Laser Gyroscope

Abstract

In this work we studied the lock-in phenomena in the fiber based ring laser gy-roscope F-RLG. A numerical model based on the use of the laser amplitude and phase rate equations is developed. The results of this model are compared to the theoretical and experimental expectations of the system and a good agreement is observed. A se-tup is built in the lab to demonstrate the functionality of the system. To overcome the lock in problem in the system, a solution based on the use of MEMS phase modulator is suggested. The Phase modulator is designed and fabricated using the DRIE tech-nology in a clean room facility in France and the fabricated structure is then tested in the lab. Both phase and frequency modulations of the laser system are demonstrated in the lab successfully. However, due to the additional loss introduced by the phase modulator when inserted in the system, we could not demonstrate the lock-in removal using it. The solution suggested to overcome this point is the use of a coated lensed fiber at the terminal connection with the phase modulator. This solution is expected to reduce greatly the diffraction and Fresnel loss in the modulator and hence improve the system performance. Another problem encountered in building the system is the multimode nature of oscillation in the very long cavity formed by the fiber. To overcome this problem a solution based on the gain starving in the laser system is suggested and demonstrated experimentally with a good success. For the continuity of the work presented in the thesis we believe that there are mainly two points of interest: the first is the practical implantation of the phase mod-ulator system using lensed fiber with anti-refection AR coating to improve its perfor-mance. We believe that this may greatly enhance the system performance. The second direction is related to the engineering of the gain starving technique to better control the single mode operation of the ring laser of long cavity fiber. This requires better understanding to the mode competition mechanism in the fiber system and can lead also to a system improvement in many directions.