A wind-cooled microslab laser based on dual-ended pumping

Abstract

This invention discloses a wind-cooled microslab laser based on dual-end pumping, belonging to the field of solid-state laser technology. The laser comprises a first and a second conductive cooling bar, alternately placed at the top and bottom ends of a slab laser crystal, presenting a dual-end pumping structure. A first and a second fast-axis collimating cylindrical lens collimate the first and second conductive cooling bars along their fast axes, respectively, before partially injecting the laser beams into the slab laser crystal. A first and a second resonant cavity mirror are located at the left and right ends of the slab laser crystal. The laser beam injected into the slab laser crystal undergoes multiple round-trip oscillations between the first and second resonant cavity mirrors after passing through the resonant cavity mirrors, before reaching the output cavity mirror. This invention significantly improves the output single-pulse energy, achieves high overall electro-optical efficiency, and boasts a compact system design.

Description

Technical Field

[0001] This invention belongs to the field of solid-state laser technology, specifically relating to a wind-cooled microslab laser based on dual-end pumping. Background Technology

[0002] Atmospheric lidar utilizes the interaction between laser and atmospheric components to obtain backscattered echo signals, enabling the detection of atmospheric aerosol concentration, measurement of gases, and atmospheric temperature and humidity parameters. The laser is the key component. Existing miniature air-cooled lasers are commonly based on the following forms: First, fiber-coupled modules directly pump rod-shaped crystals, which are limited by fiber bending radius and fiber pigtails, resulting in insufficient compactness. Second, rod-shaped side-pumped lasers offer high single-pulse energy output but suffer from significant thermal effects and often poor beam quality, failing to meet miniaturization requirements. Third, single-diode direct-pumped rod-shaped crystals meet miniaturization needs, but are limited by cavity mode size, resulting in low single-pulse output. Fourth, lasers based on Zigzag slab gain media offer high single-pulse energy output, but are limited by inherent design, often failing to reach the diffraction limit in beam quality factor.

[0003] Diode-pumped rod-shaped laser crystals, known as microchip lasers, are characterized by low single-pulse energy output, compact size, stable and reliable performance, and relatively low cost. They are primarily used in atmospheric detection applications where single-pulse energy requirements are not high, such as cloud height meters. To meet the demands of high single-pulse energy, cascaded amplifiers are often required for energy amplification. However, due to the relatively short resonant cavity length of microchip lasers (typically only around 10W pumped by diodes), the laser pulse width is often sub-nanosecond or even hundreds of picoseconds. The narrower the pulse width, the higher the peak power density, and the damage threshold of optical components becomes the main limitation for single-pulse amplification. To obtain larger single-pulse energy, the spot size often needs to be very large, resulting in poor spatial compactness and completely masking the characteristics of microchip lasers. For single-frequency atmospheric detection lidar, a wider pulse width results in a narrower Fourier-limited linewidth, often requiring a pulse width of 30ns. In reality, the laser linewidth is less than 50MHz, meaning that the sub-nanosecond or even hundreds of picosecond pulse widths of conventional microchip lasers cannot meet the requirements of single-frequency atmospheric detection lidar. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a wind-cooled microslab laser based on dual-end pumping, which simultaneously satisfies the requirements of high beam quality, large single-pulse energy, compact system size, high reliability, and high environmental adaptability.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A wind-cooled microslab laser based on dual-end pumping includes a resonant cavity mirror, a first resonant cavity mirror, a slab laser crystal, a first conductive cooling diode single bar, a first fast-axis collimating cylindrical lens, a second resonant cavity mirror, a thin-film polarizer, a passive Q-switching switch, a resonant cavity output mirror, a second fast-axis collimating cylindrical lens, and a second conductive cooling diode single bar.

[0007] The first and second conductive cooling bar strips are alternately placed at the top and bottom ends of the slab laser crystal, presenting a double-ended pumping structure;

[0008] After the first fast-axis collimating cylindrical lens and the second fast-axis collimating cylindrical lens collimate the fast-axis direction of the first and second conductive cooling single bars, respectively, a portion of the end face is injected into the slab laser crystal.

