Composite pulse laser and application method thereof

Abstract

The invention provides a composite pulse laser. The composite pulse laser comprises a total reflective mirror, a laser module, a Q switch, an output coupling mirror, a pumping driving source, a Q switch driving source and a main controller, the total reflective mirror, the Q switch, the laser module and the output coupling mirror are horizontally arranged in sequence to ensure optical coaxiality and form a laser resonant cavity; the pumping driving source is connected with the laser module and is used for controlling the pumping time of a pumping 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 pumping driving source and the Q switch driving source and used for controlling the relative delay time of the pumping driving source and the Q switch driving source. According to the invention, the defect that the common Q-switched laser in the prior art is difficult to realize the high peak power and the high average power at the same time of single light emission is overcome, and the quasi-continuous composite pulse laser with the high peak power and the high average power is output.

Description

Technical Field

[0001] The invention relates to the field of laser technology, and in particular to a composite pulse laser and an application method thereof. Background Art

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

[0003] Q-switching technology, also known as Q-switching technology, is a technology that compresses the energy of a normal continuous laser into a pulse with a very narrow width, thereby increasing the peak power of the light source by several orders of magnitude. The single-shot light emission time of an ordinary quasi-continuous Q-switched laser is in the order of ten to one hundred nanoseconds. The average power and peak power can be adjusted by adjusting the repetition frequency and the duty cycle of the pump light, that is, increasing the number of light emission times and controlling the pumping time.

[0004] When the Q-switched laser is output, the laser is a pulse array composed of a single pulse at a certain frequency. The energy of a single pulse is very high, but there is no energy after the single pulse is output. However, in the effect experiment of the interaction between laser and matter, it is generally expected that the laser can have both high peak power and average power, and it is required that after the peak power appears, it can output a long pulse laser with low peak power within a time range of microseconds. Since the Q switch opening time range of ordinary Q-switched lasers is very short, at the order of a few microseconds, this laser operation mode is difficult to achieve with ordinary Q-switched lasers. Summary of the invention

[0005] The present invention provides a composite pulse laser and an application method thereof, which are used to solve the defect in the prior art that ordinary Q-switched lasers are difficult to achieve single-shot light emission with high peak power and high average power, and realize the output of quasi-continuous composite pulse lasers with high peak power and high average power.

[0006] The present invention provides a composite pulse laser, comprising: a total 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 total reflection mirror, Q switch, laser module and output coupling mirror are arranged horizontally in sequence to ensure optical coaxiality to form a laser resonant cavity; The pump driving source is connected to the laser module and is used to control the pumping time of the pump source in the laser module; The Q switch driving source is connected to the Q switch and is used to control the Q switch opening time; The main controller is connected to the pump driving source and the Q switch driving source respectively, and is used to control the relative delay time between the pump driving source and the Q switch driving source.

[0007] According to a composite pulse laser provided by the present invention, the laser resonant cavity also includes an optically active crystal and a thin-film polarizer; the total reflection mirror, thin-film polarizer, Q switch, laser module, optically active crystal and output coupling mirror are arranged horizontally in sequence to ensure optical coaxiality to form a laser resonant cavity.

[0008] According to a composite pulse laser provided by the present invention, the laser resonant cavity includes two laser modules and two Q switches; the horizontally arranged elements are, from left to right, a total reflection mirror, a thin film polarizer, a first Q switch, a first laser module, an optical rotation crystal, a second laser module, a second Q switch and an output coupling mirror.

[0009] According to a composite pulse laser provided by the present invention, the laser module includes a pump source and a gain medium, and the laser module is a side pump type or an end pump type.

[0010] According to a composite pulse laser provided by the present invention, the gain medium is a laser crystal or a gain optical fiber.

