CN115167015A - Waveguide modulator and waveguide modulator manufacturing method - Google Patents
Waveguide modulator and waveguide modulator manufacturing method Download PDFInfo
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- CN115167015A CN115167015A CN202210793132.9A CN202210793132A CN115167015A CN 115167015 A CN115167015 A CN 115167015A CN 202210793132 A CN202210793132 A CN 202210793132A CN 115167015 A CN115167015 A CN 115167015A
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- 238000004519 manufacturing process Methods 0.000 title claims description 14
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- 238000005137 deposition process Methods 0.000 claims description 3
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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
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- 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
- G02B6/12002—Three-dimensional structures
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- 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
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- 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
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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
- G02F1/015—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 semiconductor elements having potential barriers, e.g. having a PN or PIN junction
- G02F1/025—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 semiconductor elements having potential barriers, e.g. having a PN or PIN junction in an optical waveguide structure
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- 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
- G02B2006/12035—Materials
- G02B2006/1204—Lithium niobate (LiNbO3)
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- 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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- 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
- G02B2006/12166—Manufacturing methods
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Abstract
The invention provides a waveguide modulator and a waveguide modulator preparation method, wherein the waveguide modulator comprises: the first waveguide layer, the second waveguide layer and the lithium niobate layer; and the lithium niobate layer is bonded and arranged between the first waveguide layer and the second waveguide layer. The waveguide modulator provided by the invention has the optical field phase regulation and control performance of low half-wave voltage-length product, high modulation rate and low insertion loss.
Description
Technical Field
The invention relates to the technical field of photoelectric information, in particular to a waveguide modulator and a preparation method of the waveguide modulator.
Background
The waveguide modulator is a key device in a photoelectric information processing system, and has wide application prospects in the fields of optical communication, optical calculation, optical quantum and the like. The function realized by the device is to load information on multiple degrees of freedom of photons, such as amplitude, phase, polarization, spatial mode and the like.
It is known in the related art that although the integrated waveguide modulator can increase the refractive index difference, enhance the optical field limitation, and achieve high-speed modulation of hundreds of GHz, the half-wave voltage-length product is still in the order of several V · cm. Therefore, it is still a very difficult problem for scenarios that require a large number of modulators to be integrated on-chip.
Disclosure of Invention
The invention provides a waveguide modulator and a waveguide modulator preparation method, which realize that the waveguide modulator can have the optical field phase regulation and control performance of low half-wave voltage-length product, high modulation rate and low insertion loss.
The present invention provides a waveguide modulator, comprising: the first waveguide layer, the second waveguide layer and the lithium niobate layer; and the lithium niobate layer is bonded and arranged between the first waveguide layer and the second waveguide layer.
According to a waveguide modulator provided by the present invention, the first waveguide layer and the second waveguide layer comprise a semiconductor material.
According to a waveguide modulator provided by the present invention, the first waveguide layer and the second waveguide layer include a silicon material or a germanium material.
According to the waveguide modulator provided by the invention, the first waveguide layer comprises a P-type doped silicon material, and the second waveguide layer comprises an N-type doped silicon material; alternatively, the first waveguide layer comprises an N-type doped silicon material and the second waveguide layer comprises a P-type doped silicon material.
According to the waveguide modulator provided by the invention, the layer thickness of the lithium niobate layer is 50 nm-300 nm.
The invention also provides a preparation method of the waveguide modulator, which is applied to the preparation of the waveguide modulator and comprises the following steps: obtaining a first waveguide layer, and transferring a lithium niobate layer to the first waveguide layer based on a bonding mode; forming a second waveguide layer on the other side, opposite to the first waveguide layer, of the lithium niobate layer in a deposition mode or a bonding mode; and respectively carrying out metal electrode deposition treatment on the first waveguide layer and the second waveguide layer to obtain the waveguide modulator.
According to the preparation method of the waveguide modulator provided by the invention, after the lithium niobate layer is transferred to the first waveguide layer based on the bonding mode, the method further comprises the following steps: and thinning the lithium niobate layer to ensure that the thickness of the thinned lithium niobate layer is 50 nm-300 nm.
