A 1.5-μm passively Q-switched laser

Abstract

The present invention discloses a 1.5-μm passively Q-switched laser, which includes multiple pump sources with the same working cycle and duty cycle, and a resonant cavity arranged on the light-emitting side of the multiple pump sources; the multiple pump sources are used to sequentially emit pump light at fixed time intervals within one working cycle; the pulse width of the pump source is equal to the fixed time interval; the resonant cavity uses multiple pump lights to pump a laser crystal in the resonant cavity to obtain multiple beams of 1.5-μm lasers emitted from different positions of the laser crystal, and each beam of laser is emitted after multiple reflections in the resonant cavity to obtain continuous pulsed laser. The 1.5-μm passively Q-switched laser of the present invention overcomes the disadvantage that the laser pulses output by the traditional 1.5-μm passively Q-switched laser are discontinuous under high peak power and chopped pump conditions, and can make the laser pulses output by the laser be continuous in the time domain under the chopped pump working conditions. The present invention can effectively expand the application range of the 1.5-μm passively Q-switched laser.

Description

Technical Field

[0001] The present application relates to a 1.5-micron passive Q-switched laser, belonging to the technical field of lasers. Background Art

[0002] 1.5 microns is in the eye-safe band and has good transmission properties to the atmospheric window. It is widely used in long-distance remote sensing, communications and laser medical fields. For some special fields, such as vehicle-mounted laser radar, the laser light source used has high repetition frequency, narrow laser pulse and high peak power requirements. 1.5 micron passive Q-switched laser is a method commonly used to achieve high repetition frequency, narrow pulse width, high peak power laser pulse output. It has the advantages of compact structure, small size, high safety and suitability for various test environments.

[0003] The passive Q-switched laser in the prior art pumps the laser crystal in a continuous pumping or chopper pumping mode. The laser pulse sequence generated by the laser can be divided into a continuous pulse sequence and an intermittent pulse sequence distributed at a chopper frequency in the time domain. The laser pulse frequency output by the passive Q-switched laser is closely related to the peak power of the pump source. In order to obtain high-frequency pulse output, the pump source usually needs to work under high peak power conditions. For 1.5-micron laser crystals with poor laser thermal performance, in order to protect the laser crystal from damage, the pump source can only pump the laser crystal in a chopper mode to reduce the impact of the thermal effect of the laser crystal when it is pumped at high power.

[0004] However, the laser pulses output by the chopper-pumped laser crystal are a series of discrete pulse sequences in the time domain. The discontinuous pulse sequence increases the difficulty of using the laser as a light source and limits the application range of the laser. Summary of the invention

[0005] The purpose of the present application is to provide a 1.5 micron passive Q-switched laser to solve the technical problem of the existing 1.5 micron passive Q-switched laser that the output laser pulse is discontinuous due to the use of chopping pump crystal.

[0006] The 1.5 micron passive Q-switched laser of the present invention comprises a plurality of pump sources with the same working period and working duty cycle and a resonant cavity arranged on the light-emitting side of the plurality of pump sources;

[0007] The plurality of pump sources are used to sequentially emit pump light at fixed time intervals within a working cycle;

[0008] The pulse width of the pump source is equal to the fixed time interval;

[0009] The resonant cavity uses a plurality of pump lights to pump the laser crystal in the resonant cavity, thereby obtaining a plurality of beams of 1.5 micron laser light emitted from different positions of the laser crystal. Each beam of the laser light is emitted after multiple reflections in the resonant cavity, thereby obtaining a continuous pulse laser.

[0010] Preferably, it also includes a beam splitter and a signal feedback system arranged on the light-emitting side of the resonant cavity;

[0011] The beam splitter is used to reflect a part of the pulsed laser corresponding to each pump light beam to the signal feedback system, and transmit the other part;

[0012] The signal feedback system is used to monitor the distribution of all the pulse lasers in the time domain and adjust the light emission sequence of the multiple pump sources according to the distribution.

