Nanosecond pulse laser synthesizer for laser active illumination

Abstract

The invention provides a nanosecond pulse laser synthesizer for laser active illumination, and relates to the field of laser, and the nanosecond pulse laser synthesizer comprises a resonant cavity which comprises a rear cavity mirror and an output mirror; the gain module is located in the resonant cavity; the pumping source is positioned in the resonant cavity; the multiple Q-switching modules are all located in the resonant cavity and located between the gain module and the output mirror, and the multiple Q-switching modules are arranged at intervals; and the time domain regulation and control module is used for controlling the Q-switching modules to be turned on and turned off in sequence, the Q value of the resonant cavity is gradually increased along with turning on of the Q-switching modules, so that the nanosecond pulse laser synthesis device outputs a plurality of sub-pulse lasers, and the sub-pulse lasers are subjected to time domain synthesis to form a pulse string or a total laser pulse. The nanosecond pulse laser synthesizer can synthesize a pulse string or total laser pulses of different waveforms through sub-pulses, and can also reduce the risk of damage to optical devices.

Description

Technical Field

[0001] The invention relates to the field of lasers, and in particular to a nanosecond pulse laser synthesis device for laser active illumination. Background Art

[0002] As an advanced imaging and positioning method, laser active illumination can illuminate and identify remote, dark targets. Laser active pulse systems have special requirements for laser repetition frequency, pulse energy, pulse waveform, etc. The pulse energy of the laser generated by the related laser generating device is concentrated, which can easily cause damage to optical components and make it difficult to form a variety of different laser waveforms. Summary of the invention

[0003] The present invention provides a nanosecond pulse laser synthesis device for laser active illumination, which is used to solve the technical problems of how to reduce the concentration of laser pulse energy, thereby reducing the risk of damage to optical devices, and how to form a variety of different laser waveforms.

[0004] The embodiment of the present invention provides a nanosecond pulse laser synthesis device for laser active illumination, and the nanosecond pulse laser synthesis device for laser active illumination comprises: the nanosecond pulse laser synthesis device comprises: a resonant cavity, including a rear cavity mirror and an output mirror; a gain module, located in the resonant cavity; a pump source, located in the resonant cavity; a plurality of Q-switching modules, all located in the resonant cavity and between the gain module and the output mirror, and the plurality of Q-switching modules are arranged at intervals; a time domain control module, used for controlling each of the Q-switching modules to be turned on and off in sequence, as each of the Q-switching modules is turned on, the Q value of the resonant cavity is gradually increased, so that the nanosecond pulse laser synthesis device outputs a plurality of sub-pulse lasers, and each of the sub-pulse lasers is synthesized in the time domain to form a pulse train or a total laser pulse.

[0005] In some embodiments, each of the Q-switching modules includes at least one of an electro-optical Q-switching module and an acousto-optical Q-switching module.

[0006] In some embodiments, the gain module includes a pump source, and the pump source is one of a continuous pump source, a quasi-continuous pump source, and a pulsed pump source.

[0007] In some implementations, the time domain control module is a time delayer, which outputs a delay signal according to time to control each of the Q-switching modules to start up in sequence.

[0008] In some embodiments, the time domain control module is a phase delayer, which is used to output a delayed signal according to the phase difference of the target waveform to control each of the Q-switching modules to be turned on in sequence.

[0009] In some embodiments, the resonant cavity is a dumped cavity or a non-dumped cavity.

[0010] In some embodiments, the resonant cavity is a stable resonant cavity or an unstable resonant cavity.

