CN109143621B - Lithium niobate film-based in-phase quadrature modulator and preparation method thereof - Google Patents
Lithium niobate film-based in-phase quadrature modulator and preparation method thereof Download PDFInfo
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- CN109143621B CN109143621B CN201811204697.9A CN201811204697A CN109143621B CN 109143621 B CN109143621 B CN 109143621B CN 201811204697 A CN201811204697 A CN 201811204697A CN 109143621 B CN109143621 B CN 109143621B
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- G—PHYSICS
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- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/03—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
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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
- G02F1/0311—Structural association of optical elements, e.g. lenses, polarizers, phase plates, with the crystal
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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
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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
- G02F1/0327—Operation of the cell; Circuit arrangements
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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
- G02F1/035—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
Abstract
The invention discloses an in-phase quadrature modulator based on lithium niobate, which comprises a substrate, a lithium niobate thin film, a lithium niobate optical waveguide, a 1 multiplied by 2 optical beam splitter, a Mach-Zehnder modulator and a 90-degree bias structure; the lithium niobate thin film is bonded on the substrate, and the lithium niobate optical waveguide, the 1 multiplied by 2 optical beam splitter, the Mach-Zehnder modulator and the 90-degree bias structure are all arranged on the lithium niobate thin film; the light beam is divided into two light beams by a 1 multiplied by 2 optical beam splitter, the two light beams respectively pass through different Mach-Zehnder modulators, the output ends of the Mach-Zehnder modulators output the two light beams, one light beam enters a 90-degree offset structure and then is output, and the other light beam is used for detection output. The invention has the advantages of low power consumption, miniaturization, low driving voltage and high bandwidth of high-order phase and intensity modulation devices. The invention is suitable for the field of optical signal modulation.
Description
Technical Field
The invention relates to the field of optical modulators, in particular to an in-phase quadrature modulator based on a lithium niobate thin film and a preparation method of the in-phase quadrature modulator.
Background
In-phase quadrature modulators have a very important role in the field of modern communications. The structure of the modulator consists of two parallel Mach-Zehnder modulators and a 90-degree phase biaser, two groups of signals in the same direction and in the orthogonal direction are orthogonal to each other, and phase and intensity modulation can be realized simultaneously.
With the development of silicon-based electro-optical integration technology, IQ modulators have been applied to silicon-based photonic platforms, and implement high-speed quadrature phase shift keying and dual-polarization 16-order and 32-order quadrature intensity modulated signal modulation.
The silicon-based electro-optical modulator mainly has the effects of carrier transport, carrier injection and carrier accumulation. The bandwidth and linear degree carrier transport mechanism of the modulator are optimal, but due to the fact that optical field distribution is overlapped with the non-uniformity of a transport region, nonlinear second-order distortion and third-order intermodulation distortion terms are introduced into the effect. In recent years, silicon-based hybrid integrated chips with doping concentration control or combination with III-V multiple quantum wells realize Mach-Zehnder modulators with low driving voltage, high bandwidth and high linearity in a successive manner. But in high frequency applications the microwave losses in the silicon material increase significantly, limiting the bandwidth.
The double-polarization IQ modulator based on InP has the characteristics of low driving voltage and high bandwidth, has small volume, and can be mixed and integrated with a laser and a high-speed detector. However, the refractive index change of the electro-optic effect of III-V comprises a linear term and a non-linear term, the small linear term of the electric field is dominant, and the second-order effect of the large electric field is prominent.
