A composite pulse laser and a method of using the same

Abstract

The application provides a composite pulse laser, comprising: a full reflection mirror, a laser module, a Q switch, an output coupling mirror, a pump driving source, a Q switch driving source, and a main controller; the full reflection mirror, the Q switch, the laser module, and the output coupling mirror are arranged horizontally in sequence to ensure optical coaxiality and form a laser resonant cavity; the pump driving source is connected with the laser module and is used for controlling the pumping time of the pump source in the laser module; the Q switch driving source is connected with the Q switch and is used for controlling the opening time of the Q switch; the main controller is connected with the pump driving source and the Q switch driving source respectively and is used for controlling the relative delay time of the pump driving source and the Q switch driving source. The application solves the defect that the common Q-switched laser in the prior art is difficult to realize single light emission with high peak power and high average power, and realizes quasi-continuous composite pulse laser with high peak power and high average power.

Description

Technical Field

[0001] This invention relates to the field of laser technology, and in particular to a composite pulsed laser and its application method. Background Technology

[0002] With the rapid development of laser technology, lasers are being used more and more widely, and the requirements for peak power, beam quality, and pulse width are becoming increasingly stringent. Among them, Q-switched lasers have demonstrated their application characteristics in industrial, medical, defense, and scientific research fields, and have great development potential and application scenarios.

[0003] Q-switching, also known as Q-switching technology, is a technique that compresses the energy of a normally output continuous laser into an extremely narrow pulse, thereby increasing the peak power of the light source by several orders of magnitude. The single emission time of a typical quasi-continuous-wave Q-switched laser is on the order of tens to hundreds of nanoseconds. By adjusting the repetition frequency and pump light duty cycle, i.e., increasing the number of emission pulses and controlling the pump duration, the average power and peak power can be adjusted.

[0004] In Q-switched lasers, the laser output is an array of single pulses at a specific frequency. Each single pulse has high energy, but no energy remains after it is output. However, in experiments involving the interaction of lasers with matter, it is generally desirable for the laser to possess both high peak and average power simultaneously, and for it to output long pulses with low peak power within a microsecond timeframe after the peak power is achieved. Because the Q-switching time of ordinary Q-switched lasers is very short, on the order of a few microseconds, this laser operation mode is difficult to achieve with conventional Q-switched lasers. Summary of the Invention

[0005] This invention provides a composite pulse laser and its application method, which solves the problem that ordinary Q-switched lasers in the prior art cannot achieve high peak power and high average power in a single output, and realizes a quasi-continuous composite pulse laser with high peak power and high average power output.

[0006] This invention provides a composite pulsed laser, comprising: a total reflection mirror, a laser module, a Q switch, an output coupling mirror, a pump drive source, a Q switch drive source, and a main controller;

[0007] The total reflection mirror, Q switch, laser module and output coupling mirror are arranged horizontally in sequence to ensure optical coaxiality and form a laser resonant cavity;

[0008] The pump drive source is connected to the laser module and is used to control the pumping time of the pump source in the laser module;

[0009] The Q-switch driver source is connected to the Q-switch and is used to control the Q-switch opening time;

[0010] The main controller is connected to both the pump drive source and the Q switch drive source, and is used to control the relative delay time between the pump drive source and the Q switch drive source.

[0011] According to a composite pulsed laser provided by the present invention, the laser resonant cavity further includes an optical rotator crystal and a thin-film polarizer; the total reflection mirror, the thin-film polarizer, the Q switch, the laser module, the optical rotator crystal and the output coupling mirror are arranged horizontally in sequence to ensure optical coaxiality and form a laser resonant cavity.

[0012] According to the present invention, a composite pulsed laser includes two laser modules and two Q switches in the laser resonant cavity; the horizontally arranged components from left to right are a total reflection mirror, a thin-film polarizer, a first Q switch, a first laser module, an optical rotator crystal, a second laser module, a second Q switch, and an output coupling mirror.

[0013] According to the present invention, a composite pulsed laser module includes a pump source and a gain medium, and the laser module is of the side-pumped or end-pumped type.

