CN112526484B - Silicon optical chip, forming method thereof and laser radar system - Google Patents
Silicon optical chip, forming method thereof and laser radar system Download PDFInfo
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- CN112526484B CN112526484B CN202011432941.4A CN202011432941A CN112526484B CN 112526484 B CN112526484 B CN 112526484B CN 202011432941 A CN202011432941 A CN 202011432941A CN 112526484 B CN112526484 B CN 112526484B
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- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 title claims abstract description 89
- 229910052710 silicon Inorganic materials 0.000 title claims abstract description 89
- 239000010703 silicon Substances 0.000 title claims abstract description 89
- 230000003287 optical effect Effects 0.000 title claims abstract description 87
- 238000000034 method Methods 0.000 title claims abstract description 18
- GQYHUHYESMUTHG-UHFFFAOYSA-N lithium niobate Chemical compound [Li+].[O-][Nb](=O)=O GQYHUHYESMUTHG-UHFFFAOYSA-N 0.000 claims abstract description 35
- 238000001514 detection method Methods 0.000 claims abstract description 25
- 239000010409 thin film Substances 0.000 claims abstract description 14
- 239000000758 substrate Substances 0.000 claims description 43
- 230000008878 coupling Effects 0.000 claims description 39
- 238000010168 coupling process Methods 0.000 claims description 39
- 238000005859 coupling reaction Methods 0.000 claims description 39
- 239000004065 semiconductor Substances 0.000 claims description 37
- 239000000463 material Substances 0.000 claims description 20
- 238000006243 chemical reaction Methods 0.000 claims description 7
- 238000005530 etching Methods 0.000 claims description 5
- 229910052751 metal Inorganic materials 0.000 claims description 5
- 239000002184 metal Substances 0.000 claims description 5
- 238000004544 sputter deposition Methods 0.000 claims description 5
- 230000000694 effects Effects 0.000 abstract description 13
- 230000035945 sensitivity Effects 0.000 abstract description 11
- 230000010354 integration Effects 0.000 abstract description 7
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 15
- 229910052814 silicon oxide Inorganic materials 0.000 description 13
- 238000005259 measurement Methods 0.000 description 9
- 238000010586 diagram Methods 0.000 description 6
- 229910052732 germanium Inorganic materials 0.000 description 4
- GNPVGFCGXDBREM-UHFFFAOYSA-N germanium atom Chemical compound [Ge] GNPVGFCGXDBREM-UHFFFAOYSA-N 0.000 description 4
- 239000012212 insulator Substances 0.000 description 4
- 229910052581 Si3N4 Inorganic materials 0.000 description 3
- 238000012545 processing Methods 0.000 description 3
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 description 3
- JBRZTFJDHDCESZ-UHFFFAOYSA-N AsGa Chemical compound [As]#[Ga] JBRZTFJDHDCESZ-UHFFFAOYSA-N 0.000 description 2
- 229910001218 Gallium arsenide Inorganic materials 0.000 description 2
- 229910000530 Gallium indium arsenide Inorganic materials 0.000 description 2
- KXNLCSXBJCPWGL-UHFFFAOYSA-N [Ga].[As].[In] Chemical compound [Ga].[As].[In] KXNLCSXBJCPWGL-UHFFFAOYSA-N 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 230000009977 dual effect Effects 0.000 description 2
- 230000005693 optoelectronics Effects 0.000 description 2
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 description 2
- 229910010271 silicon carbide Inorganic materials 0.000 description 2
- 230000005540 biological transmission Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000002265 prevention Effects 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
- 235000012239 silicon dioxide Nutrition 0.000 description 1
- 239000002210 silicon-based material Substances 0.000 description 1
- 230000003068 static effect Effects 0.000 description 1
- 230000026683 transduction Effects 0.000 description 1
- 238000010361 transduction Methods 0.000 description 1
Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
- G01S7/483—Details of pulse systems
- G01S7/486—Receivers
- G01S7/4861—Circuits for detection, sampling, integration or read-out
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
- G01S17/88—Lidar systems specially adapted for specific applications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
- G01S17/88—Lidar systems specially adapted for specific applications
- G01S17/95—Lidar systems specially adapted for specific applications for meteorological use
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
- G01S7/481—Constructional features, e.g. arrangements of optical elements
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
- G01S7/483—Details of pulse systems
- G01S7/486—Receivers
- G01S7/487—Extracting wanted echo signals, e.g. pulse detection
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A90/00—Technologies having an indirect contribution to adaptation to climate change
