-TM mode conversion or separation
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Abstract
The invention discloses a broadband adjustable splitting ratio polarization rotation beam splitter based on an SOI (silicon on insulator), which comprises a waveguide layer, a thermode, a buffer layer, an input end and an output end, wherein the waveguide layer comprises a three-section tapered ridge waveguide, an S-shaped bent ridge waveguide, a straight waveguide, an Archimedes spiral bent ridge waveguide, a straight ridge waveguide and an output ridge waveguide and is prepared from an SOI (silicon on insulator) material, the thermode and the buffer layer are sequentially arranged above the waveguide layer, the thermode is prepared from a TiN material, and the temperature of the thermode can be changed by applying voltage to two ends of the thermode. The invention can realize the polarization rotation, beam splitting and beam splitting ratio adjustment of input optical signals, can be applied to polarization multiplexing systems, coherent optical communication systems, optical logic gate designs and the like, and has the advantages of low insertion loss, simple process, strong reconfigurability, wide working bandwidth and the like.
Description
Technical Field
The invention relates to the technical field of optical communication, in particular to a broadband polarization rotation beam splitter with adjustable splitting ratio based on an SOI (silicon on insulator).
Background
With the gradual development of informatization, people increasingly demand ultrahigh-speed, ultra-large-capacity and ultra-low-power-consumption information transmission and processing, and thus, the vigorous development of modulation technology and multiplexing technology is brought. Various analog modulation techniques and digital modulation techniques significantly improve the spectral utilization of optical communications. Multiplexing techniques may further increase communication capacity based on modulation techniques. Polarization multiplexing is to use different polarization states to carry information for communication, and generally two orthogonal polarization states are used to carry respective information, so that under the same transmission bandwidth, polarization multiplexing can increase the transmission data amount by one time.
Polarization rotating beam splitters are indispensable optical devices in optical polarization multiplexing systems, which function to rotate the polarization state of light and to split the optical power. In order to realize the rotation and beam splitting of light, a glass slide and a prism were used in the early days, but the two devices were large in size and could not be integrated, so that a good alternative material was required in practical application. With the improvement of the micro-processing technology, people can process submicron structures with excellent quality, the technology creates conditions for the design and manufacture of Silicon-based optical waveguide devices, and the polarization rotation beam splitter based on Silicon On Insulator (SOI) can be compatible with CMOS, has the advantages of easy integration, simple manufacture, low manufacturing cost and the like, and becomes one of important devices in an optical multiplexing system.
Disclosure of Invention
The purpose of the invention is as follows: in order to overcome the defects in the prior art, the invention provides a broadband adjustable splitting ratio polarization rotation beam splitter based on an SOI (silicon on insulator), which can enable the splitting ratio of an output signal of the polarization rotation beam splitter to be adjustable, and the added adjustable characteristic enables the polarization rotation beam splitter to be more flexible in the application of an optical communication link.
The technical scheme is as follows: in order to achieve the above objects, the present invention provides a polarization rotation beam splitter with adjustable broadband splitting ratio based on SOI, wherein the beam splitter comprises a waveguide layer, a thermode and a buffer layer, the waveguide layer comprises a four-segment tapered ridge waveguide, an S-shaped curved ridge waveguide, a straight waveguide, an archimedes spiral curved ridge waveguide, a straight ridge waveguide and an output ridge waveguide, all of which are disposed on the same plane and made of SOI material, the S-shaped curved ridge waveguide and the straight waveguide, the archimedes spiral curved ridge waveguide are respectively connected with the four-segment tapered ridge waveguide, the straight ridge waveguide is connected with the S-shaped curved ridge waveguide and the straight waveguide, the output ridge waveguide is connected with the straight ridge waveguide, the thermode and the buffer layer are sequentially disposed above the waveguide layer, and the thermode is made of TiN material, the temperature of the thermode can be changed by applying a voltage across the thermode;
the beam splitter further comprises an input end and an output end for input and output of light, respectively, and the output end further comprises a first output end and a second output end.
