CN118033601A - Optical transceiver for laser radar - Google Patents
Optical transceiver for laser radar Download PDFInfo
- Publication number
- CN118033601A CN118033601A CN202410118136.6A CN202410118136A CN118033601A CN 118033601 A CN118033601 A CN 118033601A CN 202410118136 A CN202410118136 A CN 202410118136A CN 118033601 A CN118033601 A CN 118033601A
- Authority
- CN
- China
- Prior art keywords
- laser
- waveguide
- light
- lithium niobate
- optic
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
- 230000003287 optical effect Effects 0.000 title claims abstract description 61
- GQYHUHYESMUTHG-UHFFFAOYSA-N lithium niobate Chemical compound [Li+].[O-][Nb](=O)=O GQYHUHYESMUTHG-UHFFFAOYSA-N 0.000 claims abstract description 39
- 230000005540 biological transmission Effects 0.000 claims abstract description 33
- 239000010409 thin film Substances 0.000 claims abstract description 32
- 239000004065 semiconductor Substances 0.000 claims abstract description 25
- 230000008878 coupling Effects 0.000 claims abstract description 7
- 238000010168 coupling process Methods 0.000 claims abstract description 7
- 238000005859 coupling reaction Methods 0.000 claims abstract description 7
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 40
- 239000000377 silicon dioxide Substances 0.000 claims description 20
- 238000010438 heat treatment Methods 0.000 claims description 13
- 238000002310 reflectometry Methods 0.000 claims description 10
- 239000013307 optical fiber Substances 0.000 claims description 9
- 239000010408 film Substances 0.000 claims description 7
- 238000005253 cladding Methods 0.000 claims description 6
- 239000000758 substrate Substances 0.000 claims description 6
- 235000012239 silicon dioxide Nutrition 0.000 description 11
- 238000001514 detection method Methods 0.000 description 9
- 238000005259 measurement Methods 0.000 description 7
- 238000010586 diagram Methods 0.000 description 6
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 4
- 239000010931 gold Substances 0.000 description 4
- 229910052737 gold Inorganic materials 0.000 description 4
- 102100032050 Elongation of very long chain fatty acids protein 2 Human genes 0.000 description 3
- 101000921368 Homo sapiens Elongation of very long chain fatty acids protein 2 Proteins 0.000 description 3
- 230000008859 change Effects 0.000 description 3
- 230000005684 electric field Effects 0.000 description 3
- 238000012545 processing Methods 0.000 description 3
- 230000003595 spectral effect Effects 0.000 description 3
- 102100032055 Elongation of very long chain fatty acids protein 1 Human genes 0.000 description 2
- 101000771413 Homo sapiens Aquaporin-9 Proteins 0.000 description 2
- 101000921370 Homo sapiens Elongation of very long chain fatty acids protein 1 Proteins 0.000 description 2
- 229910000990 Ni alloy Inorganic materials 0.000 description 2
- 101100125012 Saccharomyces cerevisiae (strain ATCC 204508 / S288c) ECM10 gene Proteins 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 230000001427 coherent effect Effects 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 239000000835 fiber Substances 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 238000000034 method Methods 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 230000008447 perception Effects 0.000 description 2
- 239000000523 sample Substances 0.000 description 2
- 238000006467 substitution reaction Methods 0.000 description 2
- 238000000411 transmission spectrum Methods 0.000 description 2
- 238000004364 calculation method Methods 0.000 description 1
- 230000001276 controlling effect Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 229910001120 nichrome Inorganic materials 0.000 description 1
- 230000009022 nonlinear effect Effects 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 230000004044 response Effects 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- 230000001629 suppression Effects 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
Landscapes
- Optical Radar Systems And Details Thereof (AREA)
Abstract
The invention discloses an optical transceiver for a laser radar, which comprises a reflective semiconductor optical amplifier coupled through an end face and a laser external cavity based on thin film lithium niobate; the laser external cavity comprises a plurality of spot-size converters, an electro-optic phase modulator, a thermo-optic vernier filter, a reflecting mirror, a directional coupler, a multimode interferometer and a balanced photoelectric detector, and the reflective semiconductor optical amplifier is used for providing gain for the laser; the spot-size converter is used for improving the optical coupling transmission efficiency between devices; the electro-optic phase modulator and the thermo-optic vernier filter are used for adjusting the laser output wavelength of the laser; the reflector is used for adjusting feedback of the laser resonant cavity; the directional coupler is used for coupling part of laser light to the multimode interferometer; the multimode interferometer is used for mixing the echo signal and the local reference light to obtain a ranging light signal. The embodiment of the invention can output the frequency modulation continuous wave laser, and the device has high resolution and strong anti-interference capability and can be widely applied to the technical field of optical devices.