[0011] An application method of a composite pulse laser provided by the present invention comprises: Turning on a pump driving source through a main controller, and turning on a pump source in a laser module through the pump driving source for pumping, so that upper energy level particles of a gain medium in the laser module are continuously accumulated; Determine a relative delay time, and after the relative delay time has elapsed, turn on a Q switch driving source through a main controller, turn on a Q switch through the Q switch driving source, and at this time, release photons according to upper energy level particles accumulated in the laser module, form a spike pulse, and output through an output coupling mirror; After the peak pulse is formed, the laser module and the Q switch are kept turned on to form a long pulse and output it through the output coupling mirror; Acquire property information of the spike pulse and / or the long pulse, redetermine the relative delay time according to the property information, and adjust the laser emission based on the redetermined relative delay time.

[0012] According to an application method of a composite pulse laser provided by the present invention, the relative delay time is controlled by a main controller, which is greater than the formation time of the peak pulse and not higher than the laser upper energy level lifetime of the gain medium, or its order of magnitude is the same as that of the upper energy level lifetime.

[0013] According to an application method of a composite pulse laser provided by the present invention, under the condition that the pump source pumping time and the Q switch opening time are determined to be 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 greater the relative delay time, the higher the intensity of the first peak pulse of the composite pulse laser, the increased first laser energy, the narrower the pulse width of the peak pulse, the reduced second laser energy of the long pulse, and the reduced pulse width of the long pulse.

[0014] According to an application method of a composite pulse laser provided by the present invention, the acquiring of attribute information of the spike pulse and the long pulse and re-determining the relative delay time according to the attribute information specifically include: acquiring a first laser energy of the spike pulse and a second laser energy of the long pulse; determining a ratio of the first laser energy to the second laser energy; and adjusting the relative delay time according to the ratio.

[0015] According to an application method of a composite pulse laser provided by the present invention, when the Q switch opening time is greater than the pump source pumping time, when the relative delay time increases to a value within a preset range or the relative delay time is equal to the pump source pumping time, there is only a single nanosecond spike pulse, and at this time there is only the first laser energy; within the pump source pumping time, the longer the Q switch opening time is, the longer the duration of the long pulse in the laser composite pulse is, and the higher the average power of the laser is.

[0016] The present invention provides a composite pulse laser and an application method thereof, which realizes a modulated composite output of a spike pulse and a long pulse by precisely controlling the timing of a pump source and a Q switch. This composite pulse laser has both high peak power and maintains a relatively high average power, meeting the special requirements of certain application scenarios for laser performance. By adjusting parameters such as the relative delay time, the shape of the composite pulse can be flexibly regulated, including the intensity and width of the spike pulse and the duration and energy distribution of the subsequent long pulse. By precisely controlling the emission timing of the laser pulse, the utilization of the laser energy is optimized. After the spike pulse is formed, the laser module and the Q switch are kept on to form a quasi-continuous long pulse, thereby effectively converting the laser energy into useful output and improving the overall efficiency of the laser. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0018] Figure 1This is one of the schematic diagrams of the structure of the composite pulse laser provided by the present invention.

[0019] Figure 2 This is the second structural schematic diagram of the composite pulse laser provided by the present invention.

[0020] Figure 3 The present invention is a schematic flow chart of the application method of the composite pulse laser provided by the present invention.

[0021] Figure 4 It is a schematic diagram of the variation of the number of photons over time at different relative delay times provided by the present invention.

[0022] Figure 5 It is a schematic diagram of the laser output experimental results provided by the present invention.

[0023] The laser PW and QW are fixed at 200 microseconds, and the QD is adjusted to increase gradually.

[0024] Figure 6 The present invention provides a specific form of a spike pulse and a microsecond long pulse when the laser PW is fixed at 200 microseconds, the QW is fixed at 200 microseconds, and the QD is adjusted to gradually increase.

[0025] Figure 7 The present invention provides a curve showing the relationship between the peak pulse width, the average pulse power and the QD when the laser PW and QW are fixed at 200 microseconds and the QD is adjusted to gradually increase.

[0026] Figure 8 The present 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, the QW is fixed at 200 microseconds, and the QD is adjusted to gradually increase; Reference numerals: Total reflection mirror 1; laser modules 2, 2-1, 2-2; Q switches 3, 3-1, 3-2; output coupling mirror 4; pump driving source 5; Q switch driving source 6; main controller 7; optical rotation crystal 8; thin film polarizer 9. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] The single-shot light emission time of an ordinary quasi-continuous Q-switched laser is in the order of tens to hundreds of nanoseconds. The average power and peak power can be adjusted by adjusting the repetition frequency and the duty cycle of the pump light, that is, increasing the number of light emissions and controlling the pumping time.

