Measurement Of High Reflectivity Distribution For Spherical Laser Components Based On Optical Feedback Cavity Ring-down Technique

As an important branch of optical components,spherical laser components usually have a reflectivity of more than 99.9 %,and are widely used in optical systems such as laser gyroscopes,laser resonators,and ultra-precision optical manufacturing technologies.Reflectivity is one of the key factors that determine the performance and quality of a laser system.Compared with planar components,the defects and uneven reflectivity of spherical laser components which caused by the complex fabrication process will seriously affect the operation of the entire optical system.There is no complete system in the existing optical measurement technology that can detect highreflection spherical laser components quickly and accurately,and the cavity ring-down technology is the only method that can accurately detect high reflectivity.It is of the advantages of high measurement accuracy,low installation cost,simple operation,and can not be affected by light intensity fluctuations.Therefore,whether it is to ensure measurement accuracy or improve detection speed,developing the cavity ring-down technology for spherical high reflectivity distribution measurement which meet the current growing demand for detecting of the spherical laser components is very necessary.In this experiment,starting from the theory of optical cavity ring-down technology,a reflectivity measurement system is built to study the reflectivity distribution of spherical components with various specifications.Specifically include the following:(1)A variety of traditional optical components reflectivity measurement methods are introduced,and the technical background and research status about the reflectivity measurement technology of spherical components and cavity ring-down technology are systematically investigated.After comparing the advantages and applicable background of four cavity ring-down methods,the optical feedback cavity ring-down technique is chosen as the experimental method to measure the reflectivity distribution of spherical laser components.(2)Based on the basic theory of time decay,the reflectivity measurement principle of the optical feedback cavity ring-down technology was deeply understood,and the Gaussian beam ring-down cavity model was established according to the standard ABCD transmission matrix of the optical resonator,and the stability conditions of spherical components test ring-down cavity was derived.The effects of cavity length misalignment,mirror tilt and detector parameters on the reflectivity measurement of spherical components are summarized.(3)For plano-concave spherical components with different curvature radius and surface types,under the guidance of stability conditions,a folded test ring-down cavity with different cavity length was constructed.After comparing and analyzing the three methods for determining the vertex of spherical mirror,the scanning experiment research on reflectivity of spherical components was carried out.The reflectance uniformity measurements of spherical components with different curvature radius under automatic scanning measurement and manual single-point measurement are obtained.Moreover,the optimization experiments of cavity length and threshold were carried out.By comparing the scanning value and the single-point value,the relationship between the effective scanning range of reflectance and its curvature radius under a certain precision is summarized,According to this,a splicing method is proposed,which is used to detect the reflectance distribution of large-aperture spherical components.