CN110658632A - Homogenized incoherent light source device - Google Patents

Abstract

The invention relates to a homogenized incoherent light source device. The device includes an amplified spontaneous emission light source, a beam coupling unit, and a uniform light guide, wherein the amplified spontaneous emission light source, the beam coupling unit, and the uniform light guide are arranged in sequence along the beam propagation direction, and the positions are arranged at different positions. and oriented so that the light output by the amplified spontaneous emission light source is coupled to the input end face of the uniform light guide, and the ratio of the length to the aperture of the uniform light guide is greater than or equal to a preset ratio, so that the amplified spontaneous emission light source outputs The image size of the light at the output end face of the uniform light guide is greater than or equal to twice the aperture of the uniform light guide. This device has the advantages of small dependence of beam uniformity on the pumping uniformity of the light source, high utilization efficiency of the pumping light source, and good uniformity of the output two-dimensional flat-top beam. of incoherent light sources.

Description

Homogenized incoherent light source device

technical field

The invention belongs to the field of lasers for laser nuclear fusion, in particular to a homogenized incoherent light source device.

Background technique

Regardless of the application of laser-plasma physics research, material damage testing, laser processing technology, etc., it is expected to obtain uniform irradiation close to the top-hat at the laser interface. Since the 1980s, the concept of induced incoherent beam homogenization has been introduced in the field of high-power lasers to suppress the coherent modulation of the beam from the spatial or frequency domain to obtain a smooth and uniform beam. The basic idea of spatially induced incoherent technology (ISI: induced spatial incoherent) is to divide the laser beam into multiple sub-beams with a diffraction spot size equal to the irradiation area. When superimposed on a specific interface, the superposition effect will characterize weak coherence, thereby suppressing the speckle produced by coherent modulation. For example, Omega, NIKE and Shenguang devices have all tried to use binary optical devices such as random phase plates and fly-eye lens arrays to obtain relatively uniform laser irradiation, so as to carry out related research on laser-driven nuclear fusion. Due to the limitation of the processing precision of the device, the size of the beamlets cannot be infinitely reduced. Therefore, the interior of the laser beam cross-section homogenized by the binary optics still contains rapidly changing interference structures, which, like target inhomogeneities, can act as "seeds" to develop into Rayleigh-Taylor instabilities.

As shown in Fig. 1, the U.S. Naval Laboratory has developed a step-free induced incoherent beam smoothing technique by taking advantage of the wide bandwidth (~Thz) of excimer lasers, replacing binary optics with diffuse scatterers, and obtaining tilted And the flat top light intensity distribution section with curvature not more than 2%, beam uniformity RMS<2%. Since the conversion efficiency of the broadband incoherent light generated by the laser irradiation of the diffuse scatterer is very low, and only a small part of the broadband incoherent light is irradiated through the object hole to form an effective output, the effective output efficiency of the laser pulse is extremely low. According to reports, the energy intensity of the broadband incoherent light source of the NIKE device in the Naval Laboratory is only 20nJ, so a multi-stage discharge-pumped laser amplifier has to be introduced to pre-amplify the seed light energy.

As shown in Figure 2, in order to improve the laser utilization efficiency and output intensity of the seed light source, Xiang Yihuai et al. directly used the amplified spontaneous emission (ASE, Amplified Spontaneous Emission) generated by the free-running discharge-pumped krypton fluoride laser 210 as part of the For the coherent light source, the light intensity distribution with the most uniform intensity is intercepted through the irradiating object aperture (aperture) 220 to obtain a "flat-top" beam section, and the light beam passes through the image transmission lens group 230 to reach the image plane 240 . The seed light source of Tianguang No. 1 device produces an amplified spontaneous radiation energy of 30mJ, and the output energy after irradiating the object hole is about 8mJ, the energy utilization efficiency is close to 30%, and the beam uniformity is close to 2%.

