CN113204132B - End face coupler and preparation method thereof - Google Patents
End face coupler and preparation method thereof Download PDFInfo
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- CN113204132B CN113204132B CN202110493000.XA CN202110493000A CN113204132B CN 113204132 B CN113204132 B CN 113204132B CN 202110493000 A CN202110493000 A CN 202110493000A CN 113204132 B CN113204132 B CN 113204132B
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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
- G02F1/0147—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 thermo-optic effects
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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
- G02B6/122—Basic optical elements, e.g. light-guiding paths
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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
- G02B6/122—Basic optical elements, e.g. light-guiding paths
- G02B6/124—Geodesic lenses or integrated gratings
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- G—PHYSICS
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- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/26—Optical coupling means
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- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/42—Coupling light guides with opto-electronic elements
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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
- G02F1/0102—Constructional details, not otherwise provided for in this subclass
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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
- G02F1/011—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 in optical waveguides, not otherwise provided for in this subclass
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- G—PHYSICS
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- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/015—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
- 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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- 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
- G02B2006/12083—Constructional arrangements
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Abstract
The invention provides an end face coupler which comprises a first coupling region, a phase shift region and a second coupling region, wherein the first coupling region, the phase shift region and the second coupling region are sequentially arranged along the direction of an output light field of a light source; the first coupling region comprises a beam splitting structure, divides the output light field of the light source into at least two first light fields, and is coupled into the phase shifting region; the optical field in the phase shifting region is marked as a second optical field, and phase modulators are arranged in one-to-one correspondence with the second optical field; the optical field output by the phase shifting region is recorded as a third optical field, and the phase difference between the third optical fields is 0; the second coupling region comprises a beam combining structure, and the third light field is completely coupled in and combined into a terminal light field. The coupling efficiency is high, the alignment tolerance is further improved, and a new degree of freedom is increased for reducing the package insertion loss. The preparation method provided by the invention has the corresponding advantages because the end face coupler can be prepared, has good compatibility with the CMOS process, only needs one etching, and is beneficial to process optimization and production improvement.
Description
Technical Field
The invention belongs to the technical field of optical waveguides and integrated optics, and particularly relates to an end face coupler and a preparation method thereof.
Background
The coupling of the existing laser or optical fiber and other light sources and the silicon optical chip mainly comprises two modes of grating coupling and end surface coupling. The Grating coupling adopts Grating coupler vertical coupling, has the characteristic of mode field matching, has the advantages of larger alignment tolerance and realization of wafer level test, has the defects of polarization sensitivity, wavelength sensitivity, narrower bandwidth and the like, and has certain limitation in the use of a Grating coupling scheme. The existing end-face coupling scheme can realize polarization insensitivity and larger bandwidth, but has smaller alignment tolerance, and is unfavorable for realizing wafer-level packaging. Taking a DFB single-mode laser as an example, the size of a mode spot of an output light field of the laser is about 2-3 mu m, and the alignment tolerance of a corresponding 1dB end face coupler is below the micron size, so that the precision requirement on packaging equipment is higher, but the precision of the conventional commercial flip-chip bonding machine is generally +/-1 mu m, and the difficulty and cost of packaging are greatly increased by adopting the existing scheme of end face coupling under the condition, and the yield of products is difficult to ensure. The alignment deviation generally refers to the offset of the corresponding coupling position when the loss increases by 1dB, and even if the active packaging method is adopted, the larger alignment deviation still can be caused in the packaging curing process, so that the insertion loss of the device is increased. Silicon-based photonic devices, which have been widely focused in industry in recent years, are increasingly being used in the field of laser radar and active laser detection because of their unique characteristics such as low cost, ultra-small size, low power consumption, compatibility with fine process characteristics, and the like.
Therefore, research on an end face coupler and a corresponding preparation method is needed at present, packaging is convenient, alignment tolerance of a light source and a silicon optical chip can be increased, insertion loss of a device is not increased, and the yield level of a product can be guaranteed. Therefore, the deep development of integrated optical technology and the wide application of silicon-based photon devices are further promoted.
Disclosure of Invention
The present invention is directed to solving all or part of the above-mentioned problems of the prior art, and in one aspect, the present invention provides an end-face coupler. In another aspect, the invention provides a method for preparing an end-face coupler, which can be used for preparing the end-face coupler.