[0014] According to the present invention, a composite pulsed laser is provided, wherein the gain medium is a laser crystal or a gain fiber.

[0015] An application method of a composite pulsed laser provided by the present invention includes:

[0016] The pump drive source is turned on by the main controller, and the pump source inside the laser module is turned on by the pump drive source to pump, so that the upper energy level particles of the gain medium inside the laser module continue to accumulate.

[0017] A relative delay time is determined. After the relative delay time has elapsed, the Q-switch drive source is turned on by the main controller. The Q-switch is turned on by the Q-switch drive source. At this time, photons are released according to the upper energy level particles accumulated in the laser module, forming a spike pulse and outputting it through the output coupling mirror.

[0018] After the peak pulse is formed, the laser module and the Q switch remain on to form a long pulse, which is then output through the output coupling mirror.

[0019] Obtain the attribute information of the spike pulse and / or the long pulse, redetermine the relative delay time based on the attribute information, and adjust the laser emission based on the redetermined relative delay time.

[0020] According to the present invention, in a method for applying a composite pulsed laser, the relative delay time is controlled by a main controller and is greater than the formation time of the spike pulse and not higher than the lifetime of the upper laser level of the gain medium, or its order of magnitude is the same as that of the upper laser level lifetime.

[0021] According to the application method of a composite pulsed laser provided by the present invention, under the condition that the pump source pumping time and the Q switch opening time are fixed: when the sum of the Q switch opening time and the relative delay time is less than the pump source pumping time and there is laser output, the larger the relative delay time, the higher the intensity of the first peak pulse of the composite pulsed laser, the higher the energy of the first laser, the narrower the pulse width of the peak pulse, the lower the energy of the second laser of the long pulse, and the lower the pulse width of the long pulse.

[0022] According to an application method of a composite pulsed laser provided by the present invention, the step of acquiring attribute information of the spike pulse and the long pulse, and re-determining the relative delay time based on the attribute information, specifically includes: acquiring a first laser energy of the spike pulse and a second laser energy of the long pulse; determining the ratio of the first laser energy to the second laser energy; and adjusting the relative delay time based on the ratio.

[0023] According to the present invention, when the Q-switch opening time is greater than the pump source pumping time, and the relative delay time increases to the point where the difference between the relative delay time and the pump source pumping time is within a preset range or equal to the relative delay time, only a single spike pulse at the nanosecond level occurs, at which point only the first laser energy is present. During the pump source pumping time, the longer the Q-switch opening time, the longer the duration of the long pulse in the laser composite pulse, and the higher the average power of the laser.

[0024] This invention provides a composite pulsed laser and its application method. By precisely controlling the timing of the pump source and Q-switch, a modulated composite output of spike pulses and long pulses is achieved. This composite pulsed laser possesses both high peak power and maintains a relatively high average power, meeting the specific performance requirements of certain applications. By adjusting parameters such as the relative delay time, the shape of the composite pulse can be flexibly controlled, including the intensity and width of the spike pulse, as well as the duration and energy distribution of the subsequent long pulse. By precisely controlling the emission timing of the laser pulses, the utilization of laser energy is optimized. After the spike pulse is formed, the laser module and Q-switch remain in the on state, forming a quasi-continuous long pulse, thereby effectively converting laser energy into useful output and improving the overall efficiency of the laser. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0026] Figure 1This is one of the schematic diagrams of the composite pulsed laser structure provided by the present invention.

[0027] Figure 2 This is the second schematic diagram of the composite pulsed laser structure provided by the present invention.

[0028] Figure 3 This is a schematic diagram of the application method of the composite pulse laser provided by the present invention.

[0029] Figure 4 This is a schematic diagram illustrating the change in the number of photons over time under different relative delay times provided by the present invention.

[0030] Figure 5 This is a schematic diagram of the laser output experimental results provided by the present invention.