Further, in the present invention: the four-section tapered ridge waveguide comprises a first tapered ridge waveguide, a second tapered ridge waveguide, a third tapered ridge waveguide and a fourth tapered ridge waveguide which are connected in sequence, the length of the third tapered ridge waveguide is the longest, the third tapered ridge waveguide is used for polarization rotation and mode conversion, and the second tapered ridge waveguide and the fourth tapered ridge waveguide are used for matching ridge waveguides with different widths.
Further, in the present invention: the S-shaped curved ridge waveguide and the straight waveguide include a first S-shaped curved ridge waveguide and a fourth S-shaped curved ridge waveguide which are symmetrical in structure, and the light intensity and the phase on the first S-shaped curved ridge waveguide and the fourth S-shaped curved ridge waveguide are equal.
Further, in the present invention: the S-shaped curved ridge waveguide and the straight waveguide comprise a first S-shaped curved ridge waveguide, a second S-shaped curved ridge waveguide, a third S-shaped curved ridge waveguide, a fourth S-shaped curved ridge waveguide, a seventh S-shaped curved ridge waveguide, an eighth S-shaped curved ridge waveguide, a first straight waveguide and a second straight waveguide, wherein the input end of the first straight waveguide is connected with the first S-shaped curved ridge waveguide, the output end of the first straight waveguide is connected with the seventh S-shaped curved ridge waveguide, the input end of the second straight waveguide is connected with the fourth S-shaped curved ridge waveguide, and the output end of the second straight waveguide is connected with the eighth S-shaped curved ridge waveguide;
the first S-bend ridge waveguide, the second S-bend ridge waveguide, the third S-bend ridge waveguide, and the fourth S-bend ridge waveguide are respectively connected to the fourth tapered ridge waveguide, and are capable of receiving light transmitted by the fourth tapered ridge waveguide and dividing the light into 4 channels.
Further, in the present invention: the archimedean spiral curved ridge waveguide further includes a first archimedean spiral curved waveguide and a second archimedean spiral curved waveguide, the first archimedean spiral curved waveguide is connected with the second S-curved ridge waveguide, and the second archimedean spiral curved waveguide is connected with the third S-curved ridge waveguide.
Further, in the present invention: the ridge-shaped straight waveguide is a multi-mode waveguide and is used for exciting multi-mode interference.
Further, in the present invention: the output ridge waveguide also comprises a fifth tapered ridge waveguide and a sixth tapered ridge waveguide which have the same structure and are used for wide wave guide narrow waveguide evolution and used as the output end of multimode interference.
Has the advantages that: compared with the prior art, the invention has the beneficial effects that:
(1) constructing ridge waveguide internal mode hybridization by three-section tapering, thereby realizing polarization rotation and mode conversion; the phase of partial optical signals in the mode evolution process is changed by utilizing the thermode, and then the interference state of the optical signals is changed, so that the controllability of the beam splitting ratio of two output ends is realized, a new controllable degree of freedom is added for the polarization rotation beam splitter, and the polarization rotation beam splitter can be more flexibly and diversely applied to an optical communication system and can also be used for designing an optical switch, an optical route, a logic light path and the like;
(2) the waveguide structure does not need multiple times of photoetching, can be compatible with COMS in a manufacturing process, and has the potential characteristics and advantages of high response speed and low power consumption.
