CN117572673A - Optical phase modulator and preparation method thereof - Google Patents
Optical phase modulator and preparation method thereof Download PDFInfo
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- CN117572673A CN117572673A CN202311488844.0A CN202311488844A CN117572673A CN 117572673 A CN117572673 A CN 117572673A CN 202311488844 A CN202311488844 A CN 202311488844A CN 117572673 A CN117572673 A CN 117572673A
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- 238000002360 preparation method Methods 0.000 title abstract description 8
- 229910052581 Si3N4 Inorganic materials 0.000 claims abstract description 247
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 claims abstract description 236
- GQYHUHYESMUTHG-UHFFFAOYSA-N lithium niobate Chemical compound [Li+].[O-][Nb](=O)=O GQYHUHYESMUTHG-UHFFFAOYSA-N 0.000 claims abstract description 220
- 239000013078 crystal Substances 0.000 claims abstract description 168
- 238000005253 cladding Methods 0.000 claims abstract description 80
- 239000000758 substrate Substances 0.000 claims abstract description 55
- 230000003247 decreasing effect Effects 0.000 claims abstract description 14
- 239000010408 film Substances 0.000 claims description 115
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 68
- 239000000463 material Substances 0.000 claims description 33
- 239000000377 silicon dioxide Substances 0.000 claims description 33
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims description 31
- 229910052710 silicon Inorganic materials 0.000 claims description 31
- 239000010703 silicon Substances 0.000 claims description 31
- 235000012239 silicon dioxide Nutrition 0.000 claims description 31
- 239000010409 thin film Substances 0.000 claims description 28
- 238000000151 deposition Methods 0.000 claims description 25
- 238000000059 patterning Methods 0.000 claims description 19
- 230000007704 transition Effects 0.000 claims description 17
- 239000002131 composite material Substances 0.000 claims description 11
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 claims description 10
- 238000004519 manufacturing process Methods 0.000 claims description 9
- 238000005530 etching Methods 0.000 claims description 8
- 230000001902 propagating effect Effects 0.000 claims description 7
- 238000003780 insertion Methods 0.000 abstract description 10
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- 239000010410 layer Substances 0.000 description 130
- 238000000034 method Methods 0.000 description 26
- 230000008569 process Effects 0.000 description 16
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 11
- 230000015572 biosynthetic process Effects 0.000 description 11
- 229910052744 lithium Inorganic materials 0.000 description 11
- 238000004518 low pressure chemical vapour deposition Methods 0.000 description 11
- 238000010586 diagram Methods 0.000 description 10
- 230000005684 electric field Effects 0.000 description 8
- UMIVXZPTRXBADB-UHFFFAOYSA-N benzocyclobutene Chemical compound C1=CC=C2CCC2=C1 UMIVXZPTRXBADB-UHFFFAOYSA-N 0.000 description 6
- 230000000694 effects Effects 0.000 description 6
- 239000010931 gold Substances 0.000 description 6
- 230000008859 change Effects 0.000 description 4
- 238000000206 photolithography Methods 0.000 description 4
- 230000000644 propagated effect Effects 0.000 description 4
- 238000000137 annealing Methods 0.000 description 3
- 239000004020 conductor Substances 0.000 description 3
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 3
- 229910052737 gold Inorganic materials 0.000 description 3
- AMGQUBHHOARCQH-UHFFFAOYSA-N indium;oxotin Chemical compound [In].[Sn]=O AMGQUBHHOARCQH-UHFFFAOYSA-N 0.000 description 3
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 description 3
- 229910052721 tungsten Inorganic materials 0.000 description 3
- 239000010937 tungsten Substances 0.000 description 3
- 238000005137 deposition process Methods 0.000 description 2
- 239000011147 inorganic material Substances 0.000 description 2
- 238000001459 lithography Methods 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 239000011368 organic material Substances 0.000 description 2
- 238000001259 photo etching Methods 0.000 description 2
- 238000009832 plasma treatment Methods 0.000 description 2
- 238000000623 plasma-assisted chemical vapour deposition Methods 0.000 description 2
- 230000001105 regulatory effect Effects 0.000 description 2
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- 238000001039 wet etching Methods 0.000 description 2
- 229910004205 SiNX Inorganic materials 0.000 description 1
- 229910004298 SiO 2 Inorganic materials 0.000 description 1
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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
- G02F1/035—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
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
- G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
- G02B6/122—Basic optical elements, e.g. light-guiding paths
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
- G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
- G02B6/13—Integrated optical circuits characterised by the manufacturing method
- G02B6/132—Integrated optical circuits characterised by the manufacturing method by deposition of thin films
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
- G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
- G02B6/13—Integrated optical circuits characterised by the manufacturing method
- G02B6/136—Integrated optical circuits characterised by the manufacturing method by etching
-
- 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
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
- G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
- G02B2006/12133—Functions
- G02B2006/12142—Modulator
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- Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- General Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Nonlinear Science (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Chemical & Material Sciences (AREA)
- Ceramic Engineering (AREA)
- Crystallography & Structural Chemistry (AREA)
- Optical Integrated Circuits (AREA)
- Optical Modulation, Optical Deflection, Nonlinear Optics, Optical Demodulation, Optical Logic Elements (AREA)
Abstract
The invention provides an optical phase modulator and a preparation method thereof, relating to the technical field of optical phase modulators, wherein the optical phase modulator comprises a substrate; a lower cladding layer formed on the substrate; a silicon nitride waveguide core formed on the lower cladding layer; the bonding medium layer is covered on the substrate, the lower cladding layer and the silicon nitride waveguide core; the lithium niobate monocrystal slice is bonded above the silicon nitride waveguide core through a bonding medium layer; the first slope surface structure is formed on the bonding medium layer, and is positioned at one side of the lithium niobate single crystal thin sheet along the length direction of the silicon nitride waveguide core, and the height of one side of the first slope surface structure, which is far away from the lithium niobate single crystal thin sheet, is gradually decreased; an electrode formed on the lithium niobate single crystal sheet or the bonding dielectric layer; and the upper cladding layer is covered on the bonding dielectric layer, the lithium niobate monocrystal flake, the first slope structure and the electrode. The optical phase modulator is beneficial to reducing the insertion loss by arranging slope structures on one side or two sides of the bonded lithium niobate single crystal slices in the length direction of the silicon nitride waveguide core.
Description
Technical Field
The present invention relates to the field of optical phase modulators, and in particular, to an optical phase modulator and a method for manufacturing an optical phase modulator.
