CN117631146A - Polarization converter based on film lithium niobate waveguide supermode evolution - Google Patents
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- 230000010287 polarization Effects 0.000 title claims abstract description 48
- GQYHUHYESMUTHG-UHFFFAOYSA-N lithium niobate Chemical compound [Li+].[O-][Nb](=O)=O GQYHUHYESMUTHG-UHFFFAOYSA-N 0.000 title claims abstract description 38
- 238000000034 method Methods 0.000 claims abstract description 26
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- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims abstract description 8
- 238000006243 chemical reaction Methods 0.000 claims abstract description 7
- 238000005253 cladding Methods 0.000 claims abstract description 4
- 235000012239 silicon dioxide Nutrition 0.000 claims abstract description 4
- 239000000377 silicon dioxide Substances 0.000 claims abstract description 4
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims abstract description 3
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 3
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Abstract
The invention discloses a polarization converter based on film lithium niobate waveguide supermode evolution, which comprises a silicon substrate layer, an oxygen-buried layer, a lithium niobate layer and a silicon dioxide upper cladding layer which are sequentially stacked from bottom to top, wherein the lithium niobate layer comprises an input end waveguide, an input mode converter, a first S-bend waveguide, a phase shifter, a second S-bend waveguide, an output mode converter and an output end waveguide which are sequentially connected. Transverse electric fundamental mode TE of input end waveguide 0 Upon input, adiabatic evolution into transverse electric symmetric mode TE of a three waveguide system by an input mode converter s0 Transverse electric antisymmetric mode TE converted into three-waveguide system by phase shifter s1 Finally, the transverse magnetic fundamental mode TM is hybridized and evolved into an output end waveguide through an output mode converter 0 The method comprises the steps of carrying out a first treatment on the surface of the TM when the input is waveguide 0 In the input of the mouldThe now opposite mode evolution process eventually becomes TE 0 And outputting. The invention realizes the mutual conversion of two polarization states and has the advantages of large bandwidth, high extinction ratio, low insertion loss, large process tolerance and the like.
Description
Technical Field
The invention relates to an on-chip polarization converter, which is a polarization converter of a thin film lithium niobate waveguide with the advantages of large bandwidth, high extinction ratio, low insertion loss, large process tolerance and the like.
Background
The polarization converter is widely applied to the fields of quantum communication and calculation, optical networks, optical sensing and measurement and the like. The lithium niobate crystal has excellent electro-optic characteristics, an oversized transparent window and a larger second-order nonlinear coefficient, and compared with the traditional titanium diffusion or proton exchange lithium niobate waveguide, the lithium niobate crystal has high integration level by using the thin film Lithium Niobate (LNOI) etching type waveguide on an insulator, and is an important platform for manufacturing electro-optic integrated devices. There are several methods for implementing polarization converters based on thin film lithium niobate: the lithium niobate waveguide of the surface plasma is utilized to realize high-efficiency polarization rotation; coupling of different polarization modes is realized through a directional coupler; coupling of different polarization states occurs in the bending process by utilizing anisotropic characteristics, and finally polarization rotation is realized; the effect of birefringence of the lithium niobate material on the polarization characteristics of the X-cut LNOI waveguide is utilized to realize a passive LNOI polarization rotator by causing passive polarization coupling by making light propagate away from the z-axis. The existing polarization converter still has problems in terms of working bandwidth, process complexity or insertion loss, and the thin film lithium niobate platform also lacks high-performance polarization converters with large bandwidth, low power consumption and the like.
Disclosure of Invention
Aiming at the defects in the prior background art, the invention can realize TE by utilizing the waveguide supermode evolution based on the film lithium niobate 0 -TM 0 、TM 0 -TE 0 The invention aims to design a polarization converter with the advantages of large bandwidth, high extinction ratio, low insertion loss and large process tolerance. The invention can be used for optical sensors, optical element tests, optical communication systems, laser systems and the like.
Extinction of the inventionThe ratio is defined as follows: output TE 0 And TM 0 The energies of (2) are P1 and P2, respectively, the extinction ratio=10·log (P2/P1). The higher the extinction ratio, the higher the conversion efficiency. Insertion loss refers to the loss of power of a signal as it is converted by transmission. Bandwidth refers to the range of wavelengths over which a polarizer can operate effectively, while process tolerances refer to the effect of waveguide broadening on the range of wavelengths over which the device operates effectively during fabrication.
