CO2激光对熔石英表面小尺寸损伤的修复

利用10.6 μm的CO2激光对不同直径的点状损伤和不同宽度的划痕进行了修复。经过波长351 nm的紫外激光考核发现，对于直径小于80 μm的点状损伤和对于宽度小于40 μm的划痕，随着损伤点尺寸和划痕宽度的增加，修复后阈值提高程度逐渐降低。划痕的宽度在达到40 μm以后修复效果非常微弱。修复过程中，由于作用时间较短及温度分布不均产生了热应力导致样片损伤以后产生径向裂痕，后续的紫外激光会使裂痕明显扩展。当样品被置于高温退火炉内退火3 h以后，应力导致开裂的现象得到了解决。

Frequencies of intensity fluctuation in linearly chirped Gaussian pulse stacking

Intensity fluctuation in linearly chirped Gaussian pulse stacking(LCGPS) is studied systematically based on spectral analysis. Two-pulse LCGPS and multi-pulse LCGPS are analyzed with simulations based on Fourier transform. The variation of fluctuation frequencies with the number, chirp factor, time delay and pulse width of the Gaussian pulses is discussed in the case of multi-pulse LCGPS with inital pulses of the same amplitude and the same time delay. Finally a brief discussion is presented on the general case of multi-pulse LCGPS with initial pulses of different amplitude attenuation and different time delay. The results show that there are several separated frequency sidebands in the intensity spectrum of the stacked pulse, responsible for the intensity fluctuation. The higher frequency sidebands would have less contribution to the fluctuation due to smaller amplitude overlapping. The fluctuation frequencies increase with the growth of the chirp factor and time delay, and the decrease of pulse width of the initial Gaussian pulses.