Passive Q-switched pulse laser with wave band of 1.5-1.6 [mu] m

Abstract

The invention discloses a 1.5-1.6 [mu] m wave band passive Q-switched pulse laser, and belongs to the technical field of laser devices. According to the passively Q-switched pulse laser, the Er < 3 + > / Yb < 3 + > double-doped YPO4 crystal (Er < 3 + >: Yb < 3 + >: YPO4) with high thermal conductivity, long laser upper-energy-level fluorescence lifetime and high Yb < 3 + >-> Er < 3 + > energy transfer efficiency is adopted as a gain medium, and a semiconductor laser pulse pumping scheme is utilized, so that human-eye-safe 1.5-1.6 [mu] m waveband pulse laser with stable operation, high energy, high repetition frequency and narrow pulse width is realized; the light source can be used as a detection light source of laser range finders and laser radars.

Description

Technical Field

[0001] The present application relates to a 1.5-1.6 μm band passively Q-switched pulse laser, belonging to the technical field of laser devices. Background Art

[0002] 1.5-1.6μm band laser has the characteristics of high atmospheric transmittance, strong smoke penetration ability, easy detection, low background noise and high eye safety. It can be used as the detection light source of laser rangefinder and laser radar and is widely used in various civil and military fields. 3+ / Yb 3+ The laser upper level fluorescence lifetime of double-doped phosphate glass is long, reaching 7-8ms, with strong energy storage capacity, and also has high Yb 3+ →Er 3+ Energy transfer efficiency (>90%), is currently the best performance 1.5-1.6μm band commercial laser material. 3+ / Yb 3+ Using double-doped phosphate glass as a gain medium, 1535nm pulsed laser with energy higher than 100μJ and pulse width less than 10ns can be achieved at a low repetition rate of 1-10Hz. However, the thermal conductivity of phosphate glass is low (about 0.8Wm -1 K -1 ), which is easily damaged or even broken under high average pump power, and the accumulated heat cannot be effectively and quickly dissipated under high repetition rate laser operation. The thermal effect seriously weakens the performance of pulsed laser, limits the average output power and repetition rate of pulsed laser, and also increases the difficulty of designing cooling scheme for laser gain medium. Summary of the invention

[0003] The high repetition frequency of pulsed laser helps to achieve high detection speed and increase the amount of received signal data, improving the imaging accuracy and reliability of lidar; while high energy and narrow pulse width can effectively improve measurement accuracy and detection distance. Therefore, the research and development of laser radars with high thermal conductivity, long laser upper energy level fluorescence lifetime and high Yb 3+ →Er 3+ Energy transfer efficiency Er 3+ / Yb 3+ The dual-doped materials can realize high-energy, high-repetition-rate and narrow-pulse-width pulsed lasers in the 1.5-1.6μm band. Using them as detection light sources for laser rangefinders and lidars can greatly improve the performance of these instruments.

[0004] This application adopts the following technical solutions:

[0005] The present application provides a 1.5-1.6 μm band passively Q-switched pulse laser, which has high thermal conductivity, long laser upper energy level fluorescence lifetime and high Yb3+ →Er 3+ Energy transfer efficiency Er 3+ / Yb 3+ Double doped YPO4 crystal (Er 3+ :Yb 3+ :YPO4) is used as the gain medium and a semiconductor laser pulse pumping scheme is used to obtain a stable, high-energy, high-repetition-rate and narrow-pulse-width eye-safe 1.5-1.6μm band pulse laser, which can be used as a detection light source for laser rangefinders and lidars.

[0006] According to one aspect of the present application, there is provided a 1.5-1.6 μm band passively Q-switched pulse laser, comprising: a pump source, a gain medium, and a Q-switched element coaxially arranged in sequence along an optical path;

[0007] The gain medium is Er 3+ :Yb 3+ :YPO4 crystal;

[0008] The pump source is a semiconductor laser that can generate laser light in the 950nm band or the 975nm band;

[0009] The pump source adopts a pulse working mode, the pump pulse period is 0.1 to 200 ms, and the pump pulse width is 0.05 to 5 ms;

[0010] The input end face of the gain medium and the output end face of the Q-switching element are respectively plated with an input dielectric film and an output dielectric film; or,

[0011] The input end face of the gain medium is not coated with an input dielectric film, and the laser further comprises a laser cavity input mirror whose end face is coated with an input dielectric film; or,

[0012] The output end face of the Q-switching element is not coated with an output dielectric film, and the laser further comprises a laser cavity output mirror whose end face is coated with an output dielectric film; or,

[0013] The input end face of the gain medium and the output end face of the Q-switching element are not coated with a dielectric film, and the laser further comprises a laser cavity input mirror and a laser cavity output mirror, whose end faces are respectively coated with an input dielectric film and an output dielectric film;

[0014] The laser cavity input mirror is coaxially arranged between the pump source and the gain medium along the laser optical path; and the laser cavity output mirror is coaxially arranged behind the Q-switching element along the laser optical path.

