CN116165812A - High-speed polarization modulator based on submicron lithium niobate thin film and preparation method thereof - Google Patents
High-speed polarization modulator based on submicron lithium niobate thin film and preparation method thereof Download PDFInfo
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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
- G02F1/0136—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour for the control of polarisation, e.g. state of polarisation [SOP] control, polarisation scrambling, TE-TM mode conversion or separation
-
- 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
- G02F1/0009—Materials therefor
- G02F1/0018—Electro-optical materials
-
- 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
- G02F1/0102—Constructional details, not otherwise provided for in this subclass
Abstract
The utility model provides a novel polarization modulator structure realized based on a submicron lithium niobate film and a GSG electrode structure and a preparation method thereof, wherein the accurate definition of the GSG electrode on two sides of a submicron ridge waveguide is realized through the organic combination of the overlay, electroplating and corrosion processes, so that the adoption of the GSG electrode structure under the micro size and the acquisition of high modulation bandwidth are possible. In addition, an optimized structural parameter design scheme is provided based on the basic structure, so that good matching between the ridge waveguide and the modulation electrode and between the optical signal and the modulation signal is realized, and finally, low half-wave voltage and high modulation bandwidth are realized on the polarization modulator, and meanwhile, the size of the polarization modulator is further miniaturized.
Description
Technical Field
The utility model relates to the technical field of photoelectrons, in particular to a high-speed polarization modulator based on a submicron lithium niobate film and a preparation method thereof.
Background
Polarization characteristics of light are an important operation dimension in the field of optical information, so that a polarization modulator is also an electro-optical modulation device with wide application prospect. Lithium niobate is used as a multifunctional crystal, and is widely applied to various electro-optical and nonlinear devices due to the characteristics of wide transparent range, large electro-optical coefficient, large nonlinear coefficient and the like. The strong electro-optic effect (pockels effect) in lithium niobate crystals can cause their refractive index to change linearly with the applied electric field on a femtosecond time scale. By utilizing the transverse electro-optic effect of lithium niobate, a swaying domain structure of Solc filter configuration is formed by applying transverse electric fields on two sides of a periodically polarized lithium niobate crystal, and light is polarized and coupled when passing through the swaying domain structure, so that the control of an electric signal on the polarization direction of the light can be realized.
The existing lithium niobate polarization modulator is generally prepared by adopting a traditional titanium diffusion waveguide mode, a layer of metal titanium film is firstly deposited on a lithium niobate wafer, then the waveguide is prepared by high-temperature diffusion, then a periodical inversion domain is prepared on a waveguide path by utilizing a high-voltage polarization mode, finally an electrode structure is prepared by adopting an alignment scheme, and the polarization adjustment of optical signals in the waveguide can be realized by applying an electric field on the electrode. In another preparation mode, a ridge waveguide structure is prepared on a periodically polarized lithium niobate film with a micron-sized thickness by adopting a cutting mode, the ridge waveguide structure is formed by cutting a scribing groove, then electrodes are embedded into grooves at two sides of the waveguide, an electric field is applied at two sides of the ridge waveguide by the electrodes, and the polarization rotation of input light in the lithium niobate ridge waveguide is realized by utilizing a transverse electro-optic effect.
However, existing lithium niobate polarization modulator manufacturing schemes have the following problems: the larger size of the titanium-diffused lithium niobate waveguide and the micron-sized lithium niobate thin film waveguide results in a spot mode field size in the waveguide of typically 6-9 μm, so that electrode spacing of typically greater than 9 μm is required. The large electrode spacing results in a higher half-wave voltage required to achieve the electric field strength required for signal modulation, for example, the half-wave voltage length product of the currently known lithium niobate polarization modulator is not less than 13Vcm, which greatly increases the difficulty of system design and power consumption. To solve the problem of high half-wave voltages, it is necessary to first implement waveguide design and preparation for small mode fields. For the titanium diffusion technology, the smaller refractive index difference of the fiber core/cladding layer is determined in principle that the light spot constraint of a small mode field cannot be realized, and the larger refractive index difference of the fiber core/cladding layer can be realized by preparing the lithium niobate thin film ridge waveguide in a diamond blade precise cutting mode, but the processing precision is limited, and the waveguide structure of the small mode field cannot be prepared on the submicron lithium niobate thin film.