Lithium niobate, which has an outstanding linear electro-optic effect, has found widespread use in commercial high-speed phase and intensity modulators. The traditional commercial lithium niobate modulator adopts a titanium diffusion process to form a weak limit waveguide in a lithium niobate material, the area of a mode spot of the weak limit waveguide reaches dozens of microns, so that the electrode spacing at two sides is wider, and the typical value is about more than 30 um; the volume is large, namely about 135mm multiplied by 13.5mm after encapsulation, and the optical fiber transmission network is applied. With the maturity of the cutting and bonding processes of lithium niobate thin films, in recent years, research on lithium niobate thin film modulators has received extensive attention from academia and industry. The thickness of the lithium niobate thin film which is mature at present ranges from hundreds of nanometers to micrometers, and the lithium niobate thin film can be directly or indirectly bonded on silicon, silicon dioxide, quartz and sapphire substrates. Because of its higher refractive index than silicon dioxide (Δ n 0.67), a stronger confinement of the optical mode field is achieved relative to conventional bulk materials. The area of the mold spot of submicron level can be obtained by the plasma etching process. The smaller optical mode field distribution is beneficial to the metal electrode to be manufactured more tightly, is also beneficial to obtaining higher overlapping degree of an optical field and an electric field, and can obtain an electro-optical modulator with small volume, high modulation efficiency and low power consumption.
In summary, the high-frequency rf loss for the silicon-based modulator is large; the electro-optic effect linearity of III-V is insufficient; the current commercial lithium niobate IQ modulator is large in size and high in driving voltage, and a high-order phase and intensity modulation device with low loss, miniaturization, low driving voltage and high bandwidth can be obtained by applying the IQ modulator to a lithium niobate thin film.
Disclosure of Invention
The invention provides an in-phase quadrature modulator based on a lithium niobate thin film, which aims to solve the problems of large high-frequency radio frequency loss, insufficient III-V electro-optic effect linearity of a silicon-based modulator, large size and high driving voltage of the current commercial lithium niobate IQ modulator, and has the characteristics of low power consumption, miniaturization, low driving voltage and high linearity.
In order to achieve the purpose of the invention, the technical scheme is as follows: an in-phase and quadrature modulator based on lithium niobate comprises a substrate, a lithium niobate thin film arranged on the substrate, a 1 multiplied by 2 optical beam splitter A, two Mach-Zehnder modulators, a 90-degree bias structure and an optical waveguide, wherein the 1 multiplied by 2 optical beam splitter A, the two Mach-Zehnder modulators and the 90-degree bias structure are prepared on the lithium niobate thin film; the 1 multiplied by 2 optical beam splitter A is connected with the input ends of the two paths of Mach-Zehnder modulators, and the output ends of the two paths of Mach-Zehnder modulators are connected with the 90-degree offset structure.
Preferably, the lithium niobate composite material further comprises a silica cladding layer, wherein the silica cladding layer covers the lithium niobate thin film; the thickness of the silica cladding is greater than 1 μm; the Mach-Zehnder modulator and the 90-degree offset structure are connected with the other end of the metal lead.
Preferably, the mach-zehnder modulator includes a 1 × 2 optical beam splitter B, a ground metal electrode, a signal metal electrode, and a 2 × 2 optical interferometer; the two sides of the signal metal electrode are respectively provided with a grounding metal electrode in an arrangement manner, and the 1 x 2 optical beam splitter B and the 2 x 2 optical interferometer are respectively arranged at the two ends of the signal metal electrode; the light beam is divided into two light beams after passing through the 1 × 2 optical beam splitter A, B in sequence, and the two light beams respectively pass through the grounding metal electrodes and the signal metal electrodes on the two sides, form interference in the 2 × 2 optical interferometer, and output the two light beams.
Preferably, the 90 ° offset structure comprises a side metal electrode, a central metal electrode, and an optical beam combiner; two sides of the central metal electrode are respectively provided with a side metal electrode; the optical beam combiner is arranged at one end of the central metal electrode; each path of Mach-Zehnder modulator outputs two light beams, wherein one light beam passes through the space between the central metal electrode and the side metal electrode and is output through the optical beam combiner, and the other light beam is output from one side of the side metal electrode, which is far away from the central metal electrode; and the grounding metal electrode, the signal metal electrode, the side metal electrode and the central metal electrode are all connected with the metal lead on the silicon dioxide cladding.
Preferably, the width of the optical waveguide is set to be in the range of 0.8 to 1 μm; the thickness range of the lithium niobate thin film is 300-700 nm.
Preferably, the substrate is silicon or quartz or sapphire.