[0013] Preferably, the number of the pump sources is determined according to a first formula; the first formula is:

[0014] N=1 / D

[0015] Wherein, N is the number of the pump sources, and D is the duty cycle of the pump sources.

[0016] Preferably, the fixed time interval is determined according to a second formula; the second formula is:

[0017] ΔT=D×T

[0018] Wherein, ΔT is a fixed time interval, D is a duty cycle of the pump source, and T is a duty cycle of the pump source.

[0019] Preferably, the laser crystal is Er 3+ / Yb 3+ Double doped borate crystals, Er 3+ / Yb 3+ Dual-doped vanadate crystals or Er 3+ / Yb 3+ A type of doped yttrium aluminum garnet crystal.

[0020] Preferably, the pump lights emitted by the plurality of pump sources are incident on different positions of the laser crystal in a dispersed manner.

[0021] Preferably, the plurality of pump sources are arranged in an array.

[0022] Preferably, it also includes a coupling lens group arranged between the plurality of pump sources and the resonant cavity;

[0023] The coupling lens group is used to adjust the radius of the pump light incident on the laser crystal.

[0024] Preferably, it also includes a light splitting router arranged between the plurality of pump sources and the coupling lens group;

[0025] The optical splitting route is used to separate the pumping lights emitted by a plurality of pumping sources.

[0026] Preferably, the resonant cavity comprises a pump mirror, a laser crystal and a coupling output mirror arranged in sequence;

[0027] The pump mirror is used to transmit the pump light and reflect the laser light emitted from the laser crystal;

[0028] The laser crystal converts the pump light transmitted through the pump mirror into laser light and enhances the intensity of the laser light incident on the laser crystal;

[0029] The coupling output mirror is used to reflect and partially transmit the laser light emitted from the laser crystal, and the transmitted laser light is a pulsed laser.

[0030] Compared with the prior art, the 1.5 micron passive Q-switched laser of the present invention has the following beneficial effects:

[0031] The 1.5 micron passive Q-switched laser of the present invention is provided with a plurality of pump sources with the same working cycles and working duty cycles, so that the output pulse lasers are superimposed on each other to form a continuous pulse output, thereby overcoming the disadvantage that the laser pulses output by the conventional 1.5 micron passive Q-switched laser under high peak power and chopper pumping conditions are discontinuous, and the laser pulses output by the laser under chopper pumping working conditions can be continuous in the time domain. The present invention can effectively expand the application scope of the 1.5 micron passive Q-switched laser.

[0032] Due to the influence of pump light irradiation, heat load will accumulate inside the laser crystal, resulting in thermal effects. Severe thermal effects will greatly affect the quality of pulsed lasers. To overcome the above problems, the present invention sets a signal feedback system. According to the distribution of pulsed lasers in the time domain fed back by the signal feedback system, the light emission order of multiple pump sources is adjusted, and at the same time, the pump light emitted by the pump source is limited to be incident on different positions of the laser crystal in a dispersed form. Through the above settings, the thermal effects inside the laser crystal can be effectively avoided.

[0033] In order to ensure that the light output by the laser crystal pumped by the pump light is 1.5 micron laser, the present invention limits the laser crystal to Er 3+ / Yb 3+ Double doped borate crystals, Er 3+ / Yb 3+ Dual-doped vanadate crystals or Er 3+ / Yb 3+One of the double-doped yttrium aluminum garnet crystals. The above three types of laser crystals have low conversion losses, ensuring the quality of laser output.

[0034] The present invention also provides a coupling lens group to focus the pump light on different positions of the laser crystal in the resonant cavity to avoid the influence of the crystal thermal effect on each pump source.

[0035] In order to avoid mutual influence between pump lights generated by multiple pump sources, the present invention provides a splitter route, which separates each pump light path through a mechanical structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a schematic structural diagram of a 1.5 micron passively Q-switched laser of the present invention;

[0037] Figure 2 This is a schematic diagram of the structure of a 1.5 micron passively Q-switched laser in an embodiment of the present invention;

[0038] Figure 3 This is a pulse sequence diagram of the laser output by a 1.5 micron passively Q-switched laser in an embodiment of the present invention;

[0039] Figure 4 This is a sequence diagram of laser output of a 1.5-micron passively Q-switched laser in the prior art under continuous pumping and chopper pumping conditions.