[0011] An embodiment of the present scheme provides a nanosecond pulse laser synthesis device for laser active illumination, the nanosecond pulse laser synthesis device comprising: a resonant cavity including a rear cavity mirror and an output mirror, a gain module and a pump source located in the resonant cavity, and a plurality of Q-switching modules in the resonant cavity. At the same time, the nanosecond pulse laser synthesis device also comprises a time domain control module for controlling each Q-switching module to be turned on and off in sequence. As each Q-switching module is turned on and off in sequence, the nanosecond pulse laser synthesis device outputs a plurality of sub-pulse lasers in sequence, and a pulse laser of a target waveform can be synthesized through each sub-pulse laser. The target pulse laser is, for example, a pulse train or a total laser pulse. Compared with traditional lasers, traditional Q-switched pulse waveforms are Gaussian in shape with high peak power. In the process of pulse energy amplification, the pulse front gain is high and the back gain is low. The pulse waveform is further compressed in time domain, resulting in a steep front. The laser peak power converges in the time domain, which can easily damage optical components. It is difficult to further increase the laser pulse energy. Laser pulses are formed by multiple sub-pulse laser modulation, which disperses the pulse energy and reduces the peak power. The laser seed source formed by modulation has a waveform with a low front edge and a high back edge, thereby reducing the difference between the front and back edges of the amplified laser waveform, further reducing the energy convergence of the pulse waveform, and thereby reducing the risk of damage to optical components. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 A schematic structural diagram of a first nanosecond pulse laser synthesis device for laser active illumination provided by an embodiment of the present invention;

[0013] Figure 2 A schematic structural diagram of a second nanosecond pulse laser synthesis device for laser active illumination provided by an embodiment of the present invention;

[0014] Figure 3 for Figure 2 The waveform diagram of the pulsed laser output by the nanosecond pulse laser synthesis device for laser active illumination shown;

[0015] Figure 4 A schematic structural diagram of a third nanosecond pulse laser synthesis device for laser active illumination provided by an embodiment of the present invention;

[0016] Figure 5 for Figure 4 The waveform diagram of the pulsed laser output by the nanosecond pulse laser synthesis device for laser active illumination shown;

[0017] Figure 6A schematic structural diagram of a fourth nanosecond pulse laser synthesis device for laser active illumination provided by an embodiment of the present invention;

[0018] Figure 7 for Figure 6 The waveform diagram of the pulse laser output by the nanosecond pulse laser synthesis device used for laser active illumination is shown.

[0019] Description of Reference Numerals

[0020] 1. Nanosecond pulse laser synthesis device; 10. Back cavity mirror; 20. Output mirror; 30. Gain module; 40. Q-switching module; 50. Time domain control module; 60. Wave plate; 70. Polarizer. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0022] The various specific technical features in the various embodiments described in the specific implementation methods can be combined in various ways without contradiction. For example, different implementation methods can be formed by combining different specific technical features. In order to avoid unnecessary repetition, the various possible combinations of the specific technical features in the present invention will not be described separately.

[0023] It should also be noted that, in order to avoid obscuring the present invention due to unnecessary details, only structures and / or processing steps closely related to the scheme of the present invention are shown in the drawings, while other details that are not closely related to the present invention are omitted.

[0024] In addition, it should be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the following description, the terms "first\second\..." involved are merely used to distinguish different objects, and do not indicate that the objects have the same or related points. It should be understood that the directions described by the directions nouns such as "above", "below", "inside" and "outside" involved are all directions in normal use.

[0025] In the following specific implementation manner, a nanosecond pulse laser synthesis device is applied to an active lighting system to provide a pulse laser with a certain pulse frequency for the active lighting system, and can realize repeated irradiation of a target in a short time.

[0026] In some embodiments, Figure 1As shown, the nanosecond pulse laser synthesis device 1 includes: a resonant cavity, an output mirror 20, a gain module 30, a pump source, a plurality of Q-switching modules 40 and a time domain control module 50. The resonant cavity includes a back cavity mirror 10 and an output mirror 20, the gain module 30 is located in the resonant cavity to form an active optical resonant cavity, providing optical gain and feedback, and the pump source is located in the resonant cavity.

[0027] Multiple Q-switching modules 40 are all located in the resonant cavity and between the gain module 30 and the output mirror 20, wherein the Q-switching module 40 is used to adjust the Q value of the resonant cavity, and the Q value is the quality factor of the resonant cavity. Under the state of high and low Q values, high-energy ions continuously oscillate and gather energy in the resonant cavity, and finally excite to form a pulsed laser, and the wavelength and amplitude of the pulsed laser are related to the Q value. Among them, the Q-switching module 40 can be an electro-optical Q-switching module, that is, a module that adjusts the Q value of the resonant cavity through the electro-optical effect; the Q-switching module 40 can be an acousto-optical Q-switching module, that is, a module that adjusts the Q value of the resonant cavity through the acousto-optical effect; and a part of the multiple Q-switching modules 40 can be electro-optical Q-switching modules, and the other part can be acousto-optical Q-switching modules.