Preferably, the grounding metal electrode, the signal metal electrode, the side metal electrode and the central metal electrode are made of gold, silver or aluminum; the thickness of the metal is 300-1000 nm.
The invention also provides a preparation method of the lithium niobate-based in-phase quadrature modulator, which comprises the following specific steps:
step 1: bonding the lithium niobate film on a substrate directly or indirectly through a bonding medium;
step 2: covering the electron beam glue on the lithium niobate thin film by using a high-speed spin coating method;
and step 3: transferring the optical structure to an electron beam glue by using an electron beam exposure system;
and 4, step 4: using electron beam glue as a mask, in an inductive coupling-plasma system, using etching gas to realize dry etching of lithium niobate, and transferring an optical structure onto a lithium niobate thin film material;
and 5: covering the substrate with electron beam glue by using a high-speed spin coating method on the substrate obtained in the step (3);
step 6: evaporating the metal adhesion layer and the metal electrode by using an electron beam evaporation system;
and 7: and finally forming the electric structure by utilizing a metal stripping technology.
Preferably, the etching gas is argon plasma or sulfur hexafluoride/argon mixed gas plasma; the metal electrodes comprise a grounding metal electrode, a signal metal electrode, a side metal electrode and a central metal electrode; the optical structure includes an optical waveguide, a 1 x 2 optical splitter A, B, a 2 x 2 optical interferometer, an optical combiner.
Preferably, the metal electrode and the metal lead are realized by a metal stripping technology of electron beam exposure polymethyl methacrylate glue or a metal stripping technology of polymethyl methacrylate glue-stripping glue double-layer glue.
The invention has the following beneficial effects: the invention utilizes the linear electro-optic effect of lithium niobate protrusion, the refractive index change and the external electric field intensity are in linear relation, an electric field is applied to any one optical waveguide, a phase difference is generated in the other optical waveguide, interference can be generated during beam combination, voltages with opposite polarities are applied to two parallel optical waveguides, and the modulation efficiency is doubled; the invention adopts high and new manufacturing technology to lead the structure of the invention to reach the level of micron and nanometer, thus achieving miniaturization; the invention adopts metal with low resistivity as a metal electrode and the characteristics of lithium niobate, thereby realizing low power consumption and low driving voltage.
Drawings
Fig. 1 is a perspective view of a lithium niobate-based in-phase-quadrature modulator of the present invention.
Fig. 2 is a top view of a lithium niobate based in-phase-quadrature modulator of the present invention.
Fig. 3 is a schematic diagram of the parallel mach-zehnder modulator of the present invention.
Fig. 4 is a schematic view of the 90 offset configuration of the present invention.
In the figure; 1. the optical fiber comprises an optical waveguide, a 2.1 multiplied by 2 optical beam splitter A, a 3-grounded metal electrode, a 4-signal metal electrode, a 5.2 multiplied by 2 optical interferometer, a 6-side metal electrode, a 7-center metal electrode, an 8-optical beam combiner, a 9-substrate and a 10.1 multiplied by 2 optical beam splitter B.
Detailed Description
The invention is described in detail below with reference to the drawings and the detailed description.
Example 1
As shown in fig. 1 and 2, an in-phase and quadrature modulator based on lithium niobate includes a substrate, a lithium niobate thin film disposed on the substrate, a 1 × 2 optical splitter a, two mach-zehnder modulators, a 90 ° bias structure, and an optical waveguide for transmitting light beams, which are disposed on the lithium niobate thin film; the 1 multiplied by 2 optical beam splitter A is connected with the input ends of the two paths of Mach-Zehnder modulators, and the output ends of the two paths of Mach-Zehnder modulators are connected with the 90-degree offset structure.
The embodiment also comprises a silicon dioxide cladding which covers the lithium niobate thin film; the silica cladding is greater than 1 μm; and arranging a metal lead on the silica cladding, forming a window on the silica cladding, and connecting the Mach-Zehnder modulator and the 90-degree offset structure with the metal lead so as to test and package.
