CN112526675B - W-shaped silicon groove type on-chip polarization rotator based on mode mixing principle - Google Patents

W-shaped silicon groove type on-chip polarization rotator based on mode mixing principle Download PDF

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CN112526675B
CN112526675B CN202011522370.3A CN202011522370A CN112526675B CN 112526675 B CN112526675 B CN 112526675B CN 202011522370 A CN202011522370 A CN 202011522370A CN 112526675 B CN112526675 B CN 112526675B
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polarization rotator
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CN112526675A (en
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惠战强
攀登
文习建
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Xian University of Posts and Telecommunications
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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • 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
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • 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
    • G02B6/122—Basic optical elements, e.g. light-guiding paths
    • G02B6/125—Bends, branchings or intersections
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • 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
    • G02B2006/12035—Materials

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Abstract

The invention discloses a W-shaped silicon-based groove type on-chip polarization rotator based on a mode mixing principle, and belongs to the technical field of optical fiber communication. The polarization rotator includes: the substrate consists of silicon dioxide, a section of strip waveguide is arranged at the top of the substrate to form a polarization rotation area; the strip waveguide includes: the waveguide structure comprises a W-shaped groove waveguide, a left stepped waveguide and a right stepped waveguide, wherein the left stepped waveguide and the right stepped waveguide are respectively connected to two sides of the W-shaped groove waveguide; the W-shaped groove waveguide is made of silicon dioxide, and the left stepped waveguide and the right stepped waveguide are made of silicon. In the wavelength range of 300nm (1400nm-1700nm), the insertion loss IL of incident light (TE/TM fundamental mode) in the full-waveband range is less than 0.4dB, mode light is input from an input port and output from an output port, meanwhile, the polarization rotation efficiency PCE is higher than 98.6% in the full-waveband range, IL is less than 0.23dB at the center wavelength of 1550nm, and PCE is higher than 99.96%.

Description

W-type silicon-based groove type on-chip polarization rotator based on mode mixing principle
Technical Field
The invention relates to the technical field of optical fiber communication, in particular to a W-type silicon-based groove type on-chip polarization rotator based on a mode mixing principle.
Background
Silicon photonic devices compatible with CMOS (complementary metal-oxide-semiconductor) processes have received much attention over the past decades, with SOI (Silicon-on-insulator) platform based photonic integrated waveguides (PICs) taking the leading position in the scientific research field. The high refractive index difference and the sub-micron structure of the SOI material result in SOI-based PIC devices with very high birefringence, which causes polarization dependent loss and polarization mode dispersion, limiting the application of SOI devices in the optical communication direction. The most effective solution to this problem is to introduce a polarization diversity system to reduce the polarization sensitivity of the silicon-based photonic device, so that the silicon-based photonic device has better performance for any polarized light, and the polarization diversity system generally consists of a Polarization Rotator (PR) and a Polarization Beam Splitter (PBS).
The current principles for implementing a Polarization Rotator (PR) can be classified into three types, a mode evolution type, a mode coupling type, and a mode mixing type.
The mode evolution type Polarization Rotator (PR) mainly realizes the gradual rotation of a polarization plane through the gradual change of a waveguide structure, and because a part of sharp edges can appear in the structure, the difference between the final performance parameters and the simulation result is large due to the fact that large deviation often appears in the actual process due to etching precision and the like, and meanwhile, the size of a mode evolution device is often large and difficult to integrate. Mode coupling type Polarization Rotators (PR) are usually realized by directional couplers, when effective refractive indexes of a TE mode in one waveguide and a TM mode in the other waveguide are the same, phase matching conditions are met, modes between the waveguides are coupled, and rotation is realized.
A mode hybrid Polarization Rotator (PR) changes a transmission mode in a waveguide from a single mode to a hybrid mode by breaking cross-sectional symmetry so that when TE mode or TM mode light is incident, energy is oscillated in two fundamental modes in the asymmetric cross-sectional waveguide, and polarization rotation is achieved by interference between the modes. Therefore, the key point for realizing the principle is to design the waveguide with the asymmetric section, and most of the current schemes for realizing the asymmetric section realize the asymmetry of the section by mixing the silicon material and other materials so as to achieve the aim of polarization rotation. However, due to the limitation of the manufacturing process, the manufacturing difficulty of most waveguides with asymmetric cross sections is large, the tolerance is low, the manufacturing cost is increased, and the actual effect is not ideal.
