Lateral pump uniformity testing device for batten crystal

Abstract

The utility model relates to the technical field of laser testing equipment, and discloses a lath crystal side pump uniformity testing device, which comprises a seed light source, a small hole diaphragm, an Nd: YAG lath crystal, a focus lens, a 45-degree reflection attenuation sheet and a light beam analyzer which are sequentially arranged along the direction of a light path, an LD pumping module is arranged above the Nd: YAG lath crystal, and the light beam analyzer is arranged above the Nd: YAG lath crystal. A crystal heat sink is arranged below the Nd: YAG lath crystal, and the crystal heat sink is connected with the bottom of the Nd: YAG lath crystal; the device provided by the utility model is suitable for the uniformity test of the whole lath crystal in a large-mode-volume unstable-cavity solid laser, and the reliability and stability of the uniformity test are effectively improved.

Description

Technical Field

[0001] This utility model relates to the field of laser testing equipment technology, specifically a slab crystal side pump uniformity testing device. Background Technology

[0002] LD-pumped Nd:YAG slab crystal 1064nm lasers are widely used in many military and civilian solid-state lasers due to their high optical-to-optical conversion efficiency. The development of 1064nm solid-state lasers typically involves different LD pumping methods, including LD end-pumping, LD corner-pumping, and LD side-pumping. Among these, LD side-pumped slab crystals are a commonly used pumping method because their compact structure helps reduce laser size.

[0003] For high-power continuous-wave or high-energy pulsed solid-state lasers, the pump uniformity of the LD-pumped slab crystal is a crucial parameter affecting the laser's pump energy storage and extraction efficiency and beam quality. Inhomogeneous LD pumping not only reduces optical-to-optical conversion efficiency but also exacerbates the thermal lensing effect in localized regions within the crystal, altering the ABCD transmission matrix within the cavity. This leads to critical issues such as increased laser energy fluctuations, optical axis instability, and deterioration of laser beam quality.

[0004] Therefore, ensuring uniform fluorescence distribution in LDs is a primary task in the design of such lasers, requiring a testing device to determine the rationality of the LD side-pumped slab crystal pumping design. Currently, a common device for testing pump uniformity involves testing the fluorescence distribution of the LD pumped slab crystal. This is done by using a camera to image the fluorescence distribution at a specific cross-section within the crystal onto the camera's target surface via a focusing lens. This testing device is simple to operate and allows for relatively intuitive observation and judgment of the fluorescence distribution in a local area of ​​the crystal. However, it only reflects the fluorescence distribution of that specific cross-section. Alternatively, the fluorescence distribution can be tested at different locations by moving the focusing lens, but this method is not only labor-intensive but also only obtains the fluorescence distribution of each discrete cross-section. Especially for large-mode-volume pump gain modules with unstable cavities, even if the fluorescence distribution is measured at every location, it cannot explain the impact on the amplified 1064nm laser spot. Therefore, it is not suitable for testing the overall uniformity of the slab crystal in large-mode-volume unstable cavity solid-state lasers, as the amplification of the laser by different pump regions is a cumulative effect, not a localized, singular amplification. Utility Model Content

[0005] The purpose of this invention is to provide a slab crystal side-pumped uniformity testing device suitable for the overall uniformity testing of slab crystals in large-mode-volume unstable cavity solid-state lasers, and to effectively improve the reliability and stability of uniformity testing.

[0006] This utility model is implemented as follows:

[0007] A device for testing the side-pump uniformity of a slab crystal includes a seed light source, a pinhole aperture, an Nd:YAG slab crystal, a focusing lens, a 45° reflection attenuator, and a beam analyzer arranged sequentially along the optical path. An LD pump module is disposed above the Nd:YAG slab crystal, and a crystal heat sink is disposed below the Nd:YAG slab crystal. The crystal heat sink is connected to the bottom of the Nd:YAG slab crystal.

[0008] Furthermore, a light-blocking shield is provided below the 45° reflective attenuator for receiving and blocking the reflected laser light.

[0009] Furthermore, the diameter of the aperture stop is adjustable.

[0010] Compared with the prior art, the beneficial effects of this utility model are:

[0011] 1. The quality of the laser beam amplified by the LD-pumped slab crystal is tested and used as a criterion for judging the pump uniformity of the slab crystal, which is more comprehensive than conventional testing of local areas inside the slab crystal.

[0012] 2. By adjusting the effective aperture of the ceramic pinhole aperture, it is equivalent to changing the spot size of the seed light source incident on the lath crystal. This allows for the evaluation of the fluorescence distribution uniformity of the lath crystal under different spot sizes, and a more comprehensive assessment of the pump uniformity. Attached Figure Description

[0013] To more clearly illustrate the technical solutions of the embodiments of this utility model, the drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this utility model and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

[0014] Figure 1 This is a schematic diagram of the structure of this utility model.

[0015] Figure labels: 1. Seed light source; 2. Pinhole aperture; 3. LD pump module; 4. Nd:YAG slab crystal; 5. Crystal heat sink; 6. Focusing lens; 7. 45° reflection attenuator; 8. Light shield; 9. Beam analyzer. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this utility model, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this utility model without creative effort are within the scope of protection of this utility model. Therefore, the following detailed description of the embodiments of this utility model provided in the accompanying drawings is not intended to limit the scope of the claimed utility model, but merely represents selected embodiments of this utility model. All other embodiments obtained by those skilled in the art based on the embodiments of this utility model without creative effort are within the scope of protection of this utility model.

