| Laser parameter measurement system is an important part of high power laser device.It monitors and measures the laser parameters of key positions,and provides reliable measurement data for the stable operation of high power laser device.In the system of laser parameters measurement,the sampling technique which keeps high precision and low distortion is very crucial,and the measurement accuracy of laser parameters can be guaranteed by keeping the traceability of the sampling beam in the process of sampling.Laser parameters measurement puts forward technical requirements to sampling process,which equals to puts forward the corresponding technical index to the optical thin film which is used to sampling.The measurement accuracy of the laser pulse energy,laser focal spot shape of far field,laser collimating optics and la ser parameters comprehensive diagnostic are affected by the optical properties of optical thin films which including sampling rate stability,polarization and wavelength color separation stability.The measurement accuracy of laser near field and far field focal spot are influenced by the surface quality of optical thin film components used to sampling.In this paper,the optical properties of optical thin film will be analyzed and the influence of optical elements on the laser intensity distribution will be studied.1.A large number of optical thin film components used in the laser parameter measurement system of the SG3 host device are used as the sample and the data of P and S polarized light transmittance of antireflection coating,high a nti membrane and beam splitter which come from sample in different incident angles were counted.The various optical thin film transmittance parameters were analyzed in detail and the optical properties of the different films were summed up.Considering the requirement of laser parameter measurement for the optical thin film,the tolerance of different films in practical work is obtained under the existing process conditions.The results show that: the consistency error of sampling rate of antireflection coating,high ant i membrane is less than 0.3% when they used in the conditions of the incident angle is smaller than 40? and the transmittance or reflectance is greater than 99%;Beam splitter consistency error of sampling rate is less than 0.6%,when they used in the case of the incident angle is smaller than 10? and the sampling rate is greater than 10%;When the beam splitter of three wavelength is used in case of the incident angle is less than 35?,its absolute error of transmittance or reflectance can be controlled within 1%.This study provides a basic theoretical reference for the design and fabrication of optical thin films used in laser parameter measurement system.2.The influence law of “defect”of theoptical films surface on the light intensity distribution of the sample beam is studied.Based on the Fresnel diffraction theory and the evaluation function of near field uniformity,numerical simulation is carried out by using the physical model and mathematical model of amplitude modulation type “defects” and phase modulation type “defects”on optical element surface in Matlab,the influences of different typessurface “defects” on the intensity distribution of near field of sampling beam were analyzed and summarized.The result show that the size,modulation and number of the defects on the surface of the optical element affect the intensity distribution of the bea m significantly.The size is larger,the number is more and the modulation of defects system is greater,the more marked such effect of beam intensity dstribution.The mod ulation effect of the "defect" on the beam can be neglected when the "defect" shading area ratio is less than 41 10-?,the transmission distance is larger than 1m.This research provides the basis for the laser parameter measurement of optical path design and the processing of optical elements in the system. |
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