According to the preparation method of the waveguide modulator provided by the invention, the first waveguide layer comprises a P-type doped silicon material, and the second waveguide layer comprises an N-type doped silicon material; the first waveguide layer is prepared in the following way: obtaining a first silicon substrate, and carrying out P-type doping treatment on the first silicon substrate to obtain a first waveguide layer; the forming of the second waveguide layer by the deposition method or the bonding method specifically includes: forming a second silicon substrate in a deposition mode or a bonding mode; and carrying out N-type doping treatment on the second silicon substrate to obtain the second waveguide layer.
According to the preparation method of the waveguide modulator provided by the invention, the first waveguide layer comprises an N-type doped silicon material, and the second waveguide layer comprises a P-type doped silicon material; the first waveguide layer is prepared in the following way: obtaining a first silicon substrate, and carrying out N-type doping treatment on the first silicon substrate to obtain a first waveguide layer; the forming of the second waveguide layer through a deposition method or a bonding method specifically includes: forming a second silicon substrate in a deposition mode or a bonding mode; and carrying out P-type doping treatment on the second silicon substrate to obtain the second waveguide layer.
The invention also provides a preparation method of the waveguide modulator, which is applied to the preparation of the waveguide modulator and comprises the following steps: obtaining a lithium niobate layer; and respectively forming a first waveguide layer and a second waveguide layer on two sides of the lithium niobate layer based on deposition treatment.
According to the preparation method of the waveguide modulator provided by the invention, the step of obtaining the lithium niobate layer specifically comprises the following steps: obtaining a wafer plane; and processing the wafer plane based on an etching mode to obtain the lithium niobate layer with the layer thickness of 50 nm-300 nm.
According to the preparation method of the waveguide modulator provided by the invention, based on deposition treatment, a first waveguide layer and a second waveguide layer are respectively formed on two sides of the lithium niobate layer, and the preparation method specifically comprises the following steps: respectively forming an initial first waveguide layer and an initial second waveguide layer on two sides of the lithium niobate layer based on amorphous silicon deposition treatment; carrying out P-type doping treatment on the initial first waveguide layer and carrying out N-type doping treatment on the initial second waveguide layer; or, carrying out N-type doping treatment on the initial first waveguide layer and carrying out P-type doping treatment on the initial second waveguide layer so as to respectively form a first waveguide layer and a second waveguide layer on two sides of the lithium niobate layer.
The waveguide modulator comprises a first waveguide layer, a second waveguide layer and a lithium niobate layer, wherein the lithium niobate layer is bonded between the first waveguide layer and the second waveguide layer. By constructing the slit waveguide modulator structure of the first waveguide layer-the lithium niobate layer-the second waveguide layer, the waveguide modulator can be ensured to have the optical field phase regulation and control performance of low half-wave voltage-length product, high modulation rate and low insertion loss.
Drawings
In order to more clearly illustrate the technical solutions of the present invention or the prior art, the drawings needed for the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and those skilled in the art can also obtain other drawings according to the drawings without creative efforts.
FIG. 1 is a schematic diagram of a waveguide modulator according to the present invention;
FIG. 2 is a schematic cross-sectional view of a waveguide modulator according to the present invention;
FIG. 3 is a schematic diagram showing the relationship between the half-wave voltage-length product and the thickness of a lithium niobate layer obtained from a waveguide modulator according to the present invention;
FIG. 4 is a schematic diagram showing the relationship between the phase modulation amount and the voltage of the waveguide modulator having a 40nm layer thickness of the lithium niobate layer provided by the present invention;
FIG. 5 is a schematic diagram showing the relationship between the phase modulation amount and the voltage of the waveguide modulator having the layer thickness of the lithium niobate layer of the present invention of 80 nm;
FIG. 6 is a schematic flow chart of a method for fabricating a waveguide modulator according to the present invention;
FIG. 7 is a flow chart of a process for making a waveguide modulator provided by the present invention;
FIG. 8 is a second schematic flow chart of a method for manufacturing a waveguide modulator according to the present invention;
FIG. 9 is a schematic diagram of an intensity modulator based on a waveguide modulator provided by the present invention;
fig. 10 is a schematic structural diagram of a directional coupler obtained based on the waveguide modulator provided by the present invention;
reference numerals:
a waveguide modulator: 10; the first waveguide layer: 101, a first electrode and a second electrode;
a second waveguide layer: 102, and (b); lithium niobate layer: 103.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings, and it is obvious that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In the drawings, the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The described embodiments are only some, but not all embodiments of the invention. The embodiments described below with reference to the accompanying drawings are illustrative and intended to explain the present invention and should not be construed as limiting the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention. Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.
