Study On Optical Pattern Matching Of The Resonator Loss Measurement System

The optical resonator is one part of the laser. The characteristics of the laser beam can be changed by designing reasonably of the resonator structure. Low loss is one of the evaluation standards for resonator structure design, and meanwhile the loss of the resonator is related with the light mode. Thus, in this work the loss of the resonator was obtained through the analysis of the optical field of the resonator, in order to provide a basic theory for improving the structure of resonator.Based on the measurement system for the resonator loss, the external the optical path and inner optical path spot matching, and optical mode distribution of resonator are studied in this paper. In the spot matching, the astigmatic problem caused by the different curvature radius and different locations of spherical mirror is analyzed, which provides the way to eliminate astigmatic; For the study of the pattern of resonator, firstly the straight-type resonator is analyzed in the paper, and the three-dimensional of distribution map of mode in the resonator is obtained using MATLAB software, and spot radius value, phase shift value, loss value and mode numbers are calculated. By changing the structure of the resonant cavity, the influence of the cavity length, the size of the spherical mirror and curvature radius to mode are analyzed, the research shows that the resonator mode distribution is affected by the three factors, but the influence of the cavity length and the size of the spherical mirror is more significant; Based on the above, the straight-type resonator with aperture is analyzed in the paper. By changing the aperture size and locations, loss value, spot radius and mode number are affected in the resonator, and compared with the straight-type resonator, the result shows that the higher-order modes are inhibited by adding aperture, and mode numbers were reduced in the resonator;Secondly, the equivalent method is used to make the ring cavity structure equivalent to the straight cavity structure, to study the ring cavity mode. Finally, a complete program is designed using the Matlab software, and the design of interface program makes the operation and the simulation results intuitive and convenient.The research results show that the astigmatic caused by the optical components is reduced by selecting appropriate spherical mirror and locations of spherical mirror; in order to make the modes less, the higher-order mode can be inhibited by joining the aperture; For the comparatively complex structure of ring cavity mode, equivalent method can be used in the research.