Background
Stoichiometric silicon nitride (Si) prepared by Low Pressure Chemical Vapor Deposition (LPCVD) 3 N 4 ) The thin film/waveguide core has transparency in a wide wavelength range (400-2350 nm), low optical propagation loss at high optical power, silicon nitride waveguide core and silicon (Si) substrate, silicon dioxide (SiO) 2 ) Waveguide platforms composed of cladding layers enable a wide range of planar integrated devices and chip-scale solutions. The phase modulator is one of the core devices of the photonic integrated circuit, and the photonic platform based on silicon nitride can generally use thermo-optical effect, elasto-optical effect, and the like to realize optical phase modulation. But are limited by the material characteristics and device structure such as heat conduction speed, charge and discharge time, and these modulators have disadvantages in terms of speed, power and efficiency. An alternative is electro-optic modulation, but the silicon nitride electro-optic effect is very weak and must be combined with a material having a significant electro-optic effect to achieve efficient electro-optic phase modulation. Wherein, single crystal lithium niobate (LiNbO) 3 ) Has strong electro-optic effect (1550 nm: r is (r) 33 =30.8pm/V), higher refractive index (1550 nm: n is n o ＝2.21，n e =2.14), a wide light transmission window (400 nm to 5 μm) and stable physical and chemical properties, are the most competitive materials.
The thermal expansion coefficients of the lithium niobate and the silicon dioxide/silicon substrate are seriously mismatched, and the lithium niobate single crystal film is broken due to the fact that the lithium niobate single crystal film is subjected to larger thermal stress at an excessively high process temperature, so that the lithium niobate single crystal film is not compatible with the high-temperature process of the silicon nitride waveguide platform. The heterogeneous integration of lithium niobate and silicon nitride waveguide platforms is typically achieved by means of bonding. The existing lithium niobate thin film and silicon nitride waveguide core generally have two combination forms:
(1) the lithium niobate single crystal film only covers a small section of silicon nitride waveguide core to form a lithium niobate-silicon nitride ridge composite waveguide core locally, an electric field is applied to the lithium niobate to realize electric-optical phase modulation, and light before and after modulation is transmitted through the silicon nitride waveguide;
(2) the lithium niobate single crystal film covers all or most of the silicon nitride waveguide cores to form a lithium niobate-silicon nitride composite waveguide core, an electric field is applied to the lithium niobate to realize electric-optical phase modulation, and light before and after modulation is transmitted through the lithium niobate-silicon nitride composite waveguide;
When higher optical phase modulation efficiency is required, more optical field in the lithium niobate-silicon nitride composite waveguide is required to be distributed in lithium niobate, and at this time, the existing lithium niobate thin film and silicon nitride waveguide core generally have the following problems:
1) For the combined form (1) of the lithium niobate thin film and the silicon nitride waveguide core, the mode field mismatch of the propagated light from the silicon nitride waveguide to the lithium niobate-silicon nitride composite waveguide is obviously improved, and the insertion loss is obviously increased;
2) For the combination form (2) of the lithium niobate thin film and the silicon nitride waveguide core, the insertion loss is low and the influence degree is small; it has some potential problems: the lithium niobate-silicon nitride composite waveguide of the non-phase modulation region is easily interfered by an electric field, and the inherent shortages of the ridge waveguide, etc.
Disclosure of Invention
The invention aims to provide an optical phase modulator and a preparation method thereof, which are used for solving the problem of high insertion loss of the existing optical phase modulator.
A first aspect of an embodiment of the present application provides an optical phase modulator, including:
a substrate;
a lower cladding layer formed on the substrate;
a silicon nitride waveguide core formed on the lower cladding layer;
the bonding medium layer is covered on the substrate, the lower cladding layer and the silicon nitride waveguide core;
The lithium niobate monocrystal slice is bonded above the silicon nitride waveguide core through the bonding dielectric layer;
the first slope surface structure is formed on the bonding medium layer, the first slope surface structure is positioned at one side of the lithium niobate single crystal thin sheet along the length direction of the silicon nitride waveguide core, and the height of one side of the first slope surface structure, which is far away from the lithium niobate single crystal thin sheet, is gradually decreased;
an electrode formed on the lithium niobate single crystal thin sheet or the bonding dielectric layer;
and the upper cladding layer is covered on the bonding dielectric layer, the lithium niobate monocrystal flake, the first slope structure and the electrode.
In some optional embodiments of the present application, for light propagating in a length direction of the silicon nitride waveguide core, a refractive index of the first slope structure is the same as or similar to that of the lithium niobate single crystal thin sheet, a height of a top surface of the first slope structure is the same as that of the lithium niobate single crystal thin sheet, and a width of the first slope structure is the same as that of the lithium niobate single crystal thin sheet or is larger than a width of a fundamental mode field propagating in a composite waveguide composed of silicon nitride and lithium niobate.
In some optional embodiments of the present application, the material of the first slope structure is lithium niobate or non-stoichiometric silicon nitride, and a side of the first slope structure, which is close to the lithium niobate single crystal thin sheet, is connected with the lithium niobate single crystal thin sheet.
In some optional embodiments of the present application, the material of the first slope structure is silicon-rich silicon nitride.
In some optional embodiments of the present application, the first slope structure is made of silicon nitride with a stoichiometric ratio, the first slope structure and the lithium niobate single crystal thin sheet are connected by a transition material, and for light propagating in the length direction of the silicon nitride waveguide core, the refractive index of the transition material is between the first slope structure and the lithium niobate single crystal thin sheet.
In some optional embodiments of the present application, the bonding dielectric layer is silicon dioxide, and a silicon dioxide or aluminum oxide film may be deposited on a side of the lithium niobate monocrystal thin film close to the bonding dielectric layer.
In some optional embodiments of the present application, the bonding medium layer is any one of the following: a coated BCB film, a planarized silicon dioxide film, and a laminate of a planarized silicon dioxide film and an aluminum oxide film.
In some optional embodiments of the present application, the number of the electrodes is two, and the two electrodes are respectively located at two sides of the silicon nitride waveguide core.
In some optional embodiments of the present application, further comprising:
The second slope surface structure is formed on the bonding medium layer, and the second slope surface structure and the first slope surface structure are positioned on two sides of the lithium niobate single crystal thin sheet and are symmetrically or asymmetrically distributed.
A second aspect of an embodiment of the present application provides a method for manufacturing an optical phase modulator, including:
providing a silicon substrate;
forming a lower cladding layer on the substrate;
forming a silicon nitride film on the lower cladding layer and patterning to form a silicon nitride waveguide core;
forming a bonding medium layer on the substrate, the lower cladding and the silicon nitride waveguide core;
forming a lithium niobate monocrystal sheet above the bonding medium layer;
depositing a non-stoichiometric silicon nitride film on the bonding dielectric layer and the lithium niobate single crystal thin film so that the thickness of the non-stoichiometric silicon nitride film is greater than the thickness of the lithium niobate single crystal thin film;
flattening the non-stoichiometric silicon nitride film so that the thickness of the non-stoichiometric silicon nitride film is the same as the thickness of the lithium niobate single crystal thin film;
patterning the non-stoichiometric silicon nitride film on one side or two sides of the lithium niobate single crystal thin sheet along the length direction of the silicon nitride waveguide core to form a slope structure, so that the height of the slope structure on one side far away from the lithium niobate single crystal thin sheet is gradually decreased;
Forming an electrode on the lithium niobate single crystal thin sheet or the bonding medium layer;
and depositing an upper cladding layer on the bonding medium layer, the lithium niobate monocrystal flake, the slope structure and the electrode.