[0031] The laser pulse wave (PW) is fixed at 200 microseconds, the laser pulse wave (QW) is fixed at 200 microseconds, and the laser pulse wave (QD) is gradually increased.

[0032] Figure 6 This invention provides the specific forms of spike pulses and microsecond-long pulses when the laser PW and QW are fixed at 200 microseconds and QD is gradually increased.

[0033] Figure 7 This invention provides the relationship curves between the peak pulse width, average pulse power, and QD when the laser PW and QW are fixed at 200 microseconds and QD is gradually increased.

[0034] Figure 8 This invention provides the relationship between the peak pulse energy E1, the microsecond long pulse energy E2, and their ratio E1 / (E1+E1) and QD when the laser PW is fixed at 200 microseconds and the QW is fixed at 200 microseconds and the QD is gradually increased.

[0035] Figure label:

[0036] Total reflection mirror 1; laser modules 2, 2-1, 2-2; Q switches 3, 3-1, 3-2; output coupling mirror 4; pump drive source 5; Q switch drive source 6; main controller 7; optical rotator crystal 8; thin film polarizer 9. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0038] The single emission time of a typical quasi-continuously Q-switched laser is on the order of tens to hundreds of nanoseconds. The average power and peak power can be adjusted by changing the repetition frequency and pump light duty cycle, i.e., increasing the number of emission times and controlling the pump duration.

[0039] The single emission time of this invention is on the order of tens of nanoseconds to hundreds of microseconds. The frequency of the Q-switch is consistent with that of the pump source switch. After the pump source is turned on for a period of time (i.e., the relative delay time QD), the Q-switch is turned on again. The Q-switch remains on until the pump source is turned off for the current operation (continuous Q-switch on time QW), after which it is turned off. By adjusting QD, QW, and the pump light operating time and frequency, that is, in addition to controlling the pump duration and increasing the number of emission times, the switching time of Q is also controlled, thereby adjusting the average power and peak power.

[0040] The following is combined Figures 1-8 Embodiments of the present invention are described.

[0041] This invention provides a composite pulse laser, such as... Figure 1 As shown, the system includes: a total reflection mirror 1, a laser module 2, a Q switch 3, an output coupling mirror 4, a pump drive source 5, a Q switch drive source 6, and a main controller 7. The total reflection mirror 1, laser module 2, Q switch 3, and output coupling mirror 4 are arranged horizontally in sequence to ensure optical coaxiality and form a laser resonant cavity. The pump drive source 5 is connected to the laser module 2 and is used to control the pumping time of the pump source in the laser module 2. The Q switch drive source 6 is connected to the Q switch 3 and is used to control the Q switch opening time. The main controller 7 is connected to both the pump drive source 5 and the Q switch drive source 6 and is used to control the relative delay time between the pump drive source 5 and the Q switch drive source 6.

[0042] exist Figure 1 By adding an optically rotating crystal and a thin-film polarizer to the laser shown, we obtain another composite pulsed laser provided by this invention, such as... Figure 2 As shown, it includes: a total reflection mirror 1, laser modules 2-1 and 2-2, Q switches 3-1 and 3-2, an output coupling mirror 4, a pump drive source 5, a Q switch drive source 6, a main controller 7, an optical rotator crystal 8, and a thin-film polarizer 9;

[0043] The total reflection mirror 1, laser modules (including pump source and laser crystal) 2-1 and 2-2, Q switches 3-1 and 3-2, output coupler 4, optical rotator crystal 8, and thin-film polarizer 9 are placed side by side on the same horizontal line to ensure optical coaxiality and form a laser resonant cavity. Specifically, the horizontally arranged components from left to right are the total reflection mirror 1, thin-film polarizer 9, first Q switch 3-1, first laser module 2-1, optical rotator crystal 8, second laser module 2-2, second Q switch 3-2, and output coupler 4.

[0044] Pump drive source 5 is connected to laser modules 2-1 and 2-2 via circuitry to control the pumping time PW of the pump source within the laser module;

[0045] Q switch driver 6 is connected to Q switches 3-1 and 3-2 via a circuit to control the Q switch opening time QW;

[0046] The main controller 7 is connected to the pump drive source 5 and the Q switch drive source 6 via a circuit to control the relative delay time QD between the pump drive source 5 and the Q switch drive source 6.