Practice has proved that this beam homogenization scheme relies too much on the pumping uniformity of the laser, which shows that the light intensity distribution profile perpendicular to the direction of the pumping current has a large inclination and radian, as shown in the horizontal direction in Figure 3, The uniformity is also lower than the light intensity distribution in the pump direction, the vertical direction as shown in FIG. 3 . Moreover, the beam still maintains the rectangular characteristics of the discharge area during transmission, and the divergence angles in the horizontal and vertical directions are quite different, and because this short-cavity laser (cavity length 38cm) has many spatial modes, the beam forms several discrete parts in the spectrum plane , this situation is very unfavorable for the subsequent transmission amplification and uniformity maintenance of the beam. Therefore, the high-energy excimer laser devices of the Northwest Institute of Nuclear Technology and other units still adopt the scheme of homogenization of scattered light.

On the one hand, the light source energy utilization efficiency of the scattered light homogenization scheme is low, and on the other hand, the ASE light object hole homogenization scheme depends on the pumping uniformity of the light source (for discharge-pumped lasers, the discharge uniformity originating from the electrode) Due to the strong disadvantage, the present disclosure proposes a high-uniformity broadband incoherent light source device that utilizes light guide homogenization to amplify spontaneous radiation beams.

SUMMARY OF THE INVENTION

In view of the defects existing in the prior art, the purpose of the present invention is to provide a homogenized incoherent light source device, which utilizes a light guide to homogenize a broadband incoherent ASE light source, reduces the dependence of the beam uniformity on the laser pumping uniformity, and realizes two The flat-top beam intensity distribution improves the utilization efficiency of the ASE light source and relaxes the selection conditions of the front-end laser.

For achieving the above purpose, the technical scheme adopted in the present invention is as follows:

A homogenized incoherent light source device is proposed. The homogenized incoherent light source device includes an amplified spontaneous emission light source, a beam coupling unit, and a homogenized light guide, wherein the amplified spontaneous emission light source, the beam coupling unit, and the homogenized light guide are along the beam propagation direction Set in sequence, and set the position and orientation so that the light output from the amplified spontaneous emission light source is coupled to the input end face of the uniform light guide, and the ratio of the length to the aperture of the uniform light guide is greater than or equal to the preset ratio, so that The image size of the light output by the amplified spontaneous radiation light source at the output end face of the uniform light guide is greater than or equal to twice the aperture of the uniform light guide.

Further, the amplified spontaneous emission light source includes a laser, a rear cavity mirror located behind the laser, and a front window located in front of the laser, the rear cavity mirror and the front window form a laser cavity, and the rear cavity mirror for high reflectivity.

Further, the amplified spontaneous radiation beam transmitted backward by the front window is imaged inside the uniform light guide after being reflected by the rear cavity mirror and double-pass magnified.

Further, the beam coupling unit includes a first cylindrical lens and a second cylindrical lens, the first cylindrical lens is closer to the amplified spontaneous emission light source than the second cylindrical lens, and the first cylindrical lens The lens makes the light beam output from the amplified spontaneous emission light source converge along the direction of the long axis of its cross section, the second cylindrical lens makes the light beam output from the amplified spontaneous emission light source converge along the short axis direction of the cross section, and the first cylindrical surface The lens coincides with the focal plane of the second cylindrical lens, and the ratio of the focal lengths of the first cylindrical lens and the second cylindrical lens is equal to the ratio of the major and minor axes of the beam section.

Further, the light beam coupling unit includes a spherical mirror for converging the light beam output by the amplifying spontaneous radiation light source.

Further, the input end face of the uniform light guide is positioned at a position where the beam profile is equivalent to the cross section of the light guide.

Further, the uniform light guide includes prisms and cylinders made of ultraviolet quartz, and at least one of single-core ultraviolet optical fibers and hollow-core ultraviolet optical fibers.

Further, the homogenized incoherent light source device further includes an image transfer unit located in front of the output end face of the homogenized light guide.

Further, the image transmission unit includes a transmission lens, and the output end face of the uniform light guide is located on the front focal plane of the transmission lens.

Further, the image transfer unit further includes a focusing lens located behind the transmission lens.