The technical scheme adopted by the invention is as follows:
the invention comprises an input end waveguide, an input mode converter, a first S-bend waveguide, a phase shifter, a second S-bend waveguide, an output mode converter and an output end waveguide. The input end waveguide is connected with the input end of the input mode converter, the other end of the input mode converter is connected with the input end of the first S-shaped bent waveguide, the output end of the first S-shaped bent waveguide is connected with the input end of the phase shifter, the output end of the phase shifter is connected with the input end of the second S-shaped bent waveguide, the other end of the second S-shaped bent waveguide is connected with the input end of the output mode converter, and the output end of the output mode converter is connected with the output end waveguide.
The polarization converter of the invention is a transverse electric fundamental mode TE input by an input end waveguide 0 Transverse magnetic fundamental mode TM (TM) evolved into output end waveguide output 0 When the input end waveguide inputs TM 0 When in mode, the opposite mode evolution process is finally changed into TE 0 And outputting.
The input (output) mode converter consists of three waveguides forming a three-waveguide system, and the width of the middle waveguide b is from wide w b1 Changing to a narrow w b2 Simultaneously waveguide a and waveguide c on both sides, width from narrow w a1 Varying to wide w a2 . Wherein w is b1 The value of (2) is selected in the single-mode condition range supporting the two polarizations of the waveguide TE and the waveguide TM; w (w) a2 The value of (2) is selected in the condition range supporting TE polarization single mode of the waveguide; size w of narrow end a1 And w b2 Less than 0.15 μm, the minimum being determined by the process capable of being made; spacing w between waveguide b and waveguides a and c on both sides g1 The width of the three waveguides is unchanged in the process of changing, and the size is determined according to the minimum manufacturable processAnd (5) setting. The input mode converter and the output mode converter are identical and the entire input (output) mode converter is symmetrical about a horizontal center line.
The wider end of the waveguide b in the middle of the input (output) mode converter is connected with the waveguide of the input end or the output end, and the other end of the waveguide b is connected with the phase shifter through the first S-bend waveguide or the second S-bend waveguide. TE when input waveguide 0 During mode input, TE symmetric mode TE of a three-waveguide system of an input mode converter is excited s0 A wider intermediate waveguide region where the mode field energy is primarily concentrated initially, the mode field energy being distributed in waveguides on both sides through adiabatic evolution of the input mode converter; TM when the input is waveguide 0 When the mode is input, the TM supermode TM of the three-waveguide system of the input mode converter is excited s0 The mode hybridization of the transmission through the input mode converter is evolved into TE antisymmetric mode TE of a three-waveguide system s1 The mode field energy is distributed in the waveguides on both sides.
The first S-bend waveguide consists of three waveguides, and the width of the middle waveguide b is w b2 The waveguides a and c on two sides are arc shapes with two tangent sections, and the interval between the middle waveguide b and the waveguides a and c on two sides is changed from w g1 Broadening to w g2 。
The phase shifter mainly comprises a waveguide a, a waveguide b and a waveguide c, and a fixed interval w is kept among the three waveguides g2 The method comprises the steps of carrying out a first treatment on the surface of the In the phase shifter region, the width w of the waveguide a c1 Output width w of outer waveguide of input mode converter a2 Width w of waveguide b is uniform c2 Intermediate waveguide output width w with input mode converter b2 The waveguide a and the waveguide b are both straight waveguides, the waveguide c consists of two sections of symmetrical gradually-changing conical waveguides and one section of straight waveguide, and the width of the waveguide is equal to the width w of the output of the waveguide on the outer side of the input mode converter a2 Linear gradual widening to w c3 After passing through a section of straight waveguide, the width gradually changes back to w a2 . When TE symmetric mode TE s0 When inputting, light is transmitted in waveguide c and has pi phase change more than waveguide a, and symmetrical mode TE s0 Transition to the anti-symmetric mode TE s1 Output ofThe method comprises the steps of carrying out a first treatment on the surface of the Conversely, when the TE is the antisymmetric mode s1 Upon input, transition to symmetric mode TE s0 And outputting.
The input end waveguide, the input mode converter, the first S-bend waveguide, the phase shifter, the second S-bend waveguide, the output mode converter and the output end waveguide are all conical ridge waveguide structures formed by X-cut thin film lithium niobate half-etching. The polarization converter based on the thin film lithium niobate waveguide is bilaterally symmetrical about a middle vertical line.
