Backward light by stimulated Brillouin scattering (SBS) induces the final transport mirror laser damage, which has been considered a bottleneck problem in developing high-power and high-energy laser facilities. In this work, an improved continuous phase plate (CPP) model and a backward SBS model were established based on the G-S algorithm and the Fresnel diffraction transmission algorithm to simulate the backward SBS to the final transport mirror. This study discussed the propagation characteristics of backward SBS. The research results showed that the distribution of the backward SBS transmitted to the final transport mirror was determined by the phase structure of the continuous phase plate attached to the back-transmission process. By optimizing the CPP design, reducing the transmission distance, reducing the intensity modulation, and controlling the phase of the incident beam, the modulation of backward SBS can be suppressed, which has great significance in improving the laser-induced damage threshold to the final transport mirror.
The surface quality of the optical element substrate will affect the laser damage threshold of the dielectric coatings. Substrate surface scratches are one of the common damages to the substrate. In this work, the parabola-section-model lateral scratches of the 45° HR coating with a central wavelength of 1064 nm substrate are studied, and the scratches and multilayer coatings are established. The three-dimensional finite element method is used to simulate the electric field modulation generated by scratches in the fundamental frequency high-reflective film when coatings irradiated at 1064nm and 355nm . The results show that under the same conditions, greater light intensification at the shorter wavelength.The electric field enhancement of p-polarized light is larger than that of s-polarized light. For 1064nm laser, when the incident angle is 45° The electric field intensity is the highest. When the incident laser at 355nm , the maximum intensity enhancement is produced when the incident is 60à.When the laser is incident at 45°, the greater the depth of the scratch, the stronger the electric field intensity in the film. The angle at which the 355nm laser is irradiated on the surface of the recessed film determines the magnitude of the electric field enhancement. Therefore, the electric field strength is very sensitive to the angle of incidence and the depth of the scratch.
Large-diameter optical components are important parts of the high-power laser facility [1, 2], and generally have a diameter greater than 400 mm × 400 mm. It is important for the detection of the surface and internal characteristics of large-diameter optical components [3, 4]. Since large-diameter optical components have a large imaging range and a certain thickness (generally over 50 mm), how to achieve high-resolution imaging over the entire thickness of large-diameter optical components becomes a challenge. This paper proposes to use medium format CMOS to realize large field microscopy imaging to ensure that the imaging range meets the field of view requirements of large aperture optical components. At the same time, a microscopic imaging lens with a magnification of 1.5 is designed to ensure that the object resolution is 4.5μm. Simulation experiments show that the system takes advantage of microscopic imaging, wavefront coding, and medium-format large targets. The imaging system can clearly image the entire large-diameter optical component over a long depth of field, improving the detection efficiency and detection accuracy of large-diameter optical components.
The final optics of high-power laser facility are exposed to long-period, high-dose gamma irradiation. Being closest to the target, Borate glass is most affected by the irradiation. Therefore, it is very meaningful to study the effects of gamma irradiation on the optical performance and structural properties of borate glass materials. In this paper, the Co-60 source is used as the irradiation source. The borate glass material made in China is irradiated by different doses of gamma ray. The optical performance test and structural properties test are carried out. The results show that gamma ray irradiation has a great influence on the spectral transmittance and surface structure of borate glass. The research results have some guiding significance for the engineering application of borate materials.
KEYWORDS: Stray light, Absorption, Glasses, High power lasers, Laser systems engineering, Laser damage threshold, Metals, Solid state lasers, Finite element methods, Interference (communication)
In high power solid-state laser facilities, stray lights may do great damage to optical glass and metal structure and affect the transmission of the main laser and the environment cleanliness inside the facility. On the other hand, the stray may also form noise signal of the main laser pulse and affect the output quality. There are mature solutions for the controlling and absorption of parallel and divergent stray light[2]. However there are no reliable solution for the absorption of the converging stray light near its focal spot. An absorber design are proposed using multiple materials and small angle light cone. And this design can realize effective absorption of the stray light focal spot with the peak fluence up to 40J/cm2.
On a high power solid laser facility, the wavefront coding (WFC) technology has been adopted to obtain 3m-13m over-long depth of field in an array optical components defect detection system[1]; The lack of the boundary information due to the sudden boundary truncation will cause the ringing effect in the image restoration process. By using the theory of the boundary condition s(BCs), an image enlarged by the different boundary hypothesis can be given; The frequency filtering has been used to find the restored result. The frequency property of the enlarged image and the effect to the boundary of the restored image are analyzed. Effectiveness and speediness of the proposed method are demonstrated by experiment results, which can give excellent deconvolution and noise suppression restored image and reduce the boundary ringing effect under the reflective boundary conditions in a wave-front coding (WFC) system. The experiment shows the proposed algorithm can give satisfactory restoration results on the long depth of field array optical components defect detection system[1] .
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