In addition, the existing titanium diffusion lithium niobate waveguide and micron-sized lithium niobate thin film waveguide polarization modulator adopt the structure design of a lumped electrode, and the modulation bandwidth of the lumped electrode structure can only reach hundred MHz in theory, which greatly limits the application range.
Disclosure of Invention
Aiming at the problems in the prior art, the utility model provides a novel polarization modulator structure and a preparation method based on a submicron lithium niobate film and a GSG electrode structure, wherein the accurate definition of the GSG electrode on two sides of a submicron ridge waveguide is realized through the organic combination of the overlay, electroplating and corrosion processes, so that the adoption of the GSG electrode structure under the micro size and the acquisition of high modulation speed and bandwidth are possible. In addition, an optimized structural parameter design scheme is provided based on the basic structure, so that good matching between the ridge waveguide and the modulation electrode and between the optical signal and the modulation signal is realized, and finally, low half-wave voltage, high modulation speed and wide modulation bandwidth are realized on the polarization modulator, and meanwhile, the size of the polarization modulator is further miniaturized.
The first aspect of the utility model relates to a preparation method of a polarization modulator based on a submicron lithium niobate thin film, which comprises a periodic polarization step, a waveguide preparation step and a GSG electrode preparation step;
the periodic polarization step is used for carrying out periodic polarization on the submicron lithium niobate thin film to form a periodic polarization lithium niobate thin film;
the waveguide preparation step is used for etching the periodically polarized lithium niobate thin film to form a ridge waveguide on the periodically polarized lithium niobate thin film;
the GSG electrode preparation step is used for forming a GSG electrode structure on the periodically polarized lithium niobate thin film, wherein the GSG electrode structure comprises a signal electrode and first and second grounding electrodes positioned at two sides of the signal electrode, and the ridge waveguide is positioned between the grounding electrode and the signal electrode.
Further, the GSG electrode preparation step includes the sub-steps of:
a vapor deposition substep of depositing a GSG electrode metal layer on the periodically poled lithium niobate thin film by vapor deposition;
a thickening substep of increasing the thickness of the GSG electrode metal layer on the region corresponding to the GSG electrode structure by means of an electroplating process; the method comprises the steps of,
and removing the electrode forming sub-step of the GSG electrode metal layer outside the corresponding region of the GSG electrode structure.
Further, in the vapor deposition sub-step, the vapor deposition is physical vapor deposition; and/or; in the vapor deposition sub-step, the GSG electrode metal layer includes a first metal layer formed on the periodically poled lithium niobate thin film, and a second metal layer formed on the first metal layer; and/or, in the thickening substep, masking the GSG electrode metal layer outside the GSG electrode structure corresponding region with photoresist prior to the electroplating process.
Preferably, the first metal layer is a titanium layer, and the second metal layer is a gold layer; and/or the first metal layer has a thickness of 100-200nm, and the second metal layer has a thickness of 100-200 nm.
Further, the waveguide preparation step includes a mask step of forming a metal mask on the periodically poled lithium niobate thin film, and a waveguide forming sub-step of forming a ridge waveguide on the periodically poled lithium niobate thin film by means of inductively coupled plasma dry etching.
Further, the periodic polarization step comprises the sub-steps of:
a polarized electrode forming sub-step of depositing a polarized electrode metal layer on the submicron lithium niobate thin film and forming a periodic polarized electrode by carrying out photoetching on the polarized electrode metal layer; the method comprises the steps of,
and a polarization substep of periodically polarizing the submicron lithium niobate thin film by means of the periodically polarizing electrode.