Description
Technical Field
The invention relates to the technical field of optical devices, in particular to an optical transceiver device for a laser radar.
Background
Autopilot technology is rapidly evolving and becoming an important direction of development in the future traffic field. Lidar (Light Detection AND RANGING, abbreviated as Lidar) plays a critical role as one of the key perception technologies in automatic driving systems. The laser radar measures the distance, shape and speed of the surrounding environment by using laser beams, and generates a high-precision point cloud map, thereby providing key information required by environment perception and decision for the automatic driving vehicle.
Currently, the mainstream lidar is based on TOF (Time of Flight) principle, and its working principle is as follows. 1) The transmitting stage: the TOF lidar forms a narrow beam of light by emitting laser pulses (typically infrared light) and irradiates it onto a target object; 2) Light beam propagation: the emitted beam propagates through air or other medium until it impinges on the target object; 3) Reflection stage: after the light beam irradiates the target object, a part of the light is reflected by the target object; 4) A receiving stage: the receiver of the TOF lidar receives the reflected light and measures the time of flight of the light from the emission to the reception; 5) Calculating the distance: by measuring the time of flight of light, the lidar can calculate the distance from the lidar to the target object.
The defects of TOF lidar are quite apparent: 1) Limited resolution: the resolution of TOF lidars is limited by the width of the light pulse and the time accuracy of the measurement. Shorter light pulses may improve resolution but may also result in lower signal strength. Thus, in long-range measurements or in strong light environments, the resolution of TOF lidars may be reduced. 2) Multipath interference: multipath reflections or scattering of the light beam may occur when the light beam interacts with the target object. Such multipath interference can lead to measurement inaccuracies, especially in complex environments, such as where multiple reflective surfaces or optically non-uniform objects are present. 3) Poor anti-jamming capability: TOF lidar may misinterpret probe signals from other TOF lidar as echo signals corresponding to the self-transmitted probe signals.
Advantages of FMCW (Frequency Modulated Continuous Wave ) lidar versus TOF lidar: 1) High resolution and precision: FMCW LIDAR can provide higher distance and speed resolution. By frequency modulating the characteristics of the continuous waveform FMCW LIDAR, more accurate distance measurements can be obtained, especially in close range and complex environments. 2) Long distance performance: FMCW LIDAR detects echo signals by adopting a coherent detection mode, has better detection sensitivity, and therefore, the method is excellent in long-distance measurement. 3) Anti-interference performance: FMCW LIDAR because the echo signals are detected by adopting a coherent detection mode, environmental noise and detection signals from other lidar can be disregarded. 4) Price and manufacturability: FMCW LIDAR has a lower manufacturing cost relative to TOF lidar. TOF lidar typically requires high-speed electronics and complex time measurement circuitry, while FMCW LIDAR is relatively simple to manufacture and can use relatively low cost components. 5) FMCW LIDAR can accomplish the task of range finding and speed measuring simultaneously, and TOF laser radar can only be through many measurements distance, calculates their change over time, and then obtains the speed, has increased the degree of difficulty of data processing.
Disclosure of Invention
In view of the above, an object of the embodiments of the present invention is to provide an optical transceiver for a laser radar, which can output a frequency modulated continuous wave laser, and has high resolution and strong anti-interference capability.
The embodiment of the invention provides an optical transceiver for a laser radar, which comprises a reflective semiconductor optical amplifier coupled through an end face and a laser external cavity based on thin film lithium niobate; the laser external cavity comprises a first mode spot converter, an electro-optic phase modulator, a thermo-optic vernier filter, a reflecting mirror, a directional coupler, a second mode spot converter, a third mode spot converter, a multimode interferometer and a balance photoelectric detector,
The reflective semiconductor optical amplifier is used for providing gain for the laser;
the first mode spot-size converter is used for improving the light transmission efficiency between the reflective semiconductor optical amplifier and the laser external cavity;
The electro-optic phase modulator is used for finely adjusting the laser output wavelength of the laser;
the thermo-optical vernier filter is used for coarsely adjusting the laser output wavelength of the laser;
The reflector is used for providing optical feedback for the laser resonant cavity;
the directional coupler is used for coupling part of laser light to the multimode interferometer as local reference light;
the second mode spot-size converter is used for introducing laser into the optical fiber;
the third mode spot converter is used for transmitting the reflected light in the optical fiber to the outer cavity of the laser as an echo signal;
The multimode interferometer is used for mixing the echo signal and the local reference light to obtain a ranging light signal;
The balanced photodetector is used for converting the ranging light signal into an electric signal.