- Y02A90/10—Information and communication technologies [ICT] supporting adaptation to climate change, e.g. for weather forecasting or climate simulation
Landscapes
- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Computer Networks & Wireless Communication (AREA)
- General Physics & Mathematics (AREA)
- Radar, Positioning & Navigation (AREA)
- Remote Sensing (AREA)
- Electromagnetism (AREA)
- Optical Radar Systems And Details Thereof (AREA)
- Optical Modulation, Optical Deflection, Nonlinear Optics, Optical Demodulation, Optical Logic Elements (AREA)
Abstract
A silicon optical chip, a forming method thereof and a laser radar system are provided, wherein the silicon optical chip comprises: the first coupler is used for receiving laser from an external laser light source and dividing the laser into a first path of laser and a second path of laser; the frequency shifter is coupled with the first coupler to perform frequency shifting treatment on the first path of laser; the circulator is coupled with the frequency shifter, receives the first path of laser after the frequency shift treatment, transmits the first path of laser to an external detection lens, and receives reflected laser reflected by the outside from the detection lens; the frequency shifter is formed by a lithium niobate thin film. The invention can reduce optical loss, improve detection sensitivity, effectively improve acousto-optic frequency shift effect of the frequency shifter, and realize on-chip integration of the acousto-optic frequency shifter.
Description
Technical Field
The invention relates to the technical field of radars, in particular to a silicon optical chip, a forming method thereof and a laser radar system.
Background
Weather prediction is a very important piece of content for our human activities. At present, with the increase of daily demands of people and the continuous increase of demands of various fields (new energy, ocean fishing, airport weather early warning, forest fire prevention and the like), the wind measuring system has higher demands.
Existing anemometry systems have traditional mechanical as well as relatively new microwave or lidar systems. Traditional mechanical devices are relatively simple and small, but only measure nearby real-time wind speeds. However, the existing microwave or laser radar wind measuring system has the defects of large volume, complex system, high price and the like although the distance is far and the precision is relatively high.
With the development of the semiconductor optoelectronic field, optoelectronic integrated semiconductor devices have been used in various fields. Silicon-based photoelectrons are continuously developed for several years, and the appearance of on-chip acousto-optic modulators enables wind lidar based on-chip integrated silicon-based photoelectron chips to have practicability. Through setting up silicon optical chip and integrated signal processing module, can improve the system integration level of wind-finding laser radar, greatly reduce cost, improve the stability of system.
However, in the prior art, a frequency shifter (such as an acousto-optic frequency shifter) in a laser radar system adopts a discrete device, so that optical loss is large, and detection sensitivity is low. However, in a specific embodiment of the prior art, the frequency shifter made of the existing thin film material is integrated into the chip, which has the problems of low piezoelectric constant and poor acousto-optic effect.
There is a need for a lidar system that can improve the piezoelectric constant of the frequency shifter and improve the acousto-optic effect while integrating the frequency shifter on a chip to reduce optical loss and improve detection sensitivity.
Disclosure of Invention
The invention solves the technical problem of providing a silicon optical chip, a forming method thereof and a laser radar system, which can reduce optical loss, improve detection sensitivity, effectively improve acousto-optic frequency shift effect of a frequency shifter and realize on-chip integration of the acousto-optic frequency shifter.
In order to solve the above technical problems, an embodiment of the present invention provides a silicon optical chip, which is characterized by comprising: the first coupler is used for receiving laser from an external laser light source and dividing the laser into a first path of laser and a second path of laser; the frequency shifter is coupled with the first coupler to perform frequency shifting treatment on the first path of laser; the circulator is coupled with the frequency shifter, receives the first path of laser after the frequency shift treatment, transmits the first path of laser to an external detection lens, and receives reflected laser reflected by the outside from the detection lens; the frequency shifter is formed by a lithium niobate thin film.