Preferably, the periodic polarization step is configured to form a polarization width of 1-10mm, a polarization region length of 5-50mm, a polarization duty cycle of about 50%, and a polarization period Λ = λ/[ n, on the sub-micron lithium niobate film eff (TE)n eff (TM)]Lambda is the wavelength of the input light of the polarization modulator, n eff (TE) and n eff (TM) the effective refractive index of TE and TM polarized light in the ridge waveguide, respectively;
the waveguide preparation step is configured such that the ridge waveguide has a height of 400-1000nm, a width of 1-2 μm, and inclined side walls with a slope angle of 65-85 °;
the GSG electrode preparation step is configured such that the signal electrode has a width of 10-20 μm and a thickness of 0.5-2 μm, the ground electrode has a width of 20-50 μm and a thickness of 0.5-2 μm, and a spacing between the ridge waveguide and adjacent signal electrode and ground electrode is 2-4 μm.
A second aspect of the utility model relates to a high-speed polarization modulator based on a submicron lithium niobate film, comprising a ridge waveguide and a GSG electrode structure; wherein, the liquid crystal display device comprises a liquid crystal display device,
the ridge waveguide is formed in a submicron periodically polarized lithium niobate thin film;
the GSG electrode structure is formed on the periodically polarized lithium niobate thin film and comprises a signal electrode, and a first grounding electrode and a second grounding electrode which are positioned at two sides of the signal electrode;
the ridge waveguide is located between the ground electrode and the signal electrode.
Further, the polarization modulator may further include a substrate and an insulating layer between the substrate and the periodically poled lithium niobate thin film.
Optionally, the periodically poled lithium niobate thin film is a z-cut lithium niobate thin film; and/or the insulating layer is a silicon dioxide insulating layer; and/or the substrate is a lithium niobate substrate or a silicon substrate.
Preferably, the periodically poled lithium niobate thin film has a polarization width of 1 to 10mm, a polarization region length of 5 to 50mm, a polarization duty cycle of about 50%, and a polarization period Λ=λ/[ n eff (TE)-n eff (TM)]Lambda is the wavelength of the input light of the polarization modulator, n eff (TE) and n eff (TM) the effective refractive index of TE and TM polarized light in the ridge waveguide, respectively; and/or the number of the groups of groups,
the ridge waveguide has a height of 400-1000nm, a width of 1-2 μm, and sloped sidewalls with a slope angle of 65-85 DEG; and/or the number of the groups of groups,
the signal electrode has a width of 10-20 μm and a thickness of 0.5-2 μm, the ground electrode has a width of 20-50 μm and a thickness of 0.5-2 μm, and a spacing between the ridge waveguide and adjacent signal and ground electrodes is 2-4 μm.
Preferably, the high-speed polarization modulator is formed by the preparation method of the present utility model.
Drawings
The following describes the embodiments of the present utility model in further detail with reference to the drawings.
In order to more clearly illustrate the embodiments of the present utility model or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, it being obvious that the drawings in the following description are only some embodiments of the present utility model, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 shows one example of a submicron lithium niobate thin film structure for use in the present utility model;
FIG. 2 schematically illustrates a periodic polarization step for use in the preparation method of the present utility model;
FIG. 3 schematically illustrates a waveguide preparation step for use in the preparation method of the present utility model;
FIGS. 4-5 schematically illustrate GSG electrode preparation steps for use in the preparation method of the utility model;
FIG. 6 illustrates a perspective view of an exemplary submicron lithium niobate thin film-based high speed polarization modulator in accordance with the present utility model;
fig. 7 shows a modulated electric field distribution diagram under the polarization modulator structure according to fig. 6.
Detailed Description
Hereinafter, exemplary embodiments of the present utility model will be described in detail with reference to the accompanying drawings. The following examples are provided by way of illustration to fully convey the spirit of the utility model to those skilled in the art to which the utility model pertains. Thus, the present utility model is not limited to the embodiments disclosed herein.
In the present utility model, a polarization modulator realized by adopting a GSG (ground-signal-ground) electrode structure on a submicron lithium niobate film is proposed for the first time. In a basic structure of the polarization modulator, a ridge waveguide formed in a submicron-sized Periodically Poled Lithium Niobate (PPLN) film, and a GSG electrode structure for providing a modulating electric field to the ridge waveguide, wherein the GSG electrode structure is formed on the periodically poled lithium niobate film, and a ground electrode and a signal electrode are provided on both sides of the ridge waveguide to provide the modulating electric field thereto.
