CN114153085B - Thin film lithium niobate adjustable high linearity electro-optic modulator integrated chip - Google Patents
Thin film lithium niobate adjustable high linearity electro-optic modulator integrated chip Download PDFInfo
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- CN114153085B CN114153085B CN202111389369.2A CN202111389369A CN114153085B CN 114153085 B CN114153085 B CN 114153085B CN 202111389369 A CN202111389369 A CN 202111389369A CN 114153085 B CN114153085 B CN 114153085B
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- GQYHUHYESMUTHG-UHFFFAOYSA-N lithium niobate Chemical compound [Li+].[O-][Nb](=O)=O GQYHUHYESMUTHG-UHFFFAOYSA-N 0.000 title claims abstract description 90
- 239000010409 thin film Substances 0.000 title claims abstract description 80
- 230000003287 optical effect Effects 0.000 claims abstract description 102
- 238000005253 cladding Methods 0.000 claims abstract description 17
- 239000000758 substrate Substances 0.000 claims abstract description 12
- 239000010408 film Substances 0.000 claims abstract description 3
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 25
- 239000000463 material Substances 0.000 claims description 18
- 238000005530 etching Methods 0.000 claims description 15
- 235000012239 silicon dioxide Nutrition 0.000 claims description 14
- 239000000377 silicon dioxide Substances 0.000 claims description 11
- 229910052782 aluminium Inorganic materials 0.000 claims description 6
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 6
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 claims description 6
- 229910052737 gold Inorganic materials 0.000 claims description 6
- 239000010931 gold Substances 0.000 claims description 6
- 229910052710 silicon Inorganic materials 0.000 claims description 4
- 239000010703 silicon Substances 0.000 claims description 4
- 229920000642 polymer Polymers 0.000 claims description 3
- 239000010453 quartz Substances 0.000 claims description 3
- 230000003595 spectral effect Effects 0.000 abstract description 5
- 239000010410 layer Substances 0.000 description 51
- 238000010586 diagram Methods 0.000 description 8
- 230000005540 biological transmission Effects 0.000 description 5
- 238000010521 absorption reaction Methods 0.000 description 4
- 229910052751 metal Inorganic materials 0.000 description 4
- 239000002184 metal Substances 0.000 description 4
- 238000004891 communication Methods 0.000 description 2
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 239000012792 core layer Substances 0.000 description 1
- 230000008878 coupling Effects 0.000 description 1
- 238000010168 coupling process Methods 0.000 description 1
- 238000005859 coupling reaction Methods 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 230000005684 electric field Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000001939 inductive effect Effects 0.000 description 1
- 230000010354 integration Effects 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000005693 optoelectronics Effects 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 230000001902 propagating effect Effects 0.000 description 1
- 230000004044 response Effects 0.000 description 1
- 239000010936 titanium Substances 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
Classifications
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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
- G02F1/03—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 ceramics or electro-optical crystals, e.g. exhibiting Pockels effect or Kerr effect
- G02F1/0305—Constructional arrangements
- G02F1/0316—Electrodes
-
- 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
- G02F1/03—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 ceramics or electro-optical crystals, e.g. exhibiting Pockels effect or Kerr effect
- G02F1/0305—Constructional arrangements
-
- 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
- G02F1/03—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 ceramics or electro-optical crystals, e.g. exhibiting Pockels effect or Kerr effect
- G02F1/035—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 ceramics or electro-optical crystals, e.g. exhibiting Pockels effect or Kerr effect in an optical waveguide structure
- G02F1/0356—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 ceramics or electro-optical crystals, e.g. exhibiting Pockels effect or Kerr effect in an optical waveguide structure controlled by a high-frequency electromagnetic wave component in an electric waveguide structure
-
- 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
- G02F1/21—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 by interference
- G02F1/212—Mach-Zehnder type
-
- 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
- G02F1/21—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 by interference
- G02F1/225—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 by interference in an optical waveguide structure
- G02F1/2255—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 by interference in an optical waveguide structure controlled by a high-frequency electromagnetic component in an electric waveguide structure
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- Physics & Mathematics (AREA)
- Nonlinear Science (AREA)
- General Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Ceramic Engineering (AREA)
- Crystallography & Structural Chemistry (AREA)
- Electromagnetism (AREA)
- Optical Modulation, Optical Deflection, Nonlinear Optics, Optical Demodulation, Optical Logic Elements (AREA)
Abstract
The invention discloses a thin film lithium niobate adjustable high linearity electro-optical modulator integrated chip, which comprises a substrate layer, a buried oxide layer, an electro-optical modulation device layer and an upper cladding layer from bottom to top; the electro-optical modulation device layer sequentially comprises an input optical waveguide, an input spectral coupler, a super linear modulation region, a Mach-Zehnder phase modulation region, an output combiner coupler and an output optical waveguide from left to right. The super linear modulation area is composed of one or more film lithium niobate ridge optical waveguide tunable resonant cavities which are connected in sequence, and can be positioned on one or two modulation arms, and a second signal electrode and a third ground electrode which can adjust the working state of the resonant cavity are arranged at two sides of the optical waveguide in the resonant cavity. The working point of the resonant cavity is adjusted by adjusting the size of the resonant cavity and the size of the signals loaded on the electrodes on the two sides of the resonant cavity waveguide, and the integral third-order nonlinearity of the device is eliminated, so that the integrated chip of the electro-optical modulator with high linearity is realized.