[0047] After a relative delay time QD following the start of the PW signal, the QW signal is given. The characteristic time lengths of the several signals are on the order of microseconds (on the order of relaxation time of the gain medium).

[0048] According to the composite pulsed laser provided by the present invention, laser modules 2-1 and 2-2 include a pump source and a gain medium, and laser module 2 is of the side-pumped or end-pumped type.

[0049] According to the composite pulsed laser provided by the present invention, Q switches 3-1 and 3-2 can be acousto-optic Q switches.

[0050] In the composite pulsed laser provided by the present invention, the gain medium can be a laser crystal or a gain fiber.

[0051] Specifically, such as Figure 2 The diagram shows the structure of a composite pulsed laser, which includes a total reflection mirror 1, laser modules 2-1 and 2-2, Q switches 3-1 and 3-2, an output coupling mirror 4, a pump drive source 5, a Q switch drive source 6, a main controller 7, an optical rotator crystal 8, and a thin-film polarizer 9.

[0052] Among them, the main controller 7 is used to control the relative delay time QD between the pump drive source 5 and the Q switch drive source 6, the pump drive source 5 is used to control the pumping time PW of the pump source in laser modules 2-1 and 2-2, and the Q switch drive source 6 is used to control the opening time QW of Q switches 3-1 and 3-2.

[0053] Q-switch 3 can be an acousto-optic Q-switch. The acousto-optic Q-switch generates ultrasonic waves through electroacoustic conversion, causing periodic changes in the refractive index of the modulation medium. This diffracts the incident light, resulting in diffraction loss, a decrease in the Q-value, and the inability to form laser oscillation. Under optical pumping excitation, the number of inverted particles in the upper energy level continuously accumulates and reaches saturation. When the ultrasonic field is suddenly removed, the diffraction effect immediately disappears, the Q-value inside the cavity increases sharply, and laser oscillation rapidly recovers.

[0054] The following is based on Figure 2Taking the laser shown as an example, the application method of the composite pulse laser provided by the present invention will be described. The application method of the composite pulse laser described below can be referred to in correspondence with the composite pulse laser described above.

[0055] Figure 3 A schematic flowchart of the application method of the composite pulsed laser provided in the embodiments of the present invention includes the following steps:

[0056] S310: The main controller 7 turns on the pump drive source 5, and the pump drive source 5 turns on the pump source in laser module 2-1 and 2-2 to pump, so that the upper energy level particles in the gain medium in laser module 2-1 and 2-2 continue to accumulate.

[0057] According to the application method of a composite pulsed laser provided by the present invention, after the pump drive source 5 is turned on by the main controller 7, the pump source pumping time PW is determined, and the peak power of the spike pulse is increased by increasing the relative delay time QD within the pump source pumping time PW.

[0058] Specifically, the main controller 7 controls the opening and closing of the pump drive source 5 and the Q-switch drive source 6, as well as the relative delay time QD between their opening. Pump drive source 5 turns on the pump sources in laser modules 2-1 and 2-2 and controls the pumping time PW of these pump sources. Q-switch drive source 6 controls Q-switches 3-1 and 3-2 and their opening time QW. Each time light is emitted, a spike pulse (i.e., a short pulse laser output from the laser) appears first, with the laser energy being the first laser energy E1. A long pulse follows the spike pulse, and the laser outputs a microsecond long pulse laser with the laser energy being the second laser energy E2. By increasing QD, the peak power of the spike pulse is increased, achieving a high peak power and high average power quasi-continuous composite pulse laser with an adjustable E1 / E2 ratio.