The beneficial effects of the present invention are as follows:

Aiming at the low energy output efficiency in the stepless induced incoherence (EFISI) technology using the diffuse scattering light homogenization technology route, and the use of the amplified spontaneous emission homogenization technology which is strongly dependent on the uniformity of the light source, the invention proposes the use of light guide homogenization. The high-uniformity broadband incoherent light output can be realized by using the amplified spontaneous emission light source, which provides a cost-effective option for beam smoothing of high-power excimer laser systems.

The invention uses the light guide to homogenize the light intensity distribution of the amplified spontaneous radiation output by the free-running laser, realizes the output of a two-dimensional uniform "flat top" light intensity distribution section, improves the utilization efficiency of the light source, and expands the selection range of the light source. An efficient and cost-effective beam homogenization scheme is provided for laser applications in the study of laser beam-target interaction.

Compared with the broadband laser scattering homogenization light source scheme adopted by the U.S. Naval Laboratory and Northwest Nuclear Technology, the uniformity of the output flat-top beam is comparable, and both are better than 2%. However, the utilization efficiency of the pump light source has been greatly improved by nearly five orders of magnitude, and the intensity of the output homogenized broadband incoherent light has increased from the nanojoule level to the millijoule level.

Compared with the ASE illumination iris scheme sampled by the seed light source of the Tianguang-1 device, the light guide homogenization incoherent light source scheme significantly improves the beam uniformity perpendicular to the pumping direction of the light source: the ASE illumination iris can obtain a nearly flat top The beam distribution cross section is a smooth flat-top structure with a uniformity better than 2% along the pumping direction of the light source, and an arched structure with a uniformity close to 3.57% in the direction perpendicular to the pumping direction of the light source, indicating that the implementation effect of this scheme is limited by The pumping uniformity of the light source; the present invention can obtain a flat-top structure beam cross-section with uniformity close to 1.50% in both directions parallel and perpendicular to the pumping direction of the light source, indicating that this method relies on the inherent pumping uniformity of the amplified spontaneous emission light source It is smaller, which relaxes the selection conditions of the laser and reduces the difficulty of technical realization.

Further, the present invention uses the beam profile shaping component to pre-shape the beam profile of the amplified spontaneous radiation, improves the coupling efficiency of the amplified spontaneous radiation injected into the light guide, increases the utilization efficiency of the pump light source to a level close to 80%, and significantly improves the output light intensity. , which also helps to relax the intensity requirements for the pump light source.

In a word, the technical solution of the present disclosure has the advantages of less dependence of the beam uniformity on the pumping uniformity of the light source, high utilization efficiency of the pumping light source, and good uniformity of the output two-dimensional flat-top beam. Small homogenized incoherent light source.

Description of drawings

1 is a schematic diagram of the optical path layout of an example of an existing scattered light homogenization scheme;

2 is a schematic diagram of the optical path layout of an example of an existing ASE optical object hole homogenization scheme;

Fig. 3 is the light intensity distribution plan view on the image plane of the existing ASE optical object hole homogenization scheme shown in Fig. 2;

4 is a schematic diagram of the optical path layout of the homogenized incoherent light source device according to Embodiment 1 of the present disclosure;

5 is a schematic diagram of an optical path layout of a homogenized incoherent light source device according to Embodiment 2 of the present disclosure;

6a, 6b, 6c, and 6d are respectively a three-dimensional view of the light intensity distribution on the image plane, an X-Y plane view of the light intensity distribution, an X-axis graph, and a Y-axis of the homogenized incoherent light source device according to Embodiment 2 of the present disclosure. Graph;

7a and 7b are respectively schematic diagrams of the light spot profile in the height direction and the width direction during the beam transmission process of the homogenized incoherent light source device ASE according to Embodiment 1 of the present disclosure;

Figures 8a and 8b are the beam intensity distribution sections of the Apex-248 laser output in the parallel plane cavity mode and the output amplified spontaneous emission in the free running mode, respectively;

9a and 9b are a schematic diagram of the optical path layout and a cross-sectional view of the light intensity distribution of the ASE illumination diaphragm, respectively.