Description
Technical Field
The invention belongs to the technical field of integrated microwave photons, and particularly relates to a thin film lithium niobate adjustable high-linearity electro-optic modulator integrated chip.
Background
Electro-optic modulators are core devices in optical communication systems and microwave photonic systems that regulate light propagating in free space or optical waveguides by inducing a change in the refractive index of the material by an applied electric field. Among them, mach-zehnder (MZ) electro-optic modulators are the most commonly used intensity modulators in the field of optical communications.
The lithium niobate material has the advantages of high electro-optic coefficient and wide electromagnetic wave transmission window, and has wide application in high-speed modulation. The traditional lithium niobate electro-optic modulator carries out local doping on a monocrystal lithium niobate material through a titanium diffusion or proton exchange process to form a waveguide, the refractive index difference between a core layer and a cladding layer of the waveguide is small, the binding capacity of the waveguide to an optical field is poor, and meanwhile, in order to achieve the performance of low driving voltage, the length of a modulation area needs to be designed to be very long, so that the packaged electro-optic modulator still has a larger volume. The new thin film lithium niobate technology in recent years provides an effective way for solving the problem of large size of the lithium niobate electro-optic modulator, and can realize the electro-optic modulator with small size, large bandwidth and single chip integration.
The main nonlinear distortion in microwave photonic systems derives from electro-optic modulators, particularly in analog signal processing and transmission systems, which require good linearity for loading and transmitting high frequency microwave signals over long distances. The transmission characteristic curve of the MZ type electro-optic modulator based on the thin film lithium niobate platform is a sub-linear sinusoidal curve, and the nonlinearity of the electro-optic modulator can generate harmonic waves and intermodulation components, thereby causing third-order intermodulation distortion and limiting the dynamic response range of a link. The thin film lithium niobate based device adopts a ridge-shaped optical waveguide, and comprises a strip-carried structure and a thin film lithium niobate slab layer at the lower layer, wherein an optical field part exists in the ridge structure and partially exists in the slab layer, and light can diffuse outwards from the slab layer, so that crosstalk can be increased when two optical waveguides are very close to each other, and the linearity of a link can be adversely affected. Meanwhile, in order to improve the electro-optical effect efficiency, the distance between the optical waveguide and the microwave electrode of the thin film lithium niobate-based electro-optical modulator is usually small, and light overflowing from the flat plate layer is absorbed by the metal electrode, so that the absorption loss is increased, and the device performance is deteriorated.
Disclosure of Invention
The invention aims to provide a thin film lithium niobate adjustable high-linearity electro-optic modulator integrated chip, which solves the technical problems that crosstalk is increased when two optical waveguides are very close to each other in the existing thin film lithium niobate-based device, bad influence is generated on the linearity of a link, the distance between the optical waveguides and a microwave electrode of the existing thin film lithium niobate-based electro-optic modulator is usually very small, light overflowing from a flat plate layer is absorbed by a metal electrode, absorption loss is increased, and device performance is deteriorated.