A third aspect of embodiments of the present application provides a method for manufacturing an optical phase modulator, including:
providing a silicon substrate;
forming a lower cladding layer on the substrate;
forming a silicon nitride film on the lower cladding layer and patterning to form a silicon nitride waveguide core;
depositing a silicon dioxide film on the substrate, the lower cladding and the silicon nitride waveguide core and flattening to form a bonding dielectric layer;
depositing and patterning a silicon nitride film on the bonding dielectric layer so as to expose part of the bonding dielectric layer above the silicon nitride waveguide core to form a bonding area;
forming a lithium niobate single crystal sheet over the bonding region;
depositing a non-stoichiometric silicon nitride film on the bonding dielectric layer and the lithium niobate single crystal thin film so that the thickness of the non-stoichiometric silicon nitride film is greater than the thickness of the lithium niobate single crystal thin film;
flattening the non-stoichiometric silicon nitride film so that the thickness of the non-stoichiometric silicon nitride film is the same as the thickness of the lithium niobate single crystal thin film;
Patterning the silicon nitride film on one side or two sides of the lithium niobate single crystal thin sheet along the length direction of the silicon nitride waveguide core to form a slope structure, so that the height of the slope structure, which is far away from one side of the lithium niobate single crystal thin sheet, is gradually decreased;
forming an electrode on the lithium niobate single crystal thin sheet or the bonding medium layer;
and depositing an upper cladding layer on the bonding medium layer, the lithium niobate monocrystal flake, the slope structure and the electrode.
A fourth aspect of the embodiments of the present application provides a method for manufacturing an optical phase modulator, including:
providing a silicon substrate;
forming a lower cladding layer on the substrate;
forming a groove on the lower cladding layer by etching;
depositing a stoichiometric silicon nitride film on the lower cladding layer, and removing the stoichiometric silicon nitride film outside the groove through planarization to form a silicon nitride waveguide core;
forming a bonding medium layer on the substrate, the lower cladding and the silicon nitride waveguide core;
forming a lithium niobate monocrystal sheet above the bonding medium layer;
depositing a non-stoichiometric silicon nitride film on the bonding dielectric layer and the lithium niobate single crystal thin film so that the thickness of the non-stoichiometric silicon nitride film is greater than the thickness of the lithium niobate single crystal thin film;
Flattening the non-stoichiometric silicon nitride film so that the thickness of the non-stoichiometric silicon nitride film is the same as the thickness of the lithium niobate single crystal thin film;
patterning the non-stoichiometric silicon nitride film on one side or two sides of the lithium niobate single crystal thin sheet along the length direction of the silicon nitride waveguide core to form a slope structure, so that the height of the slope structure on one side far away from the lithium niobate single crystal thin sheet is gradually decreased;
forming an electrode on the lithium niobate single crystal thin sheet or the bonding medium layer;
and depositing an upper cladding layer on the bonding medium layer, the lithium niobate monocrystal flake, the slope structure and the electrode.
The technical scheme of the invention has the following beneficial technical effects:
according to the optical phase modulator provided by the embodiment of the invention, the slope structures are arranged on one side or two sides of the bonded lithium niobate monocrystal flake in the length direction of the silicon nitride waveguide core, so that the insertion loss of the silicon nitride-lithium niobate phase modulator is reduced.
Drawings
Fig. 1 is a top view of an optical phase modulator according to a first embodiment of the present invention;
FIG. 2 is a side view of one of the optical phase modulators provided in FIG. 1, taken along the direction 1;
FIG. 3 is a side view of one of the optical phase modulators provided in FIG. 1 in the direction 2;
fig. 4 is a schematic diagram of an optical phase modulator according to a second embodiment of the present invention;
fig. 5 is a method for manufacturing an optical phase modulator according to a third embodiment of the present invention;
FIGS. 6 and 7 are schematic diagrams illustrating the formation of a silicon nitride waveguide core according to a third embodiment of the present invention;
fig. 8 and 9 are schematic diagrams illustrating formation of a bonding medium layer according to a third embodiment of the present invention;
FIGS. 10 and 11 are schematic views showing formation of a lithium niobate single crystal thin sheet according to a third embodiment of the present invention;
FIGS. 12 and 13 are schematic diagrams of non-stoichiometric silicon nitride film formation according to a third embodiment of the present invention;
fig. 14 and 15 are schematic views of slope structures according to a third embodiment of the present invention;
FIGS. 16 and 17 are schematic views showing electrode formation according to a third embodiment of the present invention;
FIGS. 18-20 are schematic diagrams of upper cladding formation provided in accordance with a third embodiment of the present invention;
FIG. 21 is a schematic diagram of bonding region formation according to a fourth embodiment of the present invention;
fig. 22 is a schematic view showing formation of a lithium niobate single crystal thin sheet according to the fourth embodiment of the present invention;
FIGS. 23 and 24 are schematic diagrams illustrating non-stoichiometric silicon nitride film formation according to a fourth embodiment of the present invention;
fig. 25 is a schematic view of a slope structure according to a fourth embodiment of the present invention;
FIG. 26 is a schematic diagram of a fifth embodiment of a groove forming process;
FIGS. 27 and 28 are schematic diagrams illustrating the formation of a silicon nitride waveguide core according to a fifth embodiment of the present invention;
FIG. 29 is a schematic diagram illustrating formation of a bonding medium layer according to a fifth embodiment of the present invention;
in the drawing the view of the figure,
a substrate 1; a lower cladding layer (2); a silicon nitride waveguide core 3; a bonding medium layer 4; lithium niobate single crystal thin sheet, 5; slope structure, 6; an electrode 7; an upper cladding layer 8; a transition material 9; a non-stoichiometric silicon nitride film, 10; stoichiometric silicon nitride film, 11.
Detailed Description
The objects, technical solutions and advantages of the present invention will become more apparent by the following detailed description of the present invention with reference to the accompanying drawings. It should be understood that the description is only illustrative and is not intended to limit the scope of the invention. In addition, in the following description, descriptions of well-known structures and techniques are omitted so as not to unnecessarily obscure the present invention.
The terminology used in one or more embodiments of the application is for the purpose of describing particular embodiments only and is not intended to be limiting of one or more embodiments of the application. As used in this application in one or more embodiments and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It should also be understood that the term "and/or" as used in one or more embodiments of the present application refers to and encompasses any or all possible combinations of one or more of the associated listed items.
It should be understood that, although the terms first, second, etc. may be used in one or more embodiments of the present application to describe various information, these information should not be limited to these terms. These terms are only used to distinguish one type of information from another. For example, a first may also be referred to as a second, and similarly, a second may also be referred to as a first, without departing from the scope of one or more embodiments of the present application. The word "if" as used herein may be interpreted as "responsive to a determination" depending on the context.