[0029] The single light emission time of the present invention is in the order of ten 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. Until the pump source is turned off for this operation, the Q switch remains on (for the Q switch on time QW), and then turns off. The average power and peak power can be adjusted by adjusting QD, QW, the pump light working time, and the working frequency, that is, in addition to controlling the pumping time and increasing the number of light emission times, the Q switching time is also controlled to adjust the average power and peak power.

[0030] Combine the following Figure 1-Figure 8 Embodiments of the present invention are described.

[0031] The present invention provides a composite pulse laser, such as Figure 1 As shown, it includes: a total reflection mirror 1, a laser module 2, a Q switch 3, an output coupling mirror 4, a pump driving source 5, a Q switch driving source 6, and a main controller 7; the total reflection mirror 1, the laser module 2, the Q switch 3 and the output coupling mirror 4 are horizontally arranged in sequence to ensure optical coaxiality to form a laser resonant cavity; the pump driving source 5 is connected to the laser module 2 to control the pumping time of the pump source in the laser module 2; the Q switch driving source 6 is connected to the Q switch 3 to control the Q switch opening time; the main controller 7 is respectively connected to the pump driving source 5 and the Q switch driving source 6 to control the relative delay time between the pump driving source 5 and the Q switch driving source 6.

[0032] exist Figure 1 By adding an optically active crystal and a thin film polarizer to the laser shown in the figure, the present invention provides another composite pulse laser, 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 driving source 5, a Q switch driving source 6, a main controller 7, an optical rotation crystal 8, and a thin film polarizer 9; 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 coupling mirror 4, optical rotation crystal 8, and thin-film polarizer 9 are placed side by side and located on the same horizontal line to ensure optical coaxiality to form a laser resonant cavity; specifically, the horizontally arranged elements are, from left to right, the total reflection mirror 1, thin-film polarizer 9, the first Q switch 3-1, the first laser module 2-1, the optical rotation crystal 8, the second laser module 2-2, the second Q switch 3-2, and the output coupling mirror 4.

[0033] The pump driving source 5 is connected to the laser modules 2-1 and 2-2 through a circuit to control the pumping time PW of the pump source in the laser module; The Q switch driving source 6 is connected to the Q switches 3-1 and 3-2 through a circuit to control the Q switch opening time QW; The main controller 7 is connected to the pump driving source 5 and the Q switch driving source 6 through a circuit to control the relative delay time QD between the pump driving source 5 and the Q switch driving source 6; After a relative delay time QD from the start of the PW signal, the QW signal is given, and the characteristic time lengths of several signals are in the order of microseconds (the order of relaxation time of the gain medium).

[0034] According to the composite pulse laser provided by the present invention, the laser modules 2-1 and 2-2 include a pump source and a gain medium, and the laser module 2 is a side pump type or an end pump type.

[0035] According to the composite pulse laser provided by the present invention, the Q switches 3-1 and 3-2 can be acousto-optic Q switches.

[0036] According to the composite pulse laser provided by the present invention, the gain medium may be a laser crystal or a gain optical fiber.

[0037] Specifically, Figure 2 The figure shows a schematic diagram of the structure of a composite pulse laser; 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 driving source 5, a Q switch driving source 6, a main controller 7, an optical rotation crystal 8, and a thin film polarizer 9.

[0038] The main controller 7 is used to control the relative delay time QD between the pump driving source 5 and the Q switch driving source 6. The pump driving source 5 is used to control the pumping time PW of the pump source in the laser modules 2-1 and 2-2. The Q switch driving source 6 is used to control the opening time QW of the Q switches 3-1 and 3-2.

