Research On Measuring Technology Of Low-loss Optical Components Scattering Properties

The measurement of scattering parameters of low-loss optical components and optical thin film surface is important to obtain the information of surface micro-geometry, evaluate the quality of micro-optical surface, improve the quality of optical thin films and the thin-film deposition process. So the optical system for measuring scattering ratio of the low-loss optical components is studied in the article.After the methods of the scattering measurements are studied thoroughly in the thesis, the design of measuring system is proposed. Scattered light is collected by the integrating sphere. The acquisition and analyses of the weak signals with strong noise is realized by using the correlation detection technology. The hardware consists of optical module, sample manipulation module and signal acquisition module. Optical module realizes the modulation of light source, the choice of polarization state, the control of the light energy, laser beam shaping and the elimination of stray light. The design of sample operation control realizes the requirements which the sample can be easy to place with the non-destructive surface. The signal acquisition control module realizes the extraction of the weak optical signal in the strong noise. The software calls each functional module and achieves intelligent measurement. The design of the software system is based on Lab VIEW, which consists of five modules as follows, user login module, base light test module, integral scattering test module, backscattering test module and the report generation module. The optical measurement system with good function is developed through hardware and software system integration. Furthermore, the measurement results are analyzed in detail for finding the cause of the error. The system, with the adjustable light energy, polarization, realizes the automated measurement of the integral scattering ratio,the backscattering rate and other parameters of the low loss samples (such as high reflection mirror)with high SNR and high dynamic range in the same instrument. The system measures the integral scattering and backscattering of sample,the dynamic range of scattering ratio can reach 10～10000ppm,the repeated errors for 10-100ppm are±2ppm；100～1000ppm are±5ppm；1000～10000ppm are±10ppm.