[0015] Optionally, the Er 3+ :Yb 3+ Er in YPO4 crystal 3+ The doping concentration is 0.2~3.0at.%Yb 3+The doping concentration is 2 to 30 at.%.

[0016] This application adopts Er 3+ :Yb 3+ :YPO4 crystals are grown by the top seed flux method, and block crystals with a size of more than centimeters can be obtained. This growth technology overcomes the shortcomings of existing YPO4 crystals that use Pb2P2O7 as a flux and can only be grown by the spontaneous nucleation flux method, thus only obtaining flakes with a thickness of less than 1mm. The Er:Yb:YPO4 crystals grown belong to the tetragonal system and the space group is I41 / amd. The crystal has high thermal conductivity (about 12.0Wm -1 K -1 ), large absorption cross section (3.2×10 -20 cm 2 @975nm), long laser upper level fluorescence lifetime (about 4.2ms) and high Yb 3+ →Er 3+ Energy transfer efficiency (>90%) and other advantages make it a 1.5-1.6μm band laser gain medium with excellent comprehensive performance. Using this crystal as a gain medium is expected to achieve 1.5-1.6μm band pulsed laser with high energy, high repetition frequency and narrow pulse width.

[0017] Optionally, the transmittance of the input dielectric film at 975nm or 950nm is higher than 80%, and the transmittance at 1.5-1.6μm is lower than 0.5%;

[0018] The transmittance of the output medium film in the 1.5-1.6 μm band is 2% to 30%.

[0019] Optionally, the Q-switching element includes Co 2+ :MgAl2O4 crystal, the initial transmittance of the Q-switched element in the 1.5-1.6μm band is 70% to 97%.

[0020] Optionally, the repetition frequency of the pulse laser output by the 1.5-1.6 μm band passively Q-switched pulse laser is 5 Hz to 10 kHz.

[0021] The pulse laser realizes single-pulse laser operation in the 1.5-1.6 μm band within a pump pulse width by controlling the incident pump power. The repetition frequency of the pulse laser in the 1.5-1.6 μm band is consistent with the repetition frequency of the pump source pulse, which is 5 Hz to 10 kHz.

[0022] Optionally, the 1.5-1.6 μm band passively Q-switched pulse laser further includes a focusing coupling mirror;

[0023] When the laser includes a laser cavity input mirror, the focusing coupling mirror is coaxially arranged between the pump source and the laser cavity input mirror along the optical path;

[0024] When there is no laser cavity input mirror in the laser, the focusing coupling mirror is coaxially arranged between the pump source and the gain medium along the optical path.

[0025] The focusing coupling mirror is arranged between the pump source and the laser input mirror to focus the output light of the pump source on the gain medium.

[0026] Optionally, when the input end face of the gain medium and the output end face of the Q-switching element are respectively plated with an input dielectric film and an output dielectric film, the gain medium and the Q-switching element are coaxially attached together along the optical path;

[0027] When the input end surface of the gain medium is not plated with an input medium film, the laser cavity input mirror, the gain medium, and the Q-switching element are coaxially attached together along the optical path;

[0028] When the output end surface of the Q-switching element is not plated with an output dielectric film, the gain medium, the Q-switching element, and the laser cavity output mirror are coaxially attached together along the optical path;

[0029] When the input end face of the gain medium and the output end face of the Q-switching element are not plated with a dielectric film, the laser cavity input mirror, the gain medium, the Q-switching element and the laser cavity output mirror are coaxially attached together along the optical path.

[0030] Optionally, the gain medium and the Q-switching element are combined by optical glue or bonding.

[0031] Optionally, the laser cavity input mirror is a sapphire crystal with an input dielectric film coated on the input end face.

[0032] Optionally, the sapphire crystal and the gain medium are combined by optical glue or bonding.

[0033] The dielectric film of the laser cavity input mirror is directly plated on the input end face of the sapphire crystal, and then the output end face of the sapphire crystal is closely fitted with the input end face of the gain medium. The plated sapphire crystal is directly used as the laser cavity input mirror.