The invention has the beneficial effects that:
the input (output) mode converter adopted by the invention adopts a three-waveguide system, and the TM supermode TM of the three-waveguide system of the input mode converter can be realized by utilizing the supermode hybridization and the mode evolution principle 0 To an antisymmetric mode TE s1 Evolution of (2) and symmetric mode TE of a three waveguide system s0 Is not subject to loss-less transmission. The working mechanism has the advantages of higher extinction ratio, large bandwidth, low loss, large process tolerance and the like.
The phase shifter adopted by the invention is composed of three waveguides with different widths, wherein the waveguide c utilizes the combination mode of the slowly-changing conical waveguide and the straight waveguide, thereby realizing the multi pi phase change of the light transmitted by the waveguide c compared with the waveguide a, and finally realizing the symmetrical mode TE s0 And the anti-symmetric mode TE s1 Is provided. The design has the advantages of large bandwidth, compact structure, low loss, large process tolerance and the like.
The polarization conversion is based on the supermode adiabatic evolution and the phase shifters with different waveguide widths, and finally the high-performance polarization conversion with the working wave band of 240nm, the extinction ratio of more than 20dB and the loss of less than 0.3dB can be realized.
All thin film lithium niobate waveguides adopt half-etched conical ridge waveguide structures with the same depth, and the manufacturing process is simple and the processing cost is low.
Drawings
FIG. 1 is a schematic representation of an embodiment of the present invention.
Fig. 2 is a cross-sectional view of an embodiment ridge waveguide.
FIG. 3 (a) is a schematic diagram of the input mode converter and the input terminal in the embodimentSection, section when hybridization occurs, and mode field intensity distribution diagram at section of output terminal, TE s0 And TE (TE) s1 The white lines on the mode field plot represent the electric field amplitudes distributed laterally along the mode field mid-line.
FIG. 3 (b) is a schematic diagram of the phase shifter and at the input TE respectively s0 And TE (TE) s1 A schematic diagram of different output mode field amplitudes.
FIG. 4 (a) is a schematic diagram of an embodiment in which the input is TE for a wavelength of 1550nm 0 (a) In mode, a simulated electric field intensity propagation diagram in a designed polarization converter.
FIG. 4 (b) is a graph of input as TM for a wavelength of 1550nm in an embodiment 0 (b) In mode, a simulated electric field intensity propagation diagram in a designed polarization converter.
FIG. 5 (a) is a transmission spectrum (TE) of the polarization converter in the embodiment 0 Input).
FIG. 5 (b) is a transmission spectrum (TM) of the polarization converter in the embodiment 0 Input).
Detailed Description
The invention will be further described with reference to the drawings and examples.
The components of the figures may be exaggerated or reduced to better illustrate the present embodiments and do not represent actual device dimensions. The width and the spacing of the waveguides refer to the dimensions of the upper surface of the waveguides.
As shown in fig. 1, a polarization converter based on the supermode evolution of a thin film lithium niobate waveguide comprises an input end waveguide, an input mode converter, a first S-bend waveguide, a phase shifter, a second S-bend waveguide, an output mode converter and an output end waveguide. The input end waveguide is connected with the input end of the input mode converter, the other end of the input mode converter is connected with the input end of the first S-shaped bent waveguide, the output end of the first S-shaped bent waveguide is connected with the input end of the phase shifter, the output end of the phase shifter is connected with the input end of the second S-shaped bent waveguide, the other end of the second S-shaped bent waveguide is connected with the input end of the output mode converter, and the output end of the output mode converter is connected with the output end waveguide.
The input (output) mode converter consists of three waveguide groupsIn a three waveguide system, the width of the middle waveguide b is from a wide w b1 Changing to a narrow w b2 Simultaneously waveguide a and waveguide c on both sides, width from narrow w a1 Varying to wide w a2 . Wherein w is b1 The value of (2) is selected in the single-mode condition range supporting the two polarizations of the waveguide TE and the waveguide TM; w (w) a2 The value of (2) is selected in the condition range supporting TE polarization single mode of the waveguide; size w of narrow end a1 And w b2 Less than 0.15 μm, the minimum being determined by the process capable of being made; spacing w between waveguide b and waveguides a and c on both sides g1 The width of the three waveguides is unchanged in the process of changing, and the size is determined according to the minimum manufacturing process. The input mode converter and the output mode converter are identical and the entire input (output) mode converter is symmetrical about a horizontal center line.