Optionally, the tail of the reflective semiconductor optical amplifier is coated with a high-reflectivity film, and the head of the reflective semiconductor optical amplifier is coated with a low-reflectivity film.
Optionally, the waveguide on the reflective semiconductor optical amplifier is rotated by a preset angle.
Optionally, the first spot-size converter comprises a first transmission region and a second transmission region, and the light passes from the first transmission region to the second transmission region; the first transmission area comprises 3 thin film lithium niobate strip-shaped waveguides, the distance from the strip-shaped waveguides on two sides to the middle strip-shaped waveguide is gradually increased, and the width of the strip-shaped waveguides on two sides is thinned; the second transmission region includes a rib waveguide that gradually widens from the first transmission region to the conventional waveguide section.
Optionally, the electro-optic phase modulator includes a silica substrate, a thin film lithium niobate rib waveguide, a silica capping layer, and a double electrode.
Optionally, the thermo-optic vernier filter comprises two thermo-optic micro-ring resonant cavities connected in series, wherein each thermo-optic micro-ring resonant cavity comprises a micro-ring and a heating resistor, each micro-ring comprises a silicon dioxide substrate, a thin film lithium niobate rib waveguide and a silicon dioxide covering layer, the heating resistor is located on the surface of the silicon dioxide covering layer, and the heating resistor is located on the vertical direction of the thin film lithium niobate rib waveguide or around the vertical direction.
Optionally, the reflecting mirror includes two parallel thin film lithium niobate waveguides, two waveguide ports on the first side are connected through the waveguides, two waveguide ports on the second side are respectively used as an input port and an output port, and the two thin film lithium niobate waveguides are arranged between the three electrodes at intervals.
Optionally, the directional coupler comprises two thin film lithium niobate waveguides with parallel root portions.
Optionally, the multimode interferometer comprises two input ports and two output ports, the input ports and the output ports being disposed on opposite sides.
Optionally, the balanced photo-detector is composed of two identical photo-detectors, and the two photo-detectors are respectively connected with two output ports of the multimode interferometer.
The embodiment of the invention has the following beneficial effects: the optical transceiver of the laser radar in this embodiment includes a reflective semiconductor optical amplifier and a laser external cavity based on thin film lithium niobate, the laser external cavity includes a first mode spot converter, an electro-optic phase modulator, a thermo-optical vernier filter, a reflecting mirror, a directional coupler, a second mode spot converter, a third mode spot converter, a multimode interferometer and a balanced photodetector, the laser gain is provided by the reflective semiconductor optical amplifier, the laser is adjusted in mode, power, proportion and the like by the laser external cavity based on thin film lithium niobate, wherein the coupling efficiency is improved by the mode spot converter, the laser output wavelength is adjusted by the electro-optic phase modulator and the thermo-optical vernier filter, the feedback of the laser resonant cavity is adjusted by the reflecting mirror, the light is split by the directional coupler, the frequency is mixed by the multimode interferometer and the detection signal is carried out by the balanced photodetector, thereby outputting the frequency modulation continuous wave laser meeting the requirements.
Drawings
Fig. 1 is a schematic structural diagram of an optical transceiver device for a lidar according to an embodiment of the present invention;
FIG. 2 is a frequency chart of a frequency modulated continuous wave laser according to an embodiment of the present invention;
Fig. 3 is a schematic structural diagram of a first spot-size converter according to an embodiment of the invention;
FIG. 4 is a cross-sectional view of an electro-optic phase modulator provided by an embodiment of the present invention;
FIG. 5 is a cross-sectional view of a thermo-optic micro-ring resonator according to an embodiment of the present invention;
FIG. 6 is a schematic diagram of a reflector according to an embodiment of the present invention;
Fig. 7 is a schematic structural diagram of a directional coupler according to an embodiment of the present invention;
FIG. 8 is a schematic diagram of a multimode interferometer according to an embodiment of the present invention.
