CN214124313U - Parallel FMCW laser radar transmitting device of middle and far infrared wave band - Google Patents

Abstract

The utility model relates to a laser radar technical field, more specifically relates to a parallel FMCW laser radar emitter and method of well far infrared wave band. The laser radar transmitting device comprises a laser, an electro-optical modulator, an arbitrary function generator, a chalcogenide chip, a diffraction grating and an optical fiber link; the output port of the laser is connected with the light source input port of the electro-optical modulator, the waveform output port of the arbitrary function generator is connected with the microwave signal input port of the electro-optical modulator, and two ends of the chalcogenide chip are respectively connected with the optical signal output port of the electro-optical modulator and the diffraction grating through the lensed fiber. The utility model discloses utilize the cascade four-wave mixing effect of sulphur system microcavity, turn into single FMCW middle and far infrared frequency comb light source, reduced linear modulation narrow linewidth laser technology's complexity, greatly improved sending rate.

Description

Parallel FMCW laser radar transmitting device of middle and far infrared wave band

Technical Field

The utility model relates to a laser radar technical field, more specifically relates to a parallel FMCW laser radar emitter of well far infrared wave band.

Background

Most of the laser radars on the market currently use the "time-of-flight-TOF" technique, i.e. discrete light pulses are emitted, and a photodetector is used to detect the returned light power, thereby calculating the distance. The TOF technology has the advantages of obvious technology, mature technology, short development period and low cost, but the direct detection means causes the problems of poor anti-interference performance, short detection distance and the like, and the requirements of the vehicle-scale laser radar are difficult to meet. While the laser radar based on the Frequency Modulated Continuous Wave (FMCW) scheme can realize coherent detection, for example, patent CN111239754A, 2020.06.05 discloses a laser radar system based on a frequency modulated continuous wave and an imaging method thereof, which can effectively overcome the problems of TOF, but the FMCW laser radar is difficult to transmit in parallel due to the complexity of the current precise linear frequency modulation technology. FMCW lidar principle: due to the Doppler effect, frequency difference exists between the transmitted chirp signal (green) and the reflected chirp signal (blue), speed and distance information are related to the frequency difference, and the frequency difference information can be obtained by utilizing coherent detection, so that the distance and the speed of each pixel point are obtained. Such coherent detection based on FMCW lidar has many inherent advantages such as enhanced range resolution, direct speed detection using doppler effect, and avoidance of sunlight glare and interference. However, the measurement accuracy is very sensitive to the linearity of the chirped oblique line, coherent detection requires high light source coherence, and the technology for accurately controlling the chirped narrow-linewidth laser is very complex, which causes great difficulty in the realization of parallel measurement of the FMCW laser radar.

SUMMERY OF THE UTILITY MODEL

The utility model discloses an overcome at least one defect among the above-mentioned prior art, provide a parallel FMCW lidar transmitting device of well far infrared wave band, reduced the complexity of device, effectively improved laser emission speed, help improving lidar's measurement rate.

In order to solve the technical problem, the utility model discloses a technical scheme is: a parallel FMCW laser radar transmitting device of middle and far infrared wave bands comprises a laser, an electro-optic modulator, an arbitrary function generator, a chalcogenide chip, a diffraction grating and an optical fiber link; the output port of the laser is connected with the light source input port of the electro-optical modulator, the waveform output port of the arbitrary function generator is connected with the microwave signal input port of the electro-optical modulator, and two ends of the chalcogenide chip are respectively connected with the optical signal output port of the electro-optical modulator and the diffraction grating through the lensed fiber.

In one embodiment, the chalcogenide chip comprises a substrate, a chalcogenide micro-ring resonant cavity and a bus straight waveguide, wherein the chalcogenide micro-ring resonant cavity and the bus straight waveguide are both arranged at the top of the substrate, and the chalcogenide micro-ring resonant cavity is coupled with the bus straight waveguide. The chalcogenide chip converts continuous wave laser into a stable optical pulse sequence due to double balance of dispersion, nonlinearity, cavity pumping and loss, and generates a stable mid-far infrared waveband soliton frequency comb.

