UV laser damage is still the key issue of high power nanosecond laser systems. The operation performance of the final optics in SGII-UP facility is first reviewed. Based on a high power laser prototype, laser-induced damage of large aperture final optics at 351nm was experimentally studied, including damage initiation, growth and morphologies. The near filed of 351nm laser beam was precisely measured with a high resolution by using the precision diagnostics system (PDS) to study the effects of laser modulation and propagation on laser damage. The damage behaviors were comprehensively analyzed and the main contributors to laser damage were discussed. The development perspective of final optics system for high power laser system is briefly introduced.
In high power laser system, the upstream flaw could induce light intensification in the downstream, thus damaging the optical component. In most of the research, the shape of the defect model is ideal, for example, Gaussian shape. However, the defect in the real system is non-ideal with different shapes. In this paper, the light intensification effect caused by defects with different shapes are compared by numerical simulation. Results show the shape dependence of downstream light intensification caused by flaws. When only the linear effect is considered, the change of defect shape could change the maximum light intensification factor and the downstream location for the maximum intensity. When the nonlinear effect is also considered, the light intensification effect will be more sensitive to the shape of defects. This research can provide some reference for the beam quality control and defect management in the high power laser systems.
The latest progress on high power laser facilities in NLHPLP was reported. Based on a high power laser prototype, damage behavior of 3ω optics was experimentally tested, and the key influencing factors contributed to laser-induced damage in optics were deeply analyzed. The latest experimental results of advanced precision measurement for optical quality applied in the high power laser facility were introduced. At last, based on the accumulated works of 3ω elements damage behavior status in our laboratory, beam expanding scheme was presented to increase the total maximum output 3ω energy properly and decrease the laser induced damage risking of ω optics simultaneously.
Laser damage performance of large aperture optical components has been study under fourth harmonic of 1053nm Nd:glass laser irradiation (263nm).The threshold of optical components is very low under 263nm laser irradiation ,due to conversion of beam to higher energy photons of the quadrupled frequency (4ω), and is relative to material characteristic. A preliminary test of laser induced damage in fused silica (SiO<sub>2</sub>) and CaF<sub>2</sub>under 263nm laser is reported in this article. Thresholds of these two materials are obtained. Laser damage threshold of SiO<sub>2</sub> is found about 2 J/cm<sup>2</sup> by 1-on-1 method using pulsed 263nm laser, lower than CaF<sub>2</sub> whose threshold.
Proc. SPIE. 9142, Selected Papers from Conferences of the Photoelectronic Technology Committee of the Chinese Society of Astronautics: Optical Imaging, Remote Sensing, and Laser-Matter Interaction 2013
KEYWORDS: Signal to noise ratio, Superposition, Photodetectors, Prisms, Sensors, Silicon, Interference (communication), Data acquisition, Environmental sensing, Temperature metrology
To accurately measure the linearity of photodetectors in near-infrared waveband, based on the beam superposition method, a new design idea which use the tow-beam path and correlation methods was proposed. Using the 1053nm laser, and the Si photodetector as the experimental subject, a linearity measurement system of highly accurate photodetectors was designed. This system has over seven orders of magnitude dynamic range. The joint uncertainty is superior to 0.08%. Meanwhile, the linear factor of four different conditions which include the different size of incident beam spots, incident angles, positions and the environment temperature have been measured and analyzed. The experiment shows that the linearity of Si photodetector is ideal when the size of beam spots are bigger, the incident angles are smaller and the environment temperature is lower, moreover, the linearity of margin area is unsatisfactory.
Transverse stimulated Raman scattering (TSRS) gain coefficient of a KDP sample is measured by improved methods.
The improvements include color separation of TSRS, noise light management and acquisition of valid TSRS temporal
pulse. After extracting TSRS temporal pulse and data analysis, we obtained a TSRS gain coefficient of
0.28±0.03cm/GW for the KDP sample. Our improvements of measurement method include the following three aspects:
First, the separation of TSRS irradiation (362.2nm) from Rayleigh irradiation (351.15nm) is realized by first-order
diffraction of grating for TSRS and Rayleigh. Second, to improve the ratio of TSRS signal and noise light owing to
spurious reflection of pump radiation, we remove noise light by using band-pass filter and absorption traps. Third, by
analyzing the time delay between pump signal and noise signal, we demonstrates the valid TSRS temporal pulse can be
extracted from the noise signal and used to calculate the TSRS gain coefficient of KDP.