The end face coupler provided by the invention comprises a first coupling region, a phase shift region and a second coupling region which are sequentially arranged along the direction of an output light field of a light source; the first coupling region comprises a beam splitting structure, the beam splitting structure divides an output light field of the light source into at least two first light fields, and the first light fields are all coupled into the phase shifting region; the optical field in the phase shifting region is marked as a second optical field, and phase modulators are arranged in the phase shifting region and in one-to-one correspondence with the second optical field; the optical field output by the phase shifting region is recorded as a third optical field; at least two third light fields are arranged, and the phase difference between the third light fields is 0; the second coupling region comprises a beam combination structure, and the beam combination structure couples all the third light fields into one terminal light field. And if a phase difference exists between at least two second light fields due to alignment deviation, the phase compensation can be performed through the phase shifting region, so that no phase difference exists between the third light fields output from the phase shifting region, and the third light fields are combined into a terminal light field through the beam combining structure and output to a device, thereby improving the alignment tolerance of the light source and the silicon optical chip and improving the final coupling efficiency. The coupling loss value of the traditional end-face coupler is determined after the end-face coupler is packaged with the optical fiber or the laser, but in the packaging process, whether an active packaging or a passive packaging is adopted, the optical fiber or the laser and the silicon optical chip inevitably have some deviation. The end face coupler is provided with the phase modulator, so that after the laser or the optical fiber and the PIC are packaged, the phase modulator is controlled to perform phase modulation, the coupling loss caused by the deviation is reduced, the purpose of further reducing the coupling loss is achieved, and a new degree of freedom is added for reducing the package insertion loss.
Typically, the first coupling region, the phase shift region and the second coupling region are disposed on a silicon substrate layer. The end-face coupler is directly generated on the silicon substrate layer of the silicon optical chip, has good compatibility with the CMOS technology and is easier to prepare.
The phase modulator is a thermo-optic phase shifter, an electro-optic phase shifter or a PN junction type optical phase shifter. The phase modulators are at least two, one of the same type of thermo-optic phase shifter, electro-optic phase shifter or PN junction type optical phase shifter can be selected, and several phase shifters of different types can be selected. According to the actual application.
The phase modulator is a thermo-optic phase shifter; the thermo-optical phase shifter comprises a single-mode waveguide with a preset length, a heating unit arranged at a first interval with the single-mode waveguide, and an exposed electrode electrically connected with the heating unit; the minimum distance between the thermo-optic phase shifters is a second distance; the value of the first interval is based on the fact that the heating unit does not influence the transmission loss of the single-mode waveguide; the second interval is based on the fact that thermal crosstalk generated between the thermo-optical phase shifters is reduced to the minimum. The exposed electrode is used for electrifying the heating unit, heating and modulating the phase of the second light field in the single-mode waveguide, and the phase is changed through the adjustment of electric power by the exposed electrode so as to control the coupling light intensity. The phase modulators are all thermo-optic phase shifters, and the thermo-optic phase shifters are simple in structure and convenient to prepare, and are beneficial to simplifying the process and saving the cost.
Preferably, the value range of the first interval is 0.5 μm to 2 μm.
The second pitch is greater than 40 μm. The preset length ranges from 50 μm to 500 μm.
The beam splitting structure comprises at least two first waveguide structure units; the center distance between the first waveguide structure units is a first preset distance; the first waveguide structure unit comprises a plurality of first waveguides, and the first waveguides are gradually widened from narrow along at least a part of the direction of the output light field of the light source; the input end of the first waveguide is provided with a first conical sub-wavelength grating. The first preset distance determines the coupling loss and the alignment tolerance of the end face coupler and the light source, the larger the first preset distance is, the larger the alignment tolerance is, the coupling loss under the condition of no offset is correspondingly increased, and in practical application, the specific requirements in production can be met by setting the first preset distance and simultaneously considering the coupling loss and the alignment tolerance according to the specific use condition of the end face coupler.
Preferably, the first waveguide structure unit further comprises sub-wavelength grating waveguides arranged on two sides of the first waveguide, and a second conical sub-wavelength grating is arranged at the input end of the sub-wavelength grating waveguide; the first waveguide and the sub-wavelength grating waveguides on two sides of the first waveguide form a trident structure; the first waveguide and the sub-wavelength grating waveguide are SOI (Silicon-on-insulator) waveguides. The trident structure formed by the SOI waveguide is beneficial to further reducing coupling loss, and on the other hand, the structure is compatible with a CMOS process and is easy to prepare a waveguide layer structure.