In one embodiment, the value of the radius of the micro-ring of the chalcogenide micro-ring resonant cavity is 50um to 200um, the thickness of the micro-ring is 0.7um to 1um, the width of the micro-ring is 1.9um to 2.5um, and the FSR of the free spectrum of the cavity is 130GHz to 520 GHz.

In one embodiment, two ends of the chalcogenide chip are respectively coupled with the lensed fiber through the inverse tapered waveguide.

In one embodiment, the length value of the reverse tapered waveguide is 200 um-500 um, and the width value of the tip is 100 nm-150 nm, so that the high-efficiency coupling of the optical fiber waveguide is realized.

In one embodiment, the laser output by the laser is a narrow linewidth light source, is a middle and far infrared band, and has a central wavelength of 9.5 um-11 um. Compared with the traditional 905nm and 1550nm laser light sources, the laser transmittance of the light source is improved by more than 1 time under weather such as rain, fog and the like.

In one embodiment, the waveform generated by the arbitrary function generator is a triangular chirp signal.

In one embodiment, the bandwidth of the triangular chirp signal is 1GHz-5GHz, and the modulation rate is 100KHz-10 MHz.

In one embodiment, the diffraction grating is provided with 80-120 notches per millimeter, and the middle and far infrared frequency comb light source is subjected to light splitting diffraction.

The utility model provides a parallel FMCW laser radar emitter of well far infrared wave band's realization method specifically includes following step:

the laser emits pumping light to enter the electro-optical modulator, and meanwhile, the arbitrary function generator generates a specific waveform to enter the electro-optical modulator to perform frequency chirp modulation on the pumping light;

modulated light passes through a chalcogenide chip, soliton frequency combs are generated by utilizing a cascade four-wave mixing effect of the chalcogenide chip, chirped laser is transmitted to all generated comb teeth without distortion, and a stable light pulse sequence required by a laser radar is finally generated;

the modulated light is diffracted to all parts of the space through the diffraction grating, and the object detection is realized.

Compared with the prior art, the beneficial effects are: the utility model provides a parallel FMCW laser radar emitter of well far infrared wave band utilizes the cascaded four-wave mixing effect of sulphur system microcavity, turns into well far infrared frequency comb light source (parallel FMCW) with single FMCW, has reduced the complexity of linear frequency modulation narrow linewidth laser technology, has greatly improved sending rate; the light source that adopts simultaneously is located well far infrared wave band, compares in traditional laser radar light source 905nm and 1550nm, and the decay is little under weather such as sleet, helps improving laser radar's detection distance and security performance.

Drawings

Fig. 1 is a schematic diagram of the connection relationship of the laser radar transmitting device of the present invention.

Fig. 2 is a schematic diagram of the FMCW lidar ranging and velocity measurement principle.

Fig. 3 is a simulation diagram of the transmittance of the light source (e.g., fog weather).

FIG. 4 is a schematic diagram of a chalcogenide chip preparation process according to an embodiment of the present invention.

FIG. 5 is a schematic diagram of frequency comb generation of solitons by chalcogenide chip.

FIG. 6 is a schematic top view of a chalcogenide chip according to the present invention.

Detailed Description

The drawings are for illustrative purposes only and are not to be construed as limiting the invention; for the purpose of better illustrating the embodiments, certain features of the drawings may be omitted, enlarged or reduced, and do not represent the size of an actual product; it will be understood by those skilled in the art that certain well-known structures in the drawings and descriptions thereof may be omitted. The positional relationships depicted in the drawings are for illustrative purposes only and are not to be construed as limiting the invention.

As shown in fig. 1, the parallel FMCW lidar transmitting device for middle and far infrared bands comprises a laser 1, an electro-optical modulator 2, an arbitrary function generator 3, a chalcogenide chip 4, a diffraction grating 5 and an optical fiber link; the output port of the laser 1 is connected with the light source input port of the electro-optical modulator 2, the waveform output port of the arbitrary function generator 3 is connected with the microwave signal input port of the electro-optical modulator 2, and two ends of the chalcogenide chip 4 are respectively connected with the optical signal output port of the electro-optical modulator 2 and the diffraction grating 5 through the lensed fiber.