Disclosure of Invention
In order to solve the problems of the prior art, the invention provides a W-type silicon groove type on-chip polarization rotator based on a mode mixing principle. The polarization rotator includes: the polarization rotation device comprises a substrate, a polarization rotation unit and a polarization rotation unit, wherein the substrate is composed of silicon dioxide, and a section of strip waveguide is arranged at the top of the substrate to form a polarization rotation area; the strip waveguide includes: the waveguide comprises a W-shaped groove waveguide, a left stepped waveguide and a right stepped waveguide, wherein the left stepped waveguide and the right stepped waveguide are respectively connected to two sides of the W-shaped groove waveguide; the W-shaped groove waveguide is composed of silicon dioxide, and the left-side stepped waveguide and the right-side stepped waveguide are both composed of silicon.
And further, air is used as a medium to wrap the strip waveguide outside the left side stepped waveguide and the right side stepped waveguide.
Further, the W-type trench waveguide includes: a first waveguide, a second waveguide, a third waveguide, and a fourth waveguide; the first waveguides are vertically distributed along the Y axis, and the second waveguides are connected with the bottoms of the first waveguides and are vertical to the first waveguides; the third waveguide is connected with one end, far away from the first waveguide, of the second waveguide and is perpendicular to the second waveguide; the fourth waveguide is connected with one end, far away from the second waveguide, of the third waveguide, and is perpendicular to the third waveguide.
Further, the substrate is composed of silicon dioxide having a refractive index n at a wavelength of 1550nmSiO2＝1.445。
Further, the W-type trench waveguide is composed of silicon dioxide having a refractive index n at 1550nm wavelengthSiO21.445; the left-side stepped waveguide and the right-side stepped waveguide are both made of silicon, and the refractive index of silicon at 1550nm wavelength is nSi＝3.455。
Further, the thickness of the substrate is 2 μm.
Further, the thickness H of the strip waveguide is 400nm, the width W of the strip waveguide is 400nm, and the length of the strip waveguide along the transmission direction is LC＝4.3um。
Further, the width of the top of the left stepped waveguide is W1135 nm; the width of the connecting position of the left stepped waveguide and the second waveguide is W2120 nm; the width and height of the connection position of the left stepped waveguide and the third waveguide are H2105 nm; the height of the left stepped waveguide at one side of the fourth waveguide is H3＝150nm。
Further, the height of the position where the right stepped waveguide is in contact with the first waveguide is H 1100 nm; the width W of the contact position of the right stepped waveguide and the fourth waveguide3＝100nm。
Further, the first waveguide has a width g1The fourth waveguide has a width g of 40nm2＝25nm。
The technical scheme provided by the embodiment of the invention has the following beneficial effects: in the invention, based on a standard SOI wafer structure, a substrate is a silicon dioxide waveguide, and a section of strip waveguide consisting of a W-shaped groove waveguide made of silicon dioxide and a left step-shaped waveguide and a right step-shaped waveguide made of silicon material is arranged on the substrate; the structure forms the W-type silicon-based groove type on-chip polarization rotator, so that the insertion loss IL of incident light (TE/TM fundamental mode) in the full-wave-band range is less than 0.4dB in the wavelength range of 300nm (1400nm-1700nm), mode light is input from an input port and output from an output port, meanwhile, the polarization rotation efficiency PCE is higher than 98.6% in the full-wave-band range, IL of the 1550nm central wavelength is less than 0.23dB, and the PCE is higher than 99.96%. In addition, tolerance analysis shows that when the parameters of the coupling region of the polarization rotator deviate from +/-10 nm, the polarization rotator keeps higher polarization rotation efficiency (PCE is more than 98%) and lower insertion loss (IL is less than 0.43dB) in a 300nm bandwidth, the manufacturing tolerance is large, the polarization rotator is simple in structure and high in process feasibility, and the polarization rotator has potential application value in the field of on-chip photonic integration.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the description below are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 is a schematic structural diagram of a W-type silicon-based groove type on-chip polarization rotator based on a mode mixing principle provided by the invention;
FIG. 2 is a cross-sectional view of a W-type silicon slot on-chip polarization rotator provided by the present invention based on the principle of mode mixing;
FIG. 3 is a schematic structural diagram of a W-shaped trench waveguide provided in the present invention;
FIG. 4 is a diagram of two lowest-order mixed mode TE's provided by the present invention0And TM0A mode field profile in cross section;
FIG. 5 is a separate input TE provided by the present invention0And TM0A polarization rotation process in mode;
FIG. 6 is a graph showing the calculation of light propagation characteristics in a waveguide for an input TE using a mode Expansion Method (EME) according to the present invention0Mode conversion to output terminal TM0Mode case, calculated polarization conversion efficiency and insertion loss as a function of coupling length LCAnd a graph of the variation of the wavelength λ of the incident light;
in FIG. 7, (a) and (b) are respectively when TE is inputted0In mode ExAnd EyThe transmission distribution diagram of the optical electric field component of (c) and (d) are respectively the current input TM0In mode EyAnd ExThe transmission profile of the optical field component.