[0028] At the same time, the time domain control module 50 is used to control each Q-switching module 40 to start up in sequence. As the Q-switching modules 40 are gradually turned on, the Q value in the resonant cavity gradually changes, so that each time a Q-switching module 40 is turned on, the resonant cavity can output a sub-laser pulse. The delay control of the time domain control module 50 can adjust the start-up sequence and the start-up time interval of each Q-switching module 40, thereby controlling the output sequence and phase difference of the generated sub-laser pulses, and then the laser waveform required for the synthesis stroke can be synthesized through each sub-laser pulse. The specific control method of the nanosecond pulse laser synthesis device 1 is exemplified below in combination with different target laser waveforms.

[0029] The target laser waveform is a pulsed laser with uniform time domain. The structure of the nanosecond pulse laser synthesis device 1 is as follows: Figure 2As shown, the gain module 30 is a side pump module, the laser bar adopts a quasi-continuous pumping mode, the duty cycle is 8%, and the photoelectric crystal of the pump source adopts a Nd:YAG (neodymium-doped yttrium aluminum garnet) crystal rod, the crystal rod concentration is 0.8% atm (atomic percentage), and the size is 6 mm in diameter and 80 mm in thickness. The rear cavity mirror 10 and the output mirror 20 are curved mirrors, so that the resonant cavity forms a Gaussian mirror unstable cavity, the curvature radius of the rear cavity mirror 10 is -1000 mm, the curvature radius of the output mirror 20 is 500 mm, the unstable cavity magnification is 2 times, the Gaussian order is 2.5, the Gaussian half width is 4 mm, and the maximum reflectivity is 40%. The Q-switching module is an electro-optical Q-switching module. The Q-switching crystal uses lithium niobate, the half-wave voltage is 4500V (volts), and three Q-switching modules 40 are used. The Q-switching voltages are 2000V, 3000V, and 4500V respectively, so as to gradually improve the Q value of the laser. At the same time, the nanosecond pulse laser synthesis device 1 also includes a wave plate 60 and a polarizer 70. The wave plate is a 1 / 2 wave plate, and the polarization angle of the polarizer 70 is 56° (degrees). The time domain control module 50 is a single-chip microcomputer, with a delay control accuracy of 1ns and a delay range of 1us. The delays between the three Q-switching modules are 10ns and 12ns respectively. Figure 3 As shown, as the three Q-switching modules 40 are turned on in sequence under the control of the time domain control module 50, the resonant cavity outputs three Q-switched sub-pulses with pulse widths of 18 nanoseconds, 17 nanoseconds, and 18 nanoseconds (full width at half maximum), respectively. The three sub-laser pulses are superimposed to form a pulsed laser with time domain combination homogenization, that is, the laser pulse output with time domain homogenization is realized. Figure 3 The dashed line in the middle represents three sub-laser pulses, and the solid line represents the pulse waveform of the three sub-laser pulses superimposed and synthesized.