In one embodiment, as shown in fig. 6, the chalcogenide chip 4 includes a substrate 41, a chalcogenide micro-ring resonator 42 and a bus straight waveguide 43, the chalcogenide micro-ring resonator 42 and the bus straight waveguide 43 are both disposed on the top of the substrate 41, and the chalcogenide micro-ring resonator 42 and the bus straight waveguide 43 are coupled to each other. The utility model provides a laser radar emitter's core utilizes the kerr dissipation effect of chalcogenide chip 4, with the undistorted conduction of the triangular wave frequency modulation continuous wave frequency chirp characteristic of single frequency for each broach of production, as shown in fig. 5, under the double balance's of chromatic dispersion, nonlinearity, cavity pumping and loss condition, continuous wave laser is converted into stable light pulse sequence on the time domain to produce stable well far infrared wave band soliton comb frequently. As shown in fig. 4, the preparation process of the chalcogenide chip 4 includes the following steps:

1. deposition: depositing a chalcogenide film on the silicon oxide lower cladding layer in a thermal evaporation mode, an electron beam evaporation mode or a magnetron sputtering mode, wherein the deposition speed is not more than 5 nm/min, and the deposition thickness is 800 nm;

2. gluing: spin-coating electron beam glue on the high-nonlinearity low-loss chalcogenide film, wherein the polymer electron glue is any one of polymethacrylate PMMA, ARP, ZEP and NR-9, and the thickness of the electron glue is 1.5 um;

3. photoetching: exposing the pattern layer required by the electron beam glue, and after exposure is finished, putting the sample into a developing solution for developing to remove the electron beam glue in the exposure area, so as to form the required electron beam glue pattern layer;

4. etching: putting the sample into a reactive ion etching machine, carrying out ion bombardment and ion reactive etching on the sample, and transferring the electron beam glue pattern layer to a chalcogenide film to form a chalcogenide micro-ring resonant cavity 42 and a residual electron beam glue pattern;

5. removing residual glue: removing the polymer electronic glue through a glue removing agent to obtain the chalcogenide micro-ring resonant cavity 42, wherein the glue removing agent is acetone or 1165 glue removing agent;

6. hot reflux: the sample is sealed and placed in an annealing furnace, and the thermal reflux effect is performed on the side wall of the chalcogenide micro-ring resonant cavity 42, so that the side wall becomes smooth, the waveguide loss is reduced, and the quality factor is further improved.

In one embodiment, the value of the radius of the micro-ring of the chalcogenide micro-ring resonant cavity 42 is 50um to 200um, the thickness of the micro-ring is 0.7um to 1um, the width of the micro-ring is 1.9um to 2.5um, the FSR of the cavity free spectrum is 130GHz to 520GHz, and the Q value reaches 6 th power of 10.

In one embodiment, two ends of the chalcogenide chip 4 are respectively coupled with the lens optical fiber through the inverse tapered waveguide; the length value of the reverse tapered waveguide is 200 um-500 um, the width value of the tip is 100 nm-150 nm, and the high-efficiency coupling of the optical fiber waveguide is realized.

In one embodiment, the laser output by the laser 1 is a narrow linewidth light source, which is a middle and far infrared band, and the central wavelength is 9.5um to 11 um. Compared with the traditional 905nm and 1550nm laser light sources, the laser transmittance of the light source is improved by more than 1 time under weather such as rain, fog and the like. Traditional laser radar adopts the single-frequency light source that the wave band is 905nm and 1550nm, this light source transmissivity descends by a wide margin under weather such as rain, snow and fog, as shown in fig. 3 (PcModwin 3.7 emulation), under the distance of ground 200 meters, the transmissivity is only 20%, the application nature of laser radar has extremely deteriorated, adopt far infrared wave band in 10.5um, the transmissivity can reach more than 60% under the same condition, be more than 3 times of traditional laser radar light source, help improving laser radar's detection distance and security performance.

In one embodiment, the waveform generated by the arbitrary function generator 3 is a triangular chirp signal with a bandwidth of 1GHz-5GHz and a modulation rate of 100KHz-10 MHz.