Detailed Description
The invention will now be described in further detail with reference to the drawings and to specific examples. The step numbers in the following embodiments are set for convenience of illustration only, and the order between the steps is not limited in any way, and the execution order of the steps in the embodiments may be adaptively adjusted according to the understanding of those skilled in the art.
Current schemes for generating frequency modulated continuous wave lasers (FMCW LASER) include the following:
1) An external modulator: an external light modulator is used to modulate the laser source, and by modulating the drive signal, the frequency of the laser can be changed, achieving FMCW LASER. The optical modulator may be an electro-optic modulator or an acousto-optic modulator.
2) An internal modulator: a modulator is integrated inside the laser. The output frequency of the laser is typically modulated using a current, temperature or voltage, and by adjusting the current, temperature or voltage variation, modulation of the laser frequency can be achieved, resulting in FMCW LASER.
3) A scanning modulator: the emission of FMCW LASER can be achieved by using a scannable modulator, such as a grating or frequency shifter, to scan the beam over space or frequency, by varying the scan speed or frequency.
4) Waveguide modulator: the modulation is achieved using nonlinear effects in the optical waveguide. For example, a nonlinear phase modulator based on an optical fiber or optical waveguide may modulate the frequency of a laser by changing the phase in the optical waveguide.
As shown in fig. 1, an embodiment of the present invention provides an optical transceiver device for a laser radar, including a reflective semiconductor optical amplifier (REFLECTIVE SEMICONDUCTOR OPTICAL AMPLIFIER, RSOA) 1 coupled by an end face and a laser external cavity based on Thin film lithium niobate (Thin-film lithium niobate, TFLN); the laser external cavity comprises a first Spot-size converter (Spot-size convertor, SSC 1) 2, an electro-optic phase modulator (electro-optic phase modulator, EO PHASE SHIFTER) 3, a Thermo-optic VERNIER FILTER, TO VERNIER FILTER) 4, a mirror (Tunable sagnac loop, TSL) 5, a directional coupler (Directional coupler, DC) 6, a second Spot-size converter (Spot-size convertor, SSC 2) 7, a third Spot-size converter (Spot-size convertor, SSC 3) 8, a multimode interferometer (Multimode interferometer, MMI) 9 and a balanced photodetector 10, wherein,
A reflective semiconductor optical amplifier 1 for providing gain to the laser;
a first mode spot-size converter 2 for improving the optical transmission efficiency between the reflective semiconductor optical amplifier 1 and the laser external cavity;
An electro-optic phase modulator 3 for fine-tuning the laser output wavelength of the laser; the effective cavity length of the resonant cavity of the laser is adjusted, so that the resonant wavelength of the laser is changed, and the output laser wavelength of the laser is changed;
a thermo-optic vernier filter 4 for coarsely adjusting the laser output wavelength of the laser;
A mirror 5 for providing optical feedback to the laser resonator; wherein the reflector is part of the laser resonator;
a directional coupler 6 for coupling part of the laser light to the multimode interferometer as local reference light;
A second mode spot-size converter 7 for introducing laser light into the optical fiber to reduce laser light access loss;
The third mode spot converter 8 is used for transmitting the reflected light in the optical fiber to the outer cavity of the laser as an echo signal, so as to reduce the laser access loss;
a multimode interferometer 9 for mixing the echo signal with the local reference light to obtain a ranging light signal;
The balanced photodetector 10 converts the ranging light signal into an electrical signal. The balanced photodetector may be made of a III-V material.
FMCW LASER is a laser whose frequency varies linearly with time, referring to fig. 2, the frequency variation range B is referred to as FMCW LASER chirp bandwidth, the time for the frequency to change from the initial start to return to the initial frequency is referred to as chirp period, B determines the resolution of FMCW LIDAR ranging, and T determines the minimum time required for FMCW LIDAR to complete ranging and testing for the same target.
In this device, the tuning process of the FMCW laser is as follows: applying a driving current to RSOA; TO VERNIER FILTER is adjusted TO enable the device TO output single-mode laser; the TSL is regulated so that output laser obtains higher quality (power and side mode suppression ratio); a triangular wave voltage is applied across EO PHASE SHIFTER. By the adjustment, the laser can output the FMCW laser, the chirp bandwidth of the FMCW laser is related to the voltage peak-to-peak value of the triangular wave, and the chirp repetition period of the FMCW laser is equal to the period of the triangular wave.