In FIG. 8, (a) and (b) are input TEs, respectively0Mode and TM0The insertion loss versus polarization conversion efficiency of the polarization rotator in mode is plotted.
In FIG. 9, (a) - (d) are for Δ W1Respectively inputting TE in tolerance analysis of +/-10 nm0And TM0The transmittance curves of (e) - (h) are for Δ W1Respectively inputting TE in tolerance analysis of +/-10 nm0And TM0Graph of insertion loss versus polarization rotation efficiency.
In FIG. 10, (a) - (d) are for Δ H3Respectively inputting TE in tolerance analysis of +/-10 nm0And TM0The transmittance of (e) - (H) are plotted for Δ H3Respectively inputting TE in tolerance analysis of +/-10 nm0And TM0Graph of insertion loss versus polarization rotation efficiency.
In FIG. 11, (a) - (d) are for Δ W2Respectively inputting TE in tolerance analysis of +/-8 nm0And TM0The transmittance curves of (e) - (h) are for Δ W2Respectively inputting TE in tolerance analysis of +/-8 nm0And TM0Graph of insertion loss versus polarization rotation efficiency.
In FIG. 12, (a) - (d) are for Δ H2Respectively inputting TE in tolerance analysis of +/-8 nm0And TM0The graph of transmittance when (e) - (H) are for Δ H2Tolerance division of + -8nmRespectively inputting TE in analysis0And TM0Graph of insertion loss versus polarization rotation efficiency.
Reference numerals: 1-a substrate; 2-a strip waveguide; a 3-W type trench waveguide; 4-left side stepped waveguide; 5-right stepped waveguide; 6-a first waveguide; 7-a second waveguide; 8-a third waveguide; 9-fourth waveguide.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
It will be understood that when an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present. As used herein, the terms "upper," "lower," "left," "right," and the like are used for descriptive purposes only.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.
FIG. 1 is a schematic structural diagram of a W-type silicon-based groove type on-chip polarization rotator based on a mode mixing principle provided by the invention; FIG. 2 is a cross-sectional view of a W-type silicon-based slot-on-chip polarization rotator provided by the invention based on the mode mixing principle. Referring to fig. 1-2, the polarization rotator includes: the polarization rotation device comprises a substrate 1, wherein the substrate 1 is composed of silicon dioxide, and a section of strip waveguide 2 is arranged at the top of the substrate 1 to form a polarization rotation region; the strip waveguide 2 includes: the waveguide structure comprises a W-shaped groove waveguide 3, a left stepped waveguide 4 and a right stepped waveguide 5, wherein the left stepped waveguide 4 and the right stepped waveguide 5 are respectively connected to two sides of the W-shaped groove waveguide 3; the W-shaped groove waveguide 3 is made of silicon dioxide, and the left stepped waveguide 4 and the right stepped waveguide 5 are made of silicon.
It should be noted that the polarization rotator is focused on the interconversion between different modes, and can polarize the light beamThe polarization state is changed to another polarization state which is perpendicular to the polarization state while the information carried by the polarization signal is kept. Therefore, the polarization rotator has wide application in photonic integrated circuits, polarization division multiplexing coherent optical communication and quantum communication. With the rapid development of the information society, the structure of the polarization rotator is complicated based on a general cascade structure under the principle of the mode evolution type polarization rotator, and the manufacturing cost is increased. Therefore, the invention provides the W-shaped silicon groove type on-chip polarization rotator based on the mode mixing principle, which can not only input the optical signal TE0Conversion to TM0Mode out, and TM can also be output0Mode conversion to TE0An efficient scheme for mode output. When TE0/TM0When the mode is injected, due to the asymmetric structure of the waveguide, two mixed-mode lights are generated at the end face of the input light, and the TM is output by gradually rotating along with the transmission length0/TE0Mode(s).