In one embodiment, the diffraction grating 5 has 80-120 notches per millimeter, and performs light splitting diffraction on the mid-infrared and far-infrared frequency comb light source.

In another embodiment, a method for transmitting parallel FMCW lidar in mid-far infrared band is further provided, and the method for transmitting parallel FMCW lidar in mid-far infrared band uses the apparatus for transmitting parallel FMCW lidar in mid-far infrared band, and the method includes the following specific steps:

the laser 1 emits pumping light with the wavelength of 10.5um to enter an electro-optic modulator 2, meanwhile, an arbitrary function generator 3 generates triangular waveform frequency modulation signals to enter the electro-optic modulator 2 to perform frequency chirp modulation on the pumping light, the pumping light is changed into triangular wave frequency modulation continuous waves with the bandwidth of 1.5Ghz and the modulation rate of 100kHz after being modulated, then the modulated light enters a chalcogenide chip 4 through a lens optical fiber, a Kerr dissipation effect is utilized to generate soliton frequency combs (30 combs in the 3dB bandwidth), the frequency chirp characteristic of the soliton frequency combs is conducted to all excited frequency combs without distortion, finally, a multichannel FCMW light source is distributed and diffracted to all places in space through a diffraction grating 5, the object distance and the object speed are detected in parallel, and the emission pulse rate is increased by one order of magnitude through theoretical calculation.

Although embodiments of the present invention have been shown and described, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art without departing from the scope of the present invention.

It is obvious that the above embodiments of the present invention are only examples for clearly illustrating the present invention, and are not limitations to the embodiments of the present invention. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the claims of the present invention.

Claims (9)

1. A parallel FMCW laser radar transmitting device of middle and far infrared wave bands is characterized by comprising a laser (1), an electro-optical modulator (2), an arbitrary function generator (3), a chalcogenide chip (4), a diffraction grating (5) and an optical fiber link; the output port of the laser (1) is connected with the light source input port of the electro-optical modulator (2), the waveform output port of the arbitrary function generator (3) is connected with the microwave signal input port of the electro-optical modulator (2), and two ends of the chalcogenide chip (4) are respectively connected with the optical signal output port of the electro-optical modulator (2) and the diffraction grating (5) through lens optical fibers.

2. The transmitting device of the parallel FMCW lidar for mid-and far-infrared bands as recited in claim 1, wherein the chalcogenide chip (4) includes a substrate (41), a chalcogenide micro-ring resonator (42) and a bus straight waveguide (43), the chalcogenide micro-ring resonator (42) and the bus straight waveguide (43) are both disposed on top of the substrate (41), and the chalcogenide micro-ring resonator (42) and the bus straight waveguide (43) are coupled to each other.

3. The transmitting device of claim 2, wherein the chalcogenide micro-ring resonator (42) has a micro-ring radius value of 50 um-200 um, a micro-ring thickness of 0.7 um-1 um, a micro-ring width of 1.9 um-2.5 um, and a free cavity spectrum FSR of 130 GHz-520 GHz.

4. The transmitting device of parallel FMCW lidar for mid-and far-infrared bands as set forth in claim 2, wherein both ends of said chalcogenide chip (4) are coupled to said lensed fiber by reverse tapered waveguides.

5. The device as claimed in claim 4, wherein the length of the reverse tapered waveguide is 200 um-500 um, and the width of the tip is 100 nm-150 nm.

6. The transmitting device of parallel FMCW lidar according to any of claims 1 to 5, wherein the laser output from the laser (1) is a narrow line width source, is in mid-far infrared band, and has a center wavelength of 9.5 um-11 um.

7. The device for transmitting parallel FMCW lidar according to claim 6, wherein the arbitrary function generator (3) generates a triangular chirp signal.

8. The apparatus according to claim 7, wherein the bandwidth of the chirp signal of the triangle wave is 1GHz-5GHz and the modulation rate is 100KHz-10 MHz.

9. The transmitting device of the parallel FMCW lidar for mid-and far-infrared bands as recited in claim 7, wherein the diffraction grating (5) has 80-120 notches per mm for splitting and diffracting the mid-and far-infrared frequency comb light source.

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