The effect of laser beam size on laser-induced damage performance

Abstract

The influence of laser beam size on laser-induced damage performance, especially damage probability and the laser-induced damage threshold (LIDT), is investigated. It is found that damage probability is dependent on beam size when various damage precursors with different potential behaviors are involved. This causes the damage probability and the LIDT to be different between cases under a large-aperture beam and a small-aperture beam. Moreover, the fluence fluctuation of the large-aperture laser beam brings out hot spots, which move randomly across the beam from shot to shot. Thus this leads the most probable maximum fluence after many shots at any location on the optical component to be several times the average beam fluence. These two effects result in the difference in the damage performance of the optical component between the cases under a large-aperture and small-aperture laser.

Investigation of stimulated rotational Raman scattering of the high-power broadband laser with applied angular dispersion

“…From the threshold distances relation z tha2 > z tha1 and z thb2 > z thb1 , we can deduce that PPM can suppress the SRRS process, and the suppression effect is hardly affected by the distribution of the laser additional phase, and we think that the characteristic phase restoration length [19] of PPM pulse is longer than that of NLW pulse, which is the root cause of the suppression effect. However, reference [10] indicated that PPM could hardly suppress the SRRS process, which could be caused by the complicated intensity and phase distribution of the laser (such as hotspots [10,20] ). The influence of SAD on SRRS gain is affected by the laser additional phase because z tha3 < z tha2 while z thb3 > z thb2 : the SAD will aggravate the production of SRRS when the laser initial additional phase is constant; on the contrary, the SAD can reduce the SRRS gain if appropriate SSD parameters are adopted, when the laser initial additional phase is variable.…”

The influence of smoothing by spectral dispersion on the beam characteristics in the near field

“…When implementing SSD on a laser system, the laser peak intensity should be limited while the laser fluence uniformity should be improved; [5] otherwise, many unwanted nonlinear optical effects such as self-focusing and stimulated light scattering will occur, which lead to laser energy losses and even optical element damage. [19][20][21][22][23][24][25][26][27][28][29] Therefore, it is necessary to study how the SSD affects the laser intensity and fluence in the near field for the application of SSD and the design of laser systems. Modulation degree is one of key parameters describing the characteristics of a laser beam in the near field.…”

ATR-FTIR spectroscopic studies on density changes of fused silica induced by localized CO 2 laser treatment

“…One of the major concerns encountered for these high-cost fused silica optics is laserinduced surface damage under the exposure of high-fluence UV laser. [1][2][3][4][5][6] For the high-power UV laser facilities, such as the National Ignition Facility (NIF) in USA, [7] the Laser Mega Joule in France, [8] and the SGIII laser facility in China, [9,10] the routine operation is above the damage growth threshold of fused silica optics. Once the surface damages are initiated under the high-fluence UV laser irradiation, they will grow exponentially with subsequent laser shots, and will result in excessive light scattering and beam modulation, and they will finally lead to a shortening of the lifetime of fused silica optics.…”