[0009] The first resonant cavity mirror and the second resonant cavity mirror are located at the left and right ends of the slab laser crystal; the laser injected into the slab laser crystal undergoes multiple round-trip oscillations between the first resonant cavity mirror and the second resonant cavity mirror after passing through the resonant cavity mirror, and then reaches the resonant cavity output mirror;

[0010] The thin-film polarizer and the passive Q-switching switch are located at the front end of the resonant cavity output mirror to achieve linearly polarized pulsed laser output.

[0011] The beneficial effects of this invention are as follows:

[0012] This invention fully inherits the excellent characteristics of microstrip lasers, such as high beam quality, compact system size, high reliability, and high environmental adaptability. It also achieves high single-pulse energy and a relatively wide laser pulse width. Specifically, the conduction-cooled single bar means the laser does not require liquid cooling and can be cooled by air. The pump structure is a dual-ended pump structure, eliminating crosstalk in the pump source and improving system reliability. Pump power is greatly increased without a corresponding increase in thermal effect. The temperature field of the slab laser crystal is nearly one-dimensional, maintaining near-diffraction-limited laser output. Multi-pass reciprocating oscillation fully extracts all pump power, indirectly increasing the cavity length and cavity mode size, resulting in a significant increase in single-pulse energy and high overall electro-optic efficiency. The passively Q-switched crystal eliminates the need for external high voltage and additional electronic components, further enhancing system compactness. The laser is packaged using semiconductor packaging technology, achieving high reliability and high environmental adaptability. On the other hand, the present invention does not limit the laser band. In addition to common 1μm lasers such as 1064nm / 1319nm / 1047nm, it can be easily extended to the 1.5μm / 2μm band. Attached Figure Description

[0013] Figure 1 This is a structural diagram of a wind-cooled microslab laser based on dual-end pumping according to the present invention.

[0014] Figure label:

[0015] 1. Resonant cavity mirror; 2. First resonant cavity reflector; 3. Slab laser crystal; 4. First conductive cooling diode single bar; 5. First fast axis collimating cylindrical lens; 6. Second resonant cavity reflector; 7. Thin film polarizer; 8. Passive Q-switching switch; 9. Resonant cavity output mirror; 10. Second fast axis collimating cylindrical lens; 11. Second conductive cooling diode single bar. Detailed Implementation

[0016] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0017] This invention provides a wind-cooled micro slab laser based on dual-ended pumping. The pump source is a conductive-cooled single bar, and the pump structure is a dual-ended pumping structure. The pump power is increased by 30 times compared to a single diode. The laser crystal is a slab laser crystal. The increased pump power does not lead to a synchronous increase in thermal effect. The slab laser crystal has a nearly flat-top distribution in the width direction, and the temperature field is nearly one-dimensional. The laser output still maintains near-diffraction-limited output. The multi-pass oscillating laser spot is elliptical and is circularly symmetrical after output. The elliptical oscillating laser passes through the slab laser crystal multiple times, fully extracting all pump power, resulting in very high overall electro-optic efficiency. The Q-switching switch uses a passive Q-switching crystal to further improve the system compactness. The laser is packaged in a gold-plated shell using semiconductor packaging technology to achieve high reliability and high environmental adaptability.