[0059] The present invention will be further described below using Nd:YAG laser as an example. When Nd:YAG emits laser light in the 1064.2nm band, it is a typical four-level laser, and its rate equation is:

[0060]

[0061] In the formula, The total number of doped particles per unit volume; The number of energy level particles per unit volume; denoted as the number of upper-level particles per unit volume; v is the speed of light in the gain medium, with a refractive index of 1.82 and a speed of light of 3*10⁸ m / s. The spontaneous emission lifetime of particles at the upper laser energy level; The particle relaxation lifetime of the lower laser energy level; Let be the pump rate, and let be a linear function of the pump power; Photon number density; The stimulated emission cross section; The cavity lifetime of the photon.

[0062] The photon number lifetime is determined according to the following formula:

[0063]

[0064] In the formula, For intracavity loss, For cavity length, The reflectivity of output coupling mirror 4.

[0065] When Q-switches 3-1 and 3-2 are inserted, the cavity loss changes periodically. For example, when acousto-optic Q-switches 3-1 and 3-2 are inserted, they generate ultrasonic waves through electroacoustic conversion, causing periodic changes in the refractive index of the modulation medium. This diffracts the incident light, resulting in diffraction loss, a decrease in Q-value, and the inability to form laser oscillation. Under optical pumping excitation, the number of inverted particles in the upper energy level continuously accumulates and reaches saturation. When the ultrasonic field is suddenly removed, the diffraction effect immediately disappears, the cavity Q-value increases sharply, and laser oscillation recovers rapidly. Correspondingly, the cavity loss increases within each pump cycle T. Cavity loss due to diffraction loss Cavity loss without diffraction loss The intracavity loss alternates between the on and off states of Q switches 3-1 and 3-2. It is a function of time t, determined by the following formula:

[0066] ,

[0067] In the formula, For cavity loss with diffraction loss, The cavity loss is excluding diffraction loss, QD is the relative delay time, QW is the Q-switch turn-on time, T is each pump cycle, and N is a positive integer.

[0068] The prerequisite for laser operation is the formation of population inversion. The number of particles in the gain medium of laser modules 2-1 and 2-2 must be much greater than the number of particles in the gain medium of laser modules 2-1 and 2-2 in order to form stimulated emission.

[0069] When Q-switch 3 is off, taking acousto-optic Q-switches 3-1 and 3-2 as examples, the diffraction loss of Q-switches 3-1 and 3-2 is very high, and the fluorescence signal of the gain medium cannot pass through Q-switch 3 in the resonant cavity. At this time, if the pump sources of laser modules 2-1 and 2-2 continue to operate, while Q-switches 3-1 and 3-2 remain off, then energy will continue to accumulate in the upper energy level of the laser, and the number of particles between the upper and lower energy levels of the laser will invert far beyond the laser threshold.

[0070] S320: Determine the relative delay time. After the relative delay time, turn on the Q switch drive source 6 through the main controller 7. Turn on the Q switches 3-1 and 3-2 through the Q switch drive source 6. At this time, the photons are released according to the upper energy level particles accumulated in the laser modules 2-1 and 2-2, forming a spike pulse and outputting it through the output coupling mirror 4.

[0071] According to the present invention, in a method for applying a composite pulsed laser, the relative delay time QD is controlled by the main controller 7 and is greater than the formation time of the spike pulse but not higher than the lifetime of the upper laser level of the gain medium.

[0072] Specifically, after a relative delay, Q switches 3-1 and 3-2 are turned on. At this point, Q switches 3-1 and 3-2 are in the "on" state. Q switches 3-1 and 3-2 can be considered as lenses with high transmittance for the laser's operating wavelength, resulting in very low cavity loss. The fluorescence signal from the gain medium of laser modules 2-1 and 2-2 travels continuously back and forth at the speed of light through the total reflection mirror 1 and output coupling mirror 4 of the resonant cavity. A large number of upper-level particles in the gain medium of laser modules 2-1 and 2-2 rapidly transition to the lower energy level of the laser and release photons through stimulated emission, causing the number of upper-level particles in the gain medium to decrease to a relatively low level. This process, through stimulated emission, rapidly amplifies the laser to form a spiked laser pulse.