As shown in fig. 3, the mach-zehnder modulator in this embodiment includes a 1 × 2 optical beam splitter B, a ground metal electrode, a signal metal electrode, and a 2 × 2 optical interferometer; and the two sides of the signal metal electrode are respectively provided with a grounding metal electrode, and form a structure of a grounding metal electrode-signal metal electrode-grounding metal electrode, the grounding metal electrode and the signal metal electrode are arranged in parallel, and an optical waveguide for transmitting light beams is arranged between the grounding metal electrode and the signal metal electrode. The 1 × 2 optical beam splitter B and the 2 × 2 optical interferometer are respectively disposed at two ends of the signal metal electrode, the light beam is divided into two light beams after passing through the 1 × 2 optical beam splitter A, B in sequence, the two light beams respectively pass through the ground metal electrode and the signal metal electrode at two sides, interference is formed in the 2 × 2 optical interferometer, and the two light beams are output.
In this embodiment, two parallel mach-zehnder modulators are required to be combined to form an in-phase quadrature modulator, and the two parallel mach-zehnder modulators form a structure of 'grounded metal electrode-signal metal electrode-grounded metal electrode', which includes 3 grounded metal electrodes and 2 signal metal electrodes; two optical waveguides for transmitting light beams are arranged in each Mach-Zehnder modulator, and the two optical waveguides can be equal in length or unequal in length.
A single mach-zehnder modulator implements intensity modulation and thus can implement on-off keying (OOK) and Binary Phase Shift Keying (BPSK). The principle of adopting lithium niobate as the Mach-Zehnder modulator is as follows: lithium niobate has an outstanding linear electro-optic effect, and the refractive index change of the lithium niobate has a linear relation with the intensity of an external electric field. An electric field is applied to two sides of any one optical wave to generate a phase difference with the other optical wave, and interference is generated during beam combination. The general push-pull structure applies opposite voltage to two parallel optical waveguides, and the modulation efficiency is doubled.
As shown in fig. 4, the 90 ° offset structure in this embodiment includes a side metal electrode, a central metal electrode, and an optical beam combiner; two sides of the central metal electrode are respectively provided with a side metal electrode, an optical waveguide for transmitting light beams is arranged between the central metal electrode and the side metal electrode, and two parallel optical waveguides are arranged in a 90-degree offset structure; each Mach-Zehnder modulator outputs two light beams, wherein one light beam passes through the space between the central metal electrode and the side metal electrode and is output through the optical beam combiner, and the other light beam is output from one side of the side metal electrode, which is far away from the central metal electrode; and the grounding metal electrode, the signal metal electrode, the side metal electrode and the central metal electrode are all connected with the metal lead on the silicon dioxide cladding.
Two paths of the parallel Mach-Zehnder modulators form 90-degree phase difference through a 90-degree phase offset structure. The phase bias structure of the 90-degree phase bias structure adopts a structure of a side metal electrode-central metal electrode-side metal electrode to form an electrode structure, so that two paths of signals generate a 90-degree phase difference. Quadrature Phase Shift Keying (QPSK) of the four states 45 °, 135 °, 225 ° and 315 ° can thus be achieved. When there are multiple levels of the input electrical signal, multi-level quadrature intensity modulation (xQAM) can be achieved.
The width of the optical waveguide for transmitting the light beam is set to 0.8-1 μm in this embodiment; the thickness of the lithium niobate thin film is 300-700 nm.
In this embodiment, the substrate is silicon, quartz, or sapphire, and the lithium niobate thin film may be directly bonded to the substrate or indirectly bonded to the substrate through a bonding medium.
In this embodiment, the grounding metal electrode, the signal metal electrode, the side metal electrode, and the central metal electrode are made of metal with low resistivity, and the metal is gold, silver, or aluminum; the thickness of the metal is 300-1000 nm.