Optionally, the frequency shifter comprises a first acoustic wave reflector, an interdigital transducer, a second acoustic wave reflector, an optical annular cavity and a double electrode; the first sound wave reflector, the interdigital transducer and the second sound wave reflector are aligned along the same straight line, and the two electrodes of the double electrode are respectively positioned at two sides of the interdigital transducer.
Optionally, the frequency shifter further includes a straight waveguide, the straight waveguide including a first waveguide portion and a second waveguide portion coupled, the first waveguide portion and the second waveguide portion being spaced apart by the optical annular cavity and being optically coupled to the optical annular cavity; wherein the straight waveguide and the optical annular cavity are located together between the first acoustic reflector and the interdigital transducer or together between the interdigital transducer and the second acoustic reflector.
Optionally, in the frequency shifter, the laser is input by a first waveguide portion of the straight waveguide, coupled to an optical ring cavity, and output by a second waveguide portion of the straight waveguide after acousto-optic frequency shifting.
Optionally, the first coupler includes a first coupling silicon waveguide, and the circulator includes a circulator waveguide; the straight waveguides are stacked and connected to each other with the first coupling silicon waveguide and the circulator waveguide, respectively, within a preset range around the frequency shifter, so that the laser light is transmitted to the straight waveguides via the first coupling silicon waveguide when the frequency shifter is input, and is transmitted to the circulator waveguide via the straight waveguides when the frequency shifter is output.
Optionally, the silicon optical chip further includes: the first input end of the second coupler is coupled with the first coupler and receives the second path of laser, the second input end of the second coupler is coupled with the circulator and receives the reflected laser, and the output end of the second coupler outputs the coupled laser.
Optionally, the silicon optical chip further includes: and the detector is coupled with the output end of the second coupler so as to carry out photoelectric conversion on the coupled laser to obtain a current signal.
Optionally, the detector is a balance detector; the second coupler is provided with two coupling output ends, and the first path of coupling laser and the second path of coupling laser are respectively output; the balance detector is provided with two balance input ends which are respectively coupled with the two coupling output ends so as to respectively carry out photoelectric conversion on the first path of coupling laser and the second path of coupling laser; the phase difference between the first path of coupled laser and the second path of coupled laser is 90 degrees.
In order to solve the above technical problems, an embodiment of the present invention provides a laser radar system based on the above silicon optical chip, further including: a laser light source for emitting laser light to a first coupler in the silicon optical chip; and the detection lens is used for transmitting the laser output by the circulator in the silicon optical chip to the outside and transmitting the reflected laser reflected by the outside back to the circulator.
Optionally, the lidar system further comprises: and the transimpedance amplifier is coupled with the silicon optical chip, converts a current signal output by the silicon optical chip into a voltage signal and amplifies the voltage signal.
In order to solve the above technical problems, an embodiment of the present invention provides a method for forming a silicon optical chip, including: providing a first chip, wherein the first chip comprises a first semiconductor substrate, and a first coupler is formed on the front surface of the first semiconductor substrate; providing a second chip, wherein the second chip comprises a second semiconductor substrate and a lithium niobate material layer, and the lithium niobate material layer is positioned on the front surface of the second chip and covers the second semiconductor substrate; bonding treatment is carried out on the front surface of the first chip and the front surface of the second chip so as to obtain a bonding chip; and removing the second semiconductor substrate from the back of the second chip, and etching and metal sputtering the lithium niobate material layer to obtain the frequency shifter.
Compared with the prior art, the technical scheme of the embodiment of the invention has the following beneficial effects:
In the embodiment of the invention, the frequency shifter in the silicon optical chip is formed by adopting the lithium niobate thin film, so that the frequency shifter can be integrated on the chip, and the lithium niobate thin film has high piezoelectric constant and good acousto-optic effect, so that the optical loss can be reduced, the detection sensitivity can be improved, the acousto-optic frequency shifting effect of the frequency shifter can be effectively improved, and the on-chip integration of the acousto-optic frequency shifter can be realized.
Furthermore, the silicon optical chip further comprises a first coupler and a circulator, so that the first coupler, the circulator and the frequency shifter can be integrated into the same silicon optical chip, and compared with the prior art that all devices are discrete devices, more devices can be integrated into the same chip by adopting the scheme of the embodiment of the invention, thereby further reducing optical loss and improving detection sensitivity.