Detailed ways

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

FIG. 4 is a schematic diagram of the optical path layout of the homogenized incoherent light source device according to Embodiment 1 of the present disclosure. As shown in FIG. 4 , the homogenized incoherent light source device of Embodiment 1 includes an amplified spontaneous emission (ASE) light source 410 , a beam coupling unit 420 , and a homogenized light guide 430 . The ASE light source 410, the beam coupling unit 420, and the uniform light guide 430 are placed in sequence along the beam propagation direction, and the positions and orientations are placed so that the light emitted by the amplified spontaneous emission light source 410 is coupled to the input end face of the uniform light guide 430, and the uniform light guide The ratio of the length to the aperture of 430 is greater than or equal to the preset ratio, so that the image size of the light emitted by the amplified spontaneous emission light source 410 at the output end face of the uniform light guide 430 is greater than or equal to twice the aperture of the uniform light guide 430 .

As shown in FIG. 4 , the ASE light source 410 includes a laser, a rear cavity mirror 411 located behind the laser, and a front window located in front of the laser. The rear cavity mirror 411 and the front window form a laser cavity. The laser in the ASE light source 410 may be a free-running laser, that is, a laser that operates in a free-running mode. As an embodiment, the back cavity mirror 411 is a high-reflection mirror, which is used to increase the gain length of spontaneous radiation in the laser medium. Therefore, the high-reflection mirror increases the energy of the output light of the homogenized incoherent light source device. The open-structured laser with the open front end of the laser cavity cannot satisfy the resonance conditions for generating self-excited oscillation, so the output optical radiation is typical amplified spontaneous emission (ASE), which has the characteristics of broadband and incoherence.

Due to the poor coherence of the ASE light source 410, the beam has a large near-field divergence angle. The cross-sectional profile of the ASE beam produced by an optical cavity with a non-centrosymmetric cross-section is also not centrosymmetric, and the beam divergence angles in different directions are not consistent. In order to match the beam profile shape and size with the cross section of the uniform light guide 430 , the beam coupling unit 420 realizes the collection, profile shaping and coupling between the light beam and the uniform light guide 430 of the light output by the ASE light source. The beam coupling unit 420 includes two cylindrical lenses. The first cylindrical lens 421 is closer to the ASE light source 410 than the second cylindrical lens 422. In this embodiment, the first cylindrical lens 421 and the second cylindrical lens 422 Both are cylindrical convex lenses. The focal planes of the first cylindrical lens 421 and the second cylindrical lens 422 coincide with the rear of the input end face of the uniform light guide 430, and the ratio of the focal lengths of the first cylindrical lens 421 and the second cylindrical lens 422 is equal to the long and short axes of the beam profile. ratio (for rectangular beams, the ratio of the long and short sides). The first cylindrical lens 421 is positioned in front of the output window of the ASE light source 410, and the clear aperture is slightly larger than the beam profile of the ASE beam at this position. While completely collecting the radiation of the ASE light source, the beam output by the ASE light source 410 is long along its cross section. Axial convergence. The second cylindrical lens 422 is positioned at a position where the center of the beam profile is symmetrical (the long and short axes of the beam profile are equivalent), and the second cylindrical lens 422 makes the light beam output by the ASE light source 410 converge along the short axis direction of the cross section, so as to ensure the light output by the ASE light source. In the subsequent transmission process, the beam profile maintains center symmetry, and converges on the focal planes of the first cylindrical lens 421 and the second cylindrical lens 422 . The input end face of the dodging light guide 430 is positioned at a position where the beam profile is comparable (roughly equal) to the cross section of the light guide to ensure that as much light from the ASE light source as possible is injected into the doping light guide 430 for homogenization.

Due to the divergence characteristics of the ASE light source 410 , the spatial distribution of the light beam at the position of the uniform light guide 430 should be regarded as the image formed by the volume light source passing through the first cylindrical lens 421 and the second cylindrical lens 422 . In order to ensure the homogenization effect of the uniform light guide 430, it should be ensured that the image size of the ASE light source 410 at the output end face of the uniform light guide 430 is not less than twice the diameter of the light guide (which can be achieved by increasing the length of the uniform light guide 430). Different parts of the ASE beam (which can be regarded as sub-beams) coupled into the uniform light guide 430 are superimposed on each other at the output end face after multiple reflections to form a highly uniform flat-top light intensity distribution cross section. In addition, the ASE light beam transmitted backward near the front window of the ASE light source 410 can be imaged inside the uniform light guide 430 after being reflected by the back cavity mirror and double-pass magnified, so that the ASE beam coupled into the light guide can be as much as possible.

