Hybrid-pumped slab laser amplifier

Abstract

The application discloses a kind of hybrid pumping slab laser amplifiers, comprising: slab laser medium, side pumping source and end face pumping source;One end face of slab laser medium is laser incidence face, the other opposite end face is end face pumping face, side is side pumping face;Seed laser is incident at preset angle from laser incidence face, forms total reflection after being incident in side pumping face, and seed laser after total reflection is emitted from end face pumping face;Side pumping face is pumped by side pumping source, and forms elongated pumping area in side pumping face;End face pumping face is pumped by end face pumping source, and the center of end face pumping light is coincident with the center of seed laser, and the spot size of end face pumping light is less than or equal to the spot size of seed laser in the base mode of this face.The seed laser of the application has high mode matching degree with side pumping area, and the end face pumping area strengthens and amplifies the base mode component in seed laser, and high beam quality, high extraction efficiency laser amplification can be obtained.

Description

Technical Field

[0001] This invention relates to the field of laser amplifier technology, and more specifically to a hybrid pumped slab laser amplifier. Background Technology

[0002] High-beam-quality, high-power pulsed lasers have wide applications in lidar, laser ranging, nonlinear optics, and materials processing. Oscillation-amplification technology is an effective way to obtain such lasers. Grazing-incidence slab amplifiers are an effective structure for achieving high-gain amplification and can be used for amplifying small-signal, narrow-pulse lasers such as picosecond and nanosecond lasers. The top and bottom surfaces serve as cooling surfaces, and one side serves as the pump surface. The pump source is typically a semiconductor array or stacked array. The pump light is focused along the fast axis to form a long, narrow pump region with high energy density. The seed laser is incident from one end of the slab, undergoes total internal reflection at the pump surface, and exits from the other end. Due to the side-pumping method and the total internal reflection of the seed laser within the crystal, thermally induced wavefront distortion in the horizontal direction significantly affects the beam quality of the amplified beam, causing beam quality degradation.

[0003] Currently, the main methods for reducing beam quality degradation include:

[0004] 1) Use phase conjugate mirrors to compensate for the beam quality degradation of the amplified laser beam;

[0005] 2) Crystal pump surface bonding / photoresist undoped crystals or crystals such as sapphire enhance heat dissipation and reduce wavefront distortion;

[0006] 3) The seed laser beam and the pumping region use a low matching ratio.

[0007] However, the above methods have obvious limitations: the phase conjugate mirror method results in a complex amplification optical path structure; the bonding / photoresist method has high requirements for crystal processing technology, and the processing difficulty and cost are relatively high; the low matching ratio method results in low energy extraction efficiency. Summary of the Invention

[0008] To address the shortcomings of existing technologies, this invention provides a hybrid pumped slab laser amplifier that can achieve laser amplification with high beam quality and high extraction efficiency.

[0009] This invention discloses a hybrid pumped slab laser amplifier, comprising: a slab laser medium, a side pump source, and an end pump source;

[0010] One end face of the slab laser medium is the laser incident surface, the other opposite end face is the end face pumping surface, and the side face is the side face pumping surface; the seed laser is incident from the laser incident surface at a preset angle, and after incident, it undergoes total internal reflection at the side face pumping surface, and the seed laser after total internal reflection exits from the end face pumping surface.

[0011] The side pumping surface is pumped by the side pumping source, forming a slender pumping region on the side pumping surface; the end pumping surface is pumped by the end pumping source, the center of the end pumping light coincides with the center of the seed laser spot on the end face, and the spot size of the pumping light at that location is less than or equal to the fundamental mode spot size of the seed laser.

[0012] As a further improvement of the present invention, the two large surfaces of the slab laser medium are cooling surfaces.

[0013] As a further improvement of the present invention, the laser incident surface and the end pump surface constitute a seed laser light transmission surface, and both the laser incident surface and the end pump surface form a preset angle with the side pump surface to suppress self-excited oscillation.

[0014] As a further improvement of the present invention, the side pump source is a semiconductor array or a stacked array, and the end pump source is a fiber-coupled semiconductor laser.

[0015] As a further improvement of the present invention, the pump light emitted from the side pump source is focused in the fast axis direction by the fast axis focusing lens and then incident on the side of the slab laser medium to form a slender pump region.