[0017] Please see Figure 1 A device for testing the uniformity of side pumping of a slab crystal includes a seed light source 1, a pinhole aperture 2, an Nd:YAG slab crystal 4, a focusing lens 6, a 45° reflection attenuator 7, and a beam analyzer 9 arranged sequentially along the optical path. An LD pump module 3 is arranged above the Nd:YAG slab crystal 4, and a crystal heat sink 5 is arranged below the Nd:YAG slab crystal 4. The crystal heat sink 5 is connected to the bottom of the Nd:YAG slab crystal 4.

[0018] Below the 45° reflective attenuator 7, a light-blocking cover 8 is provided for receiving and blocking the reflected laser light.

[0019] The diameter of the aperture 2 is adjustable.

[0020] In practical applications, please refer to Figure 1 Seed light source 1 uses a 1064nm pulsed laser with an adjustable output laser energy of 10mJ to 80mJ, an adjustable repetition frequency of 1Hz to 25Hz, and a spot diameter of 5mm. A pinhole aperture 2, made of ceramic material, has an adjustable diameter of 1mm to 5mm with 1mm increments, used to control the spot diameter of the seed light source 1 incident on the slab crystal. The LD pump module 3 is a pump module composed of an 808nm LD bar array, placed at a certain distance above the slab crystal as a pump source. The Nd:YAG slab crystal 4 is welded to a crystal heat sink 5 using indium foil. The focusing lens 6 is used to focus the magnified laser light from the laser slab crystal onto the target surface of the beam analyzer 9 at the rear focal plane. A 45° reflective attenuator 7 is used to split and attenuate the laser, with a coating reflectivity of 99% at 1064nm. A light shield 8 is used to receive and block the reflected laser light.

[0021] During the test, with the LD pump light unpowered, the original spot distribution of the seed laser after passing through the slab crystal was first tested: the seed source 1 laser emitted a 1064nm pulsed laser at 20Hz, which entered the slab crystal after passing through the pinhole aperture 2, and then was focused into the beam analyzer 9 by the focusing lens. The spot distribution on the beam analyzer 9 software was recorded, including the spot size and beam divergence angle in the x and y directions, and the average beam product parameter (BPP) value in the two directions was calculated. During the test, the diameter of the pinhole aperture 2 was adjusted to three sizes: 1mm, 3mm, and 5mm, to restrict the seed laser spot to these three sizes before entering the slab crystal. The subsequent laser spot distribution was tested for each size, and the average BPP value was calculated for each. 10 BPP 30 and BPP 50 .

[0022] The LD pump module 3 is fixedly mounted 1mm to 2mm above the slab crystal via structural components, and shares a single LD drive power supply with the seed source laser 1 for synchronous triggering and power supply, also emitting light at 20Hz. At this time, the laser from the seed source 1 completes single-pass amplification after passing through the slab crystal. The amplified laser is then focused onto the camera target surface of the beam analyzer 9 by the focusing lens 6. The beam analyzer 9 software analyzes the beam distribution, records the beam size and divergence angle in the x and y directions, and calculates the average beam percentage (BPP) value. 10 '、BPP 30 'and BPP 50 '.

[0023] If the pump uniformity is good, the distribution trend of the laser gain coefficient at different spatial positions is consistent within different regions of the slab crystal. The BPP value of the seed laser remains essentially unchanged after single-pass amplification via LD pumping for the three aperture sizes of 1mm, 3mm, and 5mm, meaning that the following conditions are simultaneously met:

[0024] BPP 10 '≈BPP 10 ;

[0025] BPP 30 '≈BPP 30 ;

[0026] BPP 50 '≈BPP 50 ;

[0027] If the quality of the amplified laser beam deteriorates as the spot size of seed source 1 increases, i.e., the BPP increases, it indicates that the uniformity of the LD pump spot deteriorates under a larger mode volume. If the pump uniformity is poor, the higher-order modes of the spot, i.e., the spots at the edges of the transverse mode distribution, will also receive a large gain, and the beam quality will deteriorate significantly. The proportion of laser energy occupied by the higher-order modes of the 1064nm laser increases. At this time, it is necessary to adjust the LD pump structure or optical parameters.

[0028] This invention uses the BPP value of a magnified 1064nm laser of the same size as that of an unmagnified 1064nm laser as a criterion to determine pump uniformity, which is more comprehensive than conventional testing of local areas inside a slab crystal. If the beam quality (i.e., BPP value) of the magnified spot does not significantly deteriorate compared to the beam quality before magnification, the pump uniformity is considered good. Furthermore, by comparing the beam quality of multiple 1064nm laser spots of different sizes, the pump uniformity is evaluated more comprehensively.

[0029] The above description is merely a preferred embodiment of this utility model and is not intended to limit the utility model. Various modifications and variations can be made to this utility model by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of this utility model should be included within the protection scope of this utility model.

Claims

1. A slab crystal side-pumping uniformity test apparatus, characterized by: It comprises seed light source (1), pinhole diaphragm (2), Nd:YAG slab crystal (4), focusing mirror (6), 45° reflecting attenuating sheet (7) and light beam analyzer (9) arranged in sequence along the light path direction, LD pumping module (3) is arranged above the Nd:YAG slab crystal (4), crystal heat sink (5) is arranged below the Nd:YAG slab crystal (4), the bottom of the crystal heat sink (5) is connected with the Nd:YAG slab crystal (4).

2. A slab crystal side-pumping uniformity test device according to claim 1, wherein, The 45° reflecting attenuating sheet (7) is provided below with light shield (8) for receiving blocked reflected laser.

3. A slab crystal side-pumping uniformity test device according to claim 1, wherein, The diameter of the pinhole diaphragm (2) is adjustable.

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