Drawings
FIG. 1 is a schematic diagram of an overall structure of a broadband adjustable splitting ratio polarization rotation beam splitter based on SOI according to the present invention;
FIG. 2 is a schematic cross-sectional view of an SOI-based broadband tunable splitting ratio polarization rotating beam splitter of the present invention;
FIG. 3 is a schematic top view of a waveguide layer according to the present invention;
FIG. 4 is a graph showing the simulation result of the variation of effective refractive index and TE polarization factor with ridge width in ridge waveguide
FIG. 5 shows the corresponding TM of the present invention0When in input, the light passes through a simulation calculation result of the polarization rotation ratio after passing through the first tapered ridge waveguide, the second tapered ridge waveguide and the third tapered ridge waveguide;
FIG. 6 shows the corresponding TM of the present invention0At input, TE3The output power of the mode passing through the 1 x 4 beam splitter is schematically calculated;
FIG. 7 shows the corresponding TM of the present invention0When in input, the result of the corresponding output characteristic of the straight ridge waveguide is shown schematically;
FIG. 8 shows the corresponding TM of the present invention0When the test result is input, the whole beam splitter outputs a schematic diagram of the adjustable test result of the beam splitting specific heat.
Detailed Description
The technical scheme of the invention is further explained in detail by combining the attached drawings:
the present invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.
As shown in fig. 1, fig. 1 is a schematic view of an overall structure of a broadband tunable splitting ratio polarization rotation beam splitter based on SOI, where the beam splitter includes a waveguide layer, a thermode, and a buffer layer, where the waveguide layer includes an input waveguide 1, a four-segment tapered ridge waveguide 2, an S-shaped curved ridge waveguide and a straight waveguide 3, an archimedes spiral curved ridge waveguide 4, a straight ridge waveguide 5, and an output ridge waveguide 6, which are all disposed on the same plane and have the same thickness, and are made of SOI material, the S-shaped curved ridge waveguide and the straight waveguide 3, and the archimedes spiral curved ridge waveguide 4 are respectively connected to the four-segment tapered ridge waveguide 2, the straight ridge waveguide 5 is connected to the S-shaped curved ridge waveguide and the straight waveguide 3, and the output ridge waveguide 6 is connected to the straight ridge waveguide 5.
Referring to the schematic diagram of fig. 2, the thermode 7 and the buffer layer 8 are sequentially arranged above the waveguide layer, the thermode is made of TiN material, and the temperature of the electrodes can be changed by applying voltage to two ends of the thermode, so as to heat the waveguide layer; buffer layers 8 are arranged between the waveguide layer and the thermode 7 and below the waveguide layer, and the buffer layers 8 are made of silicon dioxide.
Referring to the schematic of fig. 3, the splitter has an input end 1 and an output end 6, and the output end further includes tapered transition waveguides 6-1 and 6-2, S-bend waveguides 6-3 and 6-4, a first output waveguide 6-5, and a second output waveguide 6-6.
Further, the four-section tapered ridge waveguide 2 further comprises a first tapered ridge waveguide 2-1, a second tapered ridge waveguide 2-2 and a third tapered ridge waveguide 2-3, which are connected in sequence, wherein the second tapered ridge waveguide 2-2 has the longest length and is used for polarization rotation and mode conversion, the first tapered ridge waveguide 2-1 and the third tapered ridge waveguide 2-3 are shorter and are used for matching ridge waveguides with different widths, and the first tapered ridge waveguide 2-1 is connected with the input waveguide 1 and is used for inputting a fundamental mode.
The S-shaped curved ridge waveguide and the straight waveguide 3 further include a first S-shaped curved ridge waveguide 3-1 and a fourth S-shaped curved ridge waveguide 3-4, straight waveguides 3-5 and 3-6, a seventh S-shaped curved ridge waveguide 3-7 and an eighth S-shaped curved ridge waveguide 3-8, which are symmetrical structures, and the optical intensity and phase on the first S-shaped curved ridge waveguide 3-1 and the fourth S-shaped curved ridge waveguide 3-4 are equal. The straight waveguides 3-5 and 3-6 are equal in length, the seventh S-shaped curved ridge waveguide 3-7 and the eighth S-shaped curved ridge waveguide 3-8 are equal in length, and equal in light intensity and phase.