[0016] As a further improvement of the present invention, the pump light emitted by the end face pump source is focused by the collimating and focusing lens group, and the center of the light spot on the end face pump surface coincides with the center of the light spot of the seed laser on the end face, and the size of the pump light spot at that point is less than or equal to the size of the fundamental mode light spot of the seed laser.

[0017] As a further improvement of the present invention, when the slab laser medium is an anisotropic medium, the polarization direction of the pump light is along the direction of the maximum absorption coefficient of the slab laser medium, and the end-face pump source is a polarization-maintaining fiber-coupled high-polarization semiconductor laser.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0019] The hybrid pumped slab laser amplifier of the present invention has a high degree of matching between the seed laser and the side pumping region, which can achieve high-efficiency amplification; the end pumping region forms a high-gain region, which enhances and amplifies the fundamental mode component in the seed laser, and the proportion of higher-order mode components in the amplified laser beam is greatly reduced, which can obtain laser with high beam quality; and the slab laser amplifier has the advantages of compact structure, high reliability and low cost. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of the single-pass hybrid pumped slab laser amplifier disclosed in Embodiment 1 of the present invention;

[0021] Figure 2 This is a schematic diagram showing the relationship between the seed laser and the pump spot at the pump end face in Embodiment 1 of the present invention;

[0022] Figure 3 This is a schematic diagram of the structure of the dual-pass hybrid pump slab laser amplifier disclosed in Embodiment 2 of the present invention.

[0023] In the picture:

[0024] 1. Seed laser; 2. Slab laser medium; 3. Side pump source; 4. Fast axis focusing mirror; 5. End face pump source; 6. Collimating focusing mirror group; 7. Bipolar mirror; 8. Single-pass amplified laser beam; 9. Pump spot at the end face; 10. Laser spot at the end face; 11. First total reflection mirror; 12. Second total reflection mirror; 13. Lens; 14. Double-pass amplified laser beam. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] The present invention will now be described in further detail with reference to the accompanying drawings:

[0027] Example 1

[0028] like Figure 1 As shown, the present invention provides a single-pass hybrid-pumped slab laser amplifier, comprising: a slab laser medium 2, a side pump source 3, and an end-face pump source 5; wherein,

[0029] The slab laser medium 2 is an Nd:YVO4 crystal cut along the a-axis. The two large surfaces of the slab laser medium 2 are cooling surfaces, cooled by a heat sink via heat conduction. The two end faces of the slab laser medium 2 are seed laser transmission surfaces; one end face is the laser incident surface, and the other opposite end face is the end-face pumping surface. The side surface of the slab laser medium 2 is the side-face pumping surface. To suppress self-excited oscillations along the transmission direction, the two end faces of the slab laser medium 2 and the side-face pumping surface form a preset angle, preferably 100°. The laser incident surface is coated with a 1064nm anti-reflection film, the side-face pumping surface with an 808nm anti-reflection film, and the end-face pumping surface with both 1064nm and 808nm anti-reflection films. The fast-axis focusing mirror 4 and the collimating focusing mirror group 6 are both coated with an 808nm anti-reflection film, and the bidirectional color mirror 7 is coated with a 1064nm total reflection and an 808nm anti-reflection bidirectional color film.

[0030] The side pump source 3 uses a semiconductor array with a wavelength of 808nm. The polarization direction of the pump light is along the c-axis of the Nd:YVO4 crystal. After the pump light is focused by the fast-axis focusing mirror 4, a pumping area of ​​1.1mm (vertical direction) × 14mm (horizontal direction) is formed on the side pumping surface of the slab laser medium 2.

[0031] A seed laser with a diameter of 1 mm is incident at a 25° angle to the side pump surface. After refraction at the laser incident surface, it undergoes total internal reflection at the side pump surface, with the center of total internal reflection located at the center of the side pump surface. The size of the seed laser on the side pump surface is 1 (vertical direction) × 12.6 mm (horizontal direction), and the matching ratios with the pump light in the horizontal and vertical directions are 0.9 and 0.91, respectively. After total internal reflection, the spot size of the seed laser on the end pump surface is approximately 1 mm (vertical direction) × 1.32 mm (horizontal direction). Due to thermally induced wavefront distortion, the wavefront distribution at the horizontal edge of the beam deteriorates, resulting in beam quality degradation.

