High Reflectivity Measurement Engineering Study

This research paper is aimed at the measurement of high reflectivity of laser mirrors . At present , the most advanced technique in this field is to measure the total loss of a passive resonant cavity . Comparing the total losses of empty cavity with cavity in which the mirror to be measured is consisted ,we can calculate the loss(including transmittance,absorption and scatter)of this mirror .Chapter one gives a simple review of the development of the technique for high reflectivity measurement of optical coatings . As the rapid development of the technique for high reflecting mirrors , the traditional methods for reflectivity measurement cannot fill the urgent needs. The so-called optical cavity decay time method has been proved to be suitable technique for measuring the very low loss of optical coatings now available . It is an extraordinary method for loss measurement , the lower the loss of the cavity , the higher the measurement precision .Chapter two introduces the theory of optical cavity decay time method .In chapter three,the experimental equipment and the principle of electocircuit design are explained in detail .The chief content of chapter four is to suppress mechanical vibration disturbances and electic disturbances. These disturbances have harmful influence on experimental measurements . The chief disturbances are the ripple of direct current power supply to scan PZT,resonant box effect of usual optical table using to weaken the environmental vibration disturbances ,and the effect of air flow . The resonant box effect is the most important . In chapter five,we use the experimental setup constructed and the cavity decay time method to measure the total loss of a passive resonant cavity,and analyse the experimental data in very detail . We conclude that,in present experimental conditions it is the uniformity and stability of laser mirror to confine the precision and repeatability of experimental results . Under steady state of laser mirror loss,the total loss of the cavity to be measured is 773. 78±0.47ppm.We measure higher loss cavities also,the results are 1715. 34±0.61ppm, 2092. 46±1.42ppm .