It should be noted that, in the embodiment of the present invention, the directional coupler and the multimode interferometer may be used interchangeably.
When the laser radar works, the laser outputs FMCW LASER, a DC or multimode interferometer is used for dividing laser into two paths, one path is used as local reference light, the other path is used as detection signals to be transmitted into a free space, echo signals are collected into an optical fiber in a lens mode and enter a lithium niobate external cavity through a third spot-size converter (SSC 3), and the echo signals are mixed with the local reference signals to obtain ranging signals; this ranging signal is changed from an optical signal to an electrical signal by a balanced photodetector and then sent to a signal processing circuit to obtain distance and speed information.
It should be noted that, the transmitting end and the receiving end of the laser radar are integrated on the LN chip, so that a complex optical fiber system is avoided, and the volume of the laser radar is greatly reduced.
Optionally, the tail of the reflective semiconductor optical amplifier is coated with a high reflectivity film and the head of the reflective semiconductor optical amplifier is coated with a low reflectivity film.
Specifically, the tail of RSOA is coated with a High-reflectivity (HR) film as a mirror of the laser resonator; the head of RSOA is coated with a thin film of low reflectivity (AR) in order to improve the light transmission efficiency between RSOA and the laser external cavity.
Optionally, the waveguide on the reflective semiconductor optical amplifier is rotated by a preset angle.
In order to avoid the RSOA from generating the lasing, the waveguide on the RSOA is rotated by a preset angle to further reduce the light reflection at the front portion, where the preset angle is determined according to practical applications, and the embodiment is not specifically limited, for example, the preset angle is set to 6-10 degrees.
Optionally, the first spot-size converter comprises a first transmission region and a second transmission region, the light passing from the first transmission region to the second transmission region; the first transmission area comprises 3 thin film lithium niobate strip-shaped waveguides, the distance from the strip-shaped waveguides on two sides to the middle strip-shaped waveguide is gradually increased, and the width of the strip-shaped waveguides on two sides is thinned; the second transmission region includes a rib waveguide that gradually widens from the first transmission region to the conventional waveguide section.
Specifically, referring to fig. 3, a represents silicon dioxide, B represents lithium niobate, the input light of the first spot-size converter is transmitted from the 3-1 region to the 3-4 region, the 3-1 region to the 3-2 region form the first region, the 3-3 region to the 3-4 region form the second region, the 3-1 region of the first spot-size converter SSC1 is three LN strip waveguides fabricated on a silicon dioxide buried oxide layer (SIO 2 BOX), and SIO 2 cladding (cladding) is provided on the waveguides by controlling the parameters Wc, wb, D such that the mode shape of the light in this structure is similar to the mode shape of the light in the RSOA waveguides. The distance from the two waveguides beside the 3-1 region to the 3-2 region to the intermediate waveguide increases gradually, and the width of the two waveguides becomes smaller so that the mode of light is concentrated gradually onto the intermediate waveguide. 3-1 region, an LN rib waveguide is fabricated on the basis of the underlying LN waveguide, the purpose of this structure being to guide optical modes from the strip LN waveguide to the rib LN waveguide. The waveguides from the 3-3 region to the 3-4 region gradually widen, guiding the mode of light to the normal width waveguide without loss. This SSC structure is rotated to a certain degree in order to match the incident angle of RSOA light.
The first mode spot-size converter has extremely low optical transmission loss (less than 1.7 dB), can greatly increase the power of laser output and improve the line width of laser.
The working principle of SSC2 is identical to that of SSC1, and this structure is to improve the transmission efficiency of light from the lithium niobate chip to the receiving fiber, so that more light is output to the subsequent optical system for laser emission through the fiber. Therefore, the parameters of Wb, wc and D are adjusted to some extent, and the structure does not need to be rotated like SSC 1.
The structure and working principle of the SSC3 are consistent with those of the SSC2, and the SSC3 is used for enabling light transmitted from a laser receiving system to enter a waveguide of a lithium niobate chip with low loss, so that the signal to noise ratio of balanced photoelectric detector detection is improved.
Optionally, the electro-optic phase modulator includes a silica substrate, a thin film lithium niobate rib waveguide, a silica cladding layer, and a double electrode.