[0030] The target laser waveform is a laser seed source with a low leading edge and a high trailing edge. The laser seed source needs to be input into a MOPA amplifier (power amplifier of a master oscillator). The MOPA amplifier has a high leading edge gain and a low trailing edge gain for the input laser signal, which will cause the amplified laser waveform to have a high leading edge and a low trailing edge. The laser seed source needs to be modulated to form a laser waveform with a low leading edge and a high trailing edge to resist this distortion trend. The structure of the nanosecond pulse laser synthesis device 1 is as follows: Figure 4 As shown, the resonant cavity adopts a flat cavity, that is, the rear cavity mirror 10 and the output mirror 20 are both plane mirrors, the reflectivity of the rear cavity mirror 10 is 99.9% @ 1064nm (the reflectivity of the laser with a wavelength of 1064 nanometers in the resonant cavity is 99.9%), and the reflectivity of the output mirror 20 is 60% @ 1064nm (the reflectivity of the laser with a wavelength of 1064 nanometers in the resonant cavity is 60%). The Q-switched crystal adopts lithium niobate, and the Q-switching voltages of the three Q-switching modules 40 are 1700V, 3000V, and 4500V respectively, which gradually improves the Q value of the laser. The time domain control module 50 is a single-chip microcomputer, which controls the delays between the three Q-switching modules to be 10ns and 12ns respectively. Figure 5As shown, as the three Q-switching modules 40 are turned on in sequence under the control of the time domain control module 50, three laser sub-pulses are generated, with pulse widths of 20ns, 16ns, and 18ns (full width at half maximum), respectively, and the amplitudes of the three laser sub-pulses gradually increase, thereby forming a laser seed source with a low leading edge and a high trailing edge. Figure 5 The dashed line in the middle represents three sub-laser pulses, and the solid line represents the pulse waveform of the three sub-laser pulses superimposed and synthesized. Compared with traditional lasers, the traditional Q-switched pulse waveform is Gaussian, with high peak power, and in the process of pulse energy amplification, the pulse front gain is high and the back gain is low. The pulse waveform is further compressed in the time domain, and the front edge is steep. The laser peak power converges in the time domain, which is easy to damage optical components. It is difficult to further increase the laser pulse energy. The laser pulse is formed by multiple sub-pulse laser modulation, which disperses the pulse energy and reduces the peak power. The laser seed source formed by modulation is a waveform with a low front edge and a high back edge, thereby reducing the difference between the front edge and the back edge of the amplified laser waveform, further reducing the energy convergence of the pulse waveform, and thus reducing the risk of damage to optical components.

[0031] The target laser waveform is a local high-repetition-rate nanosecond pulse train. The structure of the nanosecond pulse laser synthesis device 1 is as follows: Figure 6 As shown, the gain module 30 is a side pump module, the resonant cavity adopts a flat cavity, the polarizer is 56°@1064nm (the laser with a wavelength of 1064 nanometers is deflected by 56 degrees), the wave plate is a 1 / 2 wave plate, the Q-switching module 40 is an electro-optical Q-switching module, the Q-switching crystal adopts lithium niobate, and 4 Q-switching modules 40 are adopted. The Q-switching voltages are 1600V, 2500V, 3200V, and 4500V respectively, which gradually improves the Q value of the laser. The time domain control module is a single-chip microcomputer, which controls the delays between the three Q-switching modules to be 20ns, 20ns, and 20ns respectively. Figure 7 As shown, as the four Q-switching modules 40 are turned on in sequence under the control of the time domain control module 50, four laser sub-pulses are generated, and the pulse widths are 22ns, 18ns, 20ns, and 22ns (full width at half maximum), respectively. The four laser sub-pulses are spaced apart in a small phase region, thereby forming a pulse train output of 4 sub-pulses, with a time interval of 20ns between each sub-pulse, an overall pulse repetition frequency of 400Hz (Hertz), a local pulse repetition frequency of 20MHz (Hertz), and a single pulse energy of 100MJ (megajoule) level pulse laser output.

[0032] The embodiment of the present scheme provides a nanosecond pulse laser synthesis device for laser active illumination, the nanosecond pulse laser synthesis device comprises: a rear cavity mirror and an output mirror, a resonant cavity is formed between the rear cavity mirror and the output mirror, a gain module and a plurality of Q-switching modules are provided in the resonant cavity, the gain module is located between the rear cavity mirror and the Q-switching module, and the nanosecond pulse laser synthesis device also comprises a time domain control module for controlling the opening of each Q-switching module, as each Q-switching module is turned on in sequence, the nanosecond pulse laser synthesis device outputs a plurality of sub-pulse lasers in sequence, and a pulse laser of a target waveform can be synthesized by each sub-pulse laser, compared with a traditional laser, a traditional Q-switched laser The pulse waveform is Gaussian with high peak power. In the process of pulse energy amplification, the gain of the pulse front edge is high and the gain of the back edge is low. The pulse waveform is further compressed in the time domain, and a steep front edge appears. The laser peak power converges in the time domain, which is easy to damage optical components. It is difficult to further increase the laser pulse energy. Laser pulses are formed by multiple sub-pulse laser modulation, which disperses the pulse energy and reduces the peak power. The laser seed source formed by modulation is a waveform with a low front edge and a high back edge, thereby reducing the difference between the front edge and the back edge of the laser waveform after amplification, further reducing the energy convergence of the pulse waveform, and thus reducing the risk of damage to optical components.