[0039] The Q switch 3 may be an acousto-optic Q switch 3, which generates ultrasonic waves through electroacoustic conversion to cause periodic changes in the refractive index of the modulation medium, diffracting the incident light, causing diffraction loss, a decrease in the Q value, and failure of laser oscillation. Under the excitation of the optical pump, the number of energy level inversion particles accumulates continuously and reaches a saturation value. At this time, the ultrasonic field is suddenly removed, the diffraction effect disappears immediately, the Q value in the cavity increases sharply, and the laser oscillation recovers rapidly.

[0040] Below Figure 2 Taking the laser shown in FIG. 1 as an example, the application method of the composite pulse laser provided by the present invention is described. The application method of the composite pulse laser described below can correspond to the composite pulse laser described above.

[0041] Figure 3 A schematic flow chart of a method for applying a composite pulse laser provided by an embodiment of the present invention includes the following steps: S310: Turn on the pump driving source 5 through the main controller 7, turn on the pump sources in the laser modules 2-1 and 2-2 through the pump driving source 5 to pump, so that the upper energy level particles of the gain medium in the laser modules 2-1 and 2-2 are continuously accumulated.

[0042] According to an application method of a composite pulse laser provided by the present invention, after the pump driving source 5 is turned on by the main controller 7, the pump source pumping time PW is determined, and the peak power of the peak pulse is increased by increasing the relative delay time QD within the pump source pumping time PW.

[0043] Specifically, the main controller 7 is used to control the opening and closing of the pump driving source 5 and the Q switch driving source 6, as well as the relative delay time QD between the two. The pump driving source 5 is used to turn on the pump source in the laser modules 2-1 and 2-2, and control the pump source pumping time PW in the laser modules 2-1 and 2-2. The Q switch driving source 6 is used to control the Q switches 3-1 and 3-2 and the Q switch opening time QW. Each time the light is emitted, a spike pulse appears first (that is, the laser outputs a short pulse laser), and the laser energy is the first laser energy E1 at this time. A long pulse appears after the spike pulse, and the laser outputs a microsecond long pulse laser, and the laser energy is the second laser energy E2 at this time. By controlling QD to increase, the peak power of the spike pulse is increased, and a high peak power and high average power quasi-continuous composite pulse laser with an adjustable ratio of E1 to E2 is achieved.

[0044] The present invention will be further described below using Nd:YAG laser as an example. When Nd:YAG emits 1064.2nm laser, it is a typical four-level laser, and the rate equation is:

[0045] In the formula, is the total number of doping particles per unit volume; is the number of energy level particles per unit volume; is the number of upper energy level particles per unit volume; v is the speed of light in the gain medium, and the refractive index of the gain medium is 1.82, and the speed of light is 3*108m / s; is the spontaneous emission lifetime of the particle at the upper laser energy level; is the particle relaxation lifetime at the lower laser level; is the pump rate, taken as a linear function of the pump power; is the photon number density; is the stimulated emission cross section; is the intracavity lifetime of the photon.

[0046] The photon lifetime is determined by the following formula:

[0047] In the formula, is the cavity loss, is the cavity length, is the reflectivity of the output coupling mirror 4.

[0048] When Q switches 3-1 and 3-2 are inserted, the cavity loss changes periodically. For example, when the acousto-optic Q switches 3-1 and 3-2 are inserted, the acousto-optic Q switches 3-1 and 3-2 form ultrasonic waves through electroacoustic conversion, causing the refractive index of the modulation medium to change periodically, diffracting the incident light, causing diffraction loss, Q value decreases, and laser oscillation cannot be formed. Under the excitation of the optical pump, the number of energy level inversion particles accumulates continuously and reaches a saturation value. At this time, the ultrasonic field is suddenly removed, the diffraction effect disappears immediately, the Q value in the cavity increases sharply, and the laser oscillation recovers rapidly. Correspondingly, the cavity loss is 1 / 2 of the cavity loss in each pumping cycle T. Due to the presence of diffraction loss in the cavity , Cavity loss without diffraction loss It changes alternately with the turning off and on of Q switches 3-1 and 3-2. As a function of time t, it is determined by the following formula: ,

[0049] In the formula, is the cavity loss with diffraction loss, is the cavity loss without diffraction loss, QD is the relative delay time, QW is the Q switch opening time, T is each pump cycle, and N is a positive integer.