Specifically, the first waveguide is a single-mode waveguide; the first waveguides are arranged in parallel with each other.
The plurality of first waveguides are two independent single-mode waveguides which are arranged in parallel, and the first preset distance refers to the center distance between the two single-mode waveguides.
The beam combining structure comprises two second waveguide structure units arranged at a second preset distance and a third waveguide arranged between the second waveguide structure units; the second waveguide structure unit comprises a plurality of second waveguides; the third optical field enters the third waveguide through evanescent wave coupling to be combined into the terminal optical field. The beam combination structure realizes the beam combination of the third optical field in the third waveguide by adopting an evanescent wave coupling mode through the two second waveguide structure units, thereby being beneficial to realizing lower insertion loss and larger bandwidth of the device. The second preset distance influences the coupling length of the second coupling region, and the coupling length of the second coupling region can be adjusted by setting the second preset distance in order to meet specific requirements in the overall structural design of the device in practical application in cooperation with the specific design of the device.
The second waveguide is a separate single mode waveguide; the second waveguides are arranged in parallel with each other. At least a portion of the second waveguide is tapered from wide to narrow in a direction away from the phase shifting region; at least a portion of the third waveguide is gradually widened from narrow.
The second waveguide and the third waveguide are SOI (Silicon-on-insulator) waveguides.
According to another aspect of the present invention, there is provided a method for manufacturing an end-face coupler according to one aspect of the present invention, comprising: and forming the waveguide layer structures of the first coupling region, the phase shifting region and the second coupling region through one etching.
The phase shift region comprises a plurality of phase shift regions, and is characterized in that a plurality of phase shift regions are arranged on the phase shift regions.
Compared with the prior art, the invention has the main beneficial effects that:
1. The end face coupler is simple in structure, and the alignment tolerance of the light source and the silicon optical chip in the horizontal direction can be remarkably increased by coupling the external light source into the phase shift region through the first coupling region; no matter which side of the end face coupler in the horizontal direction the light source is biased, the phase difference between the second light fields caused by alignment deviation can be compensated through the phase shifting region, and the final coupling efficiency is higher; after the laser or the optical fiber and the PIC are packaged, the phase modulator can be used for carrying out phase modulation, so that the coupling loss caused by the deviation is reduced, the purpose of further reducing the coupling loss is achieved, and a new degree of freedom is added for reducing the packaging insertion loss. The beam combining structure performs light occasion beam by evanescent wave coupling mode, and the device has larger bandwidth and lower insertion loss
2. The preparation method of the end face coupler can prepare the end face coupler, has simple steps, only needs one-step etching, has good compatibility with the CMOS process, does not increase additional production process, saves cost, and is easy for enterprises to prepare the end face coupler on the basis of the existing process.
Drawings
Fig. 1 is a schematic diagram of an application scenario of an end-face coupler according to a first embodiment of the present invention.
Fig. 2 is a schematic top view of an end-face coupler according to a first embodiment of the present invention.
Fig. 3 is a schematic cross-sectional view of a thermo-optic phase shifter according to a first embodiment of the present invention.
Fig. 4 (a) and fig. 4 (b) are schematic diagrams illustrating the working principle of the end-face coupler according to the first embodiment of the present invention.
Fig. 5 is a schematic diagram of mode field distribution simulation of the end-face coupler without offset according to the first embodiment of the present invention.
Fig. 6 is a schematic diagram illustrating a relationship between heating power and alignment deviation according to the first embodiment of the present invention.
Fig. 7 is a schematic diagram of a simulation of an alignment deviation between an end-face coupler and a conventional coupling structure in a horizontal direction according to a first embodiment of the present invention.
Fig. 8 is a schematic top view of an end-face coupler according to a second embodiment of the present invention.
Fig. 9 is a schematic diagram of a method for manufacturing an end-face coupler according to a second embodiment of the present invention.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and fully, and it is apparent that the embodiments described are only some, but not all, of the embodiments of the present invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The foregoing and/or additional aspects and advantages of the present invention will be apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings. In the figures, parts of the same structure or function are denoted by the same reference numerals, and not all illustrated parts are denoted by the associated reference numerals throughout the figures, if necessary, for the sake of clarity.