As shown in fig. 3 (a), the design of the input mode converter is based on mode hybridization of a three tapered graded waveguide system by calculating the effective refractive index (n eff ) Find TM s0 - TE s1 Mode hybridization and intermediate waveguide width w b And a two-sided waveguide width w a Of (2), i.e. waveguide width w b Evolved to 0.875 μm, w a Evolving to 0.293 μm, n of these two modes eff Has an inflection point, thus when TM s0 Or TE (TE) s1 When the mode passes through the waveguide and the width is evolved into the two values, the two modes realize mutual conversion. At the same time, for supermode TE s0 Can pass through without damage.
As shown in FIG. 3 (a), the three gray scale patterns on the device represent TE in turn s0 A mode field distribution map of the overmode input location, the hybridization occurrence location and the output location; the three gray scale patterns below the device represent TM in turn s0 A mode field profile for the overmode input location, the hybridization location, and the output location. The light field amplitude distribution along the transverse middle line, TE, is noted in the output position gray scale map s1 Is in an antisymmetric mode, TE s0 Is a symmetrical mode. Below FIG. 3 (a) is a graph showing the width w of the intermediate waveguide b And a two-sided waveguide width w a At the same time, i.e. alongEffective refractive index n of three supermodes in mode evolution of input mode converter eff Is a variation of (c).
As shown in fig. 1, the phase shifter mainly comprises a waveguide a, a waveguide b and a waveguide c, and a fixed spacing w is kept between the three waveguides g2 The method comprises the steps of carrying out a first treatment on the surface of the In the phase shifter region, the width w of the waveguide a c1 Output width w of outer waveguide of input mode converter a2 Width w of waveguide b is uniform c2 Intermediate waveguide output width w with input mode converter b2 The waveguide a and the waveguide b are both straight waveguides, the waveguide c consists of two sections of symmetrical gradually-changing conical waveguides and one section of straight waveguide, and the width of the waveguide is equal to the width w of the output of the waveguide on the outer side of the input mode converter a2 Linear gradual widening to w c3 After passing through a section of straight waveguide, the width gradually changes back to w a2 。
As shown in FIG. 3 (b), TE can be realized because the waveguide a has pi-phase changes more during optical transmission because the width of the waveguide c is wider than that of the waveguide a in the phase shifter region s0 And TE (TE) s1 Is provided. As can be seen from the schematic diagram, the phase shifter will be symmetrical mode TE s0 Transition to the anti-symmetric mode TE s1 Outputting; conversely, when the TE is the antisymmetric mode s1 Upon input, transition to symmetric mode TE s0 And outputting.
In a specific implementation, the input end waveguide, the input mode converter, the first S-bend waveguide, the phase shifter, the second S-bend waveguide, the output mode converter and the output end waveguide are all conical ridge waveguide structures formed by X-cut thin film lithium niobate half etching, and the light transmission direction is along the Y direction of the lithium niobate crystal. The polarization converter based on the thin film lithium niobate waveguide is bilaterally symmetrical about a middle vertical line.
As shown in FIG. 4 (a), when TE is input 0 In mode, light field propagation is simulated in the polarization converter.
As shown in FIG. 4 (b), when the TM is entered 0 In mode, light field propagation is simulated in the polarization converter.
The operation of the invention as a polarization converter is described as follows:
for the slave input endTE for waveguide input 0 And TM 0 The fundamental mode excites the three-waveguide system of the input mode converter to generate TE symmetric mode TE s0 Sum TM supermode TM s0 . For TE s0 A mode, which can pass through the input mode converter without loss, and then enter the phase shifter through the first S-bend waveguide; while for TM s0 Mode due to the presence of TM in the mode converter s0 And TE antisymmetric mode TE s1 Is hybridized with (a) so that TM s0 Mode post-hybridization evolution to TE through input mode converter s1 The mode then enters the phase shifter through the first S-bend waveguide. TE is achieved when passing through the phase shifter due to the light traveling in waveguide c with pi phase changes more than waveguide a s0 And TE (TE) s1 Is provided. TE input to output mode converter s0 And TE (TE) s1 After the mode is hybridized and evolved by the output mode converter, the TM is output through the output end waveguide 0 And TE (TE) 0 Two fundamental modes.
The specific embodiment of the invention is as follows:
the silicon substrate layer, the oxygen-buried layer, the lithium niobate layer and the silicon dioxide upper cladding layer are sequentially stacked from bottom to top, the core layer is made of X-cut film lithium niobate material, the light transmission direction is along the Y direction of the lithium niobate crystal, the waveguide is a conical ridge waveguide, the ridge height is 200nm, the thickness of a flat plate is 200nm, the included angle between the side wall of the waveguide and the horizontal plane is 60 degrees, the thickness of the oxygen-buried layer is 3 mu m, the upper cladding layer is made of silicon dioxide, the refractive index is 1.455, the thickness is 2 mu m or more, and the cross section structure diagram of the device is shown in figure 2.