[0040] List of parts and reference numerals:

[0041] 1. The first pump source; 2. The second pump source; 3. The third pump source; 4. The fourth pump source; 5. The fifth pump source; 6. The beam splitter; 7. The first convex lens; 8. The second convex lens; 9. The pump mirror; 10. The laser crystal; 11. The coupling output mirror; 12. The beam splitter; 13. The signal monitoring system; 14. The signal modulation system; 15. The multi-channel pump system; 16. The signal feedback system. DETAILED DESCRIPTION

[0042] The 1.5 μm passive Q-switched laser in the prior art pumps the laser crystal in a continuous pumping or chopper pumping mode. The laser pulse sequence generated by the laser crystal can be divided into a continuous pulse sequence and an intermittent pulse sequence distributed at a chopper frequency in the time domain, such as Figure 4 As shown, the horizontal axis is time in seconds, and the vertical axis is the normalized signal intensity. Figure 4 (a) is continuous pump light, and its output pulse laser is (c); Figure 4 (b) is the chopped pump light, and the output pulse laser is (d). It can be seen that the pump light generated by a single pump source will cause the output pulse laser to be intermittent. In order to overcome the above problems of chopper pumping, the present application improves the 1.5 micron passive Q-switched laser.

[0043] The present invention is described in detail below in conjunction with embodiments, but the present invention is not limited to these embodiments.

[0044] like Figure 1 and Figure 2 As shown, the 1.5 micron passive Q-switched laser of the embodiment of the present invention includes a multi-channel pumping system 15, and the multi-channel pumping system 15 includes multiple pumping sources with the same working cycle and working duty cycle. The laser of the present invention also includes a resonant cavity arranged on the light-emitting side of multiple pumping sources; multiple pumping sources are used to emit pumping light in sequence at fixed time intervals within a working cycle; the pulse width of the pumping source is equal to the fixed time interval; the pumping source in the embodiment of the present invention is preferably a semiconductor pumping source, and is a pumping source that pumps the crystal in a chopper pumping working mode.

[0045] The resonant cavity of the present invention utilizes multiple pumping lights to pump different positions of the laser crystal in the resonant cavity, thereby obtaining multiple beams of 1.5 micron lasers emitted from different positions of the laser crystal. Each laser beam is emitted after multiple reflections in the resonant cavity, thereby obtaining continuous pulsed lasers.

[0046] The 1.5 micron passive Q-switched laser of the present invention is provided with a plurality of pump sources with the same working cycles and working duty cycles, and the pump sources are limited to emit pump light in sequence at fixed time intervals, wherein the pulse width of the pump source is equal to the fixed time interval, and finally the pulse lasers output by the passive Q-switched laser are superimposed on each other to form a continuous pulse output, thereby overcoming the disadvantage that the laser pulses output by the conventional 1.5 micron passive Q-switched laser under high peak power and chopper pumping conditions are discontinuous, and the laser pulses output by the laser under chopper pumping working conditions can be continuous in the time domain. The present invention can effectively expand the application scope of the 1.5 micron passive Q-switched laser.

[0047] Due to the influence of pump light irradiation, heat load will accumulate inside the laser crystal, resulting in thermal effects. Severe thermal effects will greatly affect the quality of pulsed lasers. When the crystal thermal effect is serious, the frequency of the pulsed laser will fluctuate violently, and the frequency of the output pulse will no longer be maintained at a fixed value. At this time, the superposition effect of each laser pulse will be destroyed, and the pulse output of the laser will be chaotic or even enter a chaotic state. Therefore, the present invention also provides a beam splitter 12 and a signal feedback system 16 located on the light output side of the resonant cavity;