In order to solve the technical problems, the specific technical scheme of the invention is as follows:
The integrated chip of the thin film lithium niobate adjustable high linearity electro-optical modulator is characterized by comprising a substrate layer, a buried oxide layer, an electro-optical modulation device layer and a first upper cladding layer from bottom to top;
the electro-optical modulation device layer sequentially comprises an input optical waveguide, an input spectral coupler, a super linear modulation region, a Mach-Zehnder phase modulation region, an output combined coupler and an output optical waveguide from left to right;
The Mach-Zehnder phase modulation area comprises a first modulation arm and a second modulation arm which are parallel, a first signal electrode positioned between the first modulation arm and the second modulation arm, and a first ground electrode and a second ground electrode positioned at two sides of the first modulation arm and the second modulation arm respectively; the length of the first ground electrode, the length of the first signal electrode and the length of the second ground electrode are the same, and the length of the first modulation arm and the length of the second modulation arm are the same and longer than the length of the first ground electrode;
a first deep etching area is arranged between the first light splitting output optical waveguide and the second light splitting output optical waveguide of the two output optical waveguides of the input light splitting coupler, and a second deep etching area is arranged between the first combining input optical waveguide and the second combining input optical waveguide of the two input optical waveguides of the output combining coupler; the first light splitting output optical waveguide, the first modulation arm and the first combining input optical waveguide are sequentially connected; the second light splitting output optical waveguide, the second modulation arm and the second combining input optical waveguide are sequentially connected;
The number of the super linear modulation regions may be one or two; when the super linear modulation area is one, the first super linear modulation area is positioned on the first modulation arm or the second modulation arm; when the number of the super linear modulation areas is two, the first super linear modulation area is positioned on the first modulation arm, and the second super linear modulation area is positioned on the second modulation arm;
the super linear modulation region is composed of at least one film lithium niobate ridge-shaped optical waveguide adjustable resonant cavity which is connected in sequence, and a second signal electrode and a third ground electrode which can adjust the working state of the resonant cavity are arranged at two sides of the optical waveguide in the resonant cavity;
The input optical splitting coupler and the output combining coupler can be of a Y-shaped optical waveguide structure or a multimode interference coupler structure.
Further, the substrate layer is made of silicon or quartz; the buried oxide layer is made of silicon dioxide, and the thickness of the buried oxide layer is 1-5 mu m; the first upper cladding material is silicon dioxide or polymer, and the thickness is 0.5-3 mu m.
Further, the structures of the input optical waveguide, the input spectral coupler, the first modulation arm, the second modulation arm and the output combining coupler are all thin film lithium niobate ridge optical waveguide structures, and the thin film lithium niobate ridge optical waveguide structures are longitudinally formed by thin film lithium niobate flat-plate optical waveguide layers and thin film lithium niobate strips with trapezoidal upper parts, wherein the top width of the thin film lithium niobate strips is 0.5-2 mu m, and the thickness of the thin film lithium niobate strips is 100-500nm; the thickness of the thin film lithium niobate flat plate optical waveguide layer is 50-500nm.
Further, the diameters of semicircular parts of the annular resonant cavity and the runway-shaped resonant cavity are 10-500 mu m, and the length of a straight waveguide part of the runway-shaped resonant cavity is 10-1000 mu m; a curved second signal electrode is arranged on the inner side of the optical waveguide in the annular resonant cavity, a curved third ground electrode is arranged on the outer side of the optical waveguide in the annular resonant cavity, a rectangular second signal electrode is arranged on the inner side of the straight optical waveguide in the racetrack-shaped resonant cavity, and a rectangular third ground electrode is arranged on the outer side of the straight optical waveguide in the racetrack-shaped resonant cavity.
Further, the second signal electrode and the third electrode are made of gold or aluminum, the width of the electrodes is 5-100 mu m, and the distance between the second signal electrode and the third electrode is 3-10 mu m.
Further, the first signal electrode, the first ground electrode and the second ground electrode are made of gold or aluminum, the width of the first signal electrode is 5-100 mu m, and the width of the first ground electrode and the second ground electrode is 10-300 mu m; the distance between the first signal electrode and the second ground electrode is 3-10 μm, and the distance between the first signal electrode and the first ground electrode is the same.