The S-shaped curved ridge waveguide and the straight waveguide 3 further comprise a second S-shaped curved ridge waveguide 3-2 and a third S-shaped curved ridge waveguide 3-3, wherein the first S-shaped curved ridge waveguide 3-1, the second S-shaped curved ridge waveguide 3-2, the third S-shaped curved ridge waveguide 3-3 and the fourth S-shaped curved ridge waveguide 3-4 are all connected with the third tapered ridge waveguide 2-3 and can receive light transmitted by the third tapered ridge waveguide 2-3 and divide the light into 4 paths.
Specifically, the second S-curved ridge waveguide 3-2 and the third S-curved ridge waveguide 3-3 are structurally symmetrical, and the first S-curved ridge waveguide 3-1, the second S-curved ridge waveguide 3-2, the third S-curved ridge waveguide 3-3, and the fourth S-curved ridge waveguide 3-4 together form a 1 × 4 beam splitter.
The Archimedes spiral curved ridge waveguide 4 further comprises a first Archimedes spiral curved waveguide 4-1 and a second Archimedes spiral curved waveguide 4-2, wherein the first Archimedes spiral curved waveguide 4-1 is connected with the second S-shaped curved ridge waveguide 3-2, and the second Archimedes spiral curved waveguide 4-2 is connected with the third S-shaped curved ridge waveguide 3-3, so that the optical signal loss in the second S-shaped ridge waveguide 3-2 can be zero, and crosstalk is avoided.
The straight ridge waveguide 5 is a multimode waveguide for exciting multimode interference. Further, a seventh S-curved ridge waveguide 3-7 and an eighth S-curved ridge waveguide 3-8 are connected to the straight ridge waveguide 5, respectively.
The output ridge waveguide 6 further comprises a fifth tapered ridge waveguide 6-1 and a sixth tapered ridge waveguide 6-2, which have the same structure and are respectively connected with the straight ridge waveguide 5, used for wide wave guide narrow waveguide evolution and used as an output end of multi-mode interference. The output ridge waveguide 6 further includes a first S-shaped curved ridge waveguide 6-3 and a second S-shaped curved ridge waveguide 6-4, which are structurally symmetrical to each other, for enlarging the interval between the output waveguides and preventing interference between the waveguides. Two ends of the first S-shaped bent ridge waveguide 6-3 are respectively connected with a first tapered ridge waveguide 6-1 and a first output end 6-5, and two ends of the second S-shaped bent ridge waveguide 6-4 are respectively connected with a second tapered ridge waveguide 6-2 and a second output end 6-6.
The broadband polarization rotation beam splitter with the adjustable splitting ratio based on the SOI has the working principle that: constructing a tapering 2-3 with a specific ridge width according to the horizontal and vertical refractive index nonuniformity of the ridge waveguide, so that an input TM fundamental mode is hybridized and polarization rotation is converted into a TE high-order mode, wherein the ridge width of the tapering 2-3 in the embodiment is set to be about 1.35 um; the TE high-order mode after polarization rotation is subjected to energy beam splitting and multi-mode interference, mode is converted into a TE basic mode, and the TE basic mode is output from ports of two output ends; the hot electrode 7 can increase the branch phase of the straight waveguide 3-5 in the figure 3 in mode evolution, thereby influencing the interference in the multimode straight waveguide, changing the power distribution of the two output ports, and realizing the function of the polarization rotation beam splitter with adjustable output beam splitting ratio. Specifically, the hot electrode 7 is electrified for heating, heat is transferred to the straight waveguide 3-5, the straight waveguide 3-5 is a silicon material waveguide, temperature change and refractive index change of the straight waveguide 3-5 are in a linear relation, the change rule meets 1.8 multiplied by 10 < -4 > RIU/DEG C, the refractive index is increased when the temperature is increased, and the optical transmission phase is increased.