[0048] The beam splitter 12 of the present invention is used to reflect a part of the pulse laser corresponding to each beam of pump light to the signal feedback system 16, and transmit the other part; the signal feedback system 16 is used to monitor the distribution of all pulse lasers in the time domain, and adjust the light emission order of multiple pump sources according to the distribution. The present invention uses the signal feedback system to determine the distribution of the pulse lasers corresponding to the output of each pump source in the time domain. When it is found that the frequency of a certain pulse laser is jittering, the pumping order of each pump source can be adjusted, and the light emission order of the pump source with pulse laser jitter can be delayed, so that the thermal impact between adjacent pumped parts of the laser crystal is minimized to ensure the effect of pulse superposition.

[0049] In order to achieve optimal continuous operation of multiple pump sources within one working cycle, it is necessary to limit the number of pump sources and the light emission time intervals of adjacent pump sources. The present invention limits the number of pump sources, and the number of pump sources is determined according to the first formula; the first formula is:

[0050] N=1 / D

[0051] Where N is the number of pump sources, and D is the duty cycle of the pump source. The value of N should satisfy: 1 / N is a rational number, which can be beneficial for the signal feedback system to analyze and process the signal.

[0052] The present invention further defines a fixed time interval, which is determined according to a second formula:

[0053] ΔT=D×T

[0054] Where ΔT is the fixed time interval, D is the duty cycle of the pump source, and T is the duty cycle of the pump source.

[0055] In order to obtain 1.5 micron laser, the laser crystal is set to Er 3+ / Yb 3+ Double doped borate crystals, Er 3+ / Yb 3+ Dual-doped vanadate crystals or Er 3+ / Yb 3+ A type of double-doped yttrium aluminum garnet crystal. Among them, Er 3+ / Yb 3+ The doped borate crystals include Er:Yb:YAB, Er:Yb:GdAB, Er:Yb:LuAB; Er:Yb:YAB 3+ / Yb 3+ Dual-doped vanadate crystals include Er:Yb:YVO 4 ;E 3+ / Yb 3+ The double-doped yttrium aluminum garnet crystal includes Er:Yb:YAG; the above laser crystal has a small conversion loss, which ensures the quality of laser output.

[0056] Due to the influence of pump light irradiation, heat load will accumulate inside the laser crystal, resulting in thermal effects. Severe thermal effects will greatly affect the quality of pulsed lasers. Therefore, the present invention limits the pump light emitted by multiple pump sources to be incident on different positions of the laser crystal in a dispersed form, avoiding the accumulation of heat load at the same position and ensuring the quality of pulsed lasers.

[0057] Furthermore, the present invention arranges multiple pump sources in an array so that the pump lights emitted by the multiple pump sources are incident on different positions of the laser crystal in an array form, ensuring that the thermal influence between adjacent pumped parts of the laser crystal is minimized, thereby ensuring the effect of pulse laser superposition.

[0058] In order to shape the pump light and focus the pump light on the laser crystal to avoid the loss of the pump light, the present invention sets a coupling lens group between multiple pump sources and the resonant cavity; the coupling lens group is used to adjust the radius of the pump light incident on the laser crystal. In this embodiment, the coupling lens group includes a first convex lens 7 and a second convex lens 8, and the two convex lenses are coaxial and the convex surfaces are arranged opposite to each other. The first convex lens 7 and the second convex lens 8 are preferably plano-convex lenses, which have a better focusing effect.

[0059] In order to avoid mutual influence of pumping lights emitted by multiple pumping sources, the present invention sets a splitter 6 between the multiple pumping sources and the coupling lens group; the splitter 6 separates the pumping lights by mechanical parts so that they will not influence each other.

[0060] In order to generate pulsed laser, the present invention sets a resonant cavity including a pump mirror 9, a laser crystal 10 and a coupling output mirror 11 which are arranged in sequence;

[0061] The pump mirror 9 is used to transmit the pump light and reflect the laser light emitted from the laser crystal 10; the laser crystal 10 converts the pump light transmitted through the pump mirror into laser light and enhances the intensity of the laser light incident to the laser crystal 10; the coupling output mirror 11 is used to reflect part of the laser light emitted from the laser crystal 10 and transmit another part of the laser light, and the transmitted laser light is a pulsed laser.