In the description of the present embodiment, it is to be understood that the terms "center", "longitudinal", "lateral", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience of description of the present embodiment and for simplicity of description, but do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore, should not be construed as limiting the scope of protection of the present embodiment. It should be noted that: the relative arrangement of the components, the numerical expressions, and numerical values set forth in these embodiments do not limit the scope of the present invention unless specifically stated otherwise.
The waveguide modulator provided by the invention can construct a slit waveguide modulator structure consisting of the first waveguide layer, the lithium niobate layer and the second waveguide layer, thereby ensuring that the waveguide modulator has optical field phase regulation and control performances of low half-wave voltage-length product, high modulation rate and low insertion loss.
Fig. 1 is a schematic structural view of a waveguide modulator provided by the present invention, and fig. 2 is a schematic structural cross-sectional view of the waveguide modulator provided by the present invention. The waveguide modulator provided by the present invention is described below with reference to fig. 1-2.
In an exemplary embodiment of the present invention, as can be seen in conjunction with fig. 1 and 2, the waveguide modulator 10 may include a first waveguide layer 101, a second waveguide layer 102, and a lithium niobate layer 103. The lithium niobate layer 103 is bonded between the first waveguide layer 101 and the second waveguide layer 102. It is understood that the waveguide modulator 10 may be a slot waveguide modulator structure consisting of a first waveguide layer 101-lithium niobate layer 103-second waveguide layer 102.
It should be noted that the lithium niobate layer 103 may form a slit mode, wherein the optical field may be mainly concentrated to have a high electro-optic modulation coefficient (e.g., electro-optic modulation coefficient r) for the mode field distribution of the waveguide modulator 10 33 30 pm/V) in the lithium niobate layer 103, the waveguide modulator 10 can have a high modulation efficiency.
The waveguide modulator 10 provided by the present invention is composed of a first waveguide layer 101, a second waveguide layer 102, and a lithium niobate layer 103, and the lithium niobate layer 103 is bonded and disposed between the first waveguide layer 101 and the second waveguide layer 102. By constructing the slot waveguide modulator structure of the first waveguide layer 101, the lithium niobate layer 103 and the second waveguide layer 102, the waveguide modulator 10 can be ensured to have optical field phase regulation performance with low half-wave voltage-length product, high modulation rate and low insertion loss.
In an exemplary embodiment of the present invention, the first waveguide layer 101 and the second waveguide layer 102 may include a semiconductor material. In an example, the first waveguide layer 101 and the second waveguide layer 102 may be semiconductor materials having conductivity.
In an example, the first waveguide layer 101 may be a silicon material or a germanium material.
In yet another example, the second waveguide layer 102 may also be a silicon material or a germanium material.
In an exemplary embodiment of the invention, the first waveguide layer 101 may include a P-type doped silicon material, and the second waveguide layer 102 may include an N-type doped silicon material; alternatively, the first waveguide layer 101 may include an N-type doped silicon material and the second waveguide layer 102 may include a P-type doped silicon material.
In the application process, the first waveguide layer 101 and the second waveguide layer 102 are made of doped silicon materials, such as N-type doped silicon materials or P-type doped silicon materials, which can avoid severe loss caused by the introduction of metal electrodes, and can reduce the spacing between the electrodes, so that when the same voltage is applied, the intensity of the modulation electric field in the lithium niobate layer 103 is larger, and a better modulation effect can be obtained.
To better form the slit mode with respect to the lithium niobate layer 103, the layer thickness of the lithium niobate layer 103 may be set to 50nm to 300nm in one embodiment.
In yet another example, the amount of phase modulation of the waveguide modulator 10 at a voltage per unit length can be represented by equation (1):
where Δ Φ represents a phase modulation amount; λ represents the wavelength of the modulated light; n is eff Represents the equivalent refractive index of the slit mode (corresponding to the lithium niobate layer 103); r is 33 Represents the electro-optic modulation coefficient of the lithium niobate layer 103; e microwave The distribution of the modulation electric field generated by the doped silicon electrode under the loading of unit voltage is represented, wherein the electric field is mainly distributed in the lithium niobate layer 103; e x An X component representing a light field; e denotes a light field vector.
In the application process, the relationship between the half-wave voltage-length product obtained based on the waveguide modulator 10 and the layer thickness of the lithium niobate layer 103 can be calculated based on the formula (1).