The uniform light guide 430 includes prisms and cylinders made of UV silica, and at least one of a single-core UV fiber and a hollow-core UV fiber.

As shown in FIG. 4 , the homogenized incoherent light source device of Embodiment 1 may further include an image transfer unit 440 located in front of the output end of the homogenized light guide 430 . The image transfer unit 440 may include a transmission lens 441 and a focus lens 442 . The homogenized ASE beam output by the homogenized light guide 430 is collected by the transmission lens 441, and its high uniformity flat top light intensity distribution cross section is transmitted and focused by the image transmission unit 440 including the transmission lens 441 and the focusing lens 442, and the image is imaged on the target plane ( image plane) 450, so as to achieve uniform irradiation of the target plane 450.

When the aperture of the uniform light guide 430 is sufficiently small (the aperture of the uniform light guide 430 is much smaller than the focal length of the transmission lens 441 ), the light field distribution at the output end can be regarded as a point light source with uniform intensity distribution. If the output end face of the homogenized light guide 430 is located at the front focal plane of the transmission lens 441, the homogenized light beam output by the homogenized light guide 430 will be transmitted in space in the form of quasi-parallel light. Ideally, the flat-topped light intensity distribution section at the output end of the uniform light guide 430 will be imaged to infinity by the transmission lens 441 , and after the quasi-parallel beam is focused by the focusing lens 442 , the uniform intensity beam distribution section will be at the focal plane of the focusing lens 442 . to obtain a highly homogenized flat-top light intensity distribution at the focal plane of the system. As a special case of application, the homogenized ASE beam can be transmitted long distance in free space. Since multi-level image transmission is not required, the implementation difficulty and cost of this homogenized incoherent light source device will be greatly reduced.

In Embodiment 1, when the focal length of the transmission lens 441 arranged in front of the output end of the uniform light guide 430 is much larger than the diameter of the uniform light guide 430, by adjusting the distance from the transmission lens 441 to the output end face of the uniform light guide 430, the ASE beam can be made It is transmitted in the form of quasi-parallel light. As a special case of application, this layout will facilitate long-distance beam transmission. Since the flat-top beam distribution cross section can be reproduced without using a multi-level image transmission system, this optical path layout will greatly save the cost of beam transmission.

FIG. 5 is a schematic diagram of the optical path layout of the homogenized incoherent light source device provided in Embodiment 2 of the present disclosure.

As shown in FIG. 5 , the main difference between the homogenized incoherent light source device of Embodiment 2 and Embodiment 1 is that the beam coupling unit 520 does not use a cylindrical lens, but a spherical lens, such as a spherical convex lens. The laser in the ASE light source 510 can be a free-running discharge-pumped excimer laser Apex-248. The ASE beam output by the ASE light source 510 is collected by the spherical lens located in front of the output window and coupled to the uniform light guide 530 for homogenization, and a beam cross section with uniform intensity distribution is obtained at the output end face of the uniform light guide 530 . In this embodiment, the uniform light guide 530 is a rectangular light guide.

The beam waist of the ASE beam is 396 mm from the beam coupling unit, and the dimensions are 4.2 × 1.4 mm (length × width). In order to match the cross section of the ASE beam with that of the uniform light guide 530 made of ultraviolet fused silica, the front end of the uniform light guide 530 with a cross-sectional size of 6mm×6mm is positioned 425mm away from the beam coupling unit, where the size of the beam cross section is 6×2mm, it can ensure that the ASE beam completely enters the uniform light guide 530, and the energy coupling efficiency is close to 100%. In order to ensure the beam homogenization effect, the length of the uniform light guide 530 is selected to be 500mm, and the beam size of the freely transmitted ASE beam at the output end face of the rectangular light guide 530 (925mm from the beam coupling unit) is close to 38×11mm. The ASE beam in the pumping direction of the light source (the direction of the long side of the beam section) is reflected multiple times in the uniform light guide 530 to obtain a uniform flat-top light intensity distribution on the output end face. In the vertical direction of the pumping direction of the light source, due to the small beam size (close to twice the width of the light guide) and the small divergence angle, the ASE on the outside of the light beam is reflected by the uniform light guide 530 and superimposed with the light intensity of the ASE in the middle of the light beam at the output end face. The beam intensity distribution section is homogenized from an arched profile to a flat top profile.

