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K9 glass is an important optical element of the high energy laser system. In an attempt to investigate the variation of optical properties of K9 glass before and after laser induced damage, based on the transmission terahertz time-domain spectral system, the undamaged and the damaged K9 glasses induced by laser were tested to obtain the terahertz time-domain and frequency-domain spectra and the refractive index and absorption coefficient of the samples were calculated in terahertz band for further analysis. Results show that with the increase of laser energy, from the undamaged to the damaged K9 glasses to different extent, the peak to peak value in time domain and the amplitude value in frequency domain present a decreasing trend in varying degrees, and in the 0.4 ∼ 0.5 THz band, the absorption coefficient increases continuously with a slight change of refractive index, which indicates that K9 glass not only appears the melting and fracture in the macroscopic morphology after laser-induced damage, but also forms non-bridged oxygen atoms in its microstructure with more ion bonds and free electrons and the change of ion polarization. In this regard, this paper provides a technical basis for exploring the micro characteristics of K9 glass after laser-induced damage, and lays a good foundation for the application of terahertz time-domain spectroscopy to laser-induced damage analysis.

This letter reports the temperature-dependence of high-gain operation in semi-insulating GaAs photoconductive semiconductor switches at 1.6 $\mu \text{J}$ laser diode excitation. Under the excitation of two different spot patterns, the electric field threshold for high-gain operation is investigated by varying the temperature. In addition, the switching characteristics dependence on temperature are also studied under the perpendicular spot excitation.

The correct monitoring of thin-film thickness is one of the main problems during the course of optical thin-film component manufacture, in recent years, the method which is spectrum intensity measurement of thin-film component for controlling thin-film thickness has been one of the most effective methods. When this method is used Chow spectrum intensity is real-time, correctly measured is critical. Compared with the conventional method which is mechanical scanning by stepper motor driving the grating of monochromator and receiving by photoelectrical multiplier tube, in structure, the author combines the grating spectrometer with the linear CCD, which makes the problem of spectrum intensity real-time measurement better solved, the result is satisfied. In this paper, the structure of system affecting the spectrum intensity measurement accuracy is analyzed, By experiment, the relative parameters are determined, the spectrum wavelength is calibrated, root-mean-square error is 0.234nm, which is up to the requirement of monitoring wavelength resolution in the course of thin-film deposition; The algorithm is used for the real-time compensation of spectrum intensity measurement data, which make the effect of CCD photoelectrical response non-uniformity and nonlinear less; By changing the integral time magnitude, the rate of signal to noise of the spectrum signal is improved, it satisfies the requirement of real-time thin film thickness control.