[0034] According to another aspect of the present application, there is provided an application of the above-mentioned 1.5-1.6 μm band passively Q-switched pulse laser as a detection light source for a laser rangefinder or a laser radar.

[0035] The beneficial effects of this application include:

[0036] (1) The 1.5-1.6 μm band passively Q-switched pulse laser provided in this application adopts Er 3+ :Yb 3+YPO4 crystal is used as the gain medium of passive Q-switched pulse laser in 1.5-1.6μm band. 3+ / Yb 3+ For double-doped phosphate glass, the crystal has high thermal conductivity, large absorption cross section, long laser upper level fluorescence lifetime and high Yb 3+ →Er 3+ With advantages such as energy transfer efficiency, it can achieve 1.5-1.6μm band pulse laser with high energy, high repetition rate and narrow pulse width.

[0037] (2) This application uses semiconductor laser pulse pumping Er 3+ :Yb 3+ :YPO4 crystal, by controlling the incident pump power, realizes 1.5-1.6μm band single pulse laser operation within a pump pulse width, can accurately control the repetition frequency of passive Q-switched pulse laser, and obtain highly stable pulse energy at the same time. Using eye-safe 1.5-1.6μm band pulse laser with high stability repetition frequency and output energy as the detection light source of laser rangefinder or laser radar can improve the working performance and measurement accuracy of the instrument. DETAILED DESCRIPTION

[0038] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.

[0039] Unless otherwise specified, the raw materials in the examples of this application were purchased through commercial channels.

[0040] Unless otherwise specified, conventional methods were used for testing and instrument settings were those recommended by the manufacturer.

[0041] The detection method in the embodiments of the present application is as follows: the pulsed laser energy is measured by a laser energy meter (probe model PE9-C, meter model Centauri, both are products of Ophir-Spiricon); the pulsed laser repetition frequency and pulse width are detected by an oscilloscope (photodetector model DET08C from Thorlabs, oscilloscope model DSO6102A from Agilent), and the pulse peak power is the pulse energy divided by the pulse width.

[0042] Example 1

[0043] The passive Q-switched pulse laser in the 1.5-1.6 μm band comprises a pump source, a focusing coupling mirror, a laser cavity input mirror, a gain medium, a Q-switched element and a laser cavity output mirror which are coaxially arranged in sequence along the optical path;

[0044] The laser cavity input mirror, gain medium, and Q-switching element are closely attached to each other and fixed on a copper base with a light-through hole in the middle. 2+ :MgAl2O4 crystal, the laser cavity length is 8mm;

[0045] Pump source: A 975nm semiconductor laser in pulse working mode, with a pump pulse period of 100ms (corresponding to a pump pulse repetition frequency of 10Hz) and a pump pulse width of 2ms. The pump laser is focused to Er by a focusing coupling mirror. 3+ :Yb 3 + : In YPO4 crystal, the waist diameter of the pump laser in the crystal is 400μm;

[0046] Gain medium: Top seed flux-grown (0.5 at.%) Er 3+ :(5at.%)Yb 3+ :YPO4 crystal, crystal size reaches 13×12×12mm 3 The crystal was cut into a light-transmitting cross section of 3×3 mm. 2 , a c-cut block sample with a thickness of 1.0 mm in the light-transmitting direction, and the light-transmitting end face of the block crystal sample is laser-polished. The absorption coefficient of the c-cut crystal at a wavelength of 975 nm is about 23.5 cm -1 , the single-pass absorption rate of pump light is about 90%. ;

[0047] Q-switching element: Co 2+ :MgAl2O4 crystal, light cross section is 3×3mm 2 , the thickness in the light-transmitting direction is 1.5mm, and the light-transmitting end face is laser-polished. The initial transmittance of the Q-switched crystal at 1538nm is 90%;

[0048] Laser cavity input mirror: The dielectric film is directly plated on the light-transmitting cross section of 3×3mm 2 , the input end face of the sapphire crystal with a thickness of 1.0 mm in the light transmission direction, the dielectric film has a transmittance of T = 90% at a wavelength of 975 nm and a transmittance of T = 0.2% at a wavelength of 1.5-1.6 μm;

[0049] Laser cavity output mirror: The dielectric film is plated on a K9 glass surface with a curvature radius of 50mm. The transmittance of the dielectric film in the 1.5-1.6μm band is T=10%;

[0050] Using the above laser structure, a 975 nm semiconductor laser pulse pump (0.5 at.%) Er 3+ :(5at.%)Yb 3+:YPO4 crystal, under 16W peak incident power pump, achieves single-pulse laser operation in the 1.5-1.6μm band within 2ms pump pulse width, and achieves 1538nm passively Q-switched pulse laser with 10Hz repetition rate, 210μJ pulse energy, 4.0ns pulse width and 23.3kW peak output power.