Further, the thicknesses of the second signal electrode, the third electrode, the first signal electrode, the first electrode and the second electrode are all the same and are 100nm-3 μm, and the top of the electrodes are higher than the top of the first upper cladding.
Further, buffer layers are arranged between the second signal electrode, the third electrode, the first signal electrode, the first electrode, the second electrode and the thin film lithium niobate flat plate optical waveguide, and the material is silicon dioxide, and the thickness is 10-300nm.
Further, the first deep etching region and the second deep etching region comprise a substrate layer, a buried oxide layer and a second upper cladding layer from bottom to top, and lithium niobate materials are etched and removed.
Further, the microwave signal is loaded on the first signal electrode (82) or the second signal electrode (62) alone, or the microwave signal is simultaneously loaded on the first signal electrode (82) and the second signal electrode (62).
The thin film lithium niobate adjustable high linearity electro-optic modulator integrated chip of the invention has the following advantages:
1. The integrated chip of the thin film lithium niobate adjustable high linearity electro-optic modulator provided by the invention utilizes the super linearity of the adjustable resonant cavity to compensate the sub linearity of the MZ modulator, and the second-order and third-order nonlinearity of the device can be eliminated by adjusting the size of the resonant cavity of the super linearity modulation region and the size of a signal loaded on an electrode, so that the electro-optic modulator with high linearity can be realized.
2. The invention provides a thin film lithium niobate adjustable high linearity electro-optical modulator integrated chip, which is provided with a buffer layer between a metal electrode and a thin film lithium niobate flat-plate optical waveguide layer, so that the absorption of the metal electrode to an optical mode can be weakened, and the absorption loss is reduced.
Drawings
FIG. 1 is a schematic diagram of a thin film lithium niobate tunable high linearity electro-optic modulator integrated chip of the present invention in which a super linearity modulation region is located on a modulation arm;
FIG. 2 is a schematic diagram showing the whole structure of the super linear modulation arms of the integrated chip of the lithium niobate thin film tunable high linear electro-optic modulator of the present invention;
FIG. 3 (a) is a schematic diagram of an integrated chip of a thin film lithium niobate tunable high linearity electro-optic modulator with a super linear modulation region comprising a plurality of sequentially connected annular tunable resonators on one modulation arm;
FIG. 3 (b) is a schematic diagram of an integrated chip of a thin film lithium niobate tunable high linearity electro-optic modulator with a super linear modulation region comprising a plurality of racetrack tunable vibration cavities connected in sequence and located on a modulation arm;
FIG. 4 (a) is a schematic diagram of an integrated chip of a thin film lithium niobate tunable high linearity electro-optic modulator with a super linear modulation region comprising a plurality of sequentially connected annular tunable resonators located on two modulation arms;
FIG. 4 (b) is a schematic diagram of an integrated chip of a thin film lithium niobate tunable high linearity electro-optic modulator with a super linear modulation region comprising a plurality of racetrack tunable vibration cavities connected in sequence and located on two modulation arms;
FIG. 5 is a schematic diagram of an integrated chip of a thin film lithium niobate tunable high linearity electro-optic modulator with a single annular tunable resonator in the super linear modulation region according to embodiment 1 of the present invention;
FIG. 6 is a cross-sectional view of a thin film lithium niobate tunable high linearity electro-optic modulator integrated chip with a single annular tunable resonator in the super linear modulation region at the dashed line position A according to embodiment 1 of the present invention;
FIG. 7 is a cross-sectional view of a thin film lithium niobate tunable high linearity electro-optic modulator integrated chip with a single annular tunable resonator in the super linear modulation region at the dashed line position at B in accordance with embodiment 1 of the present invention;
FIG. 8 is a graph of the transmission characteristics of a thin film lithium niobate tunable high linearity electro-optic modulator chip and MZ modulator of the present invention;
FIG. 9 is a second order nonlinear plot of a thin film lithium niobate tunable high linearity electro-optic modulator chip and MZ modulator of the present invention;
FIG. 10 is a three-order nonlinear plot of a thin film lithium niobate tunable high linearity electro-optic modulator chip and MZ modulator of the present invention.