Further, the frequency shifter comprises a first sound wave reflector, an interdigital transducer, a second sound wave reflector, an optical annular cavity, a double electrode and a straight waveguide, and through setting the position relation between the straight waveguide and other structures, the surface sound of the transmitted laser can be efficiently excited, and the measurement accuracy of the radar system is improved.
Further, the detector in the silicon optical chip is a balanced detector, and by setting the phase difference between the first path of coupling laser and the second path of coupling laser to 90 degrees, common mode noise of the first path of coupling laser and the second path of coupling laser can be restrained in the photoelectric conversion process, and the measurement accuracy of the radar system is further improved.
Further, after the front bonding of the first chip and the second chip is adopted, the semiconductor substrate is removed from the wafer back on the second chip, then the lithium niobate material layer is etched, and metal sputtering is carried out, and the frequency shifter can be effectively manufactured on the chip by adopting a flip-chip bonding mode, so that the silicon optical chip is formed.
Drawings
FIG. 1 is a schematic diagram of a first lidar system according to an embodiment of the present invention;
Fig. 2 is a schematic structural diagram of a first embodiment of the frequency shifter 104 shown in fig. 1;
Fig. 3 is a schematic structural diagram of a second embodiment of the frequency shifter 104 shown in fig. 1;
FIG. 4 is a flow chart of a method for forming a silicon photofabrication chip according to an embodiment of the invention;
Fig. 5 to 10 are schematic cross-sectional structures of devices corresponding to steps in a method for forming a silicon optical chip in a first direction according to an embodiment of the present invention;
fig. 11 is a schematic cross-sectional view of a silicon optical chip in a second direction according to an embodiment of the present invention.
Detailed Description
As described above, in the prior art, a frequency shifter (such as an acousto-optic frequency shifter) in a lidar system adopts a discrete device, which results in a larger optical loss and a lower detection sensitivity. If the frequency shifter is directly integrated into a chip, the problems of low piezoelectric constant and poor acousto-optic effect exist.
The inventor of the invention discovers that the lithium niobate thin film has high piezoelectric constant, and can efficiently excite surface sound by arranging a proper morphology to form a frequency shifter, and the lithium niobate thin film also has good acousto-optic effect, thereby being beneficial to solving the problems in the embodiment of the invention.
In the embodiment of the invention, the frequency shifter in the silicon optical chip is formed by adopting the lithium niobate thin film, so that the frequency shifter can be integrated on the chip, and the lithium niobate thin film has high piezoelectric constant and good acousto-optic effect, so that the optical loss can be reduced, the detection sensitivity can be improved, the acousto-optic frequency shifting effect of the frequency shifter can be effectively improved, and the on-chip integration of the acousto-optic frequency shifter can be realized. Furthermore, the silicon optical chip further comprises a first coupler and a circulator, so that the first coupler, the circulator and the frequency shifter can be integrated into the same silicon optical chip, and compared with the prior art that all devices are discrete devices, more devices can be integrated into the same chip by adopting the scheme of the embodiment of the invention, thereby further reducing optical loss and improving detection sensitivity.
In order to make the above objects, features and advantages of the present invention more comprehensible, embodiments accompanied with figures are described in detail below.
Referring to fig. 1, fig. 1 is a schematic structural diagram of a first lidar system according to an embodiment of the present invention. The first lidar system comprises a silicon light chip as shown by the dashed box and may further comprise a laser light source 101 and a detection lens 106.
The silicon optical chip may include a first coupler 102, a frequency shifter 104, and a circulator 105.
The first coupler 102 may be used to receive laser light from an external laser light source 101 and split the laser light into a first path of laser light and a second path of laser light.
Further, the laser light source 101 may be used to emit laser light to the first coupler 102 in the silicon photo chip.
The frequency shifter 104 may be coupled to the first coupler 102 to shift the frequency of the first laser beam. The frequency shifter 104 may be formed of a lithium niobate thin film.
The circulator 105 may be coupled to the frequency shifter 104, receive the first laser beam after the frequency shift process, transmit the first laser beam to an external detection lens 106, and receive reflected laser beams reflected from the external detection lens 106.
Further, the detection lens 106 may be used to transmit the laser light output from the circulator 105 in the silicon optical chip to the outside, and transmit the reflected laser light reflected from the outside back to the circulator 105.
