Theoretical and Experimental Investigation of Quantum Noise Induced Sensitivity Limit of a Fast Light Ring Laser Gyroscope

In a Fast-Light Ring Laser Gyroscope (FRLG), the rotation induced shift in the frequency of two counter-propagating lasers is amplified by the inverse of the group index, compared to a conventional ring laser gyroscope (RLG).nbsp; This scale factor enhancement coefficient (SFEC) can be as high as a million.nbsp; If the uncertainty in the laser frequency for an FRLG is the same as that for an RLG for otherwise identical conditions, then the factor of enhancement in measurement precision (FEMP) for an FRLG is the same as the SFEC.nbsp; However, it has been suggested that the frequency uncertainty for an FRLG based on a pair of coupled resonators may be larger than that for an RLG, due to the Petermann factor (PF), thus reducing the FEMP to a value smaller than the SFEC, and possibly to unity.nbsp; Theoretical investigation in Phase I has shown that when such an FRLG is operated far above threshold, it may be possible to achieve a value of FEMP significantly larger than unity. nbsp;We will carry out theoretical as well as experimental work to establish the maximum possible value of the FEMP that can be achieved for such an FRLG, employing intracavity gain in one cavity and intra-cavity loss in another, using Raman transitions in Rb.nbsp; In addition, we will investigate another type of FRLG in which a single ring cavity supports two counter-propagating lasers, without any cross-coupling, also realized using Raman transitions in Rb.nbsp; For each laser in this system, the nature of the eigenvalues indicates that the FEMP would also be limited by the PF.nbsp; However, it is not yet clear whether the PF exists in this case.nbsp; We will explore ways to resolve this issue theoretically, by using the approach of Langevin noise operators.nbsp; If the PF does not exist, it would indicate that for such an FRLG the FEMP can really be as larger as the SFEC.nbsp; If the PF does exist, then we will identify conditions under which the FEMP in this case can also be much larger than unity when operated far above threshold.