In this embodiment, a light beam enters from an input end of an optical waveguide, passes through a 1 × 2 optical beam splitter a, and is split into two light beams, the two light beams pass through two 1 × 2 optical beam splitters B, respectively, the 1 × 2 optical beam splitter B splits the entering light beam into two light beams, the two light beams exit from two sides of a signal metal electrode, form interference in the 2 × 2 optical interferometer, and output two light beams, one light beam passes through a space between a central metal electrode and a side metal electrode, and then is output through an optical beam combiner, and the other light beam is output from a side of the side metal electrode away from the central metal electrode.
The invention also provides a preparation method of the in-phase quadrature modulator based on the lithium niobate thin film, which comprises the following specific steps:
step 1: bonding the lithium niobate film on a substrate directly or indirectly through a bonding medium;
step 2: covering the electron beam glue on the lithium niobate thin film by using a high-speed spin coating method;
and step 3: transferring the optical structure to an electron beam glue by using an electron beam exposure system;
and 4, step 4: using electron beam glue as a mask, in an inductive coupling-plasma system, using etching gas to realize dry etching of lithium niobate, and transferring an optical structure onto a lithium niobate thin film material;
and 5: covering the substrate with electron beam glue by using a high-speed spin coating method on the substrate obtained in the step 3);
step 6: evaporating the metal adhesion layer and the metal electrode by using an electron beam evaporation system;
and 7: finally forming an electrical structure by utilizing a metal stripping technology;
and 8: covering a silicon dioxide cladding on the lithium niobate thin film and the metal electrode, arranging a metal lead on the silicon dioxide cladding, and opening a window on the silicon dioxide cladding by means of dry etching or wet etching and the like to realize the connection of the metal electrode and the metal lead and finish the manufacture.
In the embodiment, the etching gas is argon plasma or sulfur hexafluoride/argon mixed gas plasma, and the etching depth of the lithium niobate is smaller than the thickness of the film; the metal electrodes comprise a grounding metal electrode, a signal metal electrode, a side metal electrode and a central metal electrode; the optical structure includes an optical waveguide, a 1 x 2 optical splitter A, B, a 2 x 2 optical interferometer, an optical combiner.
In this embodiment, the metal electrode and the metal lead are realized by a metal stripping technique of electron beam exposure polymethyl methacrylate glue or a metal stripping technique of polymethyl methacrylate glue-stripping glue double-layer glue.
In this embodiment, the optical structure may be transferred to the hard mask by the electron beam glue, and then transferred to the lithium niobate thin film, where the hard mask is chromium, nickel, or nickel-chromium.
It should be understood that the above-described embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the claims of the present invention.
Claims (7)
1. An in-phase quadrature modulator based on lithium niobate, characterized in that: the optical fiber laser comprises a substrate, a lithium niobate film arranged on the substrate, a 1 multiplied by 2 optical beam splitter A, two Mach-Zehnder modulators, a 90-degree bias structure and an optical waveguide which is prepared on the lithium niobate film and is used for transmitting light beams, wherein the optical beam splitter A, the two Mach-Zehnder modulators and the 90-degree bias structure are prepared on the lithium niobate film; the 1 multiplied by 2 optical beam splitter A is connected with the input ends of the two paths of Mach-Zehnder modulators, and the output ends of the two paths of Mach-Zehnder modulators are connected with a 90-degree offset structure;
the silicon dioxide coating is covered on the lithium niobate thin film; the thickness of the silica cladding is greater than 1 μm; a metal lead is arranged on the silica cladding, one end of the metal lead is communicated with the outside through a window of the silica cladding, and the Mach-Zehnder modulator and the 90-degree bias structure are connected with the other end of the metal lead;
the Mach-Zehnder modulator comprises a 1 multiplied by 2 optical beam splitter B, a grounding metal electrode, a signal metal electrode and a 2 multiplied by 2 optical interferometer; the two sides of the signal metal electrode are respectively provided with a grounding metal electrode in an arrangement manner, and the 1 x 2 optical beam splitter B and the 2 x 2 optical interferometer are respectively arranged at the two ends of the signal metal electrode; the light beam is divided into two light beams after passing through the 1 × 2 optical beam splitter A, B in sequence, the two light beams respectively pass through the grounding metal electrodes and the signal metal electrodes on the two sides, interference is formed in the 2 × 2 optical interferometer, and the two light beams are output;
the 90-degree bias structure comprises a side metal electrode, a central metal electrode and an optical beam combiner; two sides of the central metal electrode are respectively provided with a side metal electrode; the optical beam combiner is arranged at one end of the central metal electrode; each path of Mach-Zehnder modulator outputs two light beams, wherein one light beam passes through the space between the central metal electrode and the side metal electrode and is output through the optical beam combiner, and the other light beam is output from one side of the side metal electrode, which is far away from the central metal electrode; and the grounding metal electrode, the signal metal electrode, the side metal electrode and the central metal electrode are all connected with the metal lead on the silicon dioxide cladding.