In the embodiment of the invention, the frequency shifter 104 in the silicon optical chip is formed by adopting the lithium niobate thin film, so that the integration of the frequency shifter 104 on the chip can be realized, and the lithium niobate thin film has high piezoelectric constant and good acousto-optic effect, so that the acousto-optic frequency shift effect of the frequency shifter can be effectively improved while the optical loss is reduced, the detection sensitivity is improved, and the on-chip integration of the acousto-optic frequency shifter is also realized. Further, the silicon optical chip further includes a first coupler 102 and a circulator 105, so that the first coupler 102, the circulator 105 and the frequency shifter 104 can be integrated into the same silicon optical chip, and compared with the prior art that each device is a discrete device, more devices can be integrated into the same chip by adopting the scheme of the embodiment of the invention, thereby further reducing optical loss and improving detection sensitivity.
Further, the frequency shifter 104 may include a first acoustic reflector, an interdigital transducer, a second acoustic reflector, an optical annular cavity, and a dual electrode.
Referring to fig. 2, fig. 2 is a schematic diagram of the frequency shifter 104 shown in fig. 1.
As shown in fig. 2, the first acoustic wave reflector 201, the interdigital transducer 202, and the second acoustic wave reflector 203 may be aligned along the same line, and the two electrodes of the dual electrode 205 are respectively located on two sides of the interdigital transducer 202.
Wherein the interdigital transducer 201 (202, 203) can be a pattern of lithium niobate thin films shaped like a finger-interdigital of two hands, which function to achieve transduction.
Further, the frequency shifter 104 may further include a straight waveguide 206, the straight waveguide 206 including a first waveguide portion and a second waveguide portion coupled, the first waveguide portion and the second waveguide portion being spaced apart by the optical annular cavity 204 and each being optically coupled to the optical annular cavity 204.
Wherein the straight waveguide 206 is located between the first acoustic reflector 201 and the interdigital transducer 202 along with the optical annular cavity 204.
Referring to fig. 3, fig. 3 is a schematic structural diagram of a second embodiment of the frequency shifter 104 shown in fig. 1.
The straight waveguide 206 and the optical annular cavity 204 may also be co-located between the interdigital transducer 202 and the second acoustic reflector 203.
In the embodiment of the present invention, the frequency shifter 104 may include a first acoustic reflector 201, an interdigital transducer 202, a second acoustic reflector 203, an optical annular cavity 204, a double electrode 205, and a straight waveguide 206, and by setting a positional relationship between the straight waveguide 206 and other structures, the surface acoustic of the transmitted laser can be efficiently excited, so as to improve the measurement accuracy of the radar system.
Further, in the frequency shifter 104, the laser light is input by a first waveguide portion of the straight waveguide 206, coupled to the optical ring cavity 204, and output by a second waveguide portion of the straight waveguide 206 after acousto-optic frequency shifting.
In particular, since the first waveguide portion of the straight waveguide 206 is optically coupled to the optical ring cavity 204, the laser light may be coupled to the optical ring cavity 204 and thus coupled to the second waveguide portion output.
Further, the first waveguide section optically coupled to the optical annular cavity 204 has a bend and the second waveguide section optically coupled to the optical annular cavity 204 also has a bend to enhance optical coupling-based light transmission.
Referring to fig. 1 and 3 in combination, the circulator 105 included in the silicon optical chip may be a multi-port device in which laser light entering each port is sequentially introduced into the next port in a preset direction. The preset direction sequence may be set based on the static bias magnetic field, and may be, for example, clockwise or counterclockwise.
The circulator 105 as shown in fig. 1 may comprise three ports, the laser light entering port 1 being transmitted into port 2 in a clockwise order and then being transmitted to an external detection lens 106, from which detection lens 106 reflected laser light reflected from the outside is received into port 2 and transmitted into port 3 in a clockwise order.
Further, the first coupler 102 may include a first coupling silicon waveguide 207 (refer to fig. 3), the circulator 105 may include a circulator waveguide 208 (refer to fig. 3), and the straight waveguide 206 may be stacked and interconnected with the first coupling silicon waveguide 207 and the circulator waveguide 208, respectively, within a preset range around the frequency shifter, such that the laser light is transmitted to the straight waveguide 206 via the first coupling silicon waveguide 207 when the frequency shifter 104 is input, and transmitted to the circulator waveguide 208 via the straight waveguide 206 when the frequency shifter 104 is output.