[ embodiment one ]
As shown in fig. 1-3, a first embodiment of the present invention provides an optical phase modulator, including: a substrate 1; a lower cladding layer 2 formed on the substrate 1; a silicon nitride waveguide core 3 formed on the lower cladding 2; the bonding medium layer 4 is covered on the substrate 1, the lower cladding layer 2 and the silicon nitride waveguide core 3; a lithium niobate single crystal slice 5 is bonded above the silicon nitride waveguide core 3 through a bonding dielectric layer 4; the first slope surface structure is formed on the bonding medium layer 4, and is positioned on one side of the lithium niobate single crystal thin sheet 5 along the length direction of the silicon nitride waveguide core 3, and the height of the first slope surface structure on one side away from the lithium niobate single crystal thin sheet 5 is gradually decreased; the second slope surface structure is formed on the bonding medium layer 4, and the second slope surface structure and the first slope surface structure are symmetrically or asymmetrically distributed on two sides of the lithium niobate single crystal thin sheet 5. An electrode 7 formed on the lithium niobate single crystal thin sheet 5 or the bonding dielectric layer 4; and an upper cladding layer 8 which covers the bonding medium layer 4, the lithium niobate monocrystal thin sheet 5, the first slope structure, the second slope structure and the electrode 7.
In the present embodiment, the substrate 1 may be, but is not limited to, a silicon substrate 1. The material of the lower cladding layer 2 may be silica, and the thickness of the lower cladding layer 2 may be 4 to 20 μm. The silicon nitride waveguide core 3 may be formed by a photolithography and etching process of a stoichiometric silicon nitride film deposited by LPCVD, or may be formed by a photonics damascene process of a stoichiometric silicon nitride film deposited by LPCVD. The silicon nitride waveguide core 3 may be a slab waveguide, a double slab waveguide, or a combination thereof, may be straight or curved, and the width and height of the silicon nitride waveguide core 3 may be determined according to optical needs. The bonding dielectric layer 4 can be inorganic or organic materials such as silicon dioxide, aluminum oxide, benzocyclobutene (BCB) and derivatives thereof, and the like, and combinations thereof; the thickness of the bonding medium layer 4 above the silicon nitride waveguide core 3 can be 10-200 nm; the flatness and roughness of the upper surface of the bonding dielectric layer 4 should satisfy bonding conditions. The lithium niobate single crystal thin sheet 5 is bonded right above the silicon nitride waveguide core 3 through the bonding dielectric layer 4. The lithium niobate single crystal flake 5 can be rectangular flake with X tangential direction, the Z crystal direction of the lithium niobate single crystal flake 5 is vertical to the length direction of the silicon nitride waveguide core 3, the Y crystal direction of the lithium niobate single crystal flake 5 is parallel to the length direction of the silicon nitride waveguide core 3, the width (3-300 μm), the thickness (100-900 nm) and the length (0.1-200 mm) of the lithium niobate single crystal flake 5 are according to optical requirements and the length of the silicon nitride waveguide core 3 The phase modulation performance requirements. And slope structures 6 are formed on the lithium niobate monocrystal thin sheet 5 along two measurements in the length direction of the silicon nitride waveguide core 3, and the heights of the slope structures 6 at the side far away from the lithium niobate gradually decrease to zero. The slope surface structure 6 comprises at least one of a first slope surface structure and a second slope surface structure, the materials of the first slope surface structure and the second slope surface structure can be the same, and the first slope surface structure and the second slope surface structure can be symmetrically arranged on two sides of the lithium niobate single crystal thin sheet 5. The slope structure 6 may be made of lithium niobate, or non-stoichiometric silicon nitride (SiN) with refractive index equal to or similar to that of lithium niobate x ) (e.g., silicon-rich silicon nitride, the refractive index of which can be adjusted by the Si content), the slope surface horizontal projection length of the slope surface structure 6 can be 5-200 μm, the height of the slope surface structure 6 can be the same as that of the lithium niobate single crystal sheet 5, and the width of the slope surface structure 6 can be the same as that of the lithium niobate single crystal sheet 5 or greater than that of a fundamental mode field propagating in a composite waveguide composed of silicon nitride and lithium niobate. Electrodes 7 are formed on the lithium niobate or on a bonding medium outside the lithium niobate on both sides of the silicon nitride waveguide core 3. The electrode 7 material can be conductive materials such as gold (Au), tungsten (W), indium Tin Oxide (ITO) and the like, the distance between the two electrodes 7 can be 4-10 mu m, the thickness of the electrode 7 can be 0.3-1 mu m, and the length direction of the electrode 7 is consistent with the length direction of the silicon nitride waveguide core 3. The upper cladding layer 8 is covered on the bonding medium layer 4, the lithium niobate monocrystal thin sheet 5, the slope structure 6, the transition material 9 and the electrode 7. The material of the upper cladding layer 8 may be silicon dioxide, and the thickness of the upper cladding layer 8 may be 2 to 20 μm.
The optical phase modulator provided by the embodiment reduces the insertion loss of the silicon nitride-lithium niobate electro-optical phase modulation device by arranging the slope structures 6 on the two sides of the lithium niobate single crystal thin sheet 5 along the length direction of the silicon nitride waveguide core 3. The ramp structure 6 is lithium niobate or non-stoichiometric silicon nitride (e.g., silicon-rich silicon nitride) having a refractive index that is the same as or similar to that of lithium niobate, reducing losses due to abrupt changes in effective refractive index and mode field mismatch. The areas outside the lithium niobate-silicon nitride heterogeneous integrated electro-optic phase modulation device are all silicon nitride waveguides, and crosstalk caused by an electric field, inherent shortages of ridge waveguides and the like are eliminated or avoided.
[ example two ]
As shown in fig. 4, a second embodiment of the present invention provides an optical phase modulator, including: a substrate 1; a lower cladding layer 2 formed on the substrate 1; a silicon nitride waveguide core 3 formed on the lower cladding 2; the bonding medium layer 4 is covered on the substrate 1, the lower cladding layer 2 and the silicon nitride waveguide core 3; a lithium niobate single crystal slice 5 is bonded above the silicon nitride waveguide core 3 through a bonding dielectric layer 4; the first slope surface structure is formed on the bonding medium layer 4, and is positioned on one side of the lithium niobate single crystal thin sheet 5 along the length direction of the silicon nitride waveguide core 3, and the height of the first slope surface structure on one side away from the lithium niobate single crystal thin sheet 5 is gradually decreased; the first slope structure is made of silicon nitride with stoichiometric ratio, the first slope structure is connected with the lithium niobate single crystal thin sheet 5 through a transition material 9, and the refractive index of the transition material 9 is between the first slope structure and the lithium niobate single crystal thin sheet 5. The second slope surface structure is formed on the bonding medium layer 4, and the second slope surface structure and the first slope surface structure are symmetrically or asymmetrically distributed on two sides of the lithium niobate single crystal thin sheet 5. An electrode 7 formed on the lithium niobate single crystal thin sheet 5 or the bonding dielectric layer 4; and an upper cladding layer 8 which covers the bonding medium layer 4, the lithium niobate monocrystal thin sheet 5, the first slope structure, the second slope structure and the electrode 7.