The figure indicates: 1. an input optical waveguide; 2. an input optical splitting coupler; 21. a first split optical output waveguide; 22. a second split optical output waveguide; 3. a first deep etching region; 4. a first modulating arm; 5. a second modulating arm; 6. a first super linear modulation region; 61. a ring resonator; 62. a second signal electrode; 63. a third ground electrode; 7. a second super linear modulation region; 8. a Mach-Zehnder phase modulation section; 81. a first ground electrode; 82. a first signal electrode; 83. a second ground electrode; 9. a second deep etching region; 10. an output combining coupler; 101. a first combining input optical waveguide; 102. a second combining input optical waveguide; 11. an output optical waveguide; 12. a substrate layer; 13. burying an oxide layer; 14. a thin film lithium niobate slab optical waveguide layer; 15. carrying a thin film lithium niobate strip; 16. a third deep etching region; 17. a first upper cladding layer; 18. and a buffer layer.
Detailed Description
In order to better understand the purpose, structure and function of the present invention, the following describes in detail a thin film lithium niobate tunable high linearity electro-optical modulator integrated chip according to the present invention with reference to the accompanying drawings.
As shown in fig. 1-10, the present invention is a thin film lithium niobate tunable high linearity electro-optic modulator integrated chip that includes, from bottom to top, a substrate layer 12, a buried oxide layer 13, an electro-optic modulation device layer, and a first upper cladding layer 17.
The electro-optical modulation device layer sequentially comprises an input optical waveguide 1, an input spectral coupler 2, a super linear modulation region, a Mach-Zehnder phase modulation region 8, an output combining coupler 10 and an output optical waveguide 11 from left to right; wherein:
The mach-zehnder phase modulation region 8 includes a first modulation arm 4 and a second modulation arm 5 that are parallel, a first signal electrode 82 located between the first modulation arm 4 and the second modulation arm 5, and a first ground electrode 81 and a second ground electrode 83 located at two sides of the first modulation arm 4 and the second modulation arm 5, respectively; the lengths of the first ground electrode 81, the first signal electrode 82 and the second ground electrode 83 are the same, and the lengths of the first modulation arm 4 and the second modulation arm 5 are the same and longer than the length of the first ground electrode 81;
A first deep etching area 3 is arranged between the first light splitting output light waveguide 21 and the second light splitting output light waveguide 22 of the two output light waveguides of the input light splitting coupler 2, and a second deep etching area 9 is arranged between the first combining input light waveguide 101 and the second combining input light waveguide 102 of the two input light waveguides of the output combining coupler 10; the first split optical output waveguide 21, the first modulation arm 4, and the first combining input optical waveguide 101 are connected in order; the second split optical output waveguide 22, the second modulation arm 5 and the second combining input waveguide 102 are connected in sequence;
The number of the super linear modulation regions may be one or two; when the super linear modulation region is one, as shown in fig. 1, the super linear modulation region includes a first super linear modulation region 6 located on the first modulation arm 4.
When there are two super linear modulation regions, as shown in fig. 2, the first super linear modulation region 6 is located on the first modulation arm 4, and the second super linear modulation region 7 is located on the second modulation arm 5.
As shown in fig. 3 (a), 3 (b), 4 (a) and 4 (b), the first super linear modulation region 6 and the second super linear modulation region 7 are composed of one or more thin film lithium niobate ridge optical waveguide adjustable resonant cavities connected in sequence, and a second signal electrode 62 and a third ground electrode 63 capable of adjusting the working state of the resonant cavities are arranged at two sides of the optical waveguide in the resonant cavities;
The input optical dividing coupler 2 and the output combining coupler 10 may be a Y optical waveguide structure or a multimode interference coupler structure.
The material of the substrate layer 12 is silicon or quartz; the buried oxide layer 13 is made of silicon dioxide, and has a thickness of 1-5 mu m; the first upper cladding layer 17 is made of silicon dioxide or polymer, and has a thickness of 0.5-3 mu m.