It is experimentally measured that the energy of the ASE pulse output by the ASE light source 510 is 45±4mJ, the energy of the broadband incoherent light pulse obtained after homogenization by the homogenizing light guide 530 is 35±3mJ, the energy utilization efficiency is close to 80%, and the loss is mainly due to the quartz Reflection loss of a uniform light guide 530 made of glass. The light beam on the output end face of the uniform light guide 530 is a rectangular flat-top structure with a size of 6mm×6mm. After the flat-top beam section is transmitted and focused by the lens, the light intensity distribution obtained by the beam section analyzer is shown in Figure 6b. It can be seen from Fig. 6a, Fig. 6b, Fig. 6c and Fig. 6d that the ASE sub-beams in the Y direction (parallel to the pumping direction of the light source) are superimposed by multiple reflections in the homogenized light guide 530, so they are output in the homogenized light guide 530. The end face obtained an ideal flat-top distribution with a uniformity of 1.33%. The roll and radian of the light intensity distribution in the X direction (perpendicular to the pumping direction of the light source) have also been significantly optimized, showing an obvious "flat-top" distribution feature. The uniformity of the flat-top part is better than 1.5%, but in this direction The ASE beam of the ASE beam has fewer reflections and stacking times in the uniform light guide 530, resulting in a relatively low proportion of the flat top portion, and the uniformity is also slightly worse than the uniformity of the light intensity distribution in the Y direction.

Overall, by implementing the light guide homogenization of the broadband incoherent light source on the ASE light source 510, the beam cross-section output with a two-dimensional flat-top distribution is obtained, and the uniformity of the flat-top part in both X-Y directions is better than 2%, It can meet the requirement of the uniformity of seed light in the application of high-energy laser device. The utilization efficiency of the amplified spontaneous radiation output by the discharge-pumped excimer laser is close to 80%, and the energy of the broadband incoherent light pulse homogenized by the light guide is also significantly higher than that of the ASE light source irradiating the pinhole method, which achieves the intended goal of the present invention.

The uniform light guide 530 used in this embodiment is a quadrangular prism processed from ultraviolet quartz glass. Although its aspect ratio is close to 80 times, its homogenization effect in the X direction is still unsatisfactory due to the transmission characteristics of the ASE light source 510 . However, further prolonging its length will increase the processing difficulty and use risk (such as breakage) of the uniform light guide 530 . Therefore, large-diameter single-core UV fibers or hollow-core UV fibers can be considered as uniform light guides. Experiments have confirmed that the homogenization effect shown in this embodiment can also be achieved by using an ultraviolet optical fiber with a core diameter of 1200 μm and a length of 100 mm.

In contrast, in Example 1, the ASE beam can be pre-shaped by two cylindrical lenses to further improve the homogenization effect and energy utilization. The optical path is shown in Figure 4, assuming that the focal length of the first cylindrical lens 421 is 330mm, placed in front of the output window of the ASE light source 410, and the ASE beam profile is compressed and shaped along the pumping direction of the light source; it is assumed that the focus is perpendicular to the pumping direction of the light source The second cylindrical lens 422 has a focal length of 110 mm, and is positioned at a distance of 220 mm from the first cylindrical lens, where a square beam profile of 7 mm×7 mm can be obtained. Since the two cylindrical lenses are confocal (the focal planes coincide), it is possible to ensure that the aspect ratio of the beam during subsequent transmission is close to 1:1.