[0073] It should be noted that if the pump source continues to operate for a period of time exceeding the spontaneous emission lifetime of the upper laser level particles in the gain medium, while Q switches 3-1 and 3-2 remain in the off state, the upper level particles will rapidly decrease to 1 / e of the original particle number through a thermal relaxation process. This process does not generate laser light and is not conducive to laser generation.

[0074] Therefore, the relative delay time QD should be greater than the peak pulse formation time, i.e. the laser setup time in the resonant cavity, on the order of microseconds, and should not exceed the laser upper level lifetime of the gain medium or be on the same order of magnitude as the upper level lifetime.

[0075] S330: After forming a spike pulse, keep laser modules 2-1 and 2-2 and Q switches 3-1 and 3-2 on to form a quasi-continuous long pulse and output it through output coupling mirror 4.

[0076] Specifically, for a period of time thereafter, the pump sources of Q switches 3-1 and 3-2 and laser modules 2-1 and 2-2 remain on. As a result, the number of particles in the upper energy level of the gain medium of laser modules 2-1 and 2-2 accumulates again due to the pumping action, and quickly forms a pulse train laser similar to a quasi-continuous laser.

[0077] S340: Acquire the attribute information of the spike pulse or long pulse, redetermine the relative delay time based on the attribute information, and adjust the laser emission based on the redetermined relative delay time.

[0078] According to the application method of a composite pulsed laser provided by the present invention, under the condition that the pump source pumping time PW and the Q switch opening time QW are fixed: when the sum of the Q switch opening time QW and the relative delay time QD is less than the pump source pumping time PW and there is laser output, the larger the relative delay time QW, the higher the intensity of the first peak pulse of the composite pulsed laser, the higher the energy of the first laser, the narrower the pulse width of the peak pulse, the lower the energy of the second laser of the long pulse, and the lower the pulse width of the long pulse.

[0079] According to the present invention, a method for applying a composite pulsed laser is provided, wherein a spike pulse and a long pulse form a composite pulse; the method involves acquiring attribute information of the spike pulse and the long pulse, and re-determining the relative delay time QD based on the attribute information, specifically including: acquiring the first laser energy E1 of the spike pulse and the second laser energy E2 of the long pulse; determining the ratio E1 / E2 of the first laser energy E1 and the second laser energy E2; and adjusting the relative delay time QD based on the ratio.

[0080] Specifically, Figure 4 The diagram shows the effect of photon quantity changing over time under different relative delay times according to the present invention. The pump source pumping time PW is 250 μs, the Q-switch opening time QW is equal to PW, and the relative delay time QD of the Q-switch opening time QW to the pump start time are different values: 117.5 μs, 120 μs, 122.5 μs, 125 μs, and 175 μs.

[0081] Once the pump source pumping time PW is determined, when the Q-switch opening time QW is greater than the pump source pumping time PW, the larger the relative delay time QD, the higher the intensity of the first peak pulse of the composite pulse laser, that is, the first laser energy E1 (peak pulse energy) increases, and the corresponding pulse width is narrower. It should be noted that although E1 increases, the laser energy E2 of the composite pulse (the sum of the energy of the peak pulse and the long pulse) remains almost unchanged, and the peak pulse occupies less of the effective width of the entire composite pulse.

[0082] In another extreme case, when the relative delay time QD increases to almost equal to PW, there is only a single nanosecond-level pulse spike, meaning all the laser energy of the composite pulse is concentrated in the spike pulse, and the laser energy E2 = E1. The ratio E1 / (E1+E2) can be calculated by measuring the laser energies E1 and E2 to determine the proportion of energy in the first spike pulse of the composite pulse. When the relative delay time QD is greater than the pulse formation time but less than the pump source pump time PW, the larger QD is, the larger the ratio of E1 to E2, E1 / E2, eventually approaching infinity.