In the present embodiment, the substrate 1 may be, but is not limited to, a silicon substrate. The material of the lower cladding layer 2 may be silica, and the thickness of the lower cladding layer 2 may be 4 to 20 μm. The silicon nitride waveguide core 3 may be formed by a photolithography and etching process of a stoichiometric silicon nitride film deposited by LPCVD, or may be formed by a photonics damascene process of a stoichiometric silicon nitride film deposited by LPCVD. The silicon nitride waveguide core 3 may be a slab waveguide, a double slab waveguide, or a combination thereof, may be straight or curved, and the width and height of the silicon nitride waveguide core 3 may be determined according to optical needs. The bonding dielectric layer 4 can be inorganic or organic materials such as silicon dioxide, aluminum oxide, benzocyclobutene (BCB) and derivatives thereof, and the like, and combinations thereof; the thickness of the bonding medium layer 4 above the silicon nitride waveguide core 3 can be 10-200 nm; the flatness and roughness of the upper surface of the bonding dielectric layer 4 should satisfy bonding conditions. The lithium niobate single crystal thin sheet 5 is bonded right above the silicon nitride waveguide core 3 through the bonding dielectric layer 4. The lithium niobate single crystal thin sheet 5 can be an X tangential rectangular thin sheet, the Z crystal direction of the lithium niobate single crystal thin sheet 5 is vertical to the length direction of the silicon nitride waveguide core 3, the Y crystal direction of the lithium niobate single crystal thin sheet 5 is parallel to the length direction of the silicon nitride waveguide core 3, and the width (3-300 μm), the thickness (100-900 nm) and the length (0.1-200 mm) of the lithium niobate single crystal thin sheet 5 are determined according to the optical requirement and the phase modulation performance requirement. And slope structures 6 are formed on the lithium niobate monocrystal thin sheet 5 along two measurements in the length direction of the silicon nitride waveguide core 3, and the heights of the slope structures 6 at the side far away from the lithium niobate gradually decrease to zero. The slope surface structure 6 comprises a first slope surface structure and a second slope surface structure, the materials of the first slope surface structure and the second slope surface structure can be the same, and the first slope surface structure and the second slope surface structure can be symmetrically arranged on two sides of the lithium niobate single crystal thin sheet 5.
The material of the ramp structure 6 may be stoichiometric silicon nitride, with the transition between lithium niobate and the ramp structure 6 being via a transition material 9. The length of the horizontal projection of the slope surface structure 6 can be 5-200 mu m, the height of the slope surface structure 6 can be the same as the height of the lithium niobate single crystal thin sheet 5, and the width of the slope surface structure 6 is the same as the width of the lithium niobate single crystal thin sheet 5 or is larger than the width of a fundamental mode field propagated in a composite waveguide formed by silicon nitride and lithium niobate; the transition material 9 may be a material having a refractive index between that of lithium niobate and silicon nitride in stoichiometric ratio, such as silicon-rich silicon nitride; the transition material 9 may have the same height as the lithium niobate single crystal thin sheet 5, the width of the transition material 9 may be the same as the width of the ramp structure 6, or the transition from the width of the lithium niobate single crystal thin sheet 5 to the width of the ramp structure 6. Electrodes 7 are formed on the lithium niobate or on a bonding medium outside the lithium niobate on both sides of the silicon nitride waveguide core 3. The electrode 7 material can be conductive materials such as gold (Au), tungsten (W), indium Tin Oxide (ITO) and the like, the distance between the two electrodes 7 can be 4-10 mu m, the thickness of the electrode 7 can be 0.3-1 mu m, and the length direction of the electrode 7 is consistent with the length direction of the silicon nitride waveguide core 3. The upper cladding layer 8 is covered on the bonding medium layer 4, the lithium niobate monocrystal thin sheet 5, the slope structure 6, the transition material 9 and the electrode 7. The material of the upper cladding layer 8 may be silicon dioxide, and the thickness of the upper cladding layer 8 may be 2 to 20 μm.
The optical phase modulator provided by the embodiment reduces the insertion loss of the silicon nitride-lithium niobate electro-optical phase modulation device by arranging the slope structures 6 on the two sides of the lithium niobate single crystal thin sheet 5 along the length direction of the silicon nitride waveguide core 3. The slope surface structure 6 adopts a refractive index transition mode, so that loss caused by abrupt change of effective refractive index and mismatching of mode fields is reduced. The areas outside the lithium niobate-silicon nitride heterogeneous integrated electro-optic phase modulation device are all silicon waveguides, and crosstalk caused by an electric field, inherent shortages of ridge waveguides and the like are eliminated or avoided.
[ example III ]
As shown in fig. 5, a third embodiment of the present invention provides a method for manufacturing an optical phase modulator, including:
step S101: providing a silicon substrate;
step S102: forming a lower cladding layer on a substrate;
step S103: forming a silicon nitride film on the lower cladding layer and patterning to form a silicon nitride waveguide core;
step S104: forming a bonding medium layer on the substrate, the lower cladding and the silicon nitride waveguide core;
step S105: forming a lithium niobate monocrystal sheet above the bonding medium layer;
step S106: depositing a non-stoichiometric silicon nitride film on the bonding dielectric layer and the lithium niobate single crystal thin sheet so that the thickness of the non-stoichiometric silicon nitride film is larger than that of the lithium niobate single crystal thin sheet;
Step S107: flattening the non-stoichiometric silicon nitride film so that the thickness of the non-stoichiometric silicon nitride film is the same as the thickness of the lithium niobate single crystal thin film;
step S108: patterning the non-stoichiometric silicon nitride film on one side or two sides of the lithium niobate single crystal thin sheet along the length direction of the silicon nitride waveguide core to form a slope structure, so that the height of the slope structure on one side far away from the lithium niobate single crystal thin sheet is gradually decreased;
step S109: forming an electrode on the lithium niobate single crystal thin sheet or the bonding medium layer;
step S110: and depositing an upper cladding layer on the bonding dielectric layer, the lithium niobate monocrystal flake, the slope structure and the electrode.
Specifically, as shown in FIGS. 6 and 7, silicon dioxide is grown on a silicon substrate by thermal oxidation to a thickness of 4 to 20 μm as a lower cladding layer of an optical waveguide; a silicon nitride film with stoichiometric ratio is deposited on a silicon dioxide lower cladding layer through LPCVD, a silicon nitride waveguide core is formed after patterning, and the width and the height of the silicon nitride waveguide core are determined according to optical requirements.
As shown in fig. 8 and 9, a silicon dioxide film is deposited on the surface of the current substrate, and the thickness of the silicon dioxide film is larger than the height of the silicon nitride waveguide core. And carrying out chemical mechanical planarization on the silicon dioxide film to ensure that the thickness of the silicon dioxide film above the silicon nitride is 10-200 nm, and the flatness and roughness of the silicon dioxide film meet the bonding conditions, thereby forming a bonding dielectric layer. The bonding dielectric layer may also be replaced by a coated BCB film, or a stack of planarized silicon dioxide film and aluminum oxide film.