The size of the spot profile during ASE beam transmission is shown in Fig. 7a and Fig. 7b. At a distance of 348mm from the first cylindrical lens 421, the size of the ASE beam cross-section is 1.2mm×1.2mm. A single-core fiber with a clear aperture of 1200μm is placed at this position as the uniform light guide 430, and an ASE coupling efficiency close to 78% can be obtained. . After the ASE distribution near the front window of the discharge cavity is double-amplified by the laser cavity, the cross-section of the light intensity distribution in the middle of the fiber (at a distance of 392±4mm from the first cylindrical lens 421) becomes a 4×0.53mm image, and other positions in the cavity Imaging is after this image position and gradually increases.

When the beam profile is larger than the diameter of the fiber, it will be reflected multiple times inside the fiber, and superimposed on the output end face of the fiber to obtain a uniform beam intensity distribution interface. Experiments have confirmed that the homogenized incoherent light source device arranged in this way has a pulse energy of 28mJ at the output end of a 200mm-long optical fiber, the light intensity distribution is a typical flat-top beam, and the uniformity of the beam in the X-Y direction is significantly improved.

The excimer laser has the characteristics of short wavelength and wide bandwidth, and is an ideal light source for implementing the homogenized incoherent light source device of the present disclosure. Next, the technical solution of the present disclosure is experimentally verified on a discharge-pumped excimer laser, and it is verified that the discharge-pumped excimer laser Apex-248 can be used. Figures 8a and 8b show cross sections of the output beam intensity distribution of the Apex-248 laser in different operating modes. When the laser operates in the parallel plane cavity mode, the output laser energy is 120±6mJ, the beam size is 22×7mm, and the cross section of the light intensity distribution is shown in Figure 8a, which is difficult to meet the practical application requirements. After removing the front cavity mirror of the parallel plane cavity, the laser is in free-running mode, and the output amplified spontaneous emission (ASE) energy is 40±4 mJ.

Referring to the seed light source layout of the skylight device, as shown in Figure 9a, the beam distribution cross-section is homogenized by using the amplified spontaneous emission (ASE) output by the laser to illuminate the Φ7mm aperture diaphragm, and the effective output ASE pulse energy obtained on the APEX-248 laser is 6.7±0.6mJ, the energy utilization efficiency of ASE light source is close to 16%. The ASE beam profile and intensity distribution section intercepted by the diaphragm are shown in Figure 9b. The non-uniformity in the horizontal direction is 8%, and the non-uniformity in the vertical direction is 6.3%, which is much larger than the maximum allowable amount that the application can accept (no uniformity≤5%). Moreover, the light intensity distribution profile is not the platform structure required to drive the planar shock wave, but has obvious slopes and radians. Obviously, for the ASE light source with poor pump uniformity, the uniformity of light intensity distribution obtained by illuminating the object hole cannot meet the requirements of the application on the uniformity of irradiation.

The invention uses the light guide to homogenize the light intensity distribution of the amplified spontaneous radiation output by the free-running laser, realizes the output of a two-dimensional uniform "flat top" light intensity distribution section, improves the utilization efficiency of the light source, and expands the selection range of the light source. An efficient and cost-effective beam homogenization scheme is provided for laser applications in the study of laser beam-target interaction.

Compared with the broadband laser scattering homogenization light source scheme adopted by the U.S. Naval Laboratory and Northwest Nuclear Technology, the uniformity of the output flat-top beam is comparable, and both are better than 2%. However, the utilization efficiency of the pump light source has been greatly improved by nearly five orders of magnitude, and the intensity of the output homogenized broadband incoherent light has increased from the nanojoule level to the millijoule level.

Compared with the ASE illumination iris scheme sampled by the seed light source of the Tianguang-1 device, the light guide homogenization incoherent light source scheme significantly improves the beam uniformity perpendicular to the pumping direction of the light source: the ASE illumination iris can obtain a nearly flat top The beam distribution cross section is a smooth flat-top structure with a uniformity better than 2% along the pumping direction of the light source, and an arched structure with a uniformity close to 3.57% in the direction perpendicular to the pumping direction of the light source, indicating that the ASE irradiation iris scheme The implementation effect of the light source is limited by the pumping uniformity of the light source; the technical solution of the present disclosure can obtain a flat-top structure beam cross-section with a uniformity close to 1.50% in both directions parallel and perpendicular to the pumping direction of the light source. The inherent pumping uniformity of the amplified spontaneous emission light source is less dependent, which relaxes the selection conditions of the laser and reduces the difficulty of technical realization.