The operations of the embodiments are depicted in the following examples in a particular order, which is presented to provide a better understanding of the details of the embodiments and to provide a thorough understanding of the invention, but is not necessarily a one-to-one correspondence with the methods of the invention, nor is it intended to limit the scope of the invention in this regard.
It should be noted that the flowcharts and block diagrams in the figures illustrate the operational processes that may be implemented by the methods according to the embodiments of the present invention. It should also be noted that in some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the intervening blocks, depending upon the objectives sought to be achieved by the steps involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems which perform the specified functions or acts, or combinations of special purpose hardware and manual operations.
Example 1
In the first embodiment of the present invention, as shown in fig. 1 and 2, the end-face coupler C includes a first coupling region i, a phase shift region X, and a second coupling region ii sequentially arranged along the direction of the output light field L 0 of the light Source; the phase shift region X comprises phase modulators, namely a first phase modulator T1 and a second phase modulator T2 which are symmetrically arranged on two sides of a central axis N of the end face coupler C; the first coupling region I comprises a beam splitting structure P, divides an output light field L 0 of a light Source into at least two first light fields L 1, and couples all first light fields L 1 into a phase shifting region X; the optical field in the phase shift region X is denoted as a second optical field L 2, in this embodiment, two second optical fields L 2, and the first phase modulator T1 and the second phase modulator T2 are disposed in one-to-one correspondence with each other. The light fields output from the phase shift region are denoted as third light fields L 3, two third light fields L 3 in this embodiment, and the phase difference between the third light fields L 3 is 0; the second coupling region II comprises a beam combining structure Q, and the second light field L 2 is coupled into the beam combining structure Q to be combined into a terminal light field L fin. In this embodiment, the first coupling region i, the phase shift region X, and the second coupling region ii are all disposed on the silicon substrate layer. The end-face coupler C is directly generated on the silicon substrate layer of the silicon optical chip, is easy to prepare and is compatible with the CMOS technology. For ease of understanding the invention in the description of the embodiments, the example case where the alignment offset is 0 refers to the output light field of the light Source being incident along the central axis N of the end-face coupler C, but the specific case of the invention is not limited thereto.
The first phase modulator T1 and the second phase modulator T2 may be a thermo-optical phase shifter, an electro-optical phase shifter, a PN junction type optical phase shifter, or the like, or may be different specific phase modulators according to actual application conditions, which is not limited. In this embodiment, the first phase modulator T1 and the second phase modulator T2 are both thermo-optic phase shifters; as shown in fig. 1, the output light field L 0 in the present embodiment is divided into two first light fields L 1, and two second light fields L 2 are respectively coupled into the phase shifting region X. One first phase modulator T1 and one second phase modulator T2 are respectively used for modulating a second light field L 2. I.e. the number of thermo-optic phase shifters is 2. The total number of first and second phase modulators T1, T2, i.e. the number of phase modulators is equal to the number of second light fields L 2. The thermo-optic phase shifter in this embodiment specifically includes a single-mode waveguide with a preset length, a heating unit Heater disposed above the single-mode waveguide with a first distance D1 therebetween, and an exposed electrode (not shown) electrically connected to the heating unit Heater. As shown in fig. 3, in this embodiment, the single-mode waveguide is an SOI waveguide, and the preset length thereof ranges from 50 μm to 500 μm, and in this embodiment, the preset lengths of the single-mode waveguides of the thermo-optic phase shifter are all equal and are 100 μm. The first distance D1 is based on the fact that the heating unit Heater does not affect the transmission loss of the single-mode waveguide. The heating unit Heater is specifically a metal wire, and has a first distance D1 from the SOI waveguide below, and the smaller the first distance D1 is, the better the smaller the waveguide loss is, and the value of the first distance D1 is 1 μm in this embodiment. in practical application, the better value range of the first interval D1 can be 0.5-2 μm so as to ensure that the transmission loss of the waveguide is not influenced. The embodiment takes the structure of the thermo-optic phase shifter as an example, but is not limited to this structure. The thermo-optic phase shifter of this embodiment is structurally designed because it is simple and can meet the application needs. The thermo-optic phase shifter with different specific structures based on other principles can also meet specific requirements according to practical application conditions, and is not limited. As shown in fig. 2, the first phase modulator T1 is spaced from the second phase modulator T2 by a second distance D2, i.e. a minimum distance between the two thermo-optic phase shifters, and the second distance D2 is generally greater than 40 μm in order to ensure that thermal crosstalk generated between the thermo-optic phase shifters is as small as possible, and one specific implementation of this embodiment is that the minimum distance between the two thermo-optic phase shifters is 50 μm. In the thermo-optic phase shifter of this embodiment, the single-mode waveguides thereof are parallel to each other, and the heating units heaters are correspondingly parallel to each other, and the minimum distance between the two thermo-optic phase shifters is the vertical distance between the opposite edges of the two heating units heaters. In some embodiments, the thermo-optic phase shifters are not necessarily arranged in parallel in the same plane, and the minimum distance between the thermo-optic phase shifters and the thermo-optic phase shifters should satisfy the predetermined second distance D2 to avoid thermal crosstalk. The exposed electrodes are used for electrifying the heating units Heater to heat and modulate the phase of the second light field L 2 in the single-mode waveguide, and the temperature of the heating unit Heater metal wire is adjusted through electric power through the exposed electrodes to respectively and specifically change the light field phases in the two single-mode waveguides so as to control the coupling light intensity.