The input optical waveguide 1, the input spectral coupler 2, the first modulation arm 4, the second modulation arm 5 and the output combining coupler 10 are all in a thin-film lithium niobate ridge optical waveguide structure, and the thin-film lithium niobate ridge optical waveguide structure is longitudinally formed by a thin-film lithium niobate flat-plate optical waveguide layer 14 and a thin-film lithium niobate strip 15 with a trapezoid upper part shape, wherein the top width of the thin-film lithium niobate strip 15 is 0.5-2 mu m, and the thickness is 100-500nm; the thin film lithium niobate slab optical waveguide layer 14 has a thickness of 50 to 500nm.
The diameter of the semicircular parts of the annular resonant cavity 61 and the runway-shaped resonant cavity is 10-500 mu m, and the length of the straight waveguide part of the runway-shaped resonant cavity is 10-1000 mu m; a curved second signal electrode 62 is placed inside the optical waveguide in the ring resonator 61, a curved third ground electrode 63 is placed outside the optical waveguide in the ring resonator 61, a rectangular second signal electrode 62 is placed inside the straight optical waveguide in the racetrack resonator, and a rectangular third ground electrode 63 is placed outside the straight optical waveguide in the racetrack resonator.
The second signal electrode 62 and the third ground electrode 63 are made of gold or aluminum, the width of the electrodes is 5-100 μm, and the distance between the second signal electrode 62 and the third ground electrode 63 is 3-10 μm.
The first signal electrode 82 and the first and second ground electrodes 81 and 83 are made of gold or aluminum, the width of the first signal electrode 82 is 5-100 μm, and the width of the first and second ground electrodes 81 and 83 is 10-300 μm; the distance between the first signal electrode 82 and the second ground electrode 83 is 3-10 μm, and the distance between the first signal electrode 82 and the first ground electrode 81 is the same.
The thicknesses of the second signal electrode 62, the third ground electrode 63, the first signal electrode 82, the first ground electrode 81 and the second ground electrode 83 are all the same and are 100nm-3 μm, and the top of the electrodes are all higher than the top of the first upper cladding layer 17.
The buffer layer 18 is arranged between the second signal electrode 62, the third ground electrode 63, the first signal electrode 82, the first ground electrode 81, the second ground electrode 83 and the thin film lithium niobate flat-plate optical waveguide layer 14, and the material is silicon dioxide, and the thickness is 10-300nm.
The first deep etching region 3 and the second deep etching region 9 comprise a substrate layer 12, a buried oxide layer 13 and a first upper cladding layer 17 from bottom to top, and lithium niobate materials are etched and removed.
The microwave signal may be simultaneously applied to the first signal electrode 82 and the second signal electrode 62, or may be separately applied to the first signal electrode 82 or the second signal electrode 62.
Example 1:
Fig. 5 is a schematic diagram of an integrated chip of a thin film lithium niobate adjustable high linearity electro-optical modulator with a super linearity modulation region being a single annular adjustable resonant cavity, two output waveguides of an input optical splitting coupler 2 are respectively connected to input ends of a first modulation arm 4 and a second modulation arm 5, a first deep etching region 3 is arranged between the output waveguides, the first super linearity modulation region 6 is located on the modulation arm on the upper portion, 61 is an annular resonant cavity, two sides of the annular waveguide are provided with a second signal electrode 62 and a third ground electrode 63 which are bent, the widest part of the second signal electrode 62 is 10 μm, the width of the third ground electrode 63 is 10 μm, a first signal electrode 82 is arranged between the first modulation arm 4 and the second modulation arm 5, the width is 14 μm, two sides are provided with a first ground electrode 81 and a second ground electrode 83, the width is 100 μm, the distance between the first signal electrode 82 and the two side ground electrodes is 5 μm, and a second deep etching region 9 is arranged between the two input waveguides of the output optical splitting coupler 10.
Fig. 6 is a cross-sectional view of a thin film lithium niobate tunable high-linearity electro-optic modulator integrated chip with a single annular tunable resonator in the super-linear modulation region at a dashed line a, and fig. 7 is a cross-sectional view of a thin film lithium niobate tunable high-linearity electro-optic modulator integrated chip with a single annular tunable resonator in the super-linear modulation region at a dashed line B. The material of the substrate layer 12 is silicon, the material of the buried oxide layer 13 is silicon dioxide, the thickness is 3 μm, the thickness of the thin-film lithium niobate planar optical waveguide layer 14 is 300nm, the thickness of the thin-film lithium niobate strip carrier 15 is 300nm, the thin-film lithium niobate planar optical waveguide layer 14 and the thin-film lithium niobate strip carrier 15 jointly form a thin-film lithium niobate ridge optical waveguide, the waveguide top width is 1 μm, the material of the first upper cladding layer 17 is silicon dioxide, the thickness is 2 μm, the thickness of the buffer layer 18 is 100nm, the thicknesses of the first ground electrode 81, the first signal electrode 82 and the second ground electrode 83 are all 1 μm, and the first upper cladding layer 17 of fig. 7 is polished to expose the electrode top.