Because GSG electrode structures often require relatively complex design and fabrication processes, it is difficult to precisely achieve and provide the required modulating electric field on the sidewalls of micron-sized lithium niobate thin film ridge waveguides having very small dimensions, in a manner that is compatible with the ridge waveguides. Accordingly, the present utility model will hereinafter also disclose a method for preparing the polarization modulator of the present utility model, and provide an optimized polarization modulator specific design scheme based on the basic structure of the polarization modulator, thereby presenting a submicron-sized lithium niobate thin film ridge waveguide structure suitable for high-speed polarization modulation, and a GSG electrode structure adapted thereto, and finally allowing advantages of low half-wave voltage and high modulation bandwidth to be realized on the polarization modulator, so that the polarization modulator is particularly suitable for application scenarios of miniaturization, high efficiency, high-speed polarization modulation, and the like.
Fig. 1 to 5 will schematically present a process for manufacturing a polarization modulator based on a submicron lithium niobate thin film according to the present utility model, which includes a periodic polarization step, a waveguide manufacturing step, and a GSG electrode manufacturing step in this order.
Fig. 1 shows one example of a submicron lithium niobate thin film structure for use in the present utility model. As shown in fig. 1, the lithium niobate thin film structure may include a lithium niobate thin film (i.e., LN thin film), an insulating layer, and a substrate in this order from top to bottom.
The lithium niobate thin film has a thickness of submicron order, which may be, for example, 0.4 to 1 μm. In examples of the utility model, the lithium niobate thin film may be a Z-cut lithium niobate thin film.
The substrate may be, for example, a lithium niobate substrate or a silicon substrate, which may have a thickness of 300-500 μm, for example.
Optionally, a thin film layer of lithium niobate, for example, siO, may also be provided between the substrate and the thin film layer 2 A layer, etc., which may have a thickness of about 2 μm, for example.
Fig. 2 schematically illustrates a periodic polarization step used in the preparation method of the present utility model for subjecting a submicron lithium niobate thin film to a periodic polarization treatment to obtain a periodic polarized lithium niobate thin film.
According to the present utility model, the periodic polarizing step may include a polarizing electrode forming sub-step for forming a periodic polarizing electrode on the submicron lithium niobate thin film and a polarizing sub-step for performing a periodic polarizing treatment on the submicron lithium niobate thin film.
In the polarized electrode forming sub-step, a polarized electrode metal layer, for example, having a thickness of several hundred nm, may be deposited on the upper surface (for example, +z-plane) of the lithium niobate thin film. As an example, the polarizing electrode may employ a metal such as Au, al, or Cr.
Then, a pattern of a polarized electrode can be defined on the electrode metal layer by means of ultraviolet lithography, and a desired periodic polarized electrode structure can be formed on the polarized electrode metal layer by etching process, as shown in fig. 2.
Accordingly, in the polarizing sub-step, a polarizing electric field is applied to the lithium niobate thin film via the periodic polarizing electrode, for example, the periodic polarizing treatment is performed on the lithium niobate thin film with the Z-axis direction as a polarizing direction, thereby obtaining a PPLN thin film structure.
Fig. 3 schematically illustrates a waveguide fabrication step used in the fabrication method of the present utility model for etching a PPLN film to form a ridge waveguide structure on the film.
According to the present utility model, the waveguide preparation step may comprise a mask step for forming a metal mask on the surface of the PPLN film and a waveguide forming sub-step for forming a ridge waveguide structure on the PPLN film by means of inductively coupled plasma dry etching.
In the masking substep, a masking metal layer may be deposited on the top surface (e.g., +z side) of the PPLN film, wherein the masking metal is, for example, nickel or chromium. Then, a pattern of a mask may be defined on the PPLN film by ultraviolet lithography, and a metal mask is formed by means of an etching process.