[0032] The end-face pump source 5 employs a polarization-maintaining fiber-coupled semiconductor module with a wavelength of 808 nm. The pump light is polarized along the c-axis of the Nd:YVO4 crystal. After being focused by the collimating focusing lens group 6, a pump region with a diameter of 0.8 mm (vertical direction) × 0.98 mm (horizontal direction) is formed at the end face of the crystal. The pump light is adjusted so that the center of the pump region coincides with the center of the seed laser. Figure 2 The pump spot 9 and laser spot 10 at the end face are shown.

[0033] The end-pump region is the fundamental mode beam region of the seed laser. Only the fundamental mode component within the seed laser is enhanced and amplified, while the region where the beam quality degrades in the horizontal direction is not amplified. Therefore, the proportion of higher-order mode components in the amplified laser beam is significantly reduced, resulting in high beam quality laser output. At the same time, the seed laser has a high mode matching ratio with both the side pump light and the end-pump light, enabling high energy extraction efficiency.

[0034] Example 2

[0035] like Figure 3 As shown, this invention provides a dual-pass hybrid slab laser amplifier. In this embodiment, the single-pass structure and parameter settings are the same as in Embodiment 1. After single-pass amplification, the beam 8 passes through the first total reflection mirror 11, lens 13, and second total reflection mirror 12 before undergoing dual-pass amplification. The distance between lens 13 and the single-pass total reflection point and the dual-pass total reflection point of the beam within the slab laser medium 2 is twice the focal length. The incident angle of the second-pass seed laser is adjusted so that the beam quality of the seed laser does not significantly degrade. At this time, the mode matching ratio between the seed laser and the side pump light is significantly reduced, but due to dual-pass amplification, the stored energy that was not extracted during single-pass amplification is extracted. Therefore, a higher energy extraction efficiency than single-pass amplification can be obtained while maintaining beam quality.

[0036] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A hybrid-pumped slab laser amplifier, characterized in that, include: Slab laser media, side-pumped source, and end-pumped source; One end face of the slab laser medium is the laser incident surface, the other opposite end face is the end face pumping surface, and the side face is the side face pumping surface; the seed laser is incident from the laser incident surface at a preset angle, and after incident, it undergoes total internal reflection at the side face pumping surface, and the seed laser after total internal reflection exits from the end face pumping surface. The side pumping surface is pumped by the side pumping source, forming a slender pumping region on the side pumping surface; the end pumping surface is pumped by the end pumping source, the center of the end pumping light coincides with the center of the seed laser, and the spot size of the end pumping light is less than or equal to the fundamental mode spot size of the seed laser on that surface.

2. The hybrid-pumped slab laser amplifier as described in claim 1, characterized in that, The two large surfaces of the slab laser medium are cooling surfaces.

3. The hybrid-pumped slab laser amplifier as described in claim 1, characterized in that, The laser incident surface and the end pump surface constitute the seed laser light transmission surface. Both the laser incident surface and the end pump surface are at a preset angle to the side pump surface to suppress self-excited oscillation.

4. The hybrid-pumped slab laser amplifier as described in claim 1, characterized in that, The side pump source is a semiconductor array or stacked array, and the end pump source is a fiber-coupled semiconductor laser.

5. The hybrid-pumped slab laser amplifier as described in claim 1, characterized in that, The pump light emitted from the side pump source is focused in the fast axis direction by the fast axis focusing lens and then incident on the side of the slab laser medium to form a slender pump region.

6. The hybrid-pumped slab laser amplifier as described in claim 1, characterized in that, The pump light emitted from the end-face pump source is focused by the collimating and focusing lens group, and the center of the light spot on the end-face pump surface coincides with the center of the light spot of the seed laser on the end face. Moreover, the size of the pump light spot at that point is less than or equal to the size of the fundamental mode light spot of the seed laser.

7. The hybrid-pumped slab laser amplifier as described in claim 1, characterized in that, When the slab laser medium is an anisotropic medium, the polarization direction of the pump light is along the direction of the maximum absorption coefficient of the slab laser medium, and the end-face pump source is a polarization-maintaining fiber-coupled high-polarization semiconductor laser.

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