In this embodiment, the beam splitting structure P includes two first waveguide structural units S1 symmetrically disposed on both sides of the central axis N; the center distance between the first waveguide structure units S1 is a first preset distance W1; the first waveguide structure unit S1 specifically includes a first waveguide 1, where the first waveguide 1 gradually widens from narrow along at least a portion of the direction of the output light field L 0 of the light Source; the input end of the first waveguide 1 is provided with a first tapered sub-wavelength grating 11. In this embodiment, two first waveguides 1 are disposed in parallel with each other. The straight waveguide portion of the first waveguide 1 continues into the phase shift region X, being of continuous integral construction with the corresponding single-mode waveguide of the thermo-optic phase shifter. In this embodiment, the first waveguide 1 is a single-mode waveguide; the first preset distance W1 is the center distance between the portions of the straight waveguides of the two first waveguides 1 in the first coupling region i, and in this embodiment, the first preset distance W1 is 2.2 μm. The first waveguide structure unit S1 in this embodiment further includes sub-wavelength grating waveguides disposed on two sides of each first waveguide 1, where an input end of the sub-wavelength grating waveguide is provided with a second cone-shaped sub-wavelength grating 12; the first waveguide 1 and the sub-wavelength grating waveguides on two sides of the first waveguide are in a trident structure. In this embodiment, each of the first waveguide structural units adopts a set of trident structures, which is beneficial to further reducing coupling loss. In this embodiment, the waveguides of the first waveguide structure unit S1 are all SOI waveguides, that is, the first waveguide 1 and the sub-wavelength grating waveguides disposed on both sides thereof, and the first tapered sub-wavelength grating 11 and the second tapered sub-wavelength grating 12 are all silicon on insulator (Si) waveguides.
In this embodiment, the beam combining structure Q includes two second waveguide structural units S2 symmetrically disposed on both sides of the central axis N, and a third waveguide 3 along the central axis of the coupler in the length direction; the center-to-center distance between the second waveguide structure units S2 is a second preset distance (not shown). The second waveguide structure unit S2 includes a second waveguide 2; the third optical field L 3 is coupled into the third waveguide 3 by evanescent waves from the second waveguide 2, respectively, to form a terminal optical field L fin. The beam combining structure Q is used for realizing beam combining in the third waveguide 3 in an evanescent wave coupling mode through the two second waveguide structure units S2, so that lower insertion loss and larger bandwidth of the device are facilitated. The second preset distance can influence the coupling length of the second coupling region II, and can be matched with the specific design of the device in practical application, and the coupling length of the second coupling region II is adjusted by setting the second preset distance so as to meet the specific requirements in the structural design of the device. The second waveguide 2 is two independent single-mode waveguides symmetrically and parallelly arranged with the center distance between two sides of the central axis N being the second preset distance. In this embodiment, the second waveguide 2 is formed by the portion of the single-mode waveguide of the thermo-optic phase shifter in the phase shift region X that continues into the beam combining structure Q. At least a portion of the second waveguide 2 is gradually narrowed by a width in a direction away from the phase shift region X; the third waveguide 3 is then gradually widened from narrow to narrow at least in part. The second waveguide 2 and the third waveguide 3 are SOI (Silicon-on-insulator) waveguides. In this embodiment, the first waveguide 1, the second waveguide 2 and the third waveguide 3 are continuous and integrated single-mode waveguides in the waveguide layer structure, which is an example for facilitating visual understanding of the present invention, and other curved forms may be provided, so long as the second distance D2 can be ensured to meet the design requirement, and the present invention is not limited. In other embodiments, the beam splitting structure P and the beam combining structure Q may be, for example, a Y beam splitter (beam combining), a1×2mmi structure, or the like, which is not limited thereto.