Thus, the mask pattern may be transferred onto the PPLN film by inductively coupled plasma dry etching (ICP) in a waveguide forming step, thereby forming a ridge waveguide structure. Those skilled in the art will appreciate that during ICP etching, the PPLN film protected by the metal mask will not be etched away, whereas the PPLN film exposed outside the metal mask will be etched away to a depth, thereby forming a ridge waveguide structure, as shown in fig. 3.
Fig. 4-5 schematically illustrate GSG electrode fabrication steps used in the fabrication methods of the present utility model for further forming GSG electrode structures on a PPLN film that has been formed with a ridge waveguide.
According to the present utility model, the GSG electrode preparation step may include a vapor deposition sub-step for forming a GSG electrode metal layer on the PPLN film by means of a vapor deposition process, a thickening sub-step for increasing a thickness of the metal layer in a region corresponding to the GSG electrode structure by means of an electroplating process, and an electrode formation sub-step for removing the metal layer in a region other than the GSG electrode structure to finally form the GSG electrode structure on the PPLN film.
In the vapor deposition sub-step, a metallic titanium layer may be deposited on the surface of the PPLN film by Physical Vapor Deposition (PVD) and then a metallic gold layer may be redeposited on the metallic titanium layer. As an example, the metallic titanium layer may have a thickness of 100-200nm and the metallic gold layer has a thickness of 100-200 nm.
Then, in the thickening substep, the region of the PPLN film outside the GSG electrode structure may be masked with photoresist by means of alignment, and then the thickness of the GSG electrode metal layer may be increased by an electroplating process.
Finally, the photoresist may be removed and the GSG electrode metal layers (e.g., metallic titanium and metallic gold) on the GSG electrode structure may be etched away in an electrode molding sub-step, whereby a complete GSG electrode structure may be precisely obtained on both sides of the ridge waveguide, as shown in fig. 4 and 5.
By means of the preparation method, a ridge waveguide structure and an adaptive GSG electrode structure are allowed to be realized on a submicron lithium niobate film in a precise and controllable manner, so that the polarization modulator structure provided by the utility model is obtained.
Under the basic structure of the polarization modulator provided by the utility model, the GSG electrode structure generates a modulating electric field for the ridge waveguide under the action of a radio frequency signal applied by a radio frequency signal source so as to form a swaying domain structure of a Solc filter configuration in the PPLN ridge waveguide by means of a transverse electro-optic effect. The optical signal is coupled into the PPLN ridge waveguide via polarization maintaining fiber and polarization coupling occurs when passing through these wobble domain structures, thereby achieving modulation in polarization. At this time, the adaptation of the ridge waveguide and GSG electrode structure in terms of structural parameters is critical for the formation of the wobble domain structure, and therefore the present utility model will be further described below as a polarization modulator structure with a specific parameter design based on this basic structure implementation.
Fig. 6 shows a perspective view of a preferred embodiment of a high-speed polarization modulator based on submicron lithium niobate thin films according to the present utility model.
As shown in fig. 6, a polarization modulator according to the present utility model may include a substrate, an insulating layer, a PPLN film ridge waveguide, and a GSG electrode structure.
The PPLN film used to form the ridge waveguide may be, for example, a Z-cut lithium niobate film.
The substrate may be, for example, a lithium niobate substrate or a silicon substrate, which may have a thickness of 300-500 μm, for example.
Optionally, a thin film layer of lithium niobate, for example, siO, may also be provided between the substrate and the thin film layer 2 A layer, etc., which may have a thickness of about 2 μm, for example.
In the preferred embodiment, the PPLN film may have a polarization width of 1-10mm, a polarization region length of 10-50mm, and a polarization duty cycle of about 50%, and a polarization period Λ=λ/[ n eff (TE)-n eff (TM)]Lambda is the wavelength of the input light of the polarization modulator, n eff (TE) and n eff (TM) is the effective refractive index of TE and TM polarized light, respectively, in the ridge waveguide.
The PPLN film ridge waveguide may have a height of 400-1000nm, a waveguide width of 1-2 μm, and sloped sidewalls, wherein the sloped sidewalls have a slope angle of 65-85 °.
In the GSG electrode structure, the signal electrode may have a width of 10-20 μm and a thickness of 0.5-2 μm, and the ground electrode may have a width of 20-50 μm and a thickness of 0.5-2 μm.
