Theoretical analysis on the rotation-induced frequency difference in ring lasers with coupled cavities

Abstract

We analyzed the effective scale factor of ring laser gyros with coupled cavities in a general way. The coupled cavities can be made of both an odd and even number of mirrors, or even fiber coil. Compared with the "zero-vector-area" design in previous publications, we use the propagation loss rather than transmittance and reflectivity of mirrors to characterize the coupled cavities, which are more universal and controllable. In addition, we found the area of the coupled cavities could further enhance the effective scale factor by 1+l/L, where l and L are the round-trip length of the ring lasers and the coupled cavity, respectively. Therefore, the scheme using coupled cavities to enhance the sensitivity is more practical. These findings are important to realize highly sensitive ring laser gyros.

Theoretical analyses of resonant frequency shift in anomalous dispersion enhanced resonant optical gyroscopes

“…The resonant frequency difference between clockwise (CW) and counterclockwise (CCW) directions can be measured accurately by optical heterodyne technique like in the cases of Ring Laser Gyroscopes (RLGs), which are active resonant optical gyroscopes. In recent years, there has been interest in the development of resonant optical gyroscopes with novel materials234, structures56789101112 and physical effects13141516171819, among which the utilization of fast light for sensitivity enhancement is a potential technique1516171819. Actually, it is the strongly anomalous dispersion that amplifies the Sagnac RFS as well as allows superluminal light propagation.…”

“…There are two schemes to generate anomalous dispersion in ROGs, i.e. coupled-resonator structures151617 and steep negative dispersion materials1819.…”

“…In the superluminal helium–neon RLGs151617, the amplification of RFS is achieved by replacing one mirror in the traditional ring laser cavity with auxiliary passive cavities, where a theoretical rotation sensitivity enhancement of about two orders of magnitude is demonstrated15. The performance of such gyros can be regulated by changing the mirrors’ properties in these coupled cavities16 or the round-trip length of the ring lasers and the coupled cavities17.…”

“…The performance of such gyros can be regulated by changing the mirrors’ properties in these coupled cavities16 or the round-trip length of the ring lasers and the coupled cavities17. However, the sensitivity of enhancement factor to rotation or equivalent frequency detuning requires real time control of complex reflection coefficient of the mirrors, which is hard to achieve in assembled devices.…”

“…Obviously, the RFS will be amplified with the group velocity be faster than the speed of light in vacuum if n g is less than 1. This is the reason that such amplification is connected with fast light1516171819. Nevertheless, the modification factor is not accurate as some approximations are made in their derivations, which lead to some inappropriate conclusions.…”