As shown in fig. 4 (a) and fig. 4 (b), the first preset distance W1 determines the coupling loss and the alignment tolerance between the end face coupler C and the light Source, and the larger the first preset distance W1, the larger the alignment tolerance, and the coupling loss will be increased without offset. The specific working principle of this embodiment is that when there is alignment deviation between the light Source and the end-face coupler C, the first light fields L 1 of the first waveguide structure units S1 respectively coupled into the two sides of the central axis N have differences in intensity and phase, and the complex amplitudes of the two first light fields L １ on the two sides of the central axis NRespectively expressed by the following two formulas: /(I)
In this embodiment, the second light field L 2, i.e. the first light field L 1, which is not phase modulated by the first phase modulator T1 or the second phase modulator T2. As shown in fig. 4 (a), when the alignment deviation Δx >0 (i.e., when it is biased toward the lower side of the central axis N), Φ 1>φ2, the phase of the second optical field L 2 at the lower side of the central axis N can be increased by heating the metal wire of the second phase modulator T2, so that the phase difference between the third optical fields L 3 of the output phase shift regions X via the single-mode waveguides at both sides of the central axis N is 0. When the alignment deviation Δx <0 (i.e., when it is biased toward the upper side of the central axis N), phi 1<φ2, as shown in fig. 4 (b), the phase of the second optical field L 2 at the lower side of the central axis N can be increased by heating the metal wire of the first phase modulator T1, so that the phase difference between the third optical fields L 3 of the output phase shifting regions X via the single-mode waveguides at both sides of the central axis N is 0. when the alignment deviation Δx=0 (i.e., when the central axis N is aligned), Φ 1=φ2, at which time no adjustment of the phase is required, the first and second phase modulators T1 and T2 are not operated, and the first, second and third light fields L 1, L 2 and L 3 are identical light fields. a schematic diagram of the mode field distribution simulation at no offset is shown in fig. 5. A schematic diagram of the heating power versus alignment shift is shown in fig. 6. The simulation results of the misalignment of the end coupler C with the two coupling structures of the prior art (trident structure, single-trifurcate structure; double trident structure, double-trifurcate structure) in the horizontal direction are shown in FIG. 7. The alignment deviation generally refers to the offset of the corresponding coupling position when the loss increases by 1dB, as shown in fig. 7, the end-face coupler C of the present embodiment has an alignment deviation of 1dB of ±1.7μm, and the alignment deviations of 1dB of the two existing sub-wavelength tri-pin structures are ±0.65 μm and ±0.77 μm, respectively. it can be seen that the alignment tolerance range of the end face coupler C of the present embodiment is larger.
Example two
As shown in fig. 8, the difference between the second embodiment and the first embodiment is that the beam splitting structure P includes 4 independent single-mode waveguides on both sides of the central axis N. Each second waveguide structure unit S2 comprises two second waveguides 2, also independent single mode waveguides. The second light field L 2 has 4, and thus corresponds to 2 first phase modulators T1 and 2 second phase modulators T2.
The preparation method of the end-face coupler in this embodiment, as shown in fig. 9, includes: forming a waveguide layer structure of the first coupling region, the phase shift region and the second coupling region through one-time etching; and a plurality of heating units are correspondingly arranged on a plurality of waveguides of the waveguide layer structure of the phase shift region at intervals of preset first intervals, and exposed electrodes are arranged on the heating units. According to the specific size and specific structure of the end face coupler with specific different wavelengths and spot sizes of the light source in practical application, other corresponding designs can be provided, and the coupler can be applied to the coupling application of various different light sources without limitation.