Under the structure of the invention, when the basic mode TM0The first tapered ridge waveguide 2-1 is input through the input end 1 and mode hybridization is carried out through the second tapered ridge waveguide 2-2, TM0Rotation of mode polarization, mode conversion to TE3A mode, wherein the first tapered ridge waveguide 2-1 and the third tapered ridge waveguide 2-3 are used to match modes of different waveguide widths; TE output from a third tapered ridge waveguide 2-3 tapered waveguide3The mode is divided into four paths by passing through a beam splitter consisting of a first S-shaped curved ridge waveguide 3-1, a second S-shaped curved ridge waveguide 3-2, a third S-shaped curved ridge waveguide 3-3, and a fourth S-shaped curved ridge waveguide 3-4. By simulating the geometric dimensions of the first S-shaped curved ridge waveguide 3-1, the second S-shaped curved ridge waveguide 3-2, the third S-shaped curved ridge waveguide 3-3 and the fourth S-shaped curved ridge waveguide 3-4, the structural parameters of which the light intensity is almost distributed in the first S-shaped curved ridge waveguide 3-1 and the fourth S-shaped curved ridge waveguide 3-4 can be found, and the specific parameters include that the transverse propagation length of the first S-shaped curved ridge waveguide 3-1 is 10 μm and the longitudinal variation is 7.374 μm; the second S-shaped curved ridge waveguide 3-2 has a transverse propagation length of 10 μm and a longitudinal variation of 5.000 μm; the third S-shaped curved ridge waveguide 3-1 has a transverse propagation length of 10 μm and a longitudinal variation of-5.000 μm; the fourth S-bend ridge waveguide 3-2 has a lateral propagation length of 10 μm and a longitudinal variation of-7.374 μm. At this time, the waveguides of the second S-shaped curved ridge waveguide 3-2 and the third S-shaped curved ridge waveguide 3-3 have almost no light, but in order to reduce optical crosstalk as much as possible, the second S-shaped curved ridge waveguide 3-2 and the third S-shaped curved ridge waveguide 3-3 are respectively connected with a first archimedes spiral curved waveguide 4-1 and a second archimedes spiral curved waveguide 4-2, which have gradually reduced curved radii, as loss lines; according to the symmetry of the first S-shaped curved ridge waveguide 3-1 and the fourth S-shaped curved ridge waveguide 3-4, the optical signals passing through the first S-shaped curved ridge waveguide 3-1 and the fourth S-shaped curved ridge waveguide 3-4 have the characteristics of same phase and same intensity, and the two optical signals pass through the straight waveguide 3-5, the straight waveguide 3-6 and the fourth S-shaped curved ridge waveguide 3-4 respectivelySeven S-shaped curved ridge waveguides 3-7 and eight S-shaped curved ridge waveguides 3-8 are transmitted to the straight ridge waveguide 5, two optical signals excite multi-mode interference in the straight ridge waveguide 5, imaging positions of two images can be obtained according to the imaging rule of the multi-mode interference, and two TE paths can be obtained by setting output ends at the positions0Outputting the mode; the straight ridge waveguide 5 outputs light from the first output end 6-5 and the second output end 6-6 respectively through the first tapered ridge waveguide 6-1 and the second tapered ridge waveguide 6-2, namely, the input TM is finished0The polarization of the mode rotates the beam splitting. The temperature of the hot electrode 7 can be changed by applying voltage to the two ends of the hot electrode 7, and the corresponding area of the waveguide layer electrode is heated, so that the transmission phase of the straight waveguide 3-5 is changed, the interference state in the straight ridge waveguide 5 is changed, the adjustment of the power distribution of the first output end 6-5 and the second output end 6-6 is completed, and the function of the polarization rotation beam splitter with the beam splitting ratio being arbitrarily adjustable is realized.