[0062] To explain the 1.5 micron passively Q-switched laser of the present invention in more detail, a specific embodiment will be described below.

[0063] The schematic diagram of the structure of the 1.5 μm passively Q-switched laser in this example is shown in Figure 2, the operating frequency of the semiconductor pump source is 20Hz, the working cycle is 0.05 seconds, and the working duty cycle is 0.2. According to the first formula and the second formula, it can be calculated that the number of required pump sources is 5 (including the first pump source 1, the second pump source 2, the third pump source 3, the fourth pump source 4 and the fifth pump source 5). The 5 pump sources emit light to the resonant cavity in turn at a time interval of 0.01 seconds. The pump light emitted by each pump source passes through the splitter 6 and the first convex lens 7 and the second convex lens 8 in the coupling lens group, and is focused by the pump mirror 9 and irradiated at different positions of the laser crystal 10. The laser crystal 10 is Er:Yb:YAB, and of course it can also be Er:Yb:GdAB, Er:Yb:LuAB, Er:Yb:YVO 4 Or one of Er:Yb:YAG. Five pump sources are irradiated at five different positions of the laser crystal 10, and the laser output optical paths generated by each pump source are independent of each other and do not interfere with each other; the pulse lasers corresponding to the first pump source 1, the second pump source 2, the third pump source 3, the fourth pump source 4 and the fifth pump source 5 are A, B, C, D, and E respectively.

[0064] The pulse sequence of the pulse laser obtained by using 5 pump sources is as follows: Figure 3 As shown, Figure 3 (1) to (5) are the pulse lasers corresponding to the first pump source 1 to the fifth pump source 5, respectively. Figure 3 (6) is a pulse sequence obtained by superimposing 5 pulse lasers obtained by using 5 pump sources. The horizontal axis is time, the unit is second, and the vertical axis is the normalized signal intensity. In this embodiment, since the duty cycle of the pump source is 0.2, the pulse only exists for 0.01 seconds in a cycle of 0.05 seconds (1 / (20Hz)). At this time, the timing of the 5 pulse lasers is monitored in real time by the signal feedback system 16. The signal feedback system in this embodiment includes: a signal monitoring unit 13 and a signal modulation unit 14. The function of the signal monitoring unit 13 is to monitor the distribution of all pulse lasers in the time domain; the function of the signal modulation unit 14 is to adjust the light emission order of multiple pump sources according to the distribution, so that each pulse is staggered by 0.01 seconds, and the sequence of each laser pulse is obtained as follows:

[0065] When only the first pump source 1 is working, the pump light is irradiated to the position A of the laser crystal 10, and the pulse laser A is emitted from A. The pulse sequence is as follows: Figure 3 As shown in (1) in .

[0066] When only the second pump source 2 is working, the pump light is irradiated to the position B of the laser crystal 10, and the pulse laser B is emitted from B. The pulse sequence is as follows: Figure 3 As shown in (2), the time interval between its pulse and the pulse at A is 0.01 second.

[0067] When only the third pump source 3 is working, the pump light is irradiated to the position C of the laser crystal 10, and the pulse laser C is emitted from C. The pulse sequence is as follows: Figure 3 As shown in (3) in the figure, the time interval between its pulse and the pulse at B is 0.01 second.

[0068] When only the fourth pump source 4 is working, the pump light is irradiated to the position D of the laser crystal 10, and the pulse laser D is emitted from D. The pulse sequence is as follows: Figure 3 As shown in (4) in the figure, the time interval between its pulse and the pulse at C is 0.01 second.

[0069] When only the fifth pump source 5 is working, the pump light is irradiated to the position E of the laser crystal 10, and the pulse laser E is emitted from E. The pulse sequence is as follows: Figure 3 As shown in (5) in the figure, the time interval between its pulse and the pulse at D is 0.01 second.