The use of certain conventional english terms or letters for the sake of clarity of description of the invention is intended to be exemplary only and not limiting of the interpretation or particular use, and should not be taken to limit the scope of the invention in terms of its possible chinese translations or specific letters. It should also be noted that in this document, relational terms such as "first" and "second" and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Specific examples are set forth herein to illustrate the structure and principles of the invention, and the above examples are provided only to assist in understanding the methods and core concepts of the invention. It will be apparent to those skilled in the art that various changes and modifications can be made to the present invention without departing from the principles of the invention, and such changes and modifications fall within the scope of the appended claims.
Claims (14)
1. An end-face coupler, characterized by: the light source comprises a first coupling region, a phase shift region and a second coupling region which are sequentially arranged along the direction of an output light field of the light source;
The first coupling region comprises a beam splitting structure, the beam splitting structure divides an output light field of the light source into at least two first light fields, and the first light fields are all coupled into the phase shifting region;
The optical field in the phase shifting region is marked as a second optical field, and phase modulators are arranged in the phase shifting region and in one-to-one correspondence with the second optical field; the optical field output by the phase shifting region is recorded as a third optical field; at least two third light fields are arranged, and the phase difference between the third light fields is 0;
the second coupling region comprises a beam combination structure, and the beam combination structure couples all the third light fields into one terminal light field.
2. An end face coupler according to claim 1, wherein: the first coupling region, the phase shift region, and the second coupling region are disposed on a silicon substrate layer.
3. An end face coupler according to claim 1, wherein: the phase modulator adopts one or more of a thermo-optic phase shifter, an electro-optic phase shifter and a PN junction type optical phase shifter.
4. An end face coupler according to claim 1, wherein: the phase modulator is a thermo-optic phase shifter;
the thermo-optical phase shifter comprises a single-mode waveguide with a preset length, a heating unit arranged at a first interval with the single-mode waveguide, and an exposed electrode electrically connected with the heating unit;
the minimum distance between the thermo-optic phase shifters is a second distance;
the value of the first interval is based on the fact that the heating unit does not influence the transmission loss of the single-mode waveguide; the second interval is based on minimizing thermal crosstalk generated between the thermo-optic phase shifters.
5. The end face coupler of claim 4 wherein: the value range of the first interval is 0.5-2 mu m.
6. The end face coupler of claim 4 wherein: the second pitch is greater than 40 μm; the preset length ranges from 50 μm to 500 μm.
7. An end face coupler according to claim 1, wherein: the beam splitting structure comprises at least two first waveguide structure units; the center distance between the first waveguide structure units is a first preset distance;
the first waveguide structure unit comprises a plurality of first waveguides, and the first waveguides are gradually widened from narrow along at least a part of the direction of the output light field of the light source; the input end of the first waveguide is provided with a first conical sub-wavelength grating.
8. The end face coupler of claim 7 wherein: the first waveguide structure unit further comprises sub-wavelength grating waveguides arranged on two sides of the first waveguide, and a second conical sub-wavelength grating is arranged at the input end of the sub-wavelength grating waveguide; the first waveguide and the sub-wavelength grating waveguides on two sides of the first waveguide form a trident structure; the first waveguide and the sub-wavelength grating waveguide are SOI waveguides.
9. The end face coupler of claim 7 wherein: the first waveguide is a single-mode waveguide; the first waveguides are arranged in parallel with each other.
10. An end face coupler according to any one of claims 1-9, wherein: the beam combining structure comprises two second waveguide structure units arranged at a second preset distance and a third waveguide arranged between the second waveguide structure units;
The second waveguide structure unit comprises a plurality of second waveguides; the third optical field enters the third waveguide through evanescent wave coupling to be combined into the terminal optical field.
11. An end face coupler according to claim 10, wherein: the second waveguide is a separate single mode waveguide; the second waveguides are arranged in parallel;
At least a portion of the second waveguide is tapered from wide to narrow in a direction away from the phase shifting region; at least a portion of the third waveguide is gradually widened from narrow.
12. An end face coupler according to claim 10, wherein: the second waveguide and the third waveguide are SOI waveguides.
13. A method of making an end-face coupler according to any one of claims 1-12, characterized by: comprising the following steps: and forming the waveguide layer structures of the first coupling region, the phase shifting region and the second coupling region through one etching.
14. The method for manufacturing an end-face coupler according to claim 13, wherein: the phase shift region comprises a plurality of phase shift regions, and is characterized in that a plurality of phase shift regions are arranged on the phase shift regions.
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