As shown in fig. 10 and 11, the surface of the bonding dielectric layer and the surface of the bonding surface of the lithium niobate single crystal wafer are subjected to plasma treatment, and after the substrate and the lithium niobate single crystal wafer are prealigned, a pressure and thermal annealing process are applied to bond the lithium niobate single crystal wafer directly above the silicon nitride waveguide core. The lithium niobate single crystal flake preferably has rectangular flake of X tangential, Z crystal direction of the lithium niobate single crystal flake is perpendicular to the length direction of the silicon nitride waveguide core, Y crystal direction of the lithium niobate single crystal flake is parallel to the length direction of the silicon nitride waveguide core, width (3-300 μm), thickness (100-900 nm) and length (0.1-200 mm) of the lithium niobate single crystal flake depend on optical requirement and phase modulation performance requirement; the surface material of the bonding dielectric layer is a silicon dioxide or aluminum oxide film, and the surface of the bonding side of the lithium niobate monocrystal thin sheet can be deposited with a silicon dioxide or aluminum oxide film with the thickness of 0-20 nm so as to realize good bonding.
As shown in fig. 12, a lower temperature deposition process (e.g., PECVD, etc.) is used to deposit non-stoichiometric silicon nitride (SiN) x ) Film 10 having a thickness greater than that of a single crystal thin sheet of lithium niobate, siN x Preferably silicon-rich silicon nitride (Si-SiN-rich) x ) Regulating Si content to enable SiN x Refractive index of film The refractive index of the lithium niobate single crystal thin slice is the same as or similar to that of the lithium niobate single crystal thin slice. As shown in fig. 13, the SiNx film was planarized to SiN x The thickness of the film is the same as that of the lithium niobate single crystal thin sheet.
As shown in fig. 14 and 15, siN is deposited on one or both sides of the lithium niobate single crystal thin sheet 5 in the longitudinal direction of the silicon nitride waveguide core 3 by a gray scale lithography and etching process x The film is formed with a ramp structure 6. The height of the slope surface structure 6 gradually becomes zero at the side far away from the lithium niobate single crystal thin sheet 5, the projection length of the slope surface structure 6 in the horizontal direction is preferably 5-200 μm, and the width of the slope surface structure 6 is the same as the width of the lithium niobate single crystal thin sheet 5 or is larger than the width of a fundamental mode field propagated in a composite waveguide composed of silicon nitride and lithium niobate.
As shown in fig. 16 and 17, two electrodes 7 are formed on the upper side of the lithium niobate single crystal thin sheet 5 or on the bonding medium outside the lithium niobate single crystal thin sheet 5 by a lift-off process, the two electrodes 7 are respectively positioned at two sides of the silicon nitride waveguide core 3, the length direction of the electrodes 7 is consistent with the length direction of the silicon nitride waveguide core 3, the distance between the two electrodes 7 is preferably 4-10 μm, the material of the electrodes 7 can be conductive materials such as gold (Au), tungsten (W) and Indium Tin Oxide (ITO), and the thickness of the electrodes 7 is preferably 0.3-1 μm.
As shown in FIGS. 18-20, siO is deposited 2 Film as upper cladding layer 8, siO 2 The thickness of the upper cladding layer 8 is preferably 2 to 10. Mu.m. Optionally, the upper cladding layer 8 is subjected to a planarization process.
According to the preparation method of the optical phase modulator, the slope structures 6 are arranged on the two sides of the lithium niobate single crystal thin sheet 5 along the length direction of the silicon nitride waveguide core 3, so that the insertion loss of the silicon nitride-lithium niobate electro-optical phase modulator is reduced. The slope structure 6 adopts silicon-rich silicon nitride with the refractive index identical to or similar to that of lithium niobate, so that loss caused by abrupt change of effective refractive index and mismatching of mode fields is reduced. The areas outside the lithium niobate-silicon nitride heterogeneous integrated electro-optic phase modulation device are all silicon nitride waveguides, and crosstalk caused by an electric field, inherent shortages of ridge waveguides and the like are eliminated or avoided.
[ example IV ]
The fourth embodiment of the invention provides a method for preparing an optical phase modulator, which comprises the following steps: providing a silicon substrate 1; forming a lower cladding layer 2 on a substrate 1; forming a silicon nitride film on the lower cladding layer 2 and patterning to form a silicon nitride waveguide core 3; depositing a silicon dioxide film on the substrate 1, the lower cladding 2 and the silicon nitride waveguide core 3 and flattening to form a bonding dielectric layer 4; depositing and patterning a silicon nitride film on the bonding dielectric layer 4 so as to expose part of the bonding dielectric layer 4 above the silicon nitride waveguide core 3 to form a bonding area; forming a lithium niobate single crystal thin sheet 5 over the bonding region; depositing a non-stoichiometric silicon nitride film 10 on the bonding dielectric layer 4 and the lithium niobate single crystal thin sheet 5 so that the thickness of the non-stoichiometric silicon nitride film 10 is greater than the thickness of the lithium niobate single crystal thin sheet 5; flattening the non-stoichiometric silicon nitride film 10 so that the thickness of the non-stoichiometric silicon nitride film 10 is the same as the thickness of the lithium niobate single crystal thin sheet 5; patterning the silicon nitride film on one side or two sides of the lithium niobate single crystal thin sheet 5 along the length direction of the silicon nitride waveguide core 3 to form a slope structure 6, so that the height of the slope structure 6 on one side far away from the lithium niobate single crystal thin sheet 5 is gradually decreased; forming an electrode 7 on the lithium niobate single crystal thin sheet 5 or the bonding medium layer 4; an upper cladding layer 8 is deposited over the bonding dielectric layer 4, the lithium niobate single crystal thin sheet 5, the slope structure 6 and the electrode 7.
Specifically, a silicon substrate 1 with a silicon oxide lower cladding layer 2, a silicon nitride waveguide core 3, and a bonding dielectric layer 4 is formed. Wherein the bonding dielectric layer 4 is made of SiO 2 。
As shown in fig. 21, a silicon nitride film is deposited on the bonding dielectric layer 4, and the silicon nitride film is thinned by photolithography, wet etching, or photolithography, dry etching, and wet etching, so that a portion of the bonding dielectric layer 4 above the silicon nitride waveguide core 3 is exposed to form a bonding region, and meanwhile, the surface roughness and flatness of the bonding dielectric layer 4 of the bonding region are ensured to still meet bonding requirements. The silicon nitride film deposited on the bonding dielectric layer 4 is a stoichiometric silicon nitride (Si) film deposited by LPCVD 3 N 4 ) The thickness of the thin film of silicon nitride is the same as that of the lithium niobate single crystal thin sheet 5 to be bonded. The length and width of the bonding region is slightly larger than (e.g. 1-20 μm) the lithium niobate single to be bondedThe length and width of the wafer 5.
As shown in fig. 22, the surface of the bonding dielectric layer 4 and the surface of the bonding surface of the lithium niobate single crystal thin sheet 5 are subjected to plasma treatment, and after the substrate 1 and the lithium niobate single crystal thin sheet 5 are pre-aligned, a pressure and a thermal annealing process are applied to bond the lithium niobate single crystal thin sheet 5 directly above the silicon nitride waveguide core 3 through the bonding dielectric layer 4.