Wherein the pitch between the PPLN film ridge waveguide and the adjacent signal electrode and ground electrode is set to 2-4 μm.
Through testing, under the structural design parameters, the influence of the dispersion of the film material and the structural dispersion of the submicron ridge waveguide is considered, the optimal matching between the radio frequency modulation signal and the group velocity of the optical signal in the submicron ridge waveguide is realized, and the good matching between the characteristic impedance of the modulation electrode and the characteristic impedance of the signal source and the load resistor is realized, so that the polarization modulator is allowed to realize higher modulation speed and more than two orders of magnitude improvement on the modulation bandwidth, and simultaneously, the smaller modulation driving voltage is also allowed to be possible to work under the voltage compatible with the CMOS technology, and the application scene of the polarization modulator is very beneficial to expansion. In addition, the preparation method provided by the utility model has simple and reliable process, allows the preparation to be realized on the submicron lithium niobate film with high precision, for example, the accurate definition of the GSG electrode on two sides of the ridge waveguide can be realized simply through the processes of alignment, electroplating and corrosion, and the obtained polarization modulator has small overall size and is easy to integrate.
Fig. 7 shows a modulated electric field profile under the polarization modulator structure according to fig. 6, showing that the modulated electric field profile provided by the GSG electrode structure is well adapted to ridge waveguides formed on submicron PPLN films, allowing high speed and high bandwidth polarization modulation.
Under the optimized polarization modulator structure, the reflection loss of the input and output of the modulated electric signal can be reduced, the existence of the GSG electrode can not bring extra absorption loss to the transmission of the optical signal, and the modulation bandwidth is improved to the level of tens of GHz. At this time, the half-wave voltage length product for the polarization modulator can be reduced to about 1Vcm, so the polarization modulator can directly use the output electric signal of the CMOS chip as the modulation electric signal without additional signal amplification, which greatly reduces the complexity of the system design, improves the integration level, and thus reduces the system power consumption.
While the utility model has been described in connection with the specific embodiments illustrated in the drawings, it will be readily appreciated by those skilled in the art that the above embodiments are merely illustrative of the principles of the utility model, which are not intended to limit the scope of the utility model, and various combinations, modifications and equivalents of the above embodiments may be made by those skilled in the art without departing from the spirit and scope of the utility model.
Claims (12)
1. A preparation method of a polarization modulator based on a submicron lithium niobate film comprises a periodic polarization step, a waveguide preparation step and a GSG electrode preparation step;
the periodic polarization step is used for carrying out periodic polarization on the submicron lithium niobate thin film to form a periodic polarization lithium niobate thin film;
the waveguide preparation step is used for etching the periodically polarized lithium niobate thin film to form a ridge waveguide on the periodically polarized lithium niobate thin film;
the GSG electrode preparation step is used for forming a GSG electrode structure on the periodically polarized lithium niobate thin film, wherein the GSG electrode structure comprises a signal electrode and first and second grounding electrodes positioned at two sides of the signal electrode, and the ridge waveguide is positioned between the grounding electrode and the signal electrode.
2. The preparation method of claim 1, wherein the GSG electrode preparation step comprises the substeps of:
a vapor deposition substep of depositing a GSG electrode metal layer on the periodically poled lithium niobate thin film by vapor deposition;
a thickening substep of increasing the thickness of the GSG electrode metal layer on the region corresponding to the GSG electrode structure by means of an electroplating process; the method comprises the steps of,
and removing the electrode forming sub-step of the GSG electrode metal layer outside the corresponding region of the GSG electrode structure.
3. The method of manufacturing of claim 2, wherein:
in the vapor deposition sub-step, the vapor deposition is physical vapor deposition; and/or;
in the vapor deposition sub-step, the GSG electrode metal layer includes a first metal layer formed on the periodically poled lithium niobate thin film, and a second metal layer formed on the first metal layer; and/or the number of the groups of groups,
in the thickening substep, the photoresist is utilized to cover the GSG electrode metal layer outside the GSG electrode structure corresponding region before the electroplating process.