Further, the embodiment of the present disclosure utilizes the beam profile shaping component to pre-shape the beam profile of the amplified spontaneous radiation, improves the coupling efficiency of the amplified spontaneous radiation injected into the light guide, increases the utilization efficiency of the pump light source to a level close to 80%, and outputs light. The strong increase is obvious, which also helps to relax the intensity requirements of the pump light source.

Table 1 Comparison of typical step-free induced incoherence (EFISI) beam homogenization techniques

In a word, the technical solution of the present disclosure has the advantages of less dependence of the beam uniformity on the pumping uniformity of the light source, high utilization efficiency of the pumping light source, and good uniformity of the output two-dimensional flat-top beam. Small homogenized incoherent light source.

Those skilled in the art should understand that the method and system described in the present invention are not limited to the embodiments described in the specific implementation manner, and the above specific description is only for the purpose of explaining the present invention, not for limiting the present invention. Those skilled in the art can obtain other embodiments according to the technical solutions of the present invention, which also belong to the technical innovation scope of the present invention, and the protection scope of the present invention is defined by the claims and their equivalents.

Claims (10)

1. A homogenized incoherent light source device is characterized by comprising an amplified spontaneous emission light source, a light beam coupling unit and an dodging light guide, wherein the amplified spontaneous emission light source, the light beam coupling unit and the dodging light guide are sequentially arranged along a light beam propagation direction and are arranged at positions and in orientations such that light output by the amplified spontaneous emission light source is coupled to an input end face of the dodging light guide, and the ratio of the length to the aperture of the dodging light guide is greater than or equal to a preset ratio, so that the size of an image formed by the light output by the amplified spontaneous emission light source at the output end face of the dodging light guide is greater than or equal to 2 times the aperture of the dodging light guide.

2. The homogenized incoherent light source device of claim 1, wherein said amplified spontaneous emission light source comprises a laser, a back cavity mirror behind said laser, and a front window in front of said laser, said back cavity mirror and said front window forming a laser cavity, said back cavity mirror being a high reflectivity mirror.

3. The homogenized incoherent light source device of claim 2, wherein the amplified radiation spontaneous emission beam transmitted back through said front window is reflected by said back cavity mirror and imaged into said dodging light guide after two-way amplification.

4. The homogenized incoherent light source device of claim 1, wherein the beam coupling unit comprises a first cylindrical lens and a second cylindrical lens, the first cylindrical lens is closer to the amplified spontaneous emission light source than the second cylindrical lens, the first cylindrical lens converges the light beam output by the amplified spontaneous emission light source in the direction of the long axis of the cross section thereof, the second cylindrical lens converges the light beam output by the amplified spontaneous emission light source in the direction of the short axis of the cross section thereof, the first cylindrical lens coincides with the focal plane of the second cylindrical lens, and the ratio of the focal lengths of the first cylindrical lens and the second cylindrical lens is equal to the ratio of the long axis and the short axis of the cross section of the light beam.

5. The homogenized incoherent light source device of claim 1, wherein the beam coupling unit comprises a spherical mirror that converges the light beam output by the amplified spontaneous emission light source.

6. The homogenized incoherent light source device of claim 1, wherein said input end face of said homogenizing light guide is positioned at a location where the beam profile corresponds to the light guide cross-section.

7. The homogenized incoherent light source device of claim 1, wherein the homogenizing light guide comprises at least one of a prism and a cylinder made of ultraviolet quartz, and a single core ultraviolet fiber and a hollow ultraviolet fiber.

8. The homogenized incoherent light source device of claim 1, further comprising an image transfer unit positioned in front of the output end face of the homogenizing light guide.

9. The homogenized incoherent light source device of claim 8, wherein the image transfer unit comprises a transmission lens, and the output end face of the homogenizing light guide is positioned on the front focal surface of the transmission lens.

10. The homogenized incoherent light source device of claim 9, wherein the image transfer unit further comprises a focusing lens positioned behind the transfer lens.

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