Fig. 3 is a schematic diagram of the relationship between the half-wave voltage-length product and the layer thickness of the lithium niobate layer obtained based on the waveguide modulator provided by the present invention.
The half-wave voltage-length product obtained by the modulator based on the traditional waveguide structure and the metal electrode is in the order of several V cm. As can be seen from fig. 3, compared with the conventional modulator, the half-wave voltage-length product of the waveguide modulator 10 provided in the present application is reduced by one to two orders of magnitude, and it is expected that the waveguide modulator 10 provided in the present application can greatly reduce the on-chip area required by the modulation device and greatly improve the integration level, thereby providing a possibility for solving a large-scale integrated modulator array.
In one embodiment, the thickness of the lithium niobate layer 103 is 40nm and 80nm, the width of the first waveguide layer 101 and the second waveguide layer 102 is 300nm, and the electro-optic phase modulator (corresponding to the waveguide modulator 10) with the length of 1mm can realize the phase modulation amount versus voltage distribution in the 1550nm communication band as shown in fig. 4 and 5, respectively.
As can be seen from fig. 4 and 5, the waveguide modulator 10 having a slit width of 40nm (corresponding to a layer thickness of the lithium niobate layer 103 of 40 nm) can realize a smaller half-wave voltage of about 0.7V. And the waveguide modulator 10 having a slit width of 80nm (corresponding to the layer thickness of the lithium niobate layer 103 of 80 nm) realizes a half-wave voltage of about 1.2V. The corresponding half-wave voltage-length products are 0.07V cm and 0.12V cm respectively. Compared with the working half-wave voltage-length product of the existing lithium niobate modulator, the half-wave voltage-length product can be reduced by one to two orders of magnitude.
As can be seen from the foregoing description, the waveguide modulator provided by the present invention is composed of a first waveguide layer, a second waveguide layer and a lithium niobate layer, and the lithium niobate layer is bonded and disposed between the first waveguide layer and the second waveguide layer. By constructing the slit waveguide modulator structure of the first waveguide layer-the lithium niobate layer-the second waveguide layer, the waveguide modulator can be ensured to have the optical field phase regulation and control performance of low half-wave voltage-length product, high modulation rate and low insertion loss.
The invention also provides a preparation method of the waveguide modulator. The preparation method of the waveguide modulator can be applied to preparation of the waveguide modulator.
Fig. 6 is a schematic flow chart of a method for manufacturing a waveguide modulator according to the present invention.
In an exemplary embodiment of the present invention, as can be seen in fig. 6, the method for manufacturing the waveguide modulator may include steps 610 to 630, which are described below.
In step 610, the first waveguide layer is obtained and the lithium niobate layer is transferred to the first waveguide layer based on a bonding method.
It should be noted that transferring the lithium niobate layer to the first waveguide layer based on a bonding manner may be understood as bonding the lithium niobate layer to the surface of the first waveguide layer.
In step 620, a second waveguide layer is formed on the other side of the lithium niobate layer opposite to the first waveguide layer by deposition or bonding.
In the application process, since the lithium niobate layer is already bonded with the first waveguide layer, it can be understood that the first waveguide layer is attached to one side of the lithium niobate layer, in this embodiment, the second waveguide layer can be formed on the other side of the lithium niobate layer (i.e., the opposite side to which the first waveguide layer is attached) by a deposition method or a bonding method, so as to form the slot waveguide modulator structure of the first waveguide layer-lithium niobate layer-second waveguide layer.
In step 630, metal electrode deposition is performed on the first waveguide layer and the second waveguide layer, respectively, to obtain the waveguide modulator.
In an exemplary embodiment of the present invention, continuing to use the embodiment described above as an example, after the lithium niobate layer is transferred to the first waveguide layer based on the bonding manner in step 610, the method for preparing the waveguide modulator may further include: and thinning the lithium niobate layer so that the thickness of the thinned lithium niobate layer is 50-300 nm. In this embodiment, by setting the layer thickness of the lithium niobate layer to be 50nm to 300nm, it can be ensured that a slit mode related to the lithium niobate layer is better formed, and a foundation is laid for ensuring that the waveguide modulator has optical field phase modulation performance of low half-wave voltage-length product, high modulation rate, and low insertion loss.