In the embodiment of the invention, by setting the positional relationship among the first coupling silicon waveguide 207, the straight waveguide 206 and the circulator waveguide 208, the surface acoustic of the transmitted laser can be efficiently excited, and the measurement accuracy of the radar system can be improved.
Further, the silicon optical chip may further include a second coupler 103, a first input end of the second coupler 103 is coupled to the first coupler 102 and receives the second path of laser light, a second input end of the second coupler 103 is coupled to the circulator 105 and receives the reflected laser light, and an output end of the second coupler 103 outputs the coupled laser light.
Further, the silicon optical chip may further include a detector 108, and the detector 108 may be coupled to an output end of the second coupler 103 to photoelectrically convert the coupled laser light to obtain a current signal.
Still further, the detector 108 may be a balanced detector; the second coupler is provided with two coupling output ends, and the first path of coupling laser and the second path of coupling laser are respectively output; the balance detector is provided with two balance input ends which are respectively coupled with the two coupling output ends so as to respectively carry out photoelectric conversion on the first path of coupling laser and the second path of coupling laser; the phases of the first path of coupled laser and the second path of coupled laser can be different by 90 degrees.
In the embodiment of the invention, the detector 108 in the silicon optical chip is set as a balance detector, and the phase difference between the first path of coupling laser and the second path of coupling laser is set to 90 degrees, so that common mode noise of the first path of coupling laser and the second path of coupling laser can be restrained in the photoelectric conversion process, and the measurement accuracy of a radar system is further improved.
Further, the lidar system may also include a transimpedance amplifier 109. The transimpedance amplifier 109 may be coupled to the silicon optical chip, and may convert a current signal output from the silicon optical chip into a voltage signal and amplify the voltage signal.
It can be understood that if the lidar system is used for wind measurement, the amplified voltage signal can be processed by a computer to obtain wind measurement information; and then sent to a signal processing module of the system for processing, and atmospheric data is extracted, so that wind measurement is realized.
Referring to fig. 4, fig. 4 is a flowchart of a method for forming a silicon optical chip according to an embodiment of the present invention. The method of forming a silicon photo chip may include steps S41 to S44:
Step S41: providing a first chip, wherein the first chip comprises a first semiconductor substrate, and a first coupler is formed on the front surface of the first semiconductor substrate;
Step S42: providing a second chip, wherein the second chip comprises a second semiconductor substrate and a lithium niobate material layer, and the lithium niobate material layer is positioned on the front surface of the second chip and covers the second semiconductor substrate;
step S43: bonding treatment is carried out on the front surface of the first chip and the front surface of the second chip so as to obtain a bonding chip;
step S44: and removing the second semiconductor substrate from the back of the second chip, and etching and metal sputtering the lithium niobate material layer to obtain the frequency shifter.
It should be noted that in step S41, the front surface of the first semiconductor substrate may be formed with all optical paths and devices except the phase shifter and the circulator, and the optical paths and devices are designed according to the specific situation, and the embodiment of the present invention is not limited to the specific optical paths and devices.
The method of forming the silicon photochip is described below with reference to fig. 5 to 10.
Fig. 5 to 10 are schematic cross-sectional structures of devices corresponding to steps in a method for forming a silicon optical chip in a first direction according to an embodiment of the present invention. The first direction may be the A1-A2 direction shown in fig. 3.
Referring to fig. 5, a first chip may include a first semiconductor substrate 501, and a silicon oxide layer 502 may be further formed on a surface of the first semiconductor substrate 501, and a silicon waveguide layer 503 may be further formed on a surface of the silicon oxide layer 502.
The first semiconductor substrate 501 may be a silicon substrate, or the material of the first semiconductor substrate 501 may further include germanium, silicon carbide, gallium arsenide, or indium gallium arsenide, and the first semiconductor substrate 501 may further be a silicon substrate on an insulator or a germanium substrate on an insulator, or a substrate with an epitaxial layer (Epi layer) grown thereon.
The material of the silicon oxide layer 502 may be silicon dioxide.