In addition, FIG. 4 shows two lowest-order mixed-mode TE respectively provided by the present invention0And TM0A mode field profile in cross section; wherein TE0Mode confinement in a predominantly W-type trench waveguide, TM0The modes are mainly distributed in the left stepped waveguide 4, and the two modes respectively account for 50%. When TE, as shown in FIG. 4(a)0When light in a polarization state is input, the two modes are almost excited equally, and because the two modes have different transmission constants in the asymmetric waveguide, 90-degree polarization rotation can be realized after the light is transmitted for a certain length L pi, so that TE (transverse electric) is enabled to be realized0Mode conversion to TM0Mode(s). TM0Mechanism at input and TE0Similarly.
FIG. 5 is a separate input TE provided by the present invention0And TM0Polarization rotation process at mode. Wherein S1And S2Two hybrid modes present in the structure, respectively. Input TE due to asymmetry of the cross-section0Or TM0In the mode, a mixed optical mode is generated in the optical waveguide. The two mixed mode polarization states S are generated by reasonably designing the size of the cross section1、S2At 45 deg. to the x-and y-axes, respectively, i.e. the transverse electric and magnetic field components in each hybrid mode are identical, so that the TE0Mode and TM0The modes are fully mixed, so that the polarization rotation function can be realized.
Further, the strip waveguide 2 is wrapped outside the left stepped waveguide 4 and the right stepped waveguide 5 by taking air as a medium. In order to increase the asymmetry of the refractive index in the vertical direction of the polarization rotator, air is used as a cladding, i.e., nAir, equal to 1.
Further, referring to fig. 3, the W-type trench waveguide 3 includes: a first waveguide 6, a second waveguide 7, a third waveguide 8 and a fourth waveguide 9; the first waveguides 6 are vertically distributed along the Y axis, and the second waveguides 7 are connected with the bottom of the first waveguides 6 and are vertical to the first waveguides 6; the third waveguide 8 is connected with one end of the second waveguide 7 far away from the first waveguide 6 and is vertical to the second waveguide 7; the fourth waveguide 9 is connected to one end of the third waveguide 8 away from the second waveguide 7, and is perpendicular to the third waveguide 8.
Further, the substrate 1 is composed of silicon dioxide having a refractive index nSiO at a wavelength of 1550nm2＝1.445。
Further, the W-type trench waveguide 3 is composed of silicon dioxide having a refractive index n at a wavelength of 1550nmSiO21.445; the left-side stepped waveguide 4 and the right-side stepped waveguide 5 are both made of silicon, and the refractive index of the silicon at 1550nm wavelength is nSi＝3.455。
Further, the thickness of the substrate 1 was 2 μm.
Further, the slab waveguide 2 has a thickness H of 400nm, a width W of 400nm, and a length L in the transmission directionC＝4.3um。
Further, the width of the top of the left stepped waveguide 4 is W1135 nm; the width of the connecting position of the left stepped waveguide 4 and the second waveguide 7 is W2120 nm; the width and height of the connecting position of the left stepped waveguide 4 and the third waveguide 8 are H2105 nm; the left stepped waveguide 4 is arranged at one side of the fourth waveguide 9 and has a height H3＝150nm。
Further, a right-side stepped waveguide5 the height of the position in contact with the first waveguide 6 is H 1100 nm; width W of contact position between right stepped waveguide 5 and fourth waveguide 93＝100nm。
Further, the first waveguide 6 has a width g140nm, the width of the fourth waveguide 9 is g2＝25nm。
Fig. 6 is a diagram for calculating the light propagation characteristics in the waveguide using the mode Expansion Method (EME) and applying the calculated light propagation characteristics to the input TE0Mode conversion to output terminal TM0In the case of the mode, the dependent coupling length L is calculatedcAnd polarization conversion efficiency with a change in wavelength λ of incident light. FIG. 4(a) shows the analysis of insertion loss with the length L of the rotation region under these conditionsCAnd the wavelength λ of the incident light, from which it can be seen that L is the function ofCTo increase the working wavelength band of the polarization rotator from short wavelength to long wavelength and to increase the input TE between 1400nm and 1700nm as much as possible0The conversion efficiency of the mode, Lc, is selected to be 4.3 μm. Similarly, the analysis of polarization conversion efficiency with rotation region length L under this condition is given in FIG. 4(b)CAnd a change in wavelength λ of the incident light. It shows that the length of the rotation area of the polarization rotator is less affected by the conversion efficiency when the length is 4.3um ± 100nm, and the performance is more affected after exceeding, so the length Lc of the rotation area of the polarization rotator is selected to be 4.3 μm, thereby obtaining all the structural parameters defining the polarization rotator: h400 nm W1＝135nm，W2＝120nm，W3＝100nm，H1＝100nm，H2＝105nm，H3＝150nm，g1＝40nm，g225nm, polarization rotation length LC4.3 μm. Under the above parameter settings, the polarization rotator can realize simultaneous realization of input polarized light TE in a wider (300nm) working wave band0Conversion to TM0And inputting polarized light TM0Conversion to TE0And (6) outputting the mode. The insertion loss is low in the bandwidth of 300nm, and the polarization conversion efficiency is excellent. Tolerance analysis shows that the polarization rotator still has high working performance in the E-to-U wave band of current optical fiber communication.