[0018] like Figure 1 As shown, the pump source consists of a first conductive cooling bar 4 and a second conductive cooling bar 11, which are placed alternately to form a double-ended pumping structure. The first fast-axis collimating cylindrical lens 5 and the second fast-axis collimating cylindrical lens 10 collimate the fast-axis direction of the first conductive cooling bar 4 and the second conductive cooling bar 11, respectively. The pump spot has a flat-top distribution along the slow axis, with part of the end face injected into the slab laser crystal 3. The temperature field of the slab laser crystal 3 is almost a one-dimensional temperature field. The resonant cavity mirror 1, the first resonant cavity reflector 2, the second resonant cavity reflector 6, and the resonant cavity output mirror 9 together constitute the laser resonant cavity. The multi-pass reciprocating oscillating laser spot is elliptical, and the beam quality is close to the diffraction limit. The resonant cavity as a whole has a multi-pass reciprocating structure, which can fully extract all pump power and has high overall electro-optic efficiency. The thin-film polarizer 7 and the passive Q-switching switch 8 realize linearly polarized pulsed laser output, and the system has high compactness. The laser is packaged in a gold-plated shell based on semiconductor packaging technology, and the whole machine can achieve high reliability and high environmental adaptability.

[0019] The resonant cavity mirror 1 is highly reflective for oscillating lasers and is used to amplify the oscillating laser through feedback gain.

[0020] The first resonant cavity reflector 2 and the second resonant cavity reflector 6 are located on both sides of the slab laser crystal 3, enabling the oscillating laser to travel back and forth multiple times, and the coating is highly reflective of the oscillating laser.

[0021] The slab laser crystal 3 is very thin in the thickness direction and also acts as an aperture stop, so that the received oscillating laser only oscillates in the fundamental mode, ensuring that the output laser is diffraction-limited. At the same time, the two large surfaces are frosted and welded to the heat sink for efficient heat dissipation. Since the thermal lens exists only in the thickness direction, the oscillating laser in the resonant cavity is elliptical, and multiple round trips fully cover the gain region to extract all pump energy.

[0022] The first conductive cooling diode bar 4 and the second conductive cooling diode bar 11 are implemented using semiconductor technology to achieve a horizontal arrangement of multiple diode single tubes. The pump power is increased by tens of times compared to a single diode. The width dimension is approximately half the width of the slab laser crystal 3. The first conductive cooling diode bar 4 and the second conductive cooling diode bar 11 pump in an alternating manner, and the pump residue will not affect the opposing diode bar, thus affecting the stability and reliability of the pump source. The divergence angle in the fast axis direction is compressed based on the first fast axis collimating cylindrical lens 5 and the second fast axis collimating cylindrical lens 10. The first fast axis collimating cylindrical lens 5 and the second fast axis collimating cylindrical lens 10 are aspherical structures with a focal length of less than 1 mm. For applications requiring extremely high assembly precision, the first conductive cooling diode single bar 4 and the second conductive cooling diode single bar 11, after fast-axis collimation, have a rectangular beam size, less than 1mm in the fast-axis direction and about 10mm in the slow-axis direction. The beam is directly injected into the pump slab laser crystal 3, achieving a perfect match between the pump and the slab laser crystal dimensions. The pump structure is a double-ended pump structure. Since the diode single bar is a conductive cooling structure, its overall size is only tens of millimeters. At the same time, the resonant cavity adopts a multi-pass folded structure and uses pulse pumping. The extremely low heat dissipation can be directly conducted to the mounting surface. The entire laser can be efficiently cooled by air cooling. The overall microstructure of the laser can achieve a large single-pulse energy output.

[0023] The thin-film polarizer 7 makes the oscillating laser a polarized laser with a transmission angle of 45°. The coating is highly transparent for oscillating light. The slab laser crystal 3 serves as the gain medium to generate spontaneous emission laser oscillation. Only horizontally polarized light is allowed to oscillate when transmitted to the thin-film polarizer 7. During the laser oscillation process, the passive Q-switched switch 8 gradually bleachs the laser. The oscillating laser is quickly output from the resonant cavity output mirror 9, forming a high-energy nanosecond-level pulsed laser output.

[0024] The passive Q-switching switch 8 is often made of Cr4+:YAG. The pump threshold, output single pulse energy, reflectivity of the resonant cavity output mirror, and small signal transmittance of the passive Q-switching switch 8 are closely related. If the small signal transmittance is too high, the pump threshold will be too low, the output single pulse energy will be low, and multiple pulses will be easily generated. If the small signal transmittance is too low, the pump threshold will be too high, ensuring that the slab laser crystal 3 can effectively store energy during the energy storage stage. Once the passive Q-switching switch 8 reaches bleaching, the photons of the resonant cavity oscillation are stimulated and amplified, and laser pulse oscillation is rapidly formed. Part of the energy is output by the resonant cavity output mirror 9.