As shown in fig. 23, a lower temperature deposition process (e.g., PECVD, etc.) is used to deposit non-stoichiometric silicon nitride (SiN) x ) Film of thickness greater than that of lithium niobate single crystal thin sheet 5, siN x Preferably silicon-rich silicon nitride (Si-SiN-rich) x ) Regulating Si content to enable SiN x The refractive index of the film is between that of LPCVD silicon nitride and that of the lithium niobate single crystal thin sheet 5. As shown in fig. 24, for SiN x Flattening the film to enable SiN x The thickness of the film is the same as that of the lithium niobate single crystal thin sheet 5, siN x Filling the gap between the LPCVD silicon nitride film on the bonding dielectric layer 4 and the lithium niobate single crystal thin sheet 5.
As shown in fig. 25, a slope structure 6 is formed on the LPCVD silicon nitride film on one side or both sides of the lithium niobate single crystal thin film 5 in the length direction of the silicon nitride waveguide core 3 by a gray scale lithography and etching process. The height of the slope surface structure 6 gradually becomes zero at the side far away from the lithium niobate single crystal thin sheet 5, the projection length of the slope surface structure 6 in the horizontal direction is preferably 5-200 μm, and the width of the slope surface structure 6 is determined according to the distribution of the light film field propagated therein.
According to the preparation method of the optical phase modulator, the slope structures 6 are arranged on the two sides of the lithium niobate single crystal thin sheet 5 along the length direction of the silicon nitride waveguide core 3, so that the insertion loss of the silicon nitride-lithium niobate electro-optical phase modulator is reduced. The slope structure 6 adopts a mode of low-loss stoichiometric silicon nitride with the same refractive index as that of lithium niobate and refractive index transition, so that loss caused by abrupt change of effective refractive index and mismatching of mode field is reduced. The areas outside the lithium niobate-silicon nitride heterogeneous integrated electro-optic phase modulation device are all silicon nitride waveguides, and crosstalk caused by an electric field, inherent shortages of ridge waveguides and the like are eliminated or avoided.
[ example five ]
The fifth embodiment of the invention provides a method for preparing an optical phase modulator, which comprises the following steps: providing a silicon substrate 1; forming a lower cladding layer 2 on a substrate 1; forming a groove on the lower cladding layer 2 by photoetching and etching; depositing a stoichiometric silicon nitride film 11 on the lower cladding layer 2, and removing the stoichiometric silicon nitride film 11 outside the groove through planarization to form a silicon nitride waveguide core 3; forming a bonding medium layer 4 on the substrate 1, the lower cladding 2 and the silicon nitride waveguide core 3; forming a lithium niobate single crystal sheet 5 above the bonding dielectric layer 4; depositing a non-stoichiometric silicon nitride film 10 on the bonding dielectric layer 4 and the lithium niobate single crystal thin sheet 5 so that the thickness of the non-stoichiometric silicon nitride film 10 is greater than the thickness of the lithium niobate single crystal thin sheet 5; flattening the non-stoichiometric silicon nitride film 10 so that the thickness of the non-stoichiometric silicon nitride film 10 is the same as the thickness of the lithium niobate single crystal thin sheet 5; patterning the non-stoichiometric silicon nitride film 10 on one side or two sides of the lithium niobate single crystal thin sheet 5 along the length direction of the silicon nitride waveguide core 3 to form a slope structure 6, so that the height of the slope structure 6 on the side far away from the lithium niobate single crystal thin sheet 5 is gradually decreased; forming an electrode 7 on the lithium niobate single crystal thin sheet 5 or the bonding medium layer 4; an upper cladding layer 8 is deposited over the bonding dielectric layer 4, the lithium niobate single crystal thin sheet 5, the slope structure 6 and the electrode 7.
In this embodiment, the silicon nitride waveguide core 3 is prepared based on a photonic damascene process. Specifically, as shown in fig. 26, a silicon dioxide lower cladding layer 2 is wet-thermally grown on a silicon substrate 1; grooves are formed on silicon dioxide through photoetching and etching processes, and the side walls of the grooves are smooth through high-temperature thermal annealing.
As shown in fig. 27, a stoichiometric silicon nitride film 11 (Si 3 N 4 Waveguide core layer) as shown in fig. 28, the silicon nitride waveguide core 3 is formed by removing the silicon nitride film outside the grooves by planarization process.
As shown in fig. 29, a material such as silicon dioxide, aluminum oxide, or a laminate thereof is deposited as the bonding dielectric layer 4.
According to the preparation method of the optical phase modulator, the slope structures 6 are arranged on the two sides of the lithium niobate single crystal thin sheet 5 along the length direction of the silicon nitride waveguide core 3, so that the insertion loss of the silicon nitride-lithium niobate electro-optical phase modulator is reduced. The slope structure 6 adopts silicon-rich silicon nitride with the refractive index identical to or similar to that of lithium niobate, so that loss caused by abrupt change of effective refractive index and mismatching of mode fields is reduced. The areas outside the lithium niobate-silicon nitride heterogeneous integrated electro-optic phase modulation device are all silicon nitride waveguides, and crosstalk caused by an electric field, inherent shortages of ridge waveguides and the like are eliminated or avoided.
In addition, the optical phase modulator and the preparation method of the optical phase modulator are also suitable for structures in which the lithium niobate single crystal thin sheet is Z tangential, and two electrodes are respectively positioned below the silicon nitride waveguide core and above the lithium niobate single crystal thin sheet.
It should be noted that, for the sake of simplicity of description, the foregoing method embodiments are all expressed as a series of combinations of actions, but it should be understood by those skilled in the art that the present application is not limited by the order of actions described, as some steps may be performed in other order or simultaneously in accordance with the present application. Further, those skilled in the art will also appreciate that the embodiments described in the specification are all preferred embodiments, and that the acts and modules referred to are not necessarily all necessary for the present application.
In the foregoing embodiments, the descriptions of the embodiments are emphasized, and for parts of one embodiment that are not described in detail, reference may be made to the related descriptions of other embodiments.
The above-disclosed preferred embodiments of the present application are provided only as an aid to the elucidation of the present application. Alternative embodiments are not intended to be exhaustive or to limit the invention to the precise forms disclosed. Obviously, many modifications and variations are possible in light of the teaching of this application. The embodiments were chosen and described in order to best explain the principles of the invention and the practical application, to thereby enable others skilled in the art to best understand and utilize the invention. This application is to be limited only by the claims and the full scope and equivalents thereof.