[0051] Example 2

[0052] The structure of the passive Q-switched pulse laser in the 1.5-1.6 μm band is the same as that in Example 1, except that the output mirror dielectric film is directly plated on the Co 2+ :Output end face of MgAl2O4 crystal.

[0053] Under the pumping condition of 19W peak incident power, a 1538nm pulsed laser with 10Hz repetition rate, 240μJ pulse energy, 4.0ns pulse width and 60kW peak output power was obtained.

[0054] Example 3

[0055] The structure and use of the passively Q-switched pulse laser in the 1.5-1.6 μm band are the same as those in Example 1, with the only difference being that the pump pulse period of the 975 nm semiconductor laser is adjusted to 10 ms (corresponding to a pump pulse repetition frequency of 100 Hz), the pump pulse width is 1 ms, and under 6 W peak incident power pumping, a single pulse laser operation in the 1.5-1.6 μm band is achieved within a pump pulse width of 1 ms, and a 1538 nm passively Q-switched pulse laser with a repetition frequency of 100 Hz, a pulse energy of 120 μJ, a pulse width of 9.0 ns, and a peak output power of 13.3 kW can be obtained.

[0056] Example 4

[0057] The structure and use of the passive Q-switched pulse laser in the 1.5-1.6 μm band are the same as those in Example 3, except that the output mirror dielectric film is directly plated on the Co 2+ : The output end face of the MgAl2O4 crystal, under the pumping of 8W peak incident power, obtains a 1538nm passively Q-switched pulse laser with a repetition rate of 100Hz, a pulse energy of 150μJ, a pulse width of 4.0ns and a peak output power of 37.5kW.

[0058] Example 5

[0059] The structure and use of the passive Q-switched pulse laser in the 1.5-1.6μm band are the same as those in Example 1, with the only difference being that the pump pulse period of the 975nm semiconductor laser is adjusted to 1ms (corresponding to a pump pulse repetition frequency of 1.0kHz), the pump pulse width is 0.3ms, and under 9W peak incident power pumping, a single-pulse laser operation in the 1.5-1.6μm band is achieved within a pump pulse width of 0.3ms, and a 1538nm passive Q-switched pulse laser with a repetition frequency of 1.0kHz, a pulse energy of 80μJ, a pulse width of 10.0ns and a peak output power of 8kW can be obtained.

[0060] Example 6

[0061] The structure and use of the passive Q-switched pulse laser in the 1.5-1.6 μm band are the same as those in Example 5, except that the output mirror dielectric film is directly plated on the Co 2+ : The output end face of the MgAl2O4 crystal, under the pumping of 10W peak incident power, obtains a 1538nm passively Q-switched pulse laser with a repetition rate of 1.0kHz, a pulse energy of 90μJ, a pulse width of 5.0ns and a peak output power of 18kW.

[0062] Example 7

[0063] The structure and use of the passively Q-switched pulse laser in the 1.5-1.6 μm band are the same as those in Example 1, with the only difference being that the pump pulse period of the 975 nm semiconductor laser is adjusted to 0.1 ms (corresponding to a pump pulse repetition frequency of 10.0 kHz), the pump pulse width is 0.05 ms, and under 11 W peak incident power pumping, a single pulse laser operation in the 1.5-1.6 μm band is achieved within a pump pulse width of 0.05 ms, and a 1538 nm passively Q-switched pulse laser with a repetition frequency of 10.0 kHz, a pulse energy of 40 μJ, a pulse width of 10.0 ns and a peak output power of 4 kW can be obtained.

[0064] Example 8

[0065] The structure and use of the passive Q-switched pulse laser in the 1.5-1.6 μm band are the same as those in Example 7, except that the output mirror dielectric film is directly plated on the Co 2+ : The output end face of the MgAl2O4 crystal, under the pumping of 12W peak incident power, obtains a 1538nm passively Q-switched pulse laser with a repetition rate of 10.0kHz, a pulse energy of 50μJ, a pulse width of 5.0ns and a peak output power of 10kW.

[0066] Embodiments 9 to 16

[0067] (1.0at.%)Er 3+ :(15at.%)Yb 3+:YPO4 crystal replaces (0.5at.%) Er in Examples 1 to 8 3 + :(5at.%)Yb 3+ :YPO4 crystal can also achieve pulse laser output similar to that of Examples 1 to 8.