In order to verify the effect of the present invention in practical application, the following simulation experiments are used for illustration:
the experiment adopts a finite difference time domain method for calculation and analysis, and the main parameters used in the simulation experiment comprise: the waveguide structure is formed by one-time etching, and the ridge waveguide adopted by the waveguide layer in the simulation has the bottom height of 70nm and the ridge height of 150nm, referring to the schematic diagram of FIG. 2; the thermo-optic coefficients of the silicon of the waveguide layer and the silicon dioxide of the buffer layer 7 are 1.84X 10-4 and 1X 10-5, respectively; the first tapered ridge waveguide 2-1, the second tapered ridge waveguide 2-2 and the third tapered ridge waveguide 2-3 gradually change the waveguide width from 0.8 mu m to 1.2 mu m, 1.5 mu m and 1.67 mu m in sequence, and the lengths of the first tapered ridge waveguide 2-1, the second tapered ridge waveguide 2-2 and the third tapered ridge waveguide 2-3 are respectively 8.15 mu m, 36.97 mu m and 15 mu m; the straight ridge waveguide 5 has a width of 6 μm and a length of 42.8 μm.
The mode effective refractive index and TE polarization factor corresponding to the waveguide width are shown in fig. 4 below by performing simulation calculation by changing the width of the ridge waveguide, and it can be seen from (a) of fig. 4 that when the ridge width is changed from 1.2 μm to 1.4 μm, TM in the waveguide0Mode will be converted to TE3A mode; more detailed polarization rotation characteristics can be found in (of) of FIG. 4b) In this range, the TM in the waveguide is seen0Die and TE3The mode is in a hybrid state, which is the basis for mode conversion or polarization rotation. As shown in FIG. 5, it can be seen that in the bandwidth 60nm range, TM0Mode capable of high rate conversion to TE3The mode, and the corresponding mode conversion efficiency is more than 91.6%, and the maximum insertion loss brought by the mode is about 0.068 dB.
The 1 × 4 beam splitter formed by the first S-shaped curved ridge waveguide 3-1, the second S-shaped curved ridge waveguide 3-2, the third S-shaped curved ridge waveguide 3-3, and the fourth S-shaped curved ridge waveguide 3-4 was subjected to simulation analysis, and the obtained splitting powers of the respective paths were as shown in fig. 6. It can be seen that the optical energy is mainly concentrated in the first and fourth S-curved ridge waveguides 3-1 and 3-4 during splitting, which introduces about 0.6dB of additional loss; at the same time, through the 1X 4 beam splitter, TE3Mode conversion to two-way TE0Mode(s).
Referring to the schematic of fig. 7, simulation calculations were performed on the straight ridge waveguide 5 as light from the seventh sigmoid curved ridge waveguide 3-7 was TE0When the ridge-shaped straight waveguide 5 is input in a mode, the output powers of the first output end 6-5 and the second output end 6-6 are respectively shown in fig. 7, wherein an output port1 corresponds to the first output end 6-5, an output port2 corresponds to the second output end 6-6, the difference between the two output ends is smaller than 1/10 of the output power within the bandwidth of 1520 nm-1580 nm, and power equalization can be basically realized.
Finally, the device is prepared through experiments, and the polarization rotation beam splitting function of the device is tested. The obtained result of the adjustable power splitting ratio is shown in fig. 8, where in (a) and (b) of fig. 8, when the incident light is 1550nm, respectively, the thermode 7 is located at the thermally adjustable condition corresponding to the straight waveguide 3-5 and the straight waveguide 3-6 (two thermodes are fabricated in the experimental preparation and located above the straight waveguide 3-5 and the straight waveguide 3-6, respectively, only the thermode located above the fifth S-shaped curved ridge waveguide 3-5 is described in fig. 1, both thermodes can work independently), and the output power is normalized, it can be seen that the splitting ratio of the first output terminal 6-5 and the second output terminal 6-6 can achieve ± 27.5dB and is continuously adjustable in this range.
In summary, the broadband polarization rotation beam splitter with the adjustable splitting ratio based on the SOI provided by the invention can realize the function of polarization rotation beam splitting, and the splitting ratio can be adjusted arbitrarily. More reconfigurable freedom makes the invention have wider application range and more flexible use as a unit device. In addition, the invention has the characteristics of miniaturization and thermal reconstruction, can be realized on a conventional SOI manufacturing platform, is completely compatible with CMOS, only needs one-time photoetching of a waveguide structure, and has wide application prospect in the aspects of optical switching networks, digital information processing, modulators, filters, multiplexing devices, system design and the like.