2. The lithium niobate-based in-phase-quadrature modulator of claim 1, wherein: the width range of the optical waveguide is set to be 0.8-1 μm; the thickness range of the lithium niobate thin film is 300-700 nm.
3. The lithium niobate-based in-phase-quadrature modulator of claim 1, wherein: the substrate is silicon or quartz or sapphire.
4. The lithium niobate-based in-phase-quadrature modulator of claim 1, wherein: the grounding metal electrode, the signal metal electrode, the side metal electrode and the central metal electrode are made of gold, silver or aluminum; the thickness of the metal is 300-1000 nm.
5. A method for preparing a lithium niobate-based in-phase-quadrature modulator as set forth in any one of claims 1 to 4, wherein: the preparation method comprises the following specific steps:
step 1: bonding the lithium niobate film on a substrate directly or indirectly through a bonding medium;
step 2: covering the electron beam glue on the lithium niobate thin film by using a high-speed spin coating method;
and step 3: transferring the optical structure to an electron beam glue by using an electron beam exposure system;
and 4, step 4: using electron beam glue as a mask, in an inductive coupling-plasma system, using etching gas to realize dry etching of lithium niobate, and transferring an optical structure onto a lithium niobate thin film material;
and 5: covering the substrate with electron beam glue by using a high-speed spin coating method on the substrate obtained in the step (3);
step 6: evaporating the metal adhesion layer and the metal electrode by using an electron beam evaporation system;
and 7: and finally forming the electric structure by utilizing a metal stripping technology.
6. The method of preparing a lithium niobate-based in-phase-quadrature modulator of claim 5, wherein: the etching gas is argon plasma or sulfur hexafluoride/argon mixed gas plasma; the metal electrodes comprise a grounding metal electrode, a signal metal electrode, a side metal electrode and a central metal electrode; the optical structure includes an optical waveguide, a 1 x 2 optical splitter A, B, a 2 x 2 optical interferometer, an optical combiner.
7. The method of preparing a lithium niobate-based in-phase-quadrature modulator of claim 6, wherein: the metal electrode and the metal lead are realized by a metal stripping technology of electron beam exposure polymethyl methacrylate glue or a metal stripping technology of polymethyl methacrylate glue-stripping glue double-layer glue.
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| CN110161625B (en) * | 2019-05-17 | 2021-03-30 | 上海交通大学 | Method for integrating silicon-based lithium niobate thin-film electro-optic modulator array |
| CN110286540A (en) * | 2019-06-25 | 2019-09-27 | 北京工业大学 | A kind of 1 × 4 lithium niobate waveguides photoswitch increasing Dare interference structure based on Mach |
| CN113671769A (en) * | 2020-05-15 | 2021-11-19 | 联合微电子中心有限责任公司 | Optical phased array based on phase shift control of lithium niobate thin film material and preparation method |
| CN114089550B (en) * | 2021-10-22 | 2024-04-19 | 江苏南里台科技有限公司 | Electro-optic modulator |
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| CN104054311A (en) * | 2011-11-11 | 2014-09-17 | 吉高迅公司 | Dual Polarization Quadrature Modulator |
| CN103873152A (en) * | 2012-12-18 | 2014-06-18 | 武汉邮电科学研究院 | Automatic bias voltage control system and method for light IQ modulator |
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