CN112688166B - Chaotic laser and laser radar - Google Patents
Chaotic laser and laser radar Download PDFInfo
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- CN112688166B CN112688166B CN201910993930.4A CN201910993930A CN112688166B CN 112688166 B CN112688166 B CN 112688166B CN 201910993930 A CN201910993930 A CN 201910993930A CN 112688166 B CN112688166 B CN 112688166B
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Abstract
The application discloses a chaotic laser and a laser radar, relates to the field of lasers, and is used for reducing the time required by the chaotic laser to enter a chaotic state. A chaotic laser comprising: the laser chip comprises a first light emitting surface and a second light emitting surface, the laser reflection unit is arranged opposite to the first light emitting surface, and the laser reflection unit and the laser chip form an outer feedback cavity; the laser chip emits laser through the first light emitting surface and the second light emitting surface; the laser reflection unit is used for reflecting the laser emitted by the first light emitting surface to the first light emitting surface and forming chaotic laser with the laser emitted by the second light emitting surface.
Description
Technical Field
The application relates to the field of lasers, in particular to a chaotic laser and a laser radar.
Background
As an active sensor, the laser radar is an indispensable key device in the fields of automatic driving, robots, unmanned aerial vehicles and the like. As shown in fig. 1, the lidar includes a laser 101, a transmitting optical module 102, a receiving optical module 103, a detector 104, and a signal processing module 105. The laser 101 generates laser, the laser is emitted by the emission optical module 102, reflected by the target object, received by the detector 104 through the receiving optical module 103, and the distance between the laser and the target object is calculated by the signal processing module 105 according to the flight time of the laser.
Because the amount of laser information emitted by the laser is very small, when interference laser exists outside, the laser radar cannot distinguish the laser emitted by the laser radar from the received reflected signal and the laser emitted by other laser radars. In the prior art, the anti-interference capability of the laser radar is improved by chaotic lasers. The lasers emitted by any two different chaotic lasers are different, and the lasers emitted by the same chaotic laser at different moments are random.
As shown in fig. 2, a pulse-based chaotic laser in the prior art includes: a Pulse Generator (PG) 201, a Laser Diode (LD) 202, a Fiber Coupler (FC) 203, a Variable Attenuator (VA) 204, a Fiber Mirror (FM) 205, a Power Meter (PM) 206, an optical Isolator (ISO) 207, a Photodetector (PD) 208, and an Oscilloscope (OSC) 209. The FC 203, VA 204, FM 205 constitute an external feedback cavity, the PG 201 drives the laser 202 to generate laser light, the laser light is reflected by the FM 205 in the external feedback cavity, and the reflected laser light is fed back into the laser 202 via the FC 203. After the laser makes many round trips in the external feedback cavity, the laser enters a chaotic state (i.e. exhibits randomness), and chaotic laser light is output by the ISO 207.
In the scheme, the external feedback cavity is composed of optical fiber separating elements, the length is generally in a meter level, and the laser does not immediately enter a chaotic state after receiving reflected laser and outputs the chaotic laser, so that the longer the external feedback cavity is, the longer the time required for the laser to enter the chaotic state is. Therefore, the effective length (randomness) of the chaotic state in each pulse laser is reduced, and the anti-interference capability is weakened.
Disclosure of Invention
The embodiment of the application provides a chaotic laser and a laser radar, which are used for reducing the time required by the chaotic laser to enter a chaotic state.
In order to achieve the above purpose, the embodiment of the present application adopts the following technical solutions:
in a first aspect, there is provided a chaotic laser comprising: the laser device comprises a laser device chip and a laser reflection unit, wherein the laser device chip comprises a first light emitting surface and a second light emitting surface, the laser reflection unit is arranged opposite to the first light emitting surface, and the laser reflection unit and the laser device chip form an outer feedback cavity; the laser chip emits laser through the first light emitting surface and the second light emitting surface; the laser reflection unit is used for reflecting the laser emitted by the first light emitting surface to the first light emitting surface and forming chaotic laser with the laser emitted by the second light emitting surface.
According to the chaotic laser provided by the embodiment of the application, the laser reflection unit and the laser chip form the outer feedback cavity, the length of the outer feedback cavity can be reduced to the centimeter level, and therefore the time required by the chaotic laser to enter a chaotic state is greatly reduced.
In one possible embodiment, the distance between the laser reflection unit and the first light emitting surface is 1-2 cm. Namely, the length of the outer feedback cavity can be 1-2 cm, thereby greatly reducing the length of the outer feedback cavity.
In one possible embodiment, the chaotic laser further comprises a laser driver, and the laser driver is configured to output a driving signal to drive the laser chip to emit laser light through the first light emitting surface and the second light emitting surface.
In a possible implementation, the chaotic laser further comprises a monitoring unit and a control unit; the monitoring unit is used for monitoring the working state of the laser chip in real time to obtain monitoring information; the control unit is used for adjusting the intensity of the laser which is reflected to the first light-emitting face by the laser reflection unit according to the monitoring information obtained by the monitoring unit. The chaotic state of the laser chip needs to meet a certain temperature condition, and the chaotic state of the laser chip can be always maintained through the feedback structure.
In a possible embodiment, the laser reflection unit is a MEMS micro-mirror, and the control unit is specifically configured to adjust a rotation angle of the MEMS micro-mirror according to the monitoring information obtained by the monitoring unit.
In a possible embodiment, the laser reflection unit is a digital micromirror device DMD, and the control unit is specifically configured to adjust the number of micromirrors turned on in the DMD according to monitoring information obtained by the monitoring unit.
In one possible embodiment, the monitoring unit is a temperature sensor, and the temperature sensor is used for detecting the operating temperature of the laser chip as the monitoring information.
In a possible implementation manner, the monitoring unit includes a light splitting device and a photodetector, the light splitting device is configured to split the chaotic laser light emitted by the second light emitting surface to obtain first split light, and the photodetector is configured to detect the first split light to obtain a time-domain waveform of the first split light, which is used as monitoring information.
In a possible implementation manner, the chaotic laser is a chaotic pulse laser, and the laser driver is specifically configured to output a pulsed driving signal to drive the laser chip to emit pulsed laser through the first light emitting surface and the second light emitting surface; the laser reflection unit is specifically used for reflecting the pulse laser emitted by the first light emitting surface to the first light emitting surface and forming chaotic pulse laser with the pulse laser emitted by the second light emitting surface. Compared with a chaotic continuous laser, the chaotic pulse laser has a larger range measurement range.
In one possible embodiment, the laser chip and the laser reflection unit are packaged in a package structure. The chaotic laser can be miniaturized and integrally packaged.
In a second aspect, a lidar is provided, which comprises a transmitting optical module, a receiving optical module, a detector, a signal processing module, and the chaotic laser of the first aspect and any implementation manner thereof.
The technical effects of the second aspect are as described in the first aspect and any of the embodiments thereof.
Drawings
Fig. 1 is a first schematic structural diagram of a laser radar according to an embodiment of the present disclosure;
fig. 2 is a schematic structural diagram of a pulse-based chaotic laser according to an embodiment of the present application;
fig. 3 is a schematic structural diagram of a laser radar according to an embodiment of the present disclosure;
fig. 4 is a first schematic structural diagram of a chaotic laser according to an embodiment of the present application;
FIG. 5 is a schematic diagram of a pulsed driving signal for a laser driving output according to an embodiment of the present disclosure;
fig. 6 is a schematic structural diagram of a chaotic laser according to an embodiment of the present application;
fig. 7 is a schematic diagram illustrating a relationship between a rotation angle θ and an optical feedback coefficient γ of a MEMS micro-mirror according to an embodiment of the present disclosure;
fig. 8 is a schematic structural diagram of a chaotic laser according to an embodiment of the present application;
fig. 9 is a schematic diagram of a relationship between the number of micromirrors turned on in the DMD and an optical feedback coefficient γ, and a front view of the DMD according to an embodiment of the present application;
fig. 10 is a schematic structural diagram of a chaotic laser according to an embodiment of the present application;
fig. 11 is a schematic structural diagram of a chaotic laser according to an embodiment of the present application;
fig. 12 is a first schematic packaging diagram of a chaotic laser according to an embodiment of the present application;
fig. 13 is a second schematic packaging diagram of a chaotic laser according to an embodiment of the present application;
fig. 14 is a third schematic packaging diagram of a chaotic laser according to an embodiment of the present application.
Detailed Description
As described above, in the prior art, the outer feedback cavity of the chaotic laser is composed of optical fiber separation elements, the length is generally in the meter level, and the laser does not immediately enter the chaotic state and outputs the chaotic laser after receiving the reflected laser, which results in that the longer the outer feedback cavity is, the longer the time required for the laser to enter the chaotic state is. Therefore, the effective length (randomness) of the chaotic state in each pulse laser is reduced, and the anti-interference capability is weakened. According to the embodiment of the application, a micro electro-mechanical system (MEMS) micro mirror or a digital micro mirror device (DMD) and the like are used as laser reflection units, and an outer feedback cavity is formed by the laser reflection units and a laser chip, so that the length of the outer feedback cavity can be reduced to the centimeter level, and the time required by the chaotic laser to enter a chaotic state is greatly reduced.
An embodiment of the present application provides a laser radar, as shown in fig. 3, which may include: chaotic laser 301, transmitting optical module 302, receiving optical module 303, detector 304 and signal processing module 305. The chaotic laser 301 generates chaotic laser, after the chaotic laser is transmitted through the transmitting optical module 302, the chaotic laser is reflected by a target object and then is received by the detector 304 through the receiving optical module 303, and the signal processing module 305 calculates the distance between the chaotic laser and the target object according to the flight time of the laser.
As shown in fig. 4, a chaotic laser provided in an embodiment of the present application may include: laser driver 401, laser chip 402, laser reflection unit 403. Optionally, the method may further include: a monitoring unit 404 and a control unit 405.
The laser chip 402 includes a first light emitting surface 4021 and a second light emitting surface 4022, the laser reflection unit 403 is disposed opposite to the first light emitting surface 4021, and the laser reflection unit 403 and the laser chip 402 form an external feedback cavity.
The laser driver 401 is configured to output a driving signal to drive the laser chip 402 to emit laser light through the first light emitting surface 4021 and the second light emitting surface 4022.
The laser reflection unit 403 is configured to reflect the laser light emitted by the first light emitting surface 4021 to the first light emitting surface 4021, and form chaotic laser light with the laser light emitted by the second light emitting surface 4022. That is to say, after the laser emitted by the laser chip 402 through the first light emitting surface 4021 is reflected by the laser reflection unit 403, the laser is repeatedly reflected in the external feedback cavity, and a part of the laser is re-coupled into the laser chip 402 through the first light emitting surface 4021, so that the laser chip enters a chaotic state.
The monitoring unit 404 is configured to monitor the operating state of the laser chip 402 in real time to obtain monitoring information.
The control unit 405 is configured to adjust intensity (referred to as an optical feedback coefficient for short) of laser light reflected by the laser reflection unit 403 to the first light emitting surface 4021 according to the monitoring information obtained by the monitoring unit 404, or, in other words, adjust intensity of laser light that is reflected by the laser reflection unit 403 and then coupled into the laser chip 402 through the first light emitting surface 4021, thereby adjusting the optical feedback coefficient of the laser reflection unit 403 and dynamic characteristics of the chaotic laser, so that the laser light emitted by the laser chip 402 through the second light emitting surface 4022 is always kept in a chaotic state.
Optionally, the chaotic laser may be a chaotic continuous light laser, that is, the laser driver 301 may be a continuous laser driver, and is configured to output a continuous driving signal to drive the laser chip 402 to emit continuous laser through the first light emitting surface 4021 and the second light emitting surface 4022. The laser reflection unit 403 is specifically configured to reflect the continuous laser light emitted by the first light emitting surface to the first light emitting surface 4021, and form chaotic continuous laser light with the continuous laser light emitted by the second light emitting surface 4022.
Alternatively, the chaotic laser may be a chaotic pulse laser, and the laser driver 401 may be a pulse laser driver, configured to output a pulse-type driving signal with a certain period and time width to drive the laser chip 402 to emit pulse laser through the first light emitting surface 4021 and the second light emitting surface 4022. The laser reflection unit 403 is specifically configured to reflect the pulse laser emitted by the first light emitting surface 4021 to the first light emitting surface 4021, and form a chaotic pulse laser with the pulse laser emitted by the second light emitting surface 4022. The embodiments of the present application take the chaotic pulse laser as an example for explanation, but are not intended to be limited thereto.
When the laser driver 401 is a pulsed laser driver, the period and time width of the pulsed laser light emitted from the laser chip 402 can also be controlled. As shown in fig. 5, the period of the pulse-type driving signal output by the laser driver 401 is T + PW, the pulse interval is T, and the time width is PW, and by adjusting these parameters, the period and the time width of the pulse laser emitted by the laser chip 402 can be adjusted.
Alternatively, the laser reflection unit 403 may be a micro electro-mechanical system (MEMS) micro-mirror or a digital micro-mirror device (DMD), and the like, and the present application is not limited thereto. MEMS micromirrors are optical MEMS devices that are fabricated using MEMS technology and integrate the micromirror with MEMS actuators. A DMD is an array of multiple high-speed digital light reflections.
When the laser reflection unit 403 is an MEMS micro-mirror, the control unit 405 is specifically configured to adjust a rotation angle of the MEMS micro-mirror according to the monitoring information obtained by the monitoring unit 404. When the laser reflection unit 403 is a DMD, the control unit 405 is specifically configured to adjust the number of micromirrors turned on in the DMD according to the monitoring information obtained by the monitoring unit 404. The operation principle of the present application in the embodiments related to the MEMS micro-mirror and the DMD will be described later.
Optionally, the distance between the laser reflection unit 403 and the first light emitting surface 4021 is 1 to 2cm. The outer feedback cavity formed by the laser reflection unit 403 and the laser chip 402 is short, so that the time required by the laser to enter a chaotic state can be greatly shortened, and the time length of a chaotic sequence in a pulse is prolonged. The anti-interference capability can be improved by using the light source as the light source of the laser radar. In addition, very short pulse type chaotic laser can be generated, which is beneficial to improving pulse repetition frequency, thereby improving point cloud density (angular resolution); on the premise of ensuring the safety of human eyes, the peak power can be further improved, and the detection distance is increased. And, the delay characteristic can be misjudged only when the detection distance is centimeter-level, and has almost no influence on the actual distance measurement.
Optionally, the monitoring unit 404 may be a temperature sensor, and the temperature sensor is configured to detect an operating temperature of the laser chip 402 as the monitoring information. The monitoring unit 404 may include a light splitter and a photodetector, the light splitter being configured to split the chaotic laser light emitted from the second light emitting surface to obtain a first split light, for example, a beam splitter or a beam splitter. The photoelectric detector is used for detecting the first light split to obtain a time domain waveform of the first light split as monitoring information.
Various possible combinations of the laser reflection unit 403 and the monitoring unit 404 are exemplarily described below.
In one possible embodiment, as shown in fig. 6, the laser reflection unit 403 may be a MEMS micro-mirror 603 and the monitoring unit 404 may be a temperature sensor 604.
The laser driver 401 outputs a pulse-type driving signal having a certain period and time width to drive the laser chip 402 to emit pulse laser light through the first light emitting surface 4021 and the second light emitting surface 4022. After being reflected by the MEMS micromirror 603, the pulse laser emitted by the laser chip 402 through the first light emitting surface 4021 is repeatedly reflected in the external feedback cavity, and a part of the laser is re-coupled into the laser chip 402 through the first light emitting surface 4021, so that the laser chip 402 enters a chaotic state and emits chaotic laser through the second light emitting surface 4022.
When the laser chip 402 needs to satisfy a certain temperature condition while maintaining the chaotic state, and the monitoring unit 404 is the temperature sensor 604, the control unit 405 may adjust the rotation angle θ of the MEMS micro-mirror 603 according to the working temperature T of the laser chip 402 measured by the temperature sensor 604, so as to adjust the size of a light spot (equivalent to the intensity of laser light) reflected to the first light emitting surface 4021 of the laser chip 402 by the MEMS micro-mirror 603, thereby adjusting the intensity of the laser light coupled into the laser chip 402 through the first light emitting surface 4021.
Specifically, the control unit 405 may obtain the intensity (optical feedback coefficient) γ of the laser light reflected to the first light emitting surface 4021 according to the working temperature T of the laser chip 402 measured by the temperature sensor 604, and then obtain the rotation angle θ of the MEMS micro-mirror 603 according to the optical feedback coefficient γ.
First, the relationship between the operating temperature T of the laser chip 402 and the intensity (optical feedback coefficient) γ of the laser light reflected to the first light emitting surface 4021 may be determined through experiments, and the control unit 405 may determine the optical feedback coefficient γ according to the relationship and the actually measured operating temperature T of the laser chip 402. Illustratively, the above relationship is shown in table 1.
TABLE 1
| Temperature of | Coefficient of optical feedback |
| T 1 ～T 2 | γ 1 ～γ 2 |
| T 3 ～T 4 | γ 3 ～γ 4 |
| T 5 ～T 6 | γ 5 ～γ 6 |
Fig. 7 is a schematic diagram showing a relationship between the rotation angle θ of the MEMS micro-mirror 603 and the optical feedback coefficient γ. Assuming that the initial state of the MEMS micro-mirror 603 is a vertical state, the height of the first light emitting surface 4021 of the laser chip 402 is D 0 The divergence angle of the laser is α, the specular reflectivity of the MEMS micro-mirror 603 is η, and the distance between the first light emitting surface 4021 and the MEMS micro-mirror 603 (i.e., the length of the external feedback cavity) is L. Under the control of the control unit 405, if the rotation angle of the MEMS micro mirror 603 is θ, the size D of the light spot reflected to the first light emitting surface 4021 of the laser chip 402 is:
d = L · [ tan (2 θ + α/2) -tan (2 θ - α/2) +2tan (α/2) ] formula 1
The optical feedback coefficient γ is:
if γ is expressed as f (θ), the control unit 405 can control the rotation angle of the MEMS micro-mirror 603 to be θ:
θ＝f -1 (gamma) formula 3
Wherein the function f -1 Is the inverse of function f.
Illustratively, assume that the operating temperature T of the laser chip 402 measured by the temperature sensor 604 satisfies T 1 ＜T＜T 2 Then, the intensity (optical feedback coefficient) γ of the laser light reflected to the first light emitting surface 4021 can be obtained from table 1 1 To gamma 2 The middle value γ is substituted into formula 3 to obtain the rotation angle θ of the MEMS micromirror 603.
In another possible embodiment, as shown in fig. 8, the laser reflection unit 403 may be a DMD 803, and the monitoring unit 404 may be a temperature sensor 804.
The laser driver 401 outputs a pulse-type driving signal having a certain period and time width to drive the laser chip 402 to emit pulse laser light through the first light emitting surface 4021 and the second light emitting surface 4022. After pulse laser emitted by the laser chip 402 through the first light emitting surface 4021 is reflected by the DMD 803, the pulse laser is repeatedly reflected in the external feedback cavity, and a part of the laser is re-coupled into the laser chip 402 through the first light emitting surface 4021, so that the laser chip 402 enters a chaotic state and emits chaotic laser through the second light emitting surface 4022.
When the laser chip 402 needs to satisfy a certain temperature condition while maintaining the chaotic state, and the monitoring unit 404 is the temperature sensor 804, the control unit 405 may adjust the number of micromirrors turned on in the DMD 803 according to the working temperature T of the laser chip 402 measured by the temperature sensor 804, thereby adjusting the intensity of the laser light reflected to the first light emitting face 4021 of the laser chip 402 by the DMD 803, so as to adjust the intensity of the laser light coupled into the laser chip 402 through the first light emitting face 4021.
Specifically, the control unit 405 may obtain the intensity (optical feedback coefficient) γ of the laser light reflected to the first light emitting surface 4021 according to the operating temperature T of the laser chip 402 measured by the temperature sensor 804, and then adjust the number of micromirrors turned on in the DMD 803 according to the optical feedback coefficient γ.
As shown in fig. 9B, which is a front view of the DMD 803, a white square indicates that the micromirror is in an "on" state (rotated by 0 °), and the laser light irradiated to the micromirror is reflected into the laser chip 402; black squares indicate the micromirror in the "off" state (rotation [ delta ] 1 ,δ 2 ]12 deg.), the laser light impinging on the micromirror is not reflected into laser chip 402.
The manner in which the intensity (optical feedback coefficient) γ of the laser light reflected to the first light emitting surface 4021 is obtained from the operating temperature T of the laser chip 402 measured by the temperature sensor 804 is described above with reference to fig. 6, and will not be repeated here.
As shown in a in fig. 9, a diagram is a relationship between the number of micromirrors turned on in the DMD 803 and the optical feedback coefficient γ. The divergence angle of the laser light emitted from the first light-emitting surface 4021 of the laser chip 402 is α, the specular reflectivity of the micromirror of the DMD 803 is η, the width of the micromirror of the DMD 803 is D, the distance between the first light-emitting surface 4021 and the DMD 803 (i.e., the length of the external feedback cavity) is L, and the height (or width) D of a light spot irradiated on the DMD 803 is:
d =2L · tan (α/2) formula 4
The number N of micromirrors illuminated by the laser on the DMD 803 is (assuming that the light spot is square, the specific calculation formula can be defined according to the specific shape of the light spot):
N＝(D/d) 2 equation 5
The control unit 405 adjusts the number M of micromirrors turned on in the DMD 803 according to the optical feedback coefficient γ to:
illustratively, it is assumed that the operating temperature T of the laser chip 402 measured by the temperature sensor 804 satisfies T 1 ＜T＜T 2 Then, the intensity (optical feedback coefficient) γ of the laser light reflected to the first light emitting surface 4021 can be obtained from table 1 as γ 1 To gamma 2 The middle value γ, then the number M of micromirrors turned on in DMD 803 is obtained by substituting γ into equation 6.
In yet another possible embodiment, as shown in fig. 10, the laser reflection unit 403 may be a MEMS micro-mirror 1003, and the monitoring unit 404 may include a light splitting device 1004 and a photodetector 1005.
The laser driver 401 outputs a pulse-type driving signal having a certain period and time width to drive the laser chip 402 to emit pulse laser light through the first light emitting surface 4021 and the second light emitting surface 4022. After being reflected by the MEMS micro-mirror 1003, the pulse laser emitted by the laser chip 402 through the first light emitting surface 4021 is repeatedly reflected in the external feedback cavity, and a part of the laser is re-coupled into the laser chip 402 through the first light emitting surface 4021, so that the laser chip 402 enters a chaotic state and emits chaotic laser through the second light emitting surface 4022.
The optical splitter 1004 splits the chaotic laser emitted by the second light emitting surface 4022 of the laser chip 402 to obtain a first split light, the photodetector 1005 detects the first split light to obtain and converts the first split light into an electrical signal to obtain a time domain waveform of the first split light, the time domain waveform is used as monitoring information, and the control unit 405 may perform chaotic state or randomness analysis according to the time domain waveform of the first split light.
Specifically, the peak distribution characteristic of the time domain waveform of the first beam splitter represents the chaotic state or randomness of the laser before beam splitting. If the laser is in a chaotic state or presents randomness, the peak value distribution is very dispersed and is close to Gaussian distribution under an ideal condition; otherwise, the peak distribution is concentrated. Therefore, the output characteristics of the laser can be monitored and controlled in real time according to the time-domain waveform of the first split light.
The control unit 405 may normalize the time-domain waveform of the first beam splitter, and then count a variance δ of a peak distribution of the time-domain waveform of the first beam splitter 0 Sum mean μ 0 (this step may be performed by the chaotic state analysis module). According to the variance delta 0 Whether or not delta is satisfied 0 ∈[δ 1 ,δ 2 ]Mean value of μ 0 Whether or not it satisfies mu 0 ∈[μ 1 ,μ 2 ]The rotation angle θ of the MEMS micro-mirror 1003 is adjusted, so as to adjust the spot size (corresponding to the intensity of the laser light) of the first light-emitting surface 4021 reflected by the MEMS micro-mirror 1003 to the laser chip 402, thereby adjusting the intensity of the laser light coupled into the laser chip 402 through the first light-emitting surface 4021. Wherein [ delta ] 1 ,δ 2 ]A variance interval [ mu ] representing the peak distribution of the time domain waveform when the laser chip 402 is in the chaotic state 1 ,μ 2 ]And represents the mean interval of the peak distribution of the time domain waveform when the laser chip 402 is in the chaotic state.
Illustratively, the variance δ of the statistical peak distribution is assumed 0 ∈[δ 1 ,δ 2 ]Mean value of μ 0 ∈[μ 1 ,μ 2 ]Then, the intensity (optical feedback coefficient) γ of the laser light reflected to the first light emitting surface 4021 can be obtained from table 2 1 To gamma 2 The middle value is gamma, and then the gamma is substituted into formula 3 to obtain the rotation angle theta of the MEMS micro-mirror 1003.
TABLE 2
| Variance delta 0 Distribution of | Mean value μ 0 Distribution of | Coefficient of optical feedback |
| [δ 1 ,δ 2 ] | [μ 1 ,μ 2 ] | γ 1 ～γ 2 |
| [δ 3 ,δ 4 ] | [μ 3 ,μ 4 ] | γ 3 ～γ 4 |
| [δ 5 ,δ 6 ] | [μ 5 ,μ 6 ] | γ 5 ～γ 6 |
In yet another possible embodiment, as shown in fig. 11, the laser reflection unit 403 may be the DMD1103 and the monitoring unit 404 may include a light splitting device 1104 and a photodetector 1105.
The laser driver 401 outputs a pulse-type driving signal having a certain period and time width to drive the laser chip 402 to emit pulse laser light through the first light emitting surface 4021 and the second light emitting surface 4022. After pulse laser emitted by the laser chip 402 through the first light emitting surface 4021 is reflected by the DMD1103, the pulse laser is repeatedly reflected in the external feedback cavity, and a part of the laser is re-coupled into the laser chip 402 through the first light emitting surface 4021, so that the laser chip 402 enters a chaotic state and emits chaotic laser through the second light emitting surface 4022.
The light splitting device 1104 splits the chaotic laser emitted by the second light emitting surface 4022 of the laser chip 402 to obtain a first split light, the photodetector 1105 detects the first split light to obtain and converts the first split light into an electrical signal to obtain a time domain waveform of the first split light, and the time domain waveform of the first split light is used as monitoring information, and the control unit 405 may perform chaotic state or randomness analysis according to the time domain waveform of the first split light.
The control unit 405 may normalize the time-domain waveform of the first beam splitter, and then count a variance δ of a peak distribution of the time-domain waveform of the first beam splitter 0 Sum mean μ 0 (this step may be performed by the chaotic state analysis module). According to the variance delta 0 Whether or not delta is satisfied 0 ∈[δ 1 ,δ 2 ]Mean value μ 0 Whether or not it satisfies mu 0 ∈[μ 1 ,μ 2 ]The number of micromirrors turned on in the DMD1103 is adjusted to adjust the intensity of the laser light reflected to the first light emitting surface 4021 of the laser chip 402 by the DMD1103, thereby adjusting the intensity of the laser light coupled into the laser chip 402 through the first light emitting surface 4021. Wherein [ delta ] 1 ,δ 2 ]A variance interval [ mu ] representing the peak distribution of the time domain waveform when the laser chip 402 is in the chaotic state 1 ,μ 2 ]And represents the mean interval of the peak distribution of the time domain waveform when the laser chip 402 is in the chaotic state.
Illustratively, the variance δ of the statistical peak distribution is assumed 0 ∈[δ 1 ,δ 2 ]Mean value μ 0 ∈[μ 1 ,μ 2 ]Then, the intensity (optical feedback coefficient) γ of the laser light reflected to the first light emitting surface 4021 is γ, which can be obtained from table 2 1 To gamma 2 The middle value γ is then substituted into equation 6 to obtain the number M of micromirrors turned on in the DMD 1103.
The chaotic laser provided by the embodiment of the application can package the laser chip 402 and the laser reflection unit 403 in a butterfly package structure or a dual in-line package structure, thereby realizing miniaturization and integrated package. The packaging structure can adopt a metal shell. Fig. 12-14 illustrate several possible packaging configurations for a chaotic laser, using a butterfly package as an example, but the present application is not intended to be limited thereto.
In fig. 12, the laser chip 402, the laser reflection unit 403, and the monitoring unit 404 may be packaged in a package structure, and the laser driver 401 and the control unit 405 may be disposed outside the package structure. In fig. 13, the laser chip 402, the laser reflection unit 403, the monitoring unit 404, and the control unit 405 may be packaged in a package structure, and the laser driver 401 may be disposed outside the package structure. In fig. 14, a laser chip 402 and a laser reflection unit 403 may be packaged in a package structure, and a laser driver 401, a monitoring unit 404, and a control unit 405 may be disposed outside the package structure. Because the laser chip 402 and the laser reflection unit 403 are packaged in the butterfly package structure or the dual in-line package structure, the structure is compact, the adjustment is flexible, and the integration is easy.
As shown in fig. 12-14, the laser driver 401 may be connected to the laser chip 402 through a pin, and the driving signal output by the laser driver 401 is introduced into the laser chip 402 through the pin. The distance between the first light emitting surface of the laser chip 402 and the laser reflection unit 403 may be 1-2 cm, forming a short external feedback cavity. The laser emitted from the laser chip 402 through the first light emitting surface reciprocates in the feedback cavity many times, a part of the laser is re-coupled into the laser chip 402, and an outgoing laser is formed on the second light emitting surface of the laser chip 402.
As shown in fig. 12 or fig. 13, the monitoring unit 404 may be directly connected to the laser chip 402. Alternatively, as shown in fig. 14, the monitoring unit 404 may be connected to the laser chip 402 through a pin. The monitoring unit 404 may monitor the operating state of the laser in real time.
As shown in fig. 12, the control unit 405 may be connected to the monitoring unit 404 through a pin, and connected to the laser reflection unit 403 through a pin. Alternatively, as shown in fig. 13, the control unit 405 may be directly connected to the monitoring unit 404 and the laser reflection unit 403. Alternatively, as shown in fig. 14, the control unit 405 may be directly connected to the monitoring unit 404 and connected to the laser reflection unit 403 through a pin.
According to the chaotic laser and the laser radar, the laser reflection unit and the laser chip form the outer feedback cavity, the length of the outer feedback cavity can be reduced to the centimeter level, and therefore the time required by the chaotic laser to enter a chaotic state is greatly reduced.
The above description is only for the specific embodiments of the present application, but the scope of the present application is not limited thereto, and any person skilled in the art can easily think of the changes or substitutions within the technical scope of the present application, and shall be covered by the scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.
Claims (8)
1. A chaotic laser, comprising: the device comprises a laser chip, a laser reflection unit, a monitoring unit and a control unit, wherein the laser chip comprises a first light emitting surface and a second light emitting surface, the laser reflection unit is arranged opposite to the first light emitting surface, and the laser reflection unit and the laser chip form an outer feedback cavity;
the laser chip emits laser through the first light emitting face and the second light emitting face;
the laser reflection unit is used for reflecting the laser emitted by the first light emitting surface to the first light emitting surface and forming chaotic laser with the laser emitted by the second light emitting surface;
the monitoring unit is used for monitoring the working state of the laser chip in real time to obtain monitoring information, wherein the monitoring information is the working temperature of the laser chip or a first spectroscopic time domain waveform obtained by spectroscopic of the chaotic laser;
the control unit is used for obtaining an optical feedback coefficient of laser reflected to the first light emitting face according to the working temperature, or counting the variance and the mean value of the peak value distribution after normalizing the time domain waveform, and obtaining the optical feedback coefficient according to the variance and the mean value;
the control unit is further configured to adjust the intensity of the laser light reflected to the first light emitting surface by the laser reflection unit according to the optical feedback coefficient.
2. The chaotic laser of claim 1, wherein a distance between the laser reflection unit and the first light emitting face is 1-2 cm.
3. The chaotic laser of any one of claims 1-2, further comprising a laser driver configured to output a driving signal to drive the laser chip to emit laser light through the first and second light emitting facets.
4. The chaotic laser of any one of claims 1-2, wherein the laser reflecting unit is a MEMS micromirror, and the control unit is specifically configured to adjust a rotation angle of the MEMS micromirror according to the monitoring information obtained by the monitoring unit.
5. The chaotic laser according to any one of claims 1-2, wherein the laser reflection unit is a Digital Micromirror Device (DMD), and the control unit is specifically configured to adjust the number of micromirrors turned on in the DMD according to monitoring information obtained by the monitoring unit.
6. The chaotic laser according to any one of claims 1-2, wherein the chaotic laser is a chaotic pulse laser, and the laser driver is specifically configured to output a pulsed driving signal to drive the laser chip to emit pulsed laser through the first light emitting face and the second light emitting face; the laser reflection unit is specifically used for reflecting the pulse laser emitted by the first light emitting surface to the first light emitting surface, and forming chaotic pulse laser with the pulse laser emitted by the second light emitting surface.
7. The chaotic laser of any one of claims 1-2, wherein the laser chip and the laser reflection unit are packaged in a package structure.
8. Lidar characterized by comprising a transmitting optical module, a receiving optical module, a detector, a signal processing module and a chaotic laser according to any one of claims 1 to 7.
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