Precision Measurement of the Fresnel Drag Coefficient Using Ring Laser

This thesis was to improve the accuracy of the measurement of the Fresnel drag coefficient in a ring laser gyroscope. Fresnel drag is a change in the speed of light passing through a transparent moving medium. This change in velocity is proportional to the refractive index and velocity of the medium. The ring laser gyroscope used for this experiment was designed to test the performance characteristics of ring laser gyro mirrors. By inserting a transparent moving medium into the laser cavity, with a known index of refraction and accurately controlling its velocity, one can introduce an artificial gyro rotation rate since the output beat frequency of the ring laser gyro will be proportional to the rotation rate of the medium. Improvement in the accuracy of the drag coefficient was necessary to test the performance of these laser gyro mirrors. To accomplish this, the measurement techniques for most of the parameters used to determine the drag coefficient were modified. Higher accuracy, better quality components and equipment were utilized. This resulted in accuracies in the measurements of most of the parameters exceeding or equaling those observed in the two previous experiments. The experimental apparatus were controlled and the data recorded using a computer. This provided simultaneous recording of the outputs and minimized the contribution of human error.