[0033] In some embodiments, Figure 2 As shown, the Q-switching module 40 is a voltage-drop electro-optical Q-switching module, and the Q-switching voltage of each Q-switching module 40 is different. The time domain control module is used to control each Q-switching module 40 to be turned on in sequence according to the Q-switching voltage from low to high, thereby gradually increasing the Q value in the resonant cavity, and as the voltage drop increases, the amplitude of the increase in the Q value of the resonant cavity decreases, thereby reducing the transient characteristics caused by the sudden change of the Q value, so that the Q value adjustment can enter the steady state faster. It should be noted that the pulse laser waveform output by the nanosecond pulse laser synthesis device 1 is related to the opening order of each Q-switching module 40, but has nothing to do with the spatial arrangement order of each Q-switching module.

[0034] In some embodiments, Figure 1 As shown, the gain module 30 includes a pump source, which is one of a continuous pump source, a quasi-continuous pump source and a pulsed pump source.

[0035] In some embodiments, Figure 1 As shown, the time domain control module 50 can be a time delay device, which controls the start-up sequence and start-up interval of each Q-switching module 40 through a time delay signal. The time domain control module 50 can also be a phase modulator, which generates precise synchronization and delay signals, and determines the delay signal according to the phase difference of the target waveform, so that each sub-pulse laser can be accurately synthesized into a pulse laser with a target waveform.

[0036] In some embodiments, Figure 1As shown, the resonant cavity is a stable resonant cavity, that is, during the oscillation of the laser in the resonant cavity, most of the laser will not leak out of the resonant cavity; or, the resonant cavity is an unstable resonant cavity. In some embodiments, part of the laser will leak out of the resonant cavity during the oscillation process.

[0037] In some embodiments, the resonant cavity can be a dumped cavity or a non-dumped cavity.

[0038] The above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present invention.

Claims

1. A nanosecond pulse laser synthesis device for laser active illumination, characterized in that: The nanosecond pulse laser synthesis device comprises: A resonant cavity, including a back cavity mirror and an output mirror; A gain module, located in the resonant cavity; A pump source is located in the resonant cavity; A plurality of Q-switching modules are all located in the resonant cavity and between the gain module and the output mirror, and the plurality of Q-switching modules are arranged at intervals; The time domain control module is used to control each of the Q-switching modules to be turned on and off in sequence, wherein as each of the Q-switching modules is turned on, the Q value of the resonant cavity gradually increases, so that the nanosecond pulse laser synthesis device outputs multiple sub-pulse lasers, and each of the sub-pulse lasers is synthesized in the time domain to form a pulse train or a total laser pulse.

2. The nanosecond pulse laser synthesis device according to claim 1, characterized in that: Each of the Q-switching modules includes at least one of an electro-optical Q-switching module and an acousto-optical Q-switching module.

3. The nanosecond pulse laser synthesis device according to claim 1, characterized in that: The pump source is one of a continuous pump source, a quasi-continuous pump source and a pulse pump source.

4. The nanosecond pulse laser synthesis device according to claim 1, characterized in that: The time domain control module is a time delayer, which outputs a delay signal according to time to control each of the Q-switching modules to start in sequence.

5. The nanosecond pulse laser synthesis device according to claim 1, characterized in that: The time domain control module is a phase delayer, which is used to output a delay signal according to the phase difference of the target waveform to control each of the Q-switching modules to be turned on in sequence.

6. The nanosecond pulse laser synthesis device according to claim 1, characterized in that: The resonant cavity is a dumped cavity or a non-dumped cavity.

7. The nanosecond pulse laser synthesis device according to claim 1, characterized in that: The resonant cavity is a stable resonant cavity or an unstable resonant cavity.

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