In still another exemplary embodiment of the present invention, the first waveguide layer may include a P-type doped silicon material, and the second waveguide layer may include an N-type doped silicon material.
The preparation of the first waveguide layer can be realized by adopting the following modes: and acquiring a first silicon substrate, and carrying out P-type doping treatment on the first silicon substrate to obtain a first waveguide layer.
The formation of the second waveguide layer by deposition or bonding may be achieved by: forming a second silicon substrate in a deposition mode or a bonding mode; and carrying out N-type doping treatment on the second silicon substrate to obtain a second waveguide layer.
In still another exemplary embodiment of the present invention, the first waveguide layer may include an N-type doped silicon material, and the second waveguide layer may include a P-type doped silicon material.
The preparation of the first waveguide layer can be realized by adopting the following modes: and obtaining a first silicon substrate, and carrying out N-type doping treatment on the first silicon substrate to obtain a first waveguide layer.
The formation of the second waveguide layer by deposition or bonding may be achieved by: forming a second silicon substrate in a deposition mode or a bonding mode; and carrying out P-type doping treatment on the second silicon substrate to obtain a second waveguide layer.
In this embodiment, by performing P-type doping or N-type doping processing on the first waveguide layer and the second waveguide layer, severe loss caused by the introduction of the metal electrode can be avoided, and the spacing between the electrodes can be reduced, so that when the same voltage is loaded, the intensity of the modulation electric field in the lithium niobate layer is larger, and a better modulation effect can be obtained.
To further illustrate the fabrication process of the waveguide modulator provided by the present invention, reference will be made to fig. 7.
Fig. 7 is a flow chart of a process for manufacturing a waveguide modulator according to the present invention.
In an exemplary embodiment of the present invention, as can be seen in conjunction with fig. 7, a silicon substrate (corresponding to SOI in the illustration) may be first acquired. Wherein the silicon substrate may comprise a SiO2 layer and a crystalline silicon layer (corresponding to c-Si in the figures). The silicon substrate may be P-doped or N-doped prior to bonding the lithium niobate layer (corresponding to the LN layer in the figures). And transferring the lithium niobate layer to the silicon substrate in a bonding mode. In fig. 7, the N-type doping process is described as an example.
Because the current lithium niobate layer bonding process can only transfer a lithium niobate layer with the thickness of 300-900 nanometers. In the scheme, the narrower the slit width (corresponding to the layer thickness of the LN layer), the smaller the half-wave voltage-length product, so that the lithium niobate layer needs to be thinned to 50nm to 300nm by methods such as argon ion etching (corresponding to LN layer thinning and ICP argon ion etching in the figure) to achieve a better phase modulation effect.
Furthermore, silicon with a certain thickness can be deposited or bonded on the lithium niobate layer and subjected to N-type doping or P-type doping treatment. Fig. 7 illustrates an example of performing the P-type doping process.
Furthermore, the doped silicon (corresponding to the first waveguide layer and the second waveguide layer) at the top and the bottom are respectively deposited with metal electrodes to form ohmic contact, so as to realize the waveguide modulator with the slit structure. In this embodiment, by constructing the slit waveguide modulator structure of the first waveguide layer-the lithium niobate layer-the second waveguide layer, the waveguide modulator can be ensured to have optical field phase modulation performance of low half-wave voltage-length product, high modulation rate, and low insertion loss.
The invention also provides another waveguide modulator preparation method. The preparation method of the waveguide modulator can also be applied to preparation of the waveguide modulator.
FIG. 8 is a second flowchart illustrating a method for fabricating a waveguide modulator according to the present invention.
In an exemplary embodiment of the present invention, as can be seen from fig. 8, the method for manufacturing a waveguide modulator may include steps 810 to 820, which will be described separately below.
In step 810, a lithium niobate layer is obtained.
In one embodiment, obtaining the lithium niobate layer may be accomplished by:
obtaining a wafer plane; and processing the wafer plane based on an etching mode to obtain a lithium niobate layer with the layer thickness of 50 nm-300 nm. The wafer plane may be understood as a lithium niobate material that is not subjected to thinning processing.
In step 820, a first waveguide layer and a second waveguide layer are formed on both sides of the lithium niobate layer, respectively, based on the deposition process.