In FIG. 7, (a)) Respectively, when TE is input0In mode ExAnd EyThe transmission profile of the photoelectric field component, from which the photoelectric field component E can be seenxGradually decreases to disappear with the increase of the transmission distance in the rotation region, and the photoelectric field component EyGradually increasing to the strongest. (c) And (d) are respectively as input TM0In mode EyAnd ExThe transmission profile of the photoelectric field component can be seen from the figure, the photoelectric field component EyGradually decreases to disappear along with the increase of the transmission distance in the rotating region, and the photoelectric field component ExGradually increasing to the strongest. It can be derived from FIG. 7 that TE is input regardless of the input0Mode is also TM0In a mode, the polarization rotator maintains better polarization rotation, and the good reciprocity of the polarization rotator is proved. The output end light field intensity also proves the high polarization conversion efficiency.
In FIG. 8, (a) and (b) are input TEs, respectively0Mode and TM0The insertion loss and polarization conversion efficiency of the polarization rotator in mode. It can be seen that TE is input regardless of the input0Or TM0In a mode, the conversion efficiency of the polarization rotator is always higher than 98.6% in the wavelength range of 1400nm-1700nm, the insertion loss is higher than 99.96% at the position of 1550nm of the central wavelength, the insertion loss is lower than 0.4dB, and the insertion loss at the position of 1550nm of the central wavelength is only 0.23 dB.
The modern DUV photoetching process can generally achieve the purposes that the flatness of the line width on a chip is superior to 0.6nm, the flatness of the line width on the chip is superior to 2.6nm, and the nonuniformity in a 200mm SOI wafer is less than 1%, so that the maximum value of the tolerance in the width direction is 1% of the width, and the maximum value of the tolerance in the height direction is 10 nm.
In FIG. 9, (a) and (b) are W1Manufacturing tolerance aw of1When the wavelength is +/-10 nm, TE is input0Output terminal TE when mode0And TM0The transmittance in the mode (c) and (d) are respectively Delta W1When the input is + -10nm, TM is input0Mode time output TE0And TM0Transmittance of the mode. It can be seen from (a) and (b) that when Δ W1Input TE ═ 10nm0Mode, output TE in the wavelength range of 1400nm-1700nm0The transmittance of the mode is less than-15 dB;when inputting TM0Mode, output terminal TM0The mode transmittance is less than-15 dB. (e) And (g) is Δ W1Respectively inputting TE when the input voltage is +10nm0And TM0Polarization Conversion Efficiency (PCE) and Insertion Loss (IL), (f) and (h) of the modes are Δ W1Respectively inputting TE when the crystal is equal to-10 nm0And TM0Polarization Conversion Efficiency (PCE) and Insertion Loss (IL) of the mode. It can be seen that Δ W1At +10nm, the two modes have PCE > 98.5%, IL < 0.45dB, and Δ W in the wavelength range of 1400-1700nm1PCE > 97.8% at 1400-1700nm wavelength range and IL <0.4 dB.