Fig. 8 is a graph of transmission characteristics of a thin film lithium niobate tunable high linearity electro-optic modulator chip and MZ modulator of the present invention, fig. 9 is a graph of second order nonlinearity of the thin film lithium niobate tunable high linearity electro-optic modulator chip and MZ modulator of the present invention, and fig. 10 is a graph of third order nonlinearity of the thin film lithium niobate tunable high linearity electro-optic modulator chip and MZ modulator of the present invention.
The second-order and third-order nonlinear components of the output light of the MZ modulator can be seen to be zero only at a specific phase working point, and the thin film lithium niobate adjustable high-linearity electro-optic modulator chip can keep zero both of the second-order and third-order nonlinearity of the output in a wider phase range, namely, the second-order and third-order nonlinearity of the modulator can be eliminated through adjusting the size of a ring, the coupling ratio and the size of a signal loaded on a first signal electrode, so that the electro-optic modulator with high linearity is realized.
It will be understood that the application has been described in terms of several embodiments, and that various changes and equivalents may be made to these features and embodiments by those skilled in the art without departing from the spirit and scope of the application. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the application without departing from the essential scope thereof. Therefore, it is intended that the application not be limited to the particular embodiment disclosed, but that the application will include all embodiments falling within the scope of the appended claims.
Claims (10)
1. The integrated chip of the thin film lithium niobate adjustable high linearity electro-optic modulator is characterized by comprising a substrate layer (12), a buried oxide layer (13), an electro-optic modulation device layer and a first upper cladding layer (17) from bottom to top;
The electro-optical modulation device layer sequentially comprises an input optical waveguide (1), an input optical splitting coupler (2), a super linear modulation region, a Mach-Zehnder phase modulation region (8), an output combining coupler (10) and an output optical waveguide (11) from left to right;
The Mach-Zehnder phase modulation area (8) comprises a first modulation arm (4) and a second modulation arm (5) which are parallel, a first signal electrode (82) positioned between the first modulation arm (4) and the second modulation arm (5), and a first ground electrode (81) and a second ground electrode (83) which are respectively positioned at two sides of the first modulation arm (4) and the second modulation arm (5); the lengths of the first ground electrode (81), the first signal electrode (82) and the second ground electrode (83) are the same, and the lengths of the first modulation arm (4) and the second modulation arm (5) are the same and longer than the length of the first ground electrode (81);
A first deep etching area (3) is arranged between a first light splitting output optical waveguide (21) and a second light splitting output optical waveguide (22) of the two output optical waveguides of the input light splitting coupler (2), and a second deep etching area (9) is arranged between a first combining input optical waveguide (101) and a second combining input optical waveguide (102) of the two input optical waveguides of the output combining coupler (10); the first light-splitting output optical waveguide (21), the first modulation arm (4) and the first combination input optical waveguide (101) are sequentially connected; the second light splitting output optical waveguide (22), the second modulation arm (5) and the second combining input optical waveguide (102) are sequentially connected;
the number of the super linear modulation regions may be one or two; when the super linear modulation area is one, the first super linear modulation area (6) is positioned on the first modulation arm (4) or the second modulation arm (5); when the number of the super linear modulation areas is two, the first super linear modulation area (6) is positioned on the first modulation arm (4), and the second super linear modulation area (7) is positioned on the second modulation arm (5);
The super linear modulation region is composed of at least one film lithium niobate ridge-shaped optical waveguide adjustable resonant cavity which is connected in sequence, and a second signal electrode (62) and a third ground electrode (63) which can adjust the working state of the resonant cavity are arranged at two sides of the optical waveguide in the resonant cavity;
the input light splitting coupler (2) and the output combining coupler (10) can be of a Y-shaped optical waveguide structure or a multimode interference coupler structure.