The input end waveguide adopts a straight waveguide, the width of which is kept the same as the width of the wide end of the intermediate waveguide b of the input (output) mode converter, and is w b1 =1.3 μm. Narrow end width w of intermediate waveguide b of input (output) mode converter b2 =0.12 μm, narrow end widths w of both side waveguides a and c a1 Wide end width w=0.12 μm a2 =0.6 μm, the spacing between the middle waveguide b and the side waveguides a and c is fixed to w g1 =0.6 μm. Input (output) mode converter length L 1 =1500 μm to ensure adiabatic evolution of the pattern.
First S-bend waveguide (second S-bend waveguide)The width of the waveguide a and the waveguide c on both sides of (a) and the width w of the wide end of the waveguide on both sides of the input (output) mode converter a2 The same is 0.6 μm, the width of the intermediate waveguide b of the first S-bend waveguide (second S-bend waveguide) and the narrow end width w of the intermediate waveguide of the input (output) mode converter b2 The same is 0.12 μm, and the distance between the middle waveguide b and the two side waveguides a and c is from w g1 =0.6 μm spread to w g2 =0.8 μm, the two side waveguides are two tangential circular arcs of the splice, respectively. Length L of first S-bend waveguide (second S-bend waveguide) 2 =40 μm to ensure TE s0 And TE (TE) s1 The mode is transmitted with very low loss.
The waveguide a in the phase shifter is a straight waveguide with width w c1 Length l=0.6 μm 3 +L 4 +L 3 24 μm; waveguide b is likewise a straight waveguide of width w c2 =0.12 μm, identical to the middle waveguide narrow end of the input (output) mode converter; the waveguide c is composed of three parts, the first part is a linear slowly-changing conical waveguide with vertical asymmetry and width of narrow end and w a2 The same width of the wide end is 0.6 mu m and the same width of the second part of the straight waveguide is w c2 Length l=1.1 μm 3 =10μm. Straight waveguide length L in the second section 4 =4μm, which length can guarantee that the implementation will TE s0 And TE (TE) s1 High-efficiency transformation. The third part is symmetrical with the first part in length L 3 Still 10 μm, wide end width 1.1 μm, narrow end width 0.6 μm. There is a fixed spacing w between the three waveguides g2 =0.8μm。
By TE 0 And TM 0 Mode conversion to examples the performance of the designed device was simulated. When TE is 0 Upon input, convert to TM 0 Mode output, simulated 1550nm wavelength transmission field is shown in FIG. 4 (a), with polarization extinction ratio greater than 20dB over the wavelength range 1440-1680nm, as shown in FIG. 5 (a). When TM 0 Upon input, convert to TE 0 Mode output, simulated 1550nm wavelength transmission field is shown in FIG. 4 (b), polarization extinction ratio is greater than 20dB in the wavelength range of 1440-1680nm, as shown in FIG. 5 (b). TE (TE) 0 Or TM 0 Insertion loss of polarization converter at mode inputLess than 0.3dB.
The above-described embodiments are intended to illustrate the present invention, not to limit it, and any modifications and variations made thereto are within the spirit of the invention and the scope of the appended claims.
Claims (7)
1. A polarization converter based on film lithium niobate waveguide supermode evolution is characterized in that: comprises a silicon substrate layer, an oxygen-buried layer, a lithium niobate layer and a silicon dioxide upper cladding layer which are sequentially laminated from bottom to top; forming a thin film lithium niobate optical waveguide on the X-cut lithium niobate layer by an etching technology; the thin film lithium niobate optical waveguide comprises an input end waveguide, an input mode converter, a first S-bend waveguide, a phase shifter, a second S-bend waveguide, an output mode converter and an output end waveguide which are connected in sequence.