In FIG. 10, (a) and (b) are H3Of (d) manufacturing tolerance Δ H3When the wavelength is +/-8 nm, inputting TE0Output terminal TE when mode0And TM0The transmittance in the mode (c) and (d) are respectively Delta H3When the input is +/-8 nm, inputting TM0Mode time output TE0And TM0Transmittance of the mode. It can be seen from (a) and (b) that when Δ H3Input TE ═ 8nm0Mode, output TE in the wavelength range of 1400nm-1700nm0The transmittance of the mode is less than-15 dB; when inputting TM0Mode output terminal TM0The mode transmittance is less than-15 dB. (e) And (g) is Δ H3Respectively inputting TE when the input voltage is +8nm0And TM0Polarization Conversion Efficiency (PCE) and Insertion Loss (IL) of the modes are Δ H, (f) and (H)3Respectively inputting TE when the input voltage is 8nm0And TM0Polarization Conversion Efficiency (PCE) and Insertion Loss (IL) of the mode. It can be seen that Δ H3When +8nm, TE0PCE > 97% in the wavelength range of 1400nm-1700nm, IL < 0.45dB, TM0The mode is PCE > 96.5%, IL < 0.45dB, delta H3PCE > 98.5% and IL < 0.42dB in the wavelength range of 1400nm-1700nm for both modes at-8 nm.
In FIG. 11, (a) and (b) are W2Manufacturing tolerance Δ W of2When the wavelength is +/-8 nm, inputting TE0Mode time output TE0And TM0Transmittance in the mode, (c) and (d) are Δ W2When the input is +/-8 nm, inputting TM0Mode time output TE0And TM0Transmittance of the mode. From (a), (b) may beIt is seen that when Δ W2Input TE ═ 8nm0Mode, 0TE at output end in wavelength range of 1400nm-1700nm0The transmittance of the mode is less than-15 dB; when inputting TM0Mode output terminal TM0The mode transmittance is less than-15 dB. (e) And (g) is Δ W2Respectively inputting TE when the input voltage is +8nm0And TM0Polarization Conversion Efficiency (PCE) and Insertion Loss (IL), (f) and (h) of the modes are Δ W2Respectively inputting TE when the input voltage is 8nm0And TM0Polarization Conversion Efficiency (PCE) and Insertion Loss (IL) of the mode. It can be seen that Δ W2When +8nm, TE0PCE > 97.5%, IL < 0.42dB, TM in the wavelength range of 1400nm-1700nm0The PCE of the mode is more than 96.5 percent, IL is less than 0.45dB, and delta W2PCE > 98.6% for both modes at-8 nm, IL <0.4 dB.
In FIG. 12, (a) and (b) are H2Manufacturing tolerance Δ H of2When the wavelength is +/-8 nm, inputting TE0Output terminal TE when mode0And TM0The transmittance in the mode (c) and (d) are respectively Delta H2When the input is +/-8 nm, inputting TM0Output terminal TE when mode0And TM0Transmittance of the mode. It can be seen from (a) and (b) that when Δ H2Input TE ═ 8nm0Mode, 0TE at output end in wavelength range of 1400nm-1700nm0The transmittance of the mode is less than-15 dB; when inputting TM0Mode output terminal TM0The mode transmittance is less than-15 dB. (e) And (g) is Δ H2Respectively inputting TE when the input voltage is +8nm0And TM0Polarization Conversion Efficiency (PCE) and Insertion Loss (IL) of the modes are Δ H, (f) and (H)2Respectively inputting TE when the input voltage is 8nm0And TM0Polarization Conversion Efficiency (PCE) and Insertion Loss (IL) of the mode. It can be seen that Δ W2When the wavelength is +8nm, the PCE of the two modes in the wavelength range of 1400nm-1700nm is more than 97.3 percent, and the IL is less than 0.42 dB; Δ H2TE at-8 nm0PCE > 98.5% for mode, IL <0.4dB, PCE > 97.6% for TM0 mode, and IL < 0.42 dB.
It is worth pointing out that, in the invention, based on the standard SOI wafer structure, the substrate is a silicon dioxide waveguide, and a section of strip waveguide composed of a W-shaped groove waveguide made of silicon dioxide and a left-side stepped waveguide and a right-side stepped waveguide made of silicon material is arranged above the silicon dioxide waveguide; the structure forms the W-type silicon-based groove type on-chip polarization rotator, so that the insertion loss IL of incident light (TE/TM fundamental mode) in the full-wave-band range is less than 0.4dB in the wavelength range of 300nm (1400nm-1700nm), mode light is input from an input port and output from an output port, meanwhile, the polarization rotation efficiency PCE is higher than 98.6% in the full-wave-band range, IL of the 1550nm central wavelength is less than 0.23dB, and the PCE is higher than 99.96%. In addition, when the structural parameters of the coupling region of the polarization rotator deviate from +/-10 nm, the polarization rotator keeps higher polarization conversion efficiency and lower insertion loss PCE > 98.6% (IL <0.4dB) in a wider wave band (1400nm-1700nm), and has simple structure and high process feasibility.