[0050] The premise of laser operation is to form a population inversion. The number of particles at the upper energy level of the gain medium of the laser modules 2-1 and 2-2 must be much larger than the number of particles at the lower energy level of the gain medium of the laser modules 2-1 and 2-2 to form stimulated radiation.

[0051] When the Q switch 3 is in the off state, taking the acousto-optic Q switches 3-1 and 3-2 as an example, the diffraction loss of the Q switches 3-1 and 3-2 is very high, and the fluorescence signal of the gain medium cannot pass through the Q switch 3 in the resonant cavity. At this time, if the pump sources of the laser modules 2-1 and 2-2 continue to work, and the Q switches 3-1 and 3-2 are always in the off state, the upper energy level of the laser will continue to accumulate energy, and the number of particles between the upper and lower energy levels of the laser will form a reversal that far exceeds the laser threshold.

[0052] S320: Determine the relative delay time. After the relative delay time has passed, turn on the Q switch driving source 6 through the main controller 7, and turn on the Q switches 3-1 and 3-2 through the Q switch driving source 6. At this time, the upper energy level particles accumulated in the laser modules 2-1 and 2-2 release photons to form a spike pulse and output it through the output coupling mirror 4.

[0053] According to an application method of a composite pulse laser provided by the present invention, the relative delay time QD is controlled by the main controller 7, which is greater than the formation time of the peak pulse and not higher than the laser upper energy level lifetime of the gain medium.

[0054] Specifically, after a relative delay time, the Q switches 3-1 and 3-2 are turned on. At this time, the Q switches 3-1 and 3-2 are in the on state. The Q switches 3-1 and 3-2 can be regarded as a lens with a high transmittance to the laser operating band light, and the cavity loss is very small. The fluorescence signal of the gain medium of the laser modules 2-1 and 2-2 continuously travels back and forth at the speed of light through the total reflection mirror 1 and the output coupling mirror 4 of the resonant cavity. A large number of upper energy level particles of the gain medium of the laser modules 2-1 and 2-2 quickly transition to the lower energy level of the laser and release photons by stimulated radiation, and the number of upper energy level particles of the gain medium drops to a not too high level. This process is rapidly amplified by the stimulated radiation process to form a spike pulse laser.

[0055] It should be pointed out that if the pump source continues to work for a time exceeding the spontaneous radiation lifetime of the upper laser energy level particles in the gain medium, and the Q switches 3-1 and 3-2 are always in the off state, the upper energy level particles will quickly drop to 1 / e of the original particle number through the thermal relaxation process. This process does not produce laser and is not conducive to laser generation.

[0056] Therefore, the relative delay time QD should be greater than the formation time of the spike pulse, that is, the laser establishment time in the resonant cavity, which is in the order of microseconds, and should not exceed the laser upper energy level lifetime of the gain medium or be of the same order of magnitude as the upper energy level lifetime.

[0057] S330: After the peak pulse is formed, the laser modules 2 - 1 and 2 - 2 and the Q switches 3 - 1 and 3 - 2 continue to be turned on to form a quasi-continuous long pulse and output it through the output coupling mirror 4 .

[0058] Specifically, in the next period of time, the pump sources of the Q switches 3-1 and 3-2 and the laser modules 2-1 and 2-2 are continuously turned on, and the number of upper energy level particles in the gain medium of the 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.

[0059] S340: Acquire attribute information of the spike pulse or the long pulse, redetermine the relative delay time according to the attribute information, and adjust the laser emission based on the redetermined relative delay time.

[0060] According to an application method of a composite pulse laser provided by the present invention, under the condition that the pump source pumping time PW and the Q switch opening time QW are determined to be 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 is, the higher the intensity of the first peak pulse of the composite pulse laser is, the energy of the first laser increases, the pulse width of the peak pulse is narrower, the second laser energy of the long pulse decreases, and the pulse width of the long pulse decreases.