It should be noted that the above-mentioned examples only represent some embodiments of the present invention, and the description thereof should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications without departing from the spirit of the present invention, and these modifications should fall within the scope of the present invention.
Claims (4)
1. A broadband adjustable splitting ratio polarization rotation beam splitter based on SOI is characterized in that: the beam splitter comprises a waveguide layer, a thermode and a buffer layer, wherein the waveguide layer comprises four sections of tapered ridge waveguides, an S-shaped bent ridge waveguide, a straight waveguide, an Archimedes spiral bent ridge waveguide, a straight ridge waveguide and an output ridge waveguide which are arranged on the same plane and are made of SOI materials, the input end of the straight ridge waveguide is connected with a seventh S-shaped bent ridge waveguide and an eighth S-shaped bent ridge waveguide, the output end of the straight ridge waveguide is connected with a fifth tapered ridge waveguide and a sixth tapered ridge waveguide, the thermode and the buffer layer are sequentially arranged above the waveguide layer, the thermode is made of TiN materials, and the temperature of the thermode is changed by applying voltage to the two ends of the thermode;
the beam splitter further comprises an input end and an output end, wherein the input end and the output end are respectively used for inputting and outputting light, and the output end further comprises a first output end and a second output end;
the four-section tapered ridge waveguide comprises a first tapered ridge waveguide, a second tapered ridge waveguide, a third tapered ridge waveguide and a fourth tapered ridge waveguide which are sequentially connected, the length of the third tapered ridge waveguide is longest and is used for polarization rotation and mode conversion, and the second tapered ridge waveguide and the fourth tapered ridge waveguide are used for matching ridge waveguides with different widths;
the S-shaped curved ridge waveguide and the straight waveguide comprise a first S-shaped curved ridge waveguide, a second S-shaped curved ridge waveguide, a third S-shaped curved ridge waveguide, a fourth S-shaped curved ridge waveguide, a seventh S-shaped curved ridge waveguide, an eighth S-shaped curved ridge waveguide, a first straight waveguide and a second straight waveguide, wherein the input end of the first straight waveguide is connected with the first S-shaped curved ridge waveguide, the output end of the first straight waveguide is connected with the seventh S-shaped curved ridge waveguide, the input end of the second straight waveguide is connected with the fourth S-shaped curved ridge waveguide, and the output end of the second straight waveguide is connected with the eighth S-shaped curved ridge waveguide;
the archimedean spiral curved ridge waveguide further includes a first archimedean spiral curved waveguide and a second archimedean spiral curved waveguide, the first archimedean spiral curved waveguide is connected with the second S-curved ridge waveguide, and the second archimedean spiral curved waveguide is connected with the third S-curved ridge waveguide.
2. The SOI-based broadband tunable splitting ratio polarization rotating beam splitter of claim 1, wherein: the S-shaped curved ridge waveguide and the straight waveguide include a first S-shaped curved ridge waveguide and a fourth S-shaped curved ridge waveguide which are symmetrical in structure, and the light intensity and the phase on the first S-shaped curved ridge waveguide and the fourth S-shaped curved ridge waveguide are equal.
3. The SOI-based broadband tunable splitting ratio polarization rotating beam splitter of claim 1, wherein: the ridge waveguide is a multimode waveguide for exciting multimode interference.
4. The SOI-based broadband tunable splitting ratio polarization rotating beam splitter of claim 3, wherein: the output ridge waveguide also comprises a fifth tapered ridge waveguide and a sixth tapered ridge waveguide which have the same structure and are used for wide wave guide narrow waveguide evolution and used as the output end of multimode interference.
Priority Applications (1)
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