In one embodiment, forming the first waveguide layer and the second waveguide layer on two sides of the lithium niobate layer respectively based on the deposition process may be implemented as follows:
respectively forming an initial first waveguide layer and an initial second waveguide layer on two sides of the lithium niobate layer based on amorphous silicon deposition treatment; and carrying out P-type doping treatment on the initial first waveguide layer and N-type doping treatment on the initial second waveguide layer, or carrying out N-type doping treatment on the initial first waveguide layer and P-type doping treatment on the initial second waveguide layer so as to form the first waveguide layer and the second waveguide layer on two sides of the lithium niobate layer respectively.
In the application process, the structure of the lithium niobate layer can be defined in the wafer plane (corresponding to the lithium niobate material which is not thinned), and firstly, the lithium niobate layer with the slit structure and the thickness of 50nm to 300nm is processed on the lithium niobate platform on the insulator by adopting a physical or chemical etching means. Then, amorphous silicon deposition is needed to obtain an initial first waveguide layer and an initial second waveguide layer. Furthermore, the silicon on both sides of the lithium niobate layer (corresponding to the initial first waveguide layer and the initial second waveguide layer) is doped with P-type and N-type respectively, so as to obtain the waveguide modulator with the slit structure. In this embodiment, by constructing the slit waveguide modulator structure of the first waveguide layer-the lithium niobate layer-the second waveguide layer, the waveguide modulator can be ensured to have optical field phase modulation performance of low half-wave voltage-length product, high modulation rate, and low insertion loss.
In one example, based on the waveguide modulator provided by the present invention, the intensity modulator may be constructed by a mach-zehnder interferometer. The structure of the intensity modulator is shown in fig. 9.
As can be seen from FIG. 9, the incident light is split into two arms (corresponding to E in the figure) via the Y-branch in In the direction shown, and finally in E out Exiting in the direction shown). The upper arm and the lower arm both adopt the slit waveguide modulator provided by the invention and adopt electrode arrangement of a push-pull structure.
During application, the directions of the electric fields applied to the two arms are opposite, so that the signs of the phase modulation amounts are opposite, and the half-wave voltage-length product required by extinction can be reduced by half. Considering that the typical output voltage of Transistor-Transistor Logic (TTL) is 3.4V and the typical output voltage of Complementary Metal Oxide Semiconductor (CMOS) is 1.2V, the device size can be calculated as shown in table 1 below. The result shows that the structure can effectively reduce the size of the on-chip intensity modulation device.
TABLE 1 device sizes for intensity modulators with different lithium niobate layer thicknesses
| Thickness of lithium niobate layer | CMOS typical voltage (1.2V) | TTL typical voltage (3.4V) |
| 40nm | 292μm | 103μm |
| 80nm | 500μm | 176μm |
The high-speed and large-scale optical switch has important significance in the application fields of optical communication, data centers and the like, and the directional coupler is a key device for constructing a large-scale optical switch array. In yet another example, a directional coupler may be constructed based on the waveguide modulator provided by the present invention. The structure of the directional coupler is shown in fig. 10. In which the incident path of the light wave is realized by means of a waveguide modulator, in fig. 10 the light wave follows E in1 Entering in the direction shown, along E out1 Is emitted in the direction shown, and is directed along E in2 Entering in the direction shown, along E out2 And exits in the direction shown.
In the application process, the working principle of the directional coupler is to change the output port of an optical signal by regulating and controlling the refractive index difference between a symmetric mode and an anti-symmetric mode. However, the phase modulation length required by the traditional silicon-based and lithium niobate devices is large, and the phase modulation length is difficult to achieveAnd (4) scale integration. The coupling waveguide spacing of the directional coupler designed based on the waveguide modulator provided by the invention is 100nm, the slit width (corresponding to the thickness of the rear layer of the lithium niobate layer) is 50nm, and the difference of the refractive indexes is 5.7 multiplied by 10 under the unit voltage application -4 and/V. Therefore, the voltage-length product required to switch the output port can be calculated to be 1.36V · mm. I.e. for a directional coupler with a coupling waveguide length of 1mm, the voltage required to switch from the through port to the other port is 1.36V. This result demonstrates the potential of the waveguide modulator of the present invention to reduce the size of the on-chip directional coupler.
Compared with the existing waveguide modulator, the low half-wave voltage-bandwidth product waveguide modulator based on the integrated lithium niobate platform has the advantages that the size can be reduced by one to two orders of magnitude, the time constant and the insertion loss of a resistor-capacitor circuit can be effectively reduced due to the reduction of the length of the modulator, and further, the possibility is provided for the large-scale integration of the waveguide modulator.