2. The thin film lithium niobate tunable high linearity electro-optic modulator integrated chip of claim 1, wherein the substrate layer (12) material is silicon or quartz; the buried oxide layer (13) is made of silicon dioxide, and the thickness is 1-5 mu m; the first upper cladding layer (17) is made of silicon dioxide or polymer, and has a thickness of 0.5-3 mu m.
3. The integrated chip of the thin film lithium niobate adjustable high linearity electro-optical modulator according to claim 1, wherein the structures of the input optical waveguide (1), the input optical splitter coupler (2), the first modulation arm (4), the second modulation arm (5) and the output combining coupler (10) are all thin film lithium niobate ridge optical waveguide structures, the thin film lithium niobate ridge optical waveguide structures are longitudinally formed by a thin film lithium niobate flat-plate optical waveguide layer (14) and a thin film lithium niobate strip carrier (15) with a trapezoid upper part shape, the top width of the thin film lithium niobate strip carrier (15) is 0.5-2 μm, and the thickness of the thin film lithium niobate strip carrier is 100-500nm; the thin film lithium niobate slab optical waveguide layer (14) has a thickness of 50-500nm.
4. The thin film lithium niobate tunable highly linear electro-optic modulator integrated chip of claim 1, wherein the thin film lithium niobate ridge optical waveguide tunable resonant cavity ring resonator (61) or racetrack resonant cavity, the semi-circular part diameters of the ring resonator (61) and racetrack resonant cavity are 10-500 μm, and the straight waveguide part length of the racetrack resonant cavity is 10-1000 μm; a curved second signal electrode (62) is placed inside the optical waveguide in the ring resonator (61), a curved third ground electrode (63) is placed outside the optical waveguide in the ring resonator (61), a rectangular second signal electrode (62) is placed inside the straight optical waveguide in the racetrack resonator, and a rectangular third ground electrode (63) is placed outside the straight optical waveguide in the racetrack resonator.
5. The thin film lithium niobate tunable high linearity electro-optic modulator integrated chip of claim 1, wherein the material of the second signal electrode (62) and the third ground electrode (63) is gold or aluminum, the width of the electrodes is 5-100 μm, and the space between the second signal electrode (62) and the third ground electrode (63) is 3-10 μm.
6. The thin film lithium niobate adjustable high linearity electro-optic modulator integrated chip of claim 1, wherein the material of the first signal electrode (82), the first ground electrode (81) and the second ground electrode (83) is gold or aluminum, the width of the first signal electrode (82) is 5-100 μm, and the width of the first ground electrode (81) and the second ground electrode (83) is 10-300 μm; the distance between the first signal electrode (82) and the second ground electrode (83) is 3-10 mu m, and the distance between the first signal electrode (82) and the first ground electrode (81) is the same.
7. The integrated chip of the thin film lithium niobate adjustable high linearity electro-optical modulator according to claim 1, wherein the thickness of the second signal electrode (62), the third electrode (63), the first signal electrode (82), the first electrode (81) and the second electrode (83) are all the same, and are 100nm-3 μm, and the top of the electrodes are all higher than the top of the first upper cladding layer (17).
8. The thin film lithium niobate tunable high linearity electro-optic modulator integrated chip of claim 1, wherein a buffer layer is provided between the second signal electrode (62), the third electrode (63), the first signal electrode (82), the first electrode (81), the second electrode (83) and the thin film lithium niobate planar optical waveguide layer (14), and the material is silicon dioxide, and the thickness is 10-300nm.
9. The thin film lithium niobate tunable high linearity electro-optic modulator integrated chip of claim 1, wherein the first (3) and second (9) deep etched regions comprise, from bottom to top, a substrate layer (12), a buried oxide layer (13) and a second upper cladding layer, the lithium niobate material being etched away.
10. The thin film lithium niobate tunable high linearity electro-optic modulator integrated chip of claim 1, wherein the microwave signal is loaded on the first signal electrode (82) or the second signal electrode (62) alone or the microwave signal is loaded on both the first signal electrode (82) and the second signal electrode (62).
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