Specifically, referring to fig. 4, a represents silicon dioxide, B represents lithium niobate, C represents gold electrode, EO PHASE SHIFTER is composed of one LN rib waveguide coated with SIO 2 and gold electrodes on two SIO 2, and the LN rib waveguide is fabricated along the y-direction of X-cut TFLN so as to utilize the maximum electro-optic coefficient of LN. By creating a potential difference across the two electrodes, an electric field is created between the electrodes, which changes the refractive index of the LN waveguide, and thus the effective cavity length of the laser resonator, and hence the resonant wavelength of the laser resonator. Because the response speed of the LN waveguide to the electric field is in the order of nanoseconds, the laser wavelength also changes very rapidly.
By reasonably designing EO PHASE SHIFTER, the laser resonator has better laser frequency adjusting capability while not bringing great transmission loss to the laser resonator, and the capability is described by modulation efficiency. Modulation efficiency is defined as: the ratio of the amount of laser frequency variation to the magnitude of the voltage applied to EO PHASE SHIFTER. Through calculation, the device can realize the modulation efficiency of 500 MHz/v.
Optionally, the thermo-optic vernier filter comprises two thermo-optic micro-ring resonant cavities connected in series, wherein each thermo-optic micro-ring resonant cavity comprises a micro-ring and a heating resistor, each micro-ring comprises a silicon dioxide substrate, a thin film lithium niobate rib waveguide and a silicon dioxide covering layer, the heating resistor is positioned on the surface of the silicon dioxide covering layer, and the heating resistor is positioned on the periphery of the thin film lithium niobate rib waveguide in the vertical direction or the vertical direction.
Specifically, referring TO fig. 5, a represents silicon dioxide, B represents lithium niobate, E represents nickel alloy, TO VERNIER FILTER is composed of two thermo-optic micro-ring resonators in series, each of the two micro-ring resonators is composed of a micro-ring and a heating resistor, and the cross-sectional view is as shown in fig. 5, the LN rib waveguide is coated with SIO 2, and the heating resistor nickel alloy is placed directly above or near the LN rib waveguide through SIO 2. The circumferences of the two micro-rings are slightly different, so that the free spectral range of the transmission spectrums (the free spectral range: the distance between transmission peaks of the transmission spectrums) is slightly different, the free spectral range is heated by applying voltage to a heating resistor, the refractive index of the micro-rings is changed by a thermo-optical effect, and the positions of resonance peaks of the micro-rings can be changed. By adjusting the positions of the resonance peaks of the two micro-rings through the heating resistor, one resonance peak is positioned at the same wavelength, low-loss transmission can be realized at the wavelength, and higher transmission loss is caused at other wavelengths, so that laser can only be generated at the low-loss transmission wavelength. By adjusting TO VERNIER FILTER, the laser can generate single-mode laser in a larger range.
Optionally, the reflecting mirror includes two parallel thin film lithium niobate waveguides, two waveguide ports on the first side are connected through the waveguide, two waveguide ports on the second side are respectively used as an input port and an output port, the two thin film lithium niobate waveguides are arranged between three gold electrodes at intervals, or a nichrome heating resistor is arranged above or near the two thin film lithium niobate waveguides.
Specifically, referring to fig. 6, m represents a lithium niobate waveguide, N represents a gold electrode, the LN waveguide portion of the TSL is a structure based on a Mach-zehnder interferometer (Mach-zender interferometer, MZI), based on a common MZI (the common MZI is formed by connecting two LN waveguides to two multimode interferometers multimode interferometer, MMI, respectively), two connected ports on one side of one MZI are connected by one waveguide to form a cycle, one of the two ports on the other side is connected to the output port of the vernier filter, and the other is connected to the input port of the second mode spot size converter. Three electrodes are placed on two arms (two waveguides in the middle of an MMI) of the MZI, and in operation, the polarities of the electrodes on the middle electrode and the two sides are opposite, so that electric fields with different directions are applied to the two arms of the MZI, the phase changes between the two arms are opposite, and by adjusting the phase difference between the two arms, the proportion of light entering the TSL from the 5-1 port to the light return from the 5-2 port can be controlled, namely the reflectivity of the TSL is adjusted.
The Q value of the laser resonant cavity can be changed by adjusting the TSL to change the reflectivity, so that indexes such as power, line width and the like of laser output laser are changed; through adjusting TSL, can make fine solution laser instrument output many longitudinal mode laser's problem.
Optionally, the directional coupler comprises two thin film lithium niobate waveguides with parallel root portions.