[0083] According to the application method of a composite pulsed laser provided by the present invention, when the Q-switch on-time QW is greater than the pump source pump time PW, and the relative delay time QD increases to a point where it differs from the pump source pump time PW within a preset range or is equal to the pump source pump time PW, only a single spike pulse at the nanosecond level occurs, and only the first laser energy E1 is present. Within the pump source pump time PW, the larger the Q-switch on-time QW, the longer the duration of the long pulse in the laser composite pulse, and the higher the average power of the laser.

[0084] Specifically, once the pump source pumping time PW and the relative delay time QD are determined, the larger the Q-switch opening time QW, the longer the duration of the subsequent small pulse train of the laser composite pulse, which will increase the average power of the laser.

[0085] Figure 5 This is a schematic diagram of the laser output experimental results of the present invention. In the diagram, the line pointing to the pump signal represents the current signal of the pump drive source 5, and the time region covered by the bidirectional arrow segment below PW is the pump source pumping time PW; the line pointing to the Q switch signal represents the current signal of the Q switch drive source 6, and the time region covered by the bidirectional arrow segment below QW is the Q switch opening time QW, and the time region covered by the bidirectional arrow segment below QD is the relative delay time QD; the line pointing to the laser intensity represents the laser intensity signal measured by the photodetector, the area pointing to E1 indicates the area below the intensity curve as laser energy E1, and the area pointing to E2 indicates the area below the intensity curve as laser energy E2.

[0086] Figure 6 , Figure 7 , Figure 8 The content shown represents a specific experimental result of this invention. The PW and QW of the Nd:YAG laser were fixed at 200 microseconds, and QD was gradually increased. Figure 6 This illustrates the specific forms of the spike pulse and the microsecond-long pulse. It can be seen that as QD increases, the spike pulse becomes stronger, the microsecond-long pulse becomes weaker, and the interval between the spike pulse and the microsecond-long pulse becomes longer, until the composite pulse consists only of the spike pulse, meaning the energy of the microsecond-long pulse in the composite pulse gradually decreases to 0.

[0087] Figure 7 This is a curve showing the relationship between spike pulse width, average pulse power, and QD. As QD (Q-switched delay time) increases, the spike pulse width continuously decreases, with the rate of decrease being initially rapid and then slowing down (decreasing curve); the spike pulse power increases, and correspondingly, the peak power of the spike pulse increases, that is, the peak power of the composite pulse increases (rising curve).

[0088] Figure 8 This relates to the spike pulse power E1, the composite pulse power E2, and their ratio E1 / (E1+E1) with QD. It can be seen that as QD increases, E1 / (E1+E2) gradually increases, meaning that once PW and QW are determined, the power ratio can be controlled by QD.

[0089] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A composite pulsed laser, characterized in that, include: Total reflection mirror, laser module, Q switch, output coupling mirror, pump drive source, Q switch drive source, main controller; The total reflection mirror, Q switch, laser module and output coupling mirror are arranged horizontally in sequence to ensure optical coaxiality and form a laser resonant cavity; The pump drive source is connected to the laser module and is used to control the pumping time of the pump source in the laser module; The laser module includes a gain medium, which is a laser crystal or a gain fiber. The Q-switch driver source is connected to the Q-switch and is used to control the Q-switch opening time; The main controller is connected to both the pump drive source and the Q switch drive source, and is used to control the relative delay time between the pump drive source and the Q switch drive source. The laser is used to turn on the pump drive source through the main controller, and then turn on the pump source inside the laser module to pump the laser, so that the upper energy level particles of the gain medium inside the laser module continue to accumulate. A relative delay time is determined. After the relative delay time has elapsed, the Q-switch driver source is turned on by the main controller, and the Q-switch is turned on by the Q-switch driver source. At this time, photons are released according to the upper-level particles accumulated in the laser module, forming a spike pulse and outputting it through the output coupling mirror. After the spike pulse is formed, the laser module and the Q-switch remain on, forming a long pulse and outputting it through the output coupling mirror. The attribute information of the spike pulse and / or the long pulse is acquired, and the relative delay time is re-determined based on the attribute information. The laser emission is adjusted based on the re-determined relative delay time. The relative delay time is controlled by the main controller and is greater than the formation time of the spike pulse and not higher than the lifetime of the upper-level laser in the gain medium, or its order of magnitude is the same as the order of magnitude of the upper-level lifetime. Acquiring the attribute information of the spike pulse and the long pulse and re-determining the relative delay time based on the attribute information specifically includes: acquiring the first laser energy of the spike pulse and the second laser energy of the long pulse; determining the ratio of the first laser energy to the second laser energy; and adjusting the relative delay time based on the ratio. The laser is also used to, under the condition that the pump source pumping time and the Q switch opening time are fixed: when the sum of the Q switch opening time and the relative delay time is less than the pump source pumping time and there is laser output, the larger the relative delay time, the higher the intensity of the first peak pulse of the composite pulse laser, the higher the energy of the first laser, the narrower the pulse width of the peak pulse, the lower the energy of the second laser of the long pulse, and the lower the pulse width of the long pulse.