[0025] The reflectivity of the coating on the output cavity mirror 9 of the resonant cavity determines the output ratio of the oscillating laser. Too low a reflectivity leads to instability of the oscillating laser, while too high a reflectivity leads to too few output photons and too high power density in the resonant cavity, which can easily damage the optical components inside the resonant cavity. The reflectivity can be theoretically evaluated based on the laser dynamics equation.

[0026] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A wind-cooled microslab laser based on dual-end pumping, characterized in that, The system includes a resonant cavity mirror, a first resonant cavity reflector, a slab laser crystal, a first conductive cooling diode single bar, a first fast-axis collimating cylindrical lens, a second resonant cavity reflector, a thin-film polarizer, a passive Q-switching switch, a resonant cavity output mirror, a second fast-axis collimating cylindrical lens, and a second conductive cooling diode single bar. The first and second conductive cooling single bar bars are staggered at the top and bottom ends of the slab laser crystal, presenting a double-ended staggered opposing pumping structure; and the width dimension of the first and second conductive cooling diode single bars is half the width of the slab laser crystal. After the first fast-axis collimating cylindrical lens and the second fast-axis collimating cylindrical lens collimate the first and second conductive cooling single bars in the fast-axis direction, respectively, the diode single bar beam size is rectangular and is directly injected into the pump slab laser crystal; wherein, the first fast-axis collimating cylindrical lens and the second fast-axis collimating cylindrical lens are aspherical structures and have a focal length of less than 1mm. The first resonant cavity mirror and the second resonant cavity mirror are located at the left and right ends of the slab laser crystal; the laser injected into the slab laser crystal undergoes multiple round-trip oscillations between the first resonant cavity mirror and the second resonant cavity mirror after passing through the resonant cavity mirror, and then reaches the resonant cavity output mirror; The thin-film polarizer and the passive Q-switching switch are located at the front end of the resonant cavity output mirror to realize linearly polarized pulsed laser output; The slab laser crystal also acts as an aperture stop, ensuring that the received oscillating laser oscillates only in the fundamental mode, and the output laser is diffraction-limited.

2. The air-cooled microslab laser based on dual-end pumping according to claim 1, characterized in that, The resonant cavity mirror is a highly reflective oscillating laser, used for feedback gain amplification of the oscillating laser.

3. The air-cooled microslab laser based on dual-end pumping according to claim 1, characterized in that, The coatings on the first and second resonant cavity mirrors are highly reflective to oscillating lasers.

4. A wind-cooled microslab laser based on dual-end pumping according to claim 1, characterized in that, The resonant cavity mirror, the first resonant cavity reflector, the second resonant cavity reflector, and the resonant cavity output mirror together constitute a laser resonant cavity, and the oscillating laser in the resonant cavity is elliptical.

5. A wind-cooled microslab laser based on dual-end pumping according to claim 1, characterized in that, The first and second conductive cooling diode single bars are implemented using semiconductor technology to achieve a horizontal arrangement of multiple groups of single diodes, and the first and second conductive cooling diode single bars are pumped alternately in opposite directions.

6. A wind-cooled microslab laser based on dual-end pumping according to claim 1, characterized in that, The thin-film polarizer makes the oscillating laser a polarized laser with a transmission angle of 45°. The coating is highly transparent for oscillating light. During laser oscillation, the passive Q-switching switch gradually bleachs the laser, and the oscillating laser is quickly output from the resonant cavity through the cavity mirror.

7. A wind-cooled microslab laser based on dual-end pumping according to claim 1, characterized in that, The reflectivity of the output cavity mirror coating of the resonant cavity determines the oscillating laser output ratio.

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