Referring to fig. 7, fig. 7 (a) shows a cross-sectional view of a directional coupler, fig. 7 (B) shows a schematic structural diagram of the directional coupler, a shows silicon dioxide, B shows lithium niobate, and DC is formed by a rib waveguide near a connecting waveguide between TSL and SSC2, and the ratio of light coupled into MMI is controlled by adjusting the length L of the waveguide and the distance between the waveguide and the connecting waveguide between TSL and SSC 2.
Optionally, the multimode interferometer comprises two input ports and two output ports, the input ports and the output ports being disposed on opposite sides.
Referring to fig. 8, the mmi causes a specially designed rib waveguide to have a total of 4 ports, and light input at one port on one side of the device (e.g., at one of ports 9-1 and 9-4) will output 1/2 of the input light intensity at the other ports (9-2 and 9-3), respectively, and vice versa.
Optionally, the balanced photo-detector is composed of two identical photo-detectors, and the two photo-detectors are respectively connected with two output ports of the multimode interferometer.
Specifically, the balanced photodetector is flip-chip bonded to the LN waveguide from two identical photodetectors fabricated from a III-V material. The optical signal from the LN waveguide is received and converted to an electrical signal, which may be transmitted to a data processing circuit outside the LN external cavity by means of electrodes or wire bonding.
The embodiment of the invention has the following beneficial effects: the optical transceiver of the laser radar in this embodiment includes a reflective semiconductor optical amplifier and a laser external cavity based on thin film lithium niobate, the laser external cavity includes a first mode spot converter, an electro-optic phase modulator, a thermo-optical vernier filter, a reflecting mirror, a directional coupler, a second mode spot converter, a third mode spot converter, a multimode interferometer and a balanced photodetector, the laser gain is provided by the reflective semiconductor optical amplifier, the laser is adjusted in mode, power, proportion and the like by the laser external cavity based on thin film lithium niobate, wherein the coupling efficiency is improved by the mode spot converter, the laser output wavelength is adjusted by the electro-optic phase modulator and the thermo-optical vernier filter, the feedback of the laser resonant cavity is adjusted by the reflecting mirror, the light is split by the directional coupler, the frequency is mixed by the multimode interferometer and the detection signal is carried out by the balanced photodetector, thereby outputting the frequency modulation continuous wave laser meeting the requirements.
While the preferred embodiment of the present application has been described in detail, the application is not limited to the embodiment, and various equivalent modifications and substitutions can be made by those skilled in the art without departing from the spirit of the application, and these equivalent modifications and substitutions are intended to be included in the scope of the present application as defined in the appended claims.
Claims (10)
1. An optical transceiver for laser radar, comprising a reflective semiconductor optical amplifier coupled by an end surface and a laser external cavity based on thin film lithium niobate; the laser external cavity comprises a first mode spot converter, an electro-optic phase modulator, a thermo-optic vernier filter, a reflecting mirror, a directional coupler, a second mode spot converter, a third mode spot converter, a multimode interferometer and a balance photoelectric detector,
The reflective semiconductor optical amplifier is used for providing gain for the laser;
the first mode spot-size converter is used for improving the light transmission efficiency between the reflective semiconductor optical amplifier and the laser external cavity;
The electro-optic phase modulator is used for finely adjusting the laser output wavelength of the laser;
the thermo-optical vernier filter is used for coarsely adjusting the laser output wavelength of the laser;
The reflector is used for providing optical feedback for the laser resonant cavity;
the directional coupler is used for coupling part of laser light to the multimode interferometer as local reference light;
the second mode spot-size converter is used for introducing laser into the optical fiber;
the third mode spot converter is used for transmitting the reflected light in the optical fiber to the outer cavity of the laser as an echo signal;
The multimode interferometer is used for mixing the echo signal and the local reference light to obtain a ranging light signal;
The balanced photodetector is used for converting the ranging light signal into an electric signal.
2. The optical transceiver of claim 1, wherein the tail portion of the reflective semiconductor optical amplifier is coated with a high reflectivity film and the head portion of the reflective semiconductor optical amplifier is coated with a low reflectivity film.
3. The optical transceiver of claim 1, wherein the waveguide on the reflective semiconductor optical amplifier is rotated by a predetermined angle.