The silicon waveguide layer 503 may be a silicon material layer or a silicon nitride layer to form a silicon waveguide after an etching process.
Referring to fig. 6, the silicon waveguide layer 503 is etched to obtain a silicon waveguide 505, and then a silicon oxide layer 504 is formed on the surface of the first semiconductor substrate.
Note that after the silicon oxide layer 504 is formed, the silicon oxide layer 504 may be planarized with the top surface of the silicon waveguide 505 as a stop layer.
Referring to fig. 7, a second chip may be provided, and the second chip may include a second semiconductor substrate 511, and a silicon oxide layer 512 may be further formed on a surface of the second semiconductor substrate 511, and further a lithium niobate material layer 513 may be formed on a surface of the silicon oxide layer 512.
The second semiconductor substrate 511 may be a silicon substrate, or the material of the second semiconductor substrate 511 may further include germanium, silicon carbide, gallium arsenide, or indium gallium arsenide, and the second semiconductor substrate 511 may further be a silicon substrate on an insulator or a germanium substrate on an insulator, or a substrate grown with an epitaxial layer (Epi layer).
The silicon oxide layer 512 may be selected from: a stacked layer of silicon nitride and silicon oxide, a silicon nitride layer, and a silicon oxide layer.
Referring to fig. 8, a bonding process is performed on the front surface of the first chip and the front surface of the second chip to obtain a bonded chip.
Referring to fig. 9, the second semiconductor substrate 511 (refer to fig. 8) is removed from the back side of the second chip, then the silicon oxide layer 512 is removed, and then the lithium niobate material layer 513 is etched to obtain lithium niobate 515.
It will be appreciated that after the lithium niobate 515 is etched, the pattern of the frequency shifter may be obtained.
Referring to fig. 10, a silicon oxide layer 514 may be formed on the back surface of the second chip to cover the lithium niobate 515 and the silicon waveguide 505 to protect them.
It should be noted that the area shown in fig. 5 to 10 may be only a part of the first chip, i.e. the part of the area for forming the frequency shifter. The first coupler may be formed on the front surface of a region not shown in the drawing.
In the embodiment of the invention, after the front surface bonding of the first chip and the second chip is adopted, the semiconductor substrate is removed from the wafer back of the second chip, and then the lithium niobate material layer is etched, so that the frequency shifter can be effectively manufactured on the chip by adopting a flip-chip bonding mode, thereby forming the silicon optical chip.
Referring to fig. 11, fig. 11 is a schematic cross-sectional view of a silicon optical chip in a second direction according to an embodiment of the present invention. The second direction may be the B1-B2 direction shown in fig. 3.
As shown, the lithium niobate 515 is stacked and interconnected with the silicon waveguide 505 such that laser light is transmitted in the direction of the arrow.
Specifically, the lithium niobate 515 corresponds to a straight waveguide in the frequency shifter, the silicon waveguide 505 corresponds to a first coupling silicon waveguide and a circulator waveguide, and the straight waveguide is stacked and connected to the first coupling silicon waveguide and the circulator waveguide, respectively, within a preset range around the frequency shifter, so that the laser light is transmitted to the straight waveguide via the first coupling silicon waveguide when the frequency shifter is input, and is transmitted to the circulator waveguide via the straight waveguide when the frequency shifter is output.
In the embodiment of the invention, by arranging the lithium niobate 515 and the silicon waveguide 505 to be stacked and connected with each other, the surface acoustic of the transmitted laser can be efficiently excited, and the measurement accuracy of the radar system can be improved.
Although the present invention is disclosed above, the present invention is not limited thereto. Various changes and modifications may be made by one skilled in the art without departing from the spirit and scope of the invention, and the scope of the invention should be assessed accordingly to that of the appended claims.
Claims (11)
1. A silicon optical chip, comprising:
The first coupler is used for receiving laser from an external laser light source and dividing the laser into a first path of laser and a second path of laser;
The frequency shifter is coupled with the first coupler to perform frequency shifting treatment on the first path of laser;
The circulator is coupled with the frequency shifter, receives the first path of laser after the frequency shift treatment, transmits the first path of laser to an external detection lens, and receives reflected laser reflected by the outside from the detection lens;
the frequency shifter is formed by a lithium niobate thin film;
The frequency shifter is obtained by adopting a first chip and a second chip to bond on the front side, removing a semiconductor substrate from the back side of the second chip, etching a lithium niobate material layer and performing metal sputtering, wherein the first chip comprises a first semiconductor substrate, the front side of the first semiconductor substrate is provided with a first coupler, the second chip comprises a second semiconductor substrate and a lithium niobate material layer, and the lithium niobate material layer is positioned on the front side of the second chip and covers the second semiconductor substrate.