2. The polarization converter based on the supermode evolution of a thin film lithium niobate waveguide according to claim 1, wherein: the input mode converter consists of three waveguides forming a three-waveguide system, and the width of the middle waveguide b is from wide w b1 Changing to a narrow w b2 Simultaneously waveguide a and waveguide c on both sides, width from narrow w a1 Varying to wide w a2 The method comprises the steps of carrying out a first treatment on the surface of the Wherein w is b1 The value of (2) is selected in the single-mode condition range supporting the two polarizations of the waveguide TE and the waveguide TM; w (w) a2 The value of (2) is selected in the condition range supporting TE polarization single mode of the waveguide; size w of narrow end a1 And w b2 Less than 0.15 μm, the minimum being determined by the process capable of being made; spacing w between waveguide b and waveguides a and c on both sides g1 The width of the three waveguides is unchanged in the changing process, and the size is determined according to the minimum manufacturable process; the input mode converter and the output mode converter are identical, and the whole input mode converter and the whole output mode converter are symmetrical about a horizontal center line.
3. A polarization converter based on thin film lithium niobate waveguide supermode evolution according to claim 1 or 2, characterized in that: the saidOne wider end of the waveguide b in the middle of the input mode converter is connected with the input end or the output end waveguide, and the other end of the waveguide b is connected with the phase shifter through a first S-bend waveguide or a second S-bend waveguide; TE when input waveguide 0 During mode input, TE symmetric mode TE of a three-waveguide system of an input mode converter is excited s0 A wider intermediate waveguide region where the mode field energy is primarily concentrated initially, the mode field energy being distributed in waveguides on both sides through adiabatic evolution of the input mode converter; TM when the input is waveguide 0 When the mode is input, the TM supermode TM of the three-waveguide system of the input mode converter is excited s0 The mode hybridization of the transmission through the input mode converter is evolved into TE antisymmetric mode TE of a three-waveguide system s1 The mode field energy is distributed in the waveguides on both sides.
4. The polarization converter based on the supermode evolution of a thin film lithium niobate waveguide according to claim 1, wherein: the first S-bend waveguide consists of three waveguides, and the width of the middle waveguide b is w b2 The waveguides a and c on two sides are arc shapes with two tangent sections, and the interval between the middle waveguide b and the waveguides a and c on two sides is changed from w g1 Broadening to w g2 。
5. The polarization converter based on the supermode evolution of a thin film lithium niobate waveguide according to claim 1, wherein: the phase shifter comprises a waveguide a, a waveguide b and a waveguide c, and a fixed interval w is kept among the three waveguides g2 The method comprises the steps of carrying out a first treatment on the surface of the In the phase shifter region, the width w of the waveguide a c1 Output width w of outer waveguide of input mode converter a2 Width w of waveguide b is uniform c2 Intermediate waveguide output width w with input mode converter b2 The waveguide a and the waveguide b are both straight waveguides, the waveguide c consists of two sections of symmetrical gradually-changing conical waveguides and one section of straight waveguide, and the width of the waveguide is equal to the width w of the output of the waveguide on the outer side of the input mode converter a2 Linear gradual widening to w c3 After passing through a section of straight waveguide, the width gradually changes back to w a2 ；
When TE symmetric mode TE s0 When inputting, light is transmitted in waveguide c and has pi phase change more than waveguide a, and symmetrical mode TE s0 Transition to the anti-symmetric mode TE s1 Outputting; conversely, when the TE is the antisymmetric mode s1 Upon input, transition to symmetric mode TE s0 And outputting.
6. The polarization converter based on the supermode evolution of a thin film lithium niobate waveguide according to claim 1, wherein: the input end waveguide, the input mode converter, the first S-bend waveguide, the phase shifter, the second S-bend waveguide, the output mode converter and the output end waveguide are all conical ridge waveguide structures formed by X-cut thin film lithium niobate half-etching; the polarization converter based on the thin film lithium niobate waveguide is bilaterally symmetrical about a middle vertical line.
7. The polarization converter based on the supermode evolution of the thin-film lithium niobate waveguide according to claim 1, wherein the working process is as follows: TE when input waveguide 0 Adiabatic evolution of mode into symmetric mode TE for a three waveguide system by an input mode converter upon mode input s0 Conversion to an antisymmetric mode TE of a three waveguide system by a phase shifter s1 Finally, the TM is hybridized and evolved into an output end waveguide through an output mode converter 0 Molding; TM when the input is waveguide 0 When the mode is input, the reverse mode evolution process is finally changed into TE 0 And outputting.
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| CN118151418A (en) * | 2024-05-09 | 2024-06-07 | 之江实验室 | Broadband thin film lithium niobate polarization independent electro-optic modulator and modulation method |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN118151418A (en) * | 2024-05-09 | 2024-06-07 | 之江实验室 | Broadband thin film lithium niobate polarization independent electro-optic modulator and modulation method |
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