[0068] 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 1.5-1.6 μm band passively Q-switched pulse laser, characterized in that: It includes: a pump source, a gain medium, and a Q-switching element which are coaxially arranged in sequence along the optical path; The gain medium is Er 3+ :Yb 3+ :YPO4 crystal; The pump source is a semiconductor laser that can generate laser light in the 950nm band or the 975nm band; The pump source adopts a pulse working mode, the pump pulse period is 0.1 to 200 ms, and the pump pulse width is 0.05 to 5 ms; The input end face of the gain medium and the output end face of the Q-switching element are respectively plated with an input dielectric film and an output dielectric film; or, The input end face of the gain medium is not coated with an input dielectric film, and the laser further comprises a laser cavity input mirror whose end face is coated with an input dielectric film; or, The output end face of the Q-switching element is not coated with an output dielectric film, and the laser further comprises a laser cavity output mirror whose end face is coated with an output dielectric film; or, The input end face of the gain medium and the output end face of the Q-switching element are not coated with a dielectric film, and the laser further comprises a laser cavity input mirror and a laser cavity output mirror, whose end faces are respectively coated with an input dielectric film and an output dielectric film; The laser cavity input mirror is coaxially arranged between the pump source and the gain medium along the laser optical path; and the laser cavity output mirror is coaxially arranged behind the Q-switching element along the laser optical path.

2. The 1.5-1.6 μm band passively Q-switched pulse laser according to claim 1, characterized in that: The Er 3+ :Yb 3+ Er in YPO4 crystal 3+ The doping concentration is 0.2~3.0at.%Yb 3+ The doping concentration is 2 to 30 at.%.

3. The 1.5-1.6 μm band passively Q-switched pulse laser according to claim 1, characterized in that: The transmittance of the input dielectric film at 975nm or 950nm is higher than 80%, and the transmittance at 1.5-1.6μm is lower than 0.5%; The transmittance of the output dielectric film in the 1.5-1.6 μm band is 2% to 30%; Preferably, the Q-switching element comprises Co 2+ :MgAl2O4 crystal, the initial transmittance of the Q-switched element in the 1.5-1.6μm band is 70% to 97%.

4. The 1.5-1.6 μm band passively Q-switched pulse laser according to claim 1, characterized in that: The repetition frequency of the pulse laser output by the 1.5-1.6 μm band passive Q-switched pulse laser is 5 Hz to 10 kHz.

5. The 1.5-1.6 μm band passively Q-switched pulse laser according to claim 1, characterized in that: The 1.5-1.6 μm band passively Q-switched pulse laser also includes a focusing coupling mirror; When the laser includes a laser cavity input mirror, the focusing coupling mirror is coaxially arranged between the pump source and the laser cavity input mirror along the optical path; When there is no laser cavity input mirror in the laser, the focusing coupling mirror is coaxially arranged between the pump source and the gain medium along the optical path.

6. The 1.5-1.6 μm band passively Q-switched pulse laser according to claim 1, characterized in that: When the input end face of the gain medium and the output end face of the Q-switching element are respectively plated with an input dielectric film and an output dielectric film, the gain medium and the Q-switching element are coaxially attached to each other along the optical path; When the input end surface of the gain medium is not plated with an input medium film, the laser cavity input mirror, the gain medium, and the Q-switching element are coaxially attached together along the optical path; When the output end surface of the Q-switching element is not plated with an output dielectric film, the gain medium, the Q-switching element, and the laser cavity output mirror are coaxially attached together along the optical path; When the input end face of the gain medium and the output end face of the Q-switching element are not plated with a dielectric film, the laser cavity input mirror, the gain medium, the Q-switching element and the laser cavity output mirror are coaxially attached together along the optical path.

7. The 1.5-1.6 μm band passively Q-switched pulse laser according to claim 6, characterized in that: The gain medium and the Q-switching element are combined by optical glue or bonding.

8. The 1.5-1.6 μm band passively Q-switched pulse laser according to claim 6, characterized in that: The laser cavity input mirror is a sapphire crystal with an input dielectric film plated on the input end face.

9. The 1.5-1.6 μm band passively Q-switched pulse laser according to claim 8, characterized in that: The sapphire crystal and the gain medium are combined by optical glue or bonding.

10. Use of the 1.5-1.6 μm band passively Q-switched pulse laser according to any one of claims 1 to 9 as a detection light source for a laser rangefinder or a laser radar.