| The Fabry-Perot cavity is widely used as a high-resolution spectrometer, a resonant cavity in laser physics, a turning selector in very high-resolution spectroscopy, a basic element in optical bistability, etc. However, it is still difficult to design a broadband multilayer dielectric mirrors with low stress in coating for Fabry-Perot cavity. It is well known that the stress has a great effect on the flatness of the substrate surface, and in some case, it may be so high as to cause a waste of the fabrication of the parallel plate with high precision. Thus it is necessary to take the coating stress into account while considering the optical properties of the coating in the Fabry-Perot cavity.The structure of a Fabry-Perot cavity, which is based on the principle of multi-beam interference, is described. And the effects of the optical properties of reflective films on the finesse fringe, the free spectral range and transmission in the Fabry-Perot cavity are analyzed in this paper. The influence of the coating stress on the performance of a Fabry-Perot cavity is also discussed. Besides, the effect factors and measuring methods of film stress are given in details. By electron-gun evaporation with IAD, TiO2 films and SiO2 films are respectively deposited on K9 and fused silica substrate. We have calculated the optical constants and film stress of them. Results show that when deposited on fused silica substrate, the stresses in TiO2 films are tensile and in SiO2 are compressive. If the broadband multilayer dielectric reflective film uses TiO2 and SiO2 as high and low index material, the stress in it will be improved a lot. Therefore, we present three kinds of layer configuration of TiO2 and SiO2 multilayer on fused silica substrate with a reflectivity of 92.5% ranging from 600nm to 900nm. Meanwhile, a complementary SiO2 antireflection coating just below the flat is used to make the film stress close to zero. |
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