[0070] When the five pump sources are adjusted by the signal feedback system 16, a pulse sequence of five laser beams superimposed on each other will be obtained at the output back end of the beam splitter 12, i.e., the passive Q-switched pulse sequence diagram of the present invention, and its time distribution is as follows: Figure 3 As shown in (6) in FIG. 1 , the pulses are continuously distributed in the time domain, which is consistent with the pulse sequence distribution during continuous pumping. It can be seen that the 1.5-micron passive Q-switched laser of the present invention can still obtain continuous pulsed laser even when the pump source is operated in chopping mode.

[0071] The above are only a few embodiments of the present application and do not constitute any form of limitation to the present application. Although the present application is disclosed as above with preferred embodiments, it is not intended to limit the present application. Any technician familiar with the profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A 1.5-μm passively Q-switched laser, characterized in that, it includes a plurality of pump sources with the same working cycle and duty cycle, and a resonant cavity arranged on the light output side of the plurality of pump sources; the plurality of pump sources are used to sequentially emit pump light at fixed time intervals within one working cycle; the pulse width of the pump source is equal to the fixed time interval; the resonant cavity pumps a laser crystal in the resonant cavity by using the plurality of pump sources to obtain multiple beams of 1.5-μm laser light emitted from different positions of the laser crystal, and each beam of the laser light is emitted after multiple reflections in the resonant cavity to obtain continuous pulsed laser light.

2. The 1.5-μm passively Q-switched laser according to claim 1, characterized in that, it further includes a beam splitter and a signal feedback system arranged on the light output side of the resonant cavity; the beam splitter is used to reflect a part of the pulsed laser light corresponding to each beam of pump light to the signal feedback system and transmit the other part; the signal feedback system is used to monitor the distribution of all the pulsed laser light in the time domain and adjust the light output sequence of the plurality of pump sources according to the distribution.

3. The 1.5-μm passively Q-switched laser according to claim 1, characterized in that, the number of the pump sources is determined according to the first formula; the first formula is: N = 1 / D wherein, N is the number of the pump sources, and D is the duty cycle of the pump source.

4. The 1.5-μm passively Q-switched laser according to claim 1, characterized in that, the fixed time interval is determined according to the second formula; the second formula is: ΔT = D×T In the formula, Δ T is a fixed time interval, D is the duty cycle of the pump source, and T is the working cycle of the pump source.

5. The 1.5-μm passively Q-switched laser according to claim 1, characterized in that, The laser crystal is Er 3+ / Yb 3+ co-doped borate crystal, Er 3+ / Yb 3+ co-doped vanadate crystal, or Er 3+ / Yb 3+ one of the co-doped yttrium aluminum garnet crystals.

6. The 1.5-μm passively Q-switched laser according to claim 1, characterized in that, the pump light emitted by the plurality of pump sources is incident on different positions of the laser crystal in a dispersed form.

7. The 1.5-μm passively Q-switched laser according to claim 6, characterized in that, the plurality of pump sources are arranged in an array.

8. The 1.5-μm passively Q-switched laser according to claim 1, characterized in that, it further includes a coupling lens group arranged between the plurality of pump sources and the resonant cavity; the coupling lens group is used to adjust the radius of the pump light incident on the laser crystal.

9. The 1.5-μm passively Q-switched laser according to claim 8, characterized in that, it further includes a beam splitting optical path arranged between the plurality of pump sources and the coupling lens group; the beam splitting optical path is used to separate the pump light emitted by the plurality of pump sources.

10. The 1.5-μm passively Q-switched laser according to any one of claims 1 to 9, characterized in that, the resonant cavity includes a pump mirror, a laser crystal and a coupling output mirror arranged in sequence; the pump mirror is used to transmit the pump light and reflect the laser light emitted from the laser crystal; the laser crystal converts the pump light transmitted by the pump mirror into laser light and enhances the laser light intensity incident on the laser crystal. The coupled output mirror is used to reflect and partially transmit the laser emitted from the laser crystal, and the transmitted laser is pulsed laser.

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