2. The composite pulsed laser according to claim 1, characterized in that, The laser resonant cavity also includes an optical rotator crystal and a thin-film polarizer; The total reflection mirror, thin-film polarizer, Q-switch, laser module, optical rotator crystal, and output coupling mirror are arranged horizontally in sequence to ensure optical coaxiality and form a laser resonant cavity.

3. The composite pulsed laser according to claim 2, characterized in that, The laser resonant cavity includes two laser modules and two Q switches; The horizontally arranged components, from left to right, are a total reflection mirror, a thin-film polarizer, a first Q-switch, a first laser module, an optical rotator crystal, a second laser module, a second Q-switch, and an output coupling mirror.

4. The composite pulsed laser according to any one of claims 1-3, characterized in that, The laser module also includes a pump source, and the laser module is either a side-pumped or end-pumped type.

5. A method for applying the composite pulsed laser as described in claim 1, characterized in that, include: The pump drive source is turned on by the main controller, and the pump source inside the laser module is turned on by the pump drive source to pump, so that the upper energy level particles of the gain medium inside the laser module continue to accumulate. A relative delay time is determined. After the relative delay time has elapsed, the Q-switch drive source is turned on by the main controller. The Q-switch is turned on by the Q-switch drive source. At this time, photons are released according to the upper energy level particles accumulated in the laser module, forming a spike pulse and outputting it through the output coupling mirror. After the peak pulse is formed, the laser module and the Q switch remain on to form a long pulse, which is then output through the output coupling mirror. Obtain the attribute information of the spike pulse and / or the long pulse, redetermine the relative delay time based on the attribute information, and adjust the laser emission based on the redetermined relative delay time; The relative delay time is controlled by the main controller and is greater than the formation time of the spike pulse and not higher than the lifetime of the upper energy level of the laser in the gain medium, or its order of magnitude is the same as that of the upper energy level lifetime. When the pump source pumping time and Q switch opening time are fixed: when the sum of the Q switch opening time and the relative delay time is less than the pump source pumping time and there is laser output, the larger the relative delay time, the higher the intensity of the first peak pulse of the composite pulse laser, the higher the energy of the first laser, the narrower the pulse width of the peak pulse, the lower the energy of the second laser of the long pulse, and the lower the pulse width of the long pulse. The step of acquiring the attribute information of the spike pulse and the long pulse, and redetermining the relative delay time based on the attribute information, specifically includes: acquiring the first laser energy of the spike pulse and the second laser energy of the long pulse; determining the ratio of the first laser energy to the second laser energy; and adjusting the relative delay time based on the ratio.

6. The application method of the composite pulsed laser according to claim 5, characterized in that, When the Q-switch opening time is greater than the pump source pumping time, and the relative delay time increases to the point where the difference between the relative delay time and the pump source pumping time is within a preset range or equal to the relative delay time, there is only a single nanosecond-level spike pulse, and at this time there is only the first laser energy. During the pump source pumping time, the longer the Q-switch is open, the longer the duration of the long pulse in the laser composite pulse, and the higher the average power of the laser.

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