[0061] According to an application method of a composite pulse laser provided by the present invention, a peak pulse and a long pulse form a composite pulse; attribute information of the peak pulse and the long pulse is obtained, and the relative delay time QD is re-determined according to the attribute information, specifically including: obtaining a first laser energy E1 of the peak pulse and a second laser energy E2 of the long pulse; determining a ratio E1 / E2 of the first laser energy E1 to the second laser energy E2; and adjusting the relative delay time QD according to the ratio.

[0062] Specifically, Figure 4 This is a diagram showing how the number of photons changes over time under different relative delay times of the present invention. The pumping time PW of the pump source is 250μs, the Q switch opening time QW is equal to PW, and the relative delay time QD of the Q switch opening time QW relative to the start time of the pumping are different values: 117.5μs, 120μs, 122.5μs, 125μs, and 175μs.

[0063] After 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 greater 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 becomes narrower; it should be pointed out that although E1 becomes larger, 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 effective width of the peak pulse in the entire composite pulse decreases.

[0064] In addition, as an extreme case, when the relative delay time QD increases to almost equal to PW, there is only a single pulse spike at the nanosecond level, that is, the laser energy of the composite pulse is all concentrated on the spike pulse, and the laser energy E2=E1. By measuring the laser energy E1 and the laser energy E2, the E1 / (E1+E2) value can be calculated as the proportion of the energy of the first spike pulse in the composite pulse. When the relative delay time QD is greater than the pulse formation time and less than the pump source pumping time PW, the larger the QD, the larger the ratio of E1 to E2 E1 / E2, and finally approaches infinity.

[0065] According to an application method of a composite pulse laser provided by the present invention, when the Q switch opening time QW is greater than the pump source pumping time PW, when the relative delay time QD increases to a value within a preset range or the two are equal to the pump source pumping time PW, there is only a single nanosecond spike pulse, and at this time there is only the first laser energy E1; within the pump source pumping time PW, the longer the Q switch opening time QW is, the longer the duration of the long pulse in the laser composite pulse is, and the higher the average power of the laser is.

[0066] Specifically, after the pump source pumping time PW and the relative delay time QD are determined, when the Q switch opening time QW is longer, the duration of the subsequent small pulse train of the laser composite pulse is longer, which will increase the average power of the laser.

[0067] Figure 5 The figure is a schematic diagram of the laser output experimental results of the present invention. The line pointed by the pump electrical signal in the figure represents the current signal of the pump driving source 5, and the time area covered by the double-headed arrow line segment below PW is the pumping time PW of the pump source; the line pointed by the Q switch electrical signal represents the current signal of the Q switch driving source 6, and the time area covered by the double-headed arrow line segment below QW is the Q switch opening time QW, and the time area covered by the double-headed arrow line segment below QD is the relative delay time QD; the line pointed by the laser intensity in the figure represents the signal of the laser intensity measured by the photoelectric probe, and the area pointed to E1 indicates that the area under the light intensity curve is the laser energy E1, and the area pointed to E2 indicates that the area under the light intensity curve is the laser energy E2.

[0068] Figure 6 , Figure 7 , Figure 8 The content shown is a specific experimental result of the present invention. The PW and QW of the Nd:YAG laser are fixed at 200 microseconds, and the QD is adjusted to gradually increase. Figure 6 It is the specific form of the spike pulse and the microsecond long pulse. It can be seen that as the QD increases, the spike pulse becomes stronger and stronger, the microsecond long pulse becomes weaker and weaker, and the interval between the spike pulse and the microsecond long pulse becomes longer and longer, until the composite pulse has only the spike pulse, that is, the microsecond long pulse energy of the composite pulse gradually decreases to 0.

[0069] Figure 7 It is the relationship curve between the spike pulse width, the average pulse power and QD. It can be seen that as QD (Q-switched delay time) increases, the spike pulse width (spike pulse width) continues to decrease, and the speed of decrease is first fast and then slow (downward curve); the energy of the spike pulse (spike pulse power) is getting bigger and bigger, and the corresponding peak power of the spike pulse is getting higher and higher, that is, the peak power of the composite pulse is getting higher and higher (upward curve).