The above-mentioned serial numbers of the embodiments of the present invention are merely for description and do not represent the merits of the embodiments.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and should not be taken as limiting the scope of the present invention, which is intended to cover any modifications, equivalents, improvements, etc. within the spirit and scope of the present invention.

Claims (9)

1. A W-type silicon-based slot-on-chip polarization rotator based on a mode-mixing principle, the polarization rotator comprising: the polarization rotation device comprises a substrate (1), wherein the substrate (1) is made of silicon dioxide, and a section of strip waveguide (2) is arranged at the top of the substrate (1) to form a polarization rotation region;
the strip waveguide (2) comprises: w type slot waveguide (3), left side notch cuttype waveguide (4) and right side notch cuttype waveguide (5), W type slot waveguide (3) include: a first waveguide (6), a second waveguide (7), a third waveguide (8) and a fourth waveguide (9); the first waveguides (6) are vertically distributed along the Y axis, and the second waveguides (7) are connected with the bottoms of the first waveguides (6) and are vertical to the first waveguides (6); the third waveguide (8) is connected with one end of the second waveguide (7) far away from the first waveguide (6) and is vertical to the second waveguide (7); the fourth waveguide (9) is connected with one end of the third waveguide (8) far away from the second waveguide (7) and is vertical to the third waveguide (8);
the left stepped waveguide (4) and the right stepped waveguide (5) are respectively connected to two sides of the W-shaped groove waveguide (3); w type slot waveguide (3) comprise silica, left side notch cuttype waveguide (4) with right side notch cuttype waveguide (5) comprise material silicon.
2. The W-type silicon-based slot-on-chip polarization rotator based on mode-mixing principle according to claim 1, wherein the strip waveguide (2) is wrapped outside the left-side stepped waveguide (4) and the right-side stepped waveguide (5) by taking air as a medium.
3. A W-type silicon-slot on-chip polarization rotator based on mode mixing principle as claimed in claim 1 characterized in that the substrate (1) is composed of silicon dioxide with refractive index nSiO at 1550nm wavelength2＝1.445。
4. A W-type silicon-trench-type on-chip polarization rotator based on mode mixing principle as claimed in claim 3 characterized in that the W-type trench waveguide (3) is composed of silica with refractive index nSiO at 1550nm wavelength21.445; the left-side stepped waveguide (4) and the right-side stepped waveguide (5) are both made of silicon, and the refractive index of silicon at 1550nm wavelength is nSi-3.455.
5. A W-type silicon slot on-chip polarization rotator based on mode mixing principle according to claim 4 characterized in that the thickness of the substrate (1) is 2 μm.
6. The W-type silicon-groove-type on-chip polarization rotator based on the mode mixing principle as claimed in claim 5, wherein the thickness H of the strip waveguide (2) is 400nm, the width W is 400nm, and the length along the transmission direction is LC＝4.3um。
7. The W-type silicon slot type on-chip polarization rotator based on the mode mixing principle as claimed in claim 6, wherein the width of the top of the left-side stepped waveguide (4) is W1135 nm; the width of the connecting position of the left stepped waveguide (4) and the second waveguide (7) is W2120 nm; the width and height of the connecting position of the left stepped waveguide (4) and the third waveguide (8) are H2105 nm; the left stepped waveguide (4) is positioned at one side of the fourth waveguide (9) and has a height H3＝150nm。
8. The W-type silicon-based groove type on-chip polarization rotator based on mode mixing principle of claim 7, wherein the height of the position where the right-side stepped waveguide (5) contacts with the first waveguide (6) is H1100 nm; the width W of the contact position of the right stepped waveguide (5) and the fourth waveguide (9)3＝100nm。
9. The W-type silicon slot on-chip polarization rotator based on mode mixing principle of claim 8, wherein the width of the first waveguide (6) is g1-40 nm, said fourth waveguide (9) having a width g2＝25nm。
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