4. The method of claim 3, wherein the first metal layer is a titanium layer and the second metal layer is a gold layer; and/or the first metal layer has a thickness of 100-200nm, and the second metal layer has a thickness of 100-200 nm.
5. The manufacturing method according to claim 2, wherein the waveguide manufacturing step includes a mask step of forming a metal mask on the periodically poled lithium niobate thin film, and a waveguide forming sub-step of forming a ridge waveguide on the periodically poled lithium niobate thin film by means of inductively coupled plasma dry etching.
6. The method of manufacturing of claim 2, wherein the step of periodically polarizing comprises the sub-steps of:
a polarized electrode forming sub-step of depositing a polarized electrode metal layer on the submicron lithium niobate thin film and forming a periodic polarized electrode by carrying out photoetching on the polarized electrode metal layer; the method comprises the steps of,
and a polarization substep of periodically polarizing the submicron lithium niobate thin film by means of the periodically polarizing electrode.
7. The production method according to any one of claims 1 to 6, wherein:
the periodic polarization step is configured to form a polarization width of 1-10mm, a polarization region length of 5-50mm, a polarization duty cycle of about 50%, and a polarization period Λ = λ/[ n, on the sub-micron lithium niobate film eff (TE)-n eff (TM)]Lambda is the wavelength of the input light of the polarization modulator, n eff (TE) and n eff (TM) the effective refractive index of TE and TM polarized light in the ridge waveguide, respectively;
the waveguide preparation step is configured such that the ridge waveguide has a height of 400-1000nm, a width of 1-2 μm, and inclined side walls with a slope angle of 65-85 °;
the GSG electrode preparation step is configured such that the signal electrode has a width of 10-20 μm and a thickness of 0.5-2 μm, the ground electrode has a width of 20-50 μm and a thickness of 0.5-2 μm, and a spacing between the ridge waveguide and adjacent signal electrode and ground electrode is 2-4 μm.
8. A submicron lithium niobate thin film-based high-speed polarization modulator, which comprises a ridge waveguide and a GSG electrode structure; wherein, the liquid crystal display device comprises a liquid crystal display device,
the ridge waveguide is formed in a submicron periodically polarized lithium niobate thin film;
the GSG electrode structure is formed on the periodically polarized lithium niobate thin film and comprises a signal electrode, and a first grounding electrode and a second grounding electrode which are positioned at two sides of the signal electrode;
the ridge waveguide is located between the ground electrode and the signal electrode.
9. The high-speed polarization modulator of claim 8, further comprising a substrate and an insulating layer between the substrate and the periodically poled lithium niobate film.
10. The high-speed polarization modulator of claim 9, wherein the periodically poled lithium niobate film is a z-cut lithium niobate film; and/or the insulating layer is a silicon dioxide insulating layer; and/or the substrate is a lithium niobate substrate or a silicon substrate.
11. The high-speed polarization modulator of claim 8, wherein:
the periodically poled lithium niobate thin film has a polarization width of 1-10mm, a polarization region length of 5-50mm, a polarization duty cycle of about 50%, and a polarization period Λ=λ/[ n ] eff (TE)-n eff (TM)]Lambda is the wavelength of the input light of the polarization modulator, n eff (TE) and n eff (TM) the effective refractive index of TE and TM polarized light in the ridge waveguide, respectively; and/or the number of the groups of groups,
the ridge waveguide has a height of 400-1000nm, a width of 1-2 μm, and sloped sidewalls with a slope angle of 65-85 DEG; and/or the number of the groups of groups,
the signal electrode has a width of 10-20 μm and a thickness of 0.5-2 μm, the ground electrode has a width of 20-50 μm and a thickness of 0.5-2 μm, and a spacing between the ridge waveguide and adjacent signal and ground electrodes is 2-4 μm.
12. A high speed polarization modulator according to claim 8 formed by the method of manufacture of any one of claims 1-6.
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| CN116931367B (en) * | 2023-09-18 | 2024-01-19 | 济南量子技术研究院 | Lithium niobate thin film ridge waveguide modulator and preparation method thereof |
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