It is to be understood that while operations are depicted in the drawings in a particular order, this is not to be understood as requiring that such operations be performed in the particular order shown or in serial order, or that all illustrated operations be performed, to achieve desirable results. In certain environments, multitasking and parallel processing may be advantageous.
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, and not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (12)
1. A waveguide modulator, comprising: the first waveguide layer, the second waveguide layer and the lithium niobate layer;
and the lithium niobate layer is bonded and arranged between the first waveguide layer and the second waveguide layer.
2. The waveguide modulator of claim 1, wherein the first waveguide layer and the second waveguide layer comprise a semiconductor material.
3. The waveguide modulator of claim 2, wherein the first and second waveguide layers comprise a silicon material or a germanium material.
4. The waveguide modulator of claim 3, wherein the first waveguide layer comprises a P-type doped silicon material and the second waveguide layer comprises an N-type doped silicon material; or,
the first waveguide layer includes an N-type doped silicon material and the second waveguide layer includes a P-type doped silicon material.
5. The waveguide modulator of claim 1, wherein the layer thickness of the lithium niobate layer is 50nm to 300nm.
6. A waveguide modulator manufacturing method, wherein the manufacturing method is applied to manufacture the waveguide modulator according to any one of claims 1 to 5, and the manufacturing method comprises:
obtaining a first waveguide layer, and transferring a lithium niobate layer to the first waveguide layer based on a bonding mode;
forming a second waveguide layer on the other side, opposite to the first waveguide layer, of the lithium niobate layer in a deposition mode or a bonding mode;
and respectively carrying out metal electrode deposition treatment on the first waveguide layer and the second waveguide layer to obtain the waveguide modulator.
7. The method of preparing a waveguide modulator as defined in claim 6 wherein, after said bonding-based transfer of the lithium niobate layer to the first waveguide layer, the method further comprises:
and thinning the lithium niobate layer to ensure that the thickness of the thinned lithium niobate layer is 50 nm-300 nm.
8. The method of claim 6, wherein the first waveguide layer comprises a P-type doped silicon material and the second waveguide layer comprises an N-type doped silicon material;
the first waveguide layer is prepared in the following way:
obtaining a first silicon substrate, and carrying out P-type doping treatment on the first silicon substrate to obtain a first waveguide layer;
the forming of the second waveguide layer by the deposition method or the bonding method specifically includes:
forming a second silicon substrate in a deposition mode or a bonding mode;
and carrying out N-type doping treatment on the second silicon substrate to obtain the second waveguide layer.
9. The method of claim 6, wherein the first waveguide layer comprises an N-type doped silicon material and the second waveguide layer comprises a P-type doped silicon material;
the first waveguide layer is prepared in the following way:
acquiring a first silicon substrate, and carrying out N-type doping treatment on the first silicon substrate to obtain a first waveguide layer;
the forming of the second waveguide layer by the deposition method or the bonding method specifically includes:
forming a second silicon substrate in a deposition mode or a bonding mode;
and carrying out P-type doping treatment on the second silicon substrate to obtain the second waveguide layer.
10. A method for manufacturing a waveguide modulator, which is applied to manufacture the waveguide modulator according to any one of claims 1 to 5, the method comprising:
obtaining a lithium niobate layer;
and respectively forming a first waveguide layer and a second waveguide layer on two sides of the lithium niobate layer based on deposition treatment.
11. The method of claim 10, wherein said obtaining a lithium niobate layer comprises:
obtaining a wafer plane;
and processing the wafer plane based on an etching mode to obtain the lithium niobate layer with the layer thickness of 50 nm-300 nm.
12. The method according to claim 10, wherein the forming a first waveguide layer and a second waveguide layer on both sides of the lithium niobate layer, respectively, based on a deposition process, specifically comprises:
forming an initial first waveguide layer and an initial second waveguide layer on two sides of the lithium niobate layer respectively based on amorphous silicon deposition treatment;
carrying out P-type doping treatment on the initial first waveguide layer and carrying out N-type doping treatment on the initial second waveguide layer; or,
and carrying out N-type doping treatment on the initial first waveguide layer and P-type doping treatment on the initial second waveguide layer so as to respectively form a first waveguide layer and a second waveguide layer on two sides of the lithium niobate layer.
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