Claims (13)
1. An optical phase modulator, comprising:
a substrate (1);
a lower cladding layer (2) formed on the substrate (1);
a silicon nitride waveguide core (3) formed on the lower cladding layer (2);
a bonding medium layer (4) which covers the substrate (1), the lower cladding (2) and the silicon nitride waveguide core (3);
a lithium niobate single crystal wafer (5) bonded above the silicon nitride waveguide core (3) through the bonding dielectric layer (4);
the first slope structure is formed on the bonding medium layer (4), the first slope structure is positioned on one side of the lithium niobate single crystal thin sheet (5) along the length direction of the silicon nitride waveguide core (3), and the height of the first slope structure on one side away from the lithium niobate single crystal thin sheet (5) is gradually decreased;
an electrode (7) formed on the lithium niobate single crystal thin sheet (5) or the bonding dielectric layer (4);
and the upper cladding layer (8) is covered on the bonding medium layer (4), the lithium niobate monocrystal thin sheet (5), the first slope structure and the electrode (7).
2. An optical phase modulator according to claim 1, characterized in that for light propagating in the length direction of the silicon nitride waveguide core (3), the refractive index of the first slope structure is the same as or similar to that of the lithium niobate single crystal sheet (5), the height of the top surface of the first slope structure is the same as that of the lithium niobate single crystal sheet (5), and the width of the first slope structure is the same as that of the lithium niobate single crystal sheet (5) or greater than that of the fundamental mode field propagating in a composite waveguide composed of silicon nitride and lithium niobate.
3. An optical phase modulator according to claim 1, wherein the material of the first slope structure is non-stoichiometric silicon nitride, and the side of the first slope structure near the lithium niobate single crystal thin sheet (5) is connected with the lithium niobate single crystal thin sheet (5).
4. An optical phase modulator according to claim 1 wherein the first slope structure is made of lithium niobate or non-stoichiometric silicon nitride.
5. An optical phase modulator according to claim 1, characterized in that the material of the first slope structure is stoichiometric silicon nitride, the first slope structure and the lithium niobate single crystal thin sheet (5) are connected by a transition material (9), and for light propagating in the length direction of the silicon nitride waveguide core (3), the refractive index of the transition material (9) is between the first slope structure and the lithium niobate single crystal thin sheet (5).
6. An optical phase modulator according to claim 1, characterized in that the bonding dielectric layer (4) is silicon dioxide, and the side of the lithium niobate single crystal thin sheet (5) close to the bonding dielectric layer (4) can be deposited with a silicon dioxide or aluminum oxide thin film.
7. An optical phase modulator according to claim 1, characterized in that the bonding medium layer (4) is any one of the following: a coated BCB film, a planarized silicon dioxide film, and a laminate of a planarized silicon dioxide film and an aluminum oxide film.
8. An optical phase modulator according to claim 1, characterized in that the number of electrodes (7) is two, two of the electrodes (7) being located on each side of the silicon nitride waveguide core (3).
9. An optical phase modulator according to claim 1, wherein the lithium niobate single crystal sheet is Z-tangential, and the two electrodes are located below the silicon nitride waveguide core and above the lithium niobate single crystal sheet, respectively.
10. An optical phase modulator according to any one of claims 1-9, further comprising:
the second slope surface structure is formed on the bonding medium layer (4), and the second slope surface structure and the first slope surface structure are positioned on two sides of the lithium niobate single crystal thin sheet (5) and are symmetrically or asymmetrically distributed.
11. A method of making an optical phase modulator comprising:
providing a silicon substrate;
forming a lower cladding layer on the substrate;
Forming a silicon nitride film on the lower cladding layer and patterning to form a silicon nitride waveguide core;
forming a bonding medium layer on the substrate, the lower cladding and the silicon nitride waveguide core;
forming a lithium niobate monocrystal sheet above the bonding medium layer;
depositing a non-stoichiometric silicon nitride film on the bonding dielectric layer and the lithium niobate single crystal thin film so that the thickness of the non-stoichiometric silicon nitride film is greater than the thickness of the lithium niobate single crystal thin film;
flattening the non-stoichiometric silicon nitride film so that the thickness of the non-stoichiometric silicon nitride film is the same as the thickness of the lithium niobate single crystal thin film;
patterning the non-stoichiometric silicon nitride film on one side or two sides of the lithium niobate single crystal thin sheet along the length direction of the silicon nitride waveguide core to form a slope structure, so that the height of the slope structure on one side far away from the lithium niobate single crystal thin sheet is gradually decreased;
forming an electrode on the lithium niobate single crystal thin sheet or the bonding medium layer;
and depositing an upper cladding layer on the bonding medium layer, the lithium niobate monocrystal flake, the slope structure and the electrode.
12. A method of making an optical phase modulator comprising:
Providing a silicon substrate;
forming a lower cladding layer on the substrate;
forming a silicon nitride film on the lower cladding layer and patterning to form a silicon nitride waveguide core;
depositing a silicon dioxide film on the substrate, the lower cladding and the silicon nitride waveguide core and flattening to form a bonding dielectric layer;
depositing and patterning a silicon nitride film on the bonding dielectric layer so as to expose part of the bonding dielectric layer above the silicon nitride waveguide core to form a bonding area;
forming a lithium niobate single crystal sheet over the bonding region;
depositing a non-stoichiometric silicon nitride film on the bonding dielectric layer and the lithium niobate single crystal thin film so that the thickness of the non-stoichiometric silicon nitride film is greater than the thickness of the lithium niobate single crystal thin film;
flattening the non-stoichiometric silicon nitride film so that the thickness of the non-stoichiometric silicon nitride film is the same as the thickness of the lithium niobate single crystal thin film;
patterning the silicon nitride film on one side or two sides of the lithium niobate single crystal thin sheet along the length direction of the silicon nitride waveguide core to form a slope structure, so that the height of the slope structure, which is far away from one side of the lithium niobate single crystal thin sheet, is gradually decreased;
Forming an electrode on the lithium niobate single crystal thin sheet or the bonding medium layer;
and depositing an upper cladding layer on the bonding medium layer, the lithium niobate monocrystal flake, the slope structure and the electrode.
13. A method of making an optical phase modulator comprising:
providing a silicon substrate;
forming a lower cladding layer on the substrate;
forming a groove on the lower cladding layer by etching;
depositing a stoichiometric silicon nitride film on the lower cladding layer, and removing the stoichiometric silicon nitride film outside the groove through planarization to form a silicon nitride waveguide core;
forming a bonding medium layer on the substrate, the lower cladding and the silicon nitride waveguide core;
forming a lithium niobate monocrystal sheet above the bonding medium layer;
depositing a non-stoichiometric silicon nitride film on the bonding dielectric layer and the lithium niobate single crystal thin film so that the thickness of the non-stoichiometric silicon nitride film is greater than the thickness of the lithium niobate single crystal thin film;
flattening the non-stoichiometric silicon nitride film so that the thickness of the non-stoichiometric silicon nitride film is the same as the thickness of the lithium niobate single crystal thin film;
Patterning the non-stoichiometric silicon nitride film on one side or two sides of the lithium niobate single crystal thin sheet along the length direction of the silicon nitride waveguide core to form a slope structure, so that the height of the slope structure on one side far away from the lithium niobate single crystal thin sheet is gradually decreased;
forming an electrode on the lithium niobate single crystal thin sheet or the bonding medium layer;
and depositing an upper cladding layer on the bonding medium layer, the lithium niobate monocrystal flake, the slope structure and the electrode.
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