[0070] Figure 8 It is the relationship between the peak pulse energy E1 (spike pulse power), the microsecond long pulse energy E2 (composite pulse power), and their ratio E1 / (E1+E1) and QD. It can be seen that as QD increases, E1 / (E1+E2) gradually increases, that is, after PW and QW are determined, the power ratio can be adjusted by QD.

[0071] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A composite pulse laser, characterized in that: include: Total reflection mirror, laser module, Q switch, output coupling mirror, pump driving source, Q switch driving source, main controller; The total reflection mirror, Q switch, laser module and output coupling mirror are arranged horizontally in sequence to ensure optical coaxiality to form a laser resonant cavity; The pump driving source is connected to the laser module and is used to control the pumping time of the pump source in the laser module; The Q switch driving source is connected to the Q switch and is used to control the Q switch opening time; The main controller is connected to the pump driving source and the Q switch driving source respectively, and is used to control the relative delay time between the pump driving source and the Q switch driving source.

2. The composite pulse laser according to claim 1, characterized in that: The laser resonant cavity also includes an optically active crystal and a thin-film polarizer; The total reflection mirror, thin-film polarizing plate, Q switch, laser module, optical rotation crystal and output coupling mirror are horizontally arranged in sequence to ensure optical coaxiality, thus forming a laser resonance cavity.

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

4. The composite pulse laser according to any one of claims 1 to 3, characterized in that: The laser module comprises a pump source and a gain medium, and the laser module is in a side pump form or an end pump form.

5. The composite pulse laser according to claim 4, characterized in that: The gain medium is a laser crystal or a gain optical fiber.

6. A method for applying the composite pulse laser according to claim 1, characterized in that: include: Turning on a pump driving source through a main controller, and turning on a pump source in a laser module through the pump driving source for pumping, so that upper energy level particles of a gain medium in the laser module are continuously accumulated; Determine a relative delay time, and after the relative delay time has elapsed, turn on a Q switch driving source through a main controller, turn on a Q switch through the Q switch driving source, and at this time, release photons according to upper energy level particles accumulated in the laser module, form a spike pulse, and output through an output coupling mirror; After the peak pulse is formed, the laser module and the Q switch are kept turned on to form a long pulse and output it through the output coupling mirror; Acquire property information of the spike pulse and / or the long pulse, redetermine the relative delay time according to the property information, and adjust the laser emission based on the redetermined relative delay time.

7. The application method of the composite pulse laser according to claim 6, characterized in that: The relative delay time is controlled by a main controller, which is greater than the formation time of the peak pulse and not higher than the laser upper energy level lifetime of the gain medium, or its order of magnitude is the same as that of the upper energy level lifetime.

8. The application method of the composite pulse laser according to claim 7, characterized in that: When the pump source pumping time and the Q switch opening time are determined to be fixed: When the sum of the Q switch opening time and the relative delay time is less than the pumping time of the pump source and there is laser output, the greater the relative delay time, the higher the intensity of the first peak pulse of the composite pulse laser, the increased first laser energy, the narrower the pulse width of the peak pulse, the reduced second laser energy of the long pulse, and the reduced pulse width of the long pulse.

9. The application method of the composite pulse laser according to claim 6, characterized in that: The acquiring the attribute information of the peak pulse and the long pulse, and re-determining the relative delay time according to the attribute information specifically includes: Acquiring a first laser energy of the peak pulse and a second laser energy of the long pulse; determining a ratio of the first laser energy to the second laser energy; The relative delay time is adjusted according to the ratio.

10. The application method of the composite pulse laser according to claim 6, characterized in that: When the Q switch opening time is greater than the pump source pumping time, and the relative delay time increases to a value within a preset range or equal to the pump source pumping time, there is only a single spike pulse at the nanosecond level, and at this time there is only the first laser energy; During the pumping time of the pump source, the longer the Q switch is turned on, the longer the duration of the long pulse in the laser composite pulse is, and the higher the average power of the laser is.

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