4. The optical transceiver of claim 1, wherein the first spot-size converter comprises a first transmission region and a second transmission region, and wherein light passes from the first transmission region to the second transmission region; the first transmission area comprises 3 thin film lithium niobate strip-shaped waveguides, the distance from the strip-shaped waveguides on two sides to the middle strip-shaped waveguide is gradually increased, and the width of the strip-shaped waveguides on two sides is thinned; the second transmission region includes a rib waveguide that gradually widens from the first transmission region to the conventional waveguide section.
5. The optical transceiver of claim 1, wherein the electro-optic phase modulator comprises a silica substrate, a thin film lithium niobate rib waveguide, a silica cladding layer, and a double electrode.
6. The optical transceiver of claim 1, wherein the thermo-optic vernier filter comprises two thermo-optic micro-ring resonators connected in series, the thermo-optic micro-ring resonators comprising a micro-ring comprising a silica substrate, a thin film lithium niobate rib waveguide, and a silica cladding layer, and a heating resistor located on a surface of the silica cladding layer, the heating resistor located in a vertical direction of the thin film lithium niobate rib waveguide or around the vertical direction.
7. The optical transceiver of claim 1, wherein the reflecting mirror comprises two parallel thin film lithium niobate waveguides, the two waveguide ports on the first side are connected by the waveguide, the two waveguide ports on the second side are respectively used as an input port and an output port, and the two thin film lithium niobate waveguides are arranged between the three electrodes at intervals.
8. The optical transceiver of claim 1, wherein the directional coupler comprises two thin film lithium niobate waveguides having parallel root portions.
9. The optical transceiver of claim 1, wherein the multimode interferometer comprises two input ports and two output ports, the input ports and the output ports being disposed on opposite sides.
10. The optical transceiver of claim 9, wherein the balanced photodetector comprises two identical photodetectors, the two photodetectors being connected to two output ports of the multimode interferometer, respectively.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202410118136.6A CN118033601A (en) | 2024-01-26 | 2024-01-26 | Optical transceiver for laser radar |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202410118136.6A CN118033601A (en) | 2024-01-26 | 2024-01-26 | Optical transceiver for laser radar |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN118033601A true CN118033601A (en) | 2024-05-14 |
Family
ID=90994348
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202410118136.6A Pending CN118033601A (en) | 2024-01-26 | 2024-01-26 | Optical transceiver for laser radar |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN118033601A (en) |
-
2024
- 2024-01-26 CN CN202410118136.6A patent/CN118033601A/en active Pending
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US10578740B2 (en) | Coherent optical distance measurement apparatus and method | |
| WO2021128824A1 (en) | Laser radar based on silicon optical chip | |
| US11579294B2 (en) | Lidar system with integrated frequency shifter for true doppler detection | |
| CN110907915B (en) | Chip-level laser radar with enhanced range performance | |
| US11614543B2 (en) | Transimpedance amplifier for Lidar system | |
| US11573297B2 (en) | Lidar system with integrated circulator | |
| US11474206B2 (en) | Hybrid optical phase array and MEMS beamsteering for chip-scale Lidar system | |
| JPH10300853A (en) | Laser speedmeter and laser range finder using coherent detection | |
| Poulton | Integrated LIDAR with optical phased arrays in silicon photonics | |
| WO2024094099A1 (en) | Laser radar | |
| WO2023273565A1 (en) | Frequency-tunable semiconductor laser | |
| CN111077508B (en) | Multi-photon chip laser radar system architecture | |
| US11867844B2 (en) | Lidar spectrum analyzer | |
| CN110907916B (en) | Coherent detection using back-plate exit | |
| CN111796297A (en) | Parallel frequency modulation continuous wave laser ranging device based on erbium glass laser | |
| CN104792418A (en) | End surface inclined reflected light waveguide Fourier spectrograph | |
| US5530778A (en) | Direction finding apparatus using tunable fiber optic delay line | |
| CN118033601A (en) | Optical transceiver for laser radar | |
| CN116577804B (en) | FMCW laser radar based on chip integration | |
| CN220773254U (en) | On-chip laser radar system based on continuous wave frequency modulation | |
| Zhang et al. | Monolithic FMCW tunable laser with high modulation linearity and narrow linewidth | |
| KR20230170078A (en) | Light source for FMCW lidar devices | |
| CN112436377A (en) | Parallel FMCW laser radar transmitting device and method for middle and far infrared wave bands | |
| TW202333430A (en) | Method for providing a broadband chirped laser signal, tunable solid state laser device, and high resolution fast response lidar imaging system | |
| CN116710740A (en) | Photonic integrated circuit |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination |