Pulse width adjustable laser and pulse width modulation method thereof

Abstract

The invention relates to the technical field of laser, and provides a pulse width adjustable laser, which comprises a light emitting assembly and a resonant cavity length adjusting assembly, and is characterized in that the light emitting assembly is used for emitting laser; and the resonant cavity length adjusting assembly is used for adjusting the length of the resonant cavity through which the laser passes. The invention also provides a pulse width modulation method of the laser, which comprises the following steps of: S1, preparing the light emitting component, and emitting laser by adopting the light emitting component; s2, using the resonant cavity length adjusting assembly to adjust the length of the resonant cavity; s3, the resonant cavity length adjusting assembly with the adjusted resonant cavity length receives the laser and outputs the laser, the resonant cavity length adjusting assembly is adopted to adjust the length of the resonant cavity through which the laser passes, and therefore the pulse width from the nanosecond level to the microsecond level can be output, and the requirement for different detection distances of the laser radar can be met.

Description

Technical Field

[0001] This invention relates to the field of laser technology, specifically to a pulse-width-tunable laser and its pulse-width modulation method. Background Technology

[0002] In the field of lidar weather radar, the detection range is mainly determined by the coordinated adaptation of laser pulse energy and pulse width, which is the core challenge for achieving accurate environmental monitoring. Short-range detection requires "narrow pulse width + low energy" to ensure accuracy; medium-range detection requires "medium pulse width + medium energy" to balance efficiency and interference; and long-range detection requires "long pulse width and high energy" to overcome atmospheric attenuation. Traditional lasers can only output lasers with fixed pulse widths, making it difficult to simultaneously meet the differentiated needs of lidar in short-range, medium-range, and long-range scenarios. Summary of the Invention

[0003] The purpose of this invention is to provide a pulse width adjustable laser and its pulse width modulation method, which can at least solve some of the defects in the prior art.

[0004] To achieve the above objectives, embodiments of the present invention provide the following technical solution: a pulse-width tunable laser, comprising an optical emitting component and a resonant cavity length adjustment component.

[0005] The light emitting component is used to emit laser light;

[0006] The resonant cavity length adjustment component is used to adjust the length of the resonant cavity through which the laser passes.

[0007] Furthermore, the resonant cavity length adjustment component includes several passive optical fibers of different lengths and a selection structure for selecting one of the passive optical fibers as the laser transmission fiber.

[0008] Furthermore, the selection structure includes two motor optical switches, each having an optical fiber input end and several optical fiber output ends, each optical fiber output end being connected to each of the passive optical fibers, and the two motor optical switches being respectively located at both ends of the passive optical fibers.

[0009] Furthermore, the passive optical fiber is a quartz optical fiber.

[0010] Furthermore, the light emitting component includes a laser crystal for emitting laser light and a pulsed xenon lamp for exciting the laser crystal to emit light.

[0011] Furthermore, the laser crystal is Nd:YAG with a doping concentration of 0.5%at to 1.0%at, a length of 70 to 100 mm, and a diameter of 4 to 6 mm.

[0012] Furthermore, the pulsed xenon lamp is a water-cooled pulsed xenon lamp with an inner diameter of 4~6mm, an arc length of 75~105mm, and a maximum pumping energy of 30J.

[0013] Furthermore, the optical emitting component also includes a passive Q-switch disposed on the laser optical path.

[0014] Furthermore, the laser output by the resonant cavity length adjustment component is emitted through the output mirror, and an infrared plano-convex lens is provided between the resonant cavity length adjustment component and the output mirror.

[0015] The present invention also provides the following technical solution: a pulse width modulation method for a laser, characterized by comprising the following steps:

[0016] S1, Prepare the light emitting component and use the light emitting component to emit laser light;

[0017] S2, the length of the resonant cavity is adjusted using the resonant cavity length adjustment component;

[0018] S3, the resonant cavity length adjustment component, after adjusting the resonant cavity length, receives the laser and outputs it.

[0019] Compared with the prior art, the beneficial effects of the present invention are: by using a resonant cavity length adjustment component to adjust the length of the resonant cavity through which the laser passes, the output pulse width can be adjusted from nanosecond to microsecond, which can meet the needs of different detection distances of lidar. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of a pulse-width adjustable laser provided in an embodiment of the present invention;

[0021] In the attached diagram, the following labels are used: 1-reflector; 2-laser crystal; 3-pulsed xenon lamp; 4-infrared plano-convex lens; 5-passive Q-switch; 6-infrared plano-convex lens; 7-first motor optical switch; 8-passive optical fiber; 9-second motor optical switch; 10-infrared plano-convex lens; 11-output mirror. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] Please see Figure 1This invention provides a pulse-width-adjustable laser, including an optical emitting component and a resonant cavity length adjustment component. The optical emitting component is used to emit laser light; the resonant cavity length adjustment component is used to adjust the length of the resonant cavity through which the laser light passes. In this embodiment, by using the resonant cavity length adjustment component to adjust the length of the resonant cavity through which the laser light passes, a pulse width ranging from nanoseconds to microseconds can be achieved, which can meet the needs of lidar for different detection distances.

[0024] Please see Figure 1 The resonant cavity length adjustment component includes several passive optical fibers 8 of different lengths and a selection structure for selecting one of the passive optical fibers 8 as the laser transmission fiber. In this embodiment, multiple passive optical fibers 8 are used to adjust the resonant cavity length. Specifically, the passive optical fibers 8 have different lengths. By selecting passive optical fibers 8 of different lengths to transmit the laser, the resonant cavity length can be adjusted. As shown in this embodiment, three passive optical fibers 8 can be 10m, 50m, and 100m respectively. By selecting different passive optical fibers 8, different resonant cavity lengths can be adjusted.

[0025] Please see Figure 1The selection structure includes two motor-driven optical switches, namely a first motor-driven optical switch 7 and a second motor-driven optical switch 9. Each motor-driven optical switch has an optical fiber input end and several optical fiber output ends. Each optical fiber output end is connected to a passive optical fiber 8. The two motor-driven optical switches are respectively located at both ends of the passive optical fiber 8. In this embodiment, motor-driven optical switches can be used to select different passive optical fibers 8. Each passive optical fiber 8 is connected to the upper, middle, and lower ports of the optical fiber output end of the motor-driven optical switch. The motor-driven optical switch is a 3×1 optical switch, with one optical fiber input end and three optical fiber output ends. The optical fiber output ends can be fixed, and the input end and the three output ends can be aligned by driving the motor to control the input light to output from different output ends. To select which optical fiber output end to output from, the position of the motor is switched by rotating the motor. For example, to allow the laser to pass through the uppermost passive optical fiber 8, the motors of the two motor-driven optical switches must align their respective output ports with the uppermost passive optical fiber 8, thus ensuring light passage. Specifically, when the drive motor rotates to align the input and output ends of the motor optical switch, the laser passes through the upper passive fiber but not the middle or lower passive fibers. At this point, the resonant cavity length is at its minimum, and with a pump energy of 10J, the output laser output is 10ns and 5mJ, suitable for short-range detection. When the drive motor rotates to align the input and output ends of the motor optical switch, the laser passes through the middle passive fiber but not the upper or lower passive fibers. At this point, the resonant cavity length is moderate, and with a pump energy of 20J, the output laser output is 400ns and 30mJ, suitable for medium-range detection. When the drive motor rotates to align the input and output ends of the motor optical switch, the laser passes through the lower passive fiber but not the upper or middle passive fibers. At this point, the resonant cavity length is at its maximum, and with a pump energy of 30J, the output laser output is 1us and 100mJ, suitable for long-range detection. Preferably, the passive fiber 8 is a quartz fiber. This embodiment uses three passive optical fibers 8. In actual operation, we can select more passive optical fibers 8 as needed to allow for a wider adjustment range and more precise adjustment. Multiple motor-driven optical switches can be used in conjunction to ensure that each passive optical fiber 8 can be controlled.

[0026] Please see Figure 1The light-emitting component includes a laser crystal 2 for emitting laser light and a pulsed xenon lamp 3 for exciting the laser crystal 2 to emit light. In this embodiment, the energy of the pulsed xenon lamp 3 excites the laser crystal 2 to emit laser light. The laser light is reflected by a reflector 1 to an infrared plano-convex lens 4, then passes through a passive Q-switch 5, and then through an infrared plano-convex lens 6 before being emitted by a resonant cavity length adjustment component. After the cavity length of the resonant cavity is adjusted by the resonant cavity length adjustment component, it passes through an infrared plano-convex lens 10 and is finally output by an output mirror 1111. Preferably, the laser crystal 2 is Nd:YAG with a doping concentration of 0.5%at to 1.0%at, a length of 70~100mm, and a diameter of 4~6mm. The pulsed xenon lamp 3 is a water-cooled pulsed xenon lamp 3 with an inner diameter of 4~6mm, an arc length of 75~105mm, and a maximum pump energy of 30J. The curvature of the infrared plano-convex lens 4 can be between 40~60mm, and the curvatures of the infrared plano-convex lens 6 and the infrared plano-convex lens 10 can both be between 15~25mm. The passive Q-switch 5 is made of Cr:YAG with an initial transmittance of 15%-30%, a diameter of 8 to 10 mm, and a thickness of 2 to 3 mm. The output mirror 11 is an infrared planar partial reflector 1 with a reflection angle of 0° and a reflectivity of 5%-10%.

[0027] Please see Figure 1 This invention also provides a laser pulse width modulation method, characterized by the following steps: S1, preparing an optical emitting component and emitting laser light using the optical emitting component; S2, adjusting the length of the resonant cavity using the resonant cavity length adjustment component; S3, receiving and outputting the laser light using the resonant cavity length adjustment component with the adjusted resonant cavity length. When pulse width adjustment is required, the length of the resonant cavity corresponding to the required pulse width is adjusted using the resonant cavity length adjustment component, and then the laser light is output from the resonant cavity length adjustment component to obtain the corresponding laser pulse width. This allows the modulated laser to output pulse widths from nanoseconds to micrometers, while simultaneously meeting the needs of different detection distances for lidar.

[0028] Please see Figure 1In step S3, the specific adjustment method involves using a motor-driven optical switch to select different passive optical fibers 8. Each passive optical fiber 8 is connected to one of the three ports (upper, middle, and lower) of the optical fiber output end of the motor-driven optical switch. The motor-driven optical switch is a 3×1 optical switch, with one optical fiber input end and three optical fiber output ends. The optical fiber output ends can be fixed, and the input end and the three output ends are aligned by driving the motor to control the input light to be output from different output ends. To select which optical fiber output end to output from, the position of the motor is switched by rotating the motor. For example, to allow the laser to pass through the uppermost passive optical fiber 8, the motors of the two motor-driven optical switches need to align their respective output ports with the uppermost passive optical fiber 8, thus ensuring that the light passes through. Specifically, when the drive motor rotates to align the input and output ends of the motor optical switch, the laser passes through the upper passive fiber but not the middle or lower passive fibers. At this point, the resonant cavity length is at its minimum, and with a pump energy of 10J, the output laser output is 10ns and 5mJ, suitable for short-range detection. When the drive motor rotates to align the input and output ends of the motor optical switch, the laser passes through the middle passive fiber but not the upper or lower passive fibers. At this point, the resonant cavity length is moderate, and with a pump energy of 20J, the output laser output is 400ns and 30mJ, suitable for medium-range detection. When the drive motor rotates to align the input and output ends of the motor optical switch, the laser passes through the lower passive fiber but not the upper or middle passive fibers. At this point, the resonant cavity length is at its maximum, and with a pump energy of 30J, the output laser output is 1us and 100mJ, suitable for long-range detection. Preferably, the passive fiber 8 is a quartz fiber. This embodiment uses three passive optical fibers 8. In actual operation, we can select more passive optical fibers 8 as needed to allow for a wider adjustment range and more precise adjustment. Multiple motor-driven optical switches can be used in conjunction to ensure that each passive optical fiber 8 can be controlled.

[0029] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A pulse width adjustable laser, characterized by: The light emitting assembly and the resonant cavity length adjusting assembly, The light emitting assembly is used for emitting laser. The resonant cavity length adjusting assembly is used for adjusting the length of the resonant cavity through which the laser passes.

2. The adjustable pulse width laser of claim 1, wherein: The resonant cavity length adjusting assembly comprises several passive optical fibers with different lengths and a selection structure for selecting one of the passive optical fibers as a laser transmission optical fiber.

3. The adjustable pulse width laser of claim 2, wherein: the first and second pulse width control signals are generated by a pulse width control circuit. The selection structure comprises two motorized optical switches with optical fiber input ends and several optical fiber output ends, each of which is in communication with each of the passive optical fibers, and the two motorized optical switches are arranged at two ends of the passive optical fibers.

4. The adjustable pulse width laser of claim 2, wherein: The passive optical fiber is a quartz optical fiber.

5. The adjustable pulse width laser of claim 1, wherein: The light emitting assembly comprises a laser crystal for emitting laser and a pulsed xenon lamp for exciting the laser crystal to emit light.

6. The adjustable pulse width laser of claim 5, wherein: The laser crystal is Nd:YAG with a doping concentration of 0.5%at to 1.0%at, a length of 70-100 mm and a diameter of 4-6 mm.

7. The adjustable pulse width laser of claim 5, wherein: the first and second pulse width control signals are generated by a pulse width control circuit. The pulsed xenon lamp is a water-cooled pulsed xenon lamp with an inner diameter of 4-6 mm, an arc length of 75-105 mm and a maximum pumping energy of 30 J.

8. The adjustable pulse width laser of claim 1, wherein: The light emitting assembly further comprises a passive Q switch arranged in the laser light path.

9. The adjustable pulse width laser of claim 1, wherein: The laser output by the resonant cavity length adjusting assembly is emitted through an output mirror, and an infrared plano-convex lens is arranged between the resonant cavity length adjusting assembly and the output mirror.

10. A method of pulse width modulation of a laser, characterized by, The method comprises the following steps: S1, preparing a light emitting assembly and emitting laser by using the light emitting assembly; S2, adjusting the length of the resonant cavity by using the resonant cavity length adjusting assembly; S3, the resonant cavity length adjusting assembly with the adjusted resonant cavity length receives the laser and outputs.

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