2. The silicon optical chip of claim 1 wherein the frequency shifter comprises a first acoustic reflector, an interdigital transducer, a second acoustic reflector, an optical annular cavity, and a double electrode;
The first sound wave reflector, the interdigital transducer and the second sound wave reflector are aligned along the same straight line, and the two electrodes of the double electrode are respectively positioned at two sides of the interdigital transducer.
3. The silicon photonics chip of claim 2 wherein,
The frequency shifter further comprises a straight waveguide, wherein the straight waveguide comprises a first waveguide part and a second waveguide part which are coupled, the optical annular cavity is arranged between the first waveguide part and the second waveguide part at intervals, and the first waveguide part and the second waveguide part are both optically coupled with the optical annular cavity;
Wherein the straight waveguide and the optical annular cavity are located together between the first acoustic reflector and the interdigital transducer or together between the interdigital transducer and the second acoustic reflector.
4. A silicon optical chip as defined in claim 3 wherein, in the frequency shifter, the laser light is input by a first waveguide portion of the straight waveguide, coupled to an optical ring cavity, and output by a second waveguide portion of the straight waveguide after acousto-optic frequency shifting.
5. The silicon optical chip of claim 4 wherein the first coupler comprises a first coupled silicon waveguide and the circulator comprises a circulator waveguide;
The straight waveguides are stacked and connected to each other with the first coupling silicon waveguide and the circulator waveguide, respectively, within a preset range around the frequency shifter, so that the laser light is transmitted to the straight waveguides via the first coupling silicon waveguide when the frequency shifter is input, and is transmitted to the circulator waveguide via the straight waveguides when the frequency shifter is output.
6. The silicon photonics chip of claim 1, further comprising:
The first input end of the second coupler is coupled with the first coupler and receives the second path of laser, the second input end of the second coupler is coupled with the circulator and receives the reflected laser, and the output end of the second coupler outputs the coupled laser.
7. The silicon photonics chip of claim 6, further comprising:
and the detector is coupled with the output end of the second coupler so as to carry out photoelectric conversion on the coupled laser to obtain a current signal.
8. The silicon optical chip of claim 7, wherein the detector is a balanced detector; the second coupler is provided with two coupling output ends, and the first path of coupling laser and the second path of coupling laser are respectively output;
the balance detector is provided with two balance input ends which are respectively coupled with the two coupling output ends so as to respectively carry out photoelectric conversion on the first path of coupling laser and the second path of coupling laser;
The phase difference between the first path of coupled laser and the second path of coupled laser is 90 degrees.
9. A lidar system based on the silicon photonics chip of any of claims 1 to 8, further comprising:
a laser light source for emitting laser light to a first coupler in the silicon optical chip;
And the detection lens is used for transmitting the laser output by the circulator in the silicon optical chip to the outside and transmitting the reflected laser reflected by the outside back to the circulator.
10. The lidar system of claim 9, further comprising:
And the transimpedance amplifier is coupled with the silicon optical chip, converts a current signal output by the silicon optical chip into a voltage signal and amplifies the voltage signal.
11. A method of forming a silicon photonics chip in accordance with any of claims 1 to 8 comprising:
providing a first chip, wherein the first chip comprises a first semiconductor substrate, and a first coupler is formed on the front surface of the first semiconductor substrate;
Providing a second chip, wherein the second chip comprises a second semiconductor substrate and a lithium niobate material layer, and the lithium niobate material layer is positioned on the front surface of the second chip and covers the second semiconductor substrate;
Bonding treatment is carried out on the front surface of the first chip and the front surface of the second chip so as to obtain a bonding chip;
and removing the second semiconductor substrate from the back of the second chip, and etching and metal sputtering the lithium niobate material layer to obtain the frequency shifter.
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