Coupled resonator gyroscopes: what works and what does not

This paper reviews a number of optical gyroscope architectures utilizing either slow or fast light that have been recently proposed in the literature to enhance rotation sensitivity, with a view to separate the schemes that offer a genuine enhancement from the ones that do not. The overall conclusion is that although slow-light coupled-resonator systems have interesting applications in other fields, for example for filtering or switching, none of the schemes proposed to date enable any enhancement in rotation sensitivity. Simple guidelines are outlined in an attempt to help clear misconceptions and hopefully reduce the number of erroneous publications on this subject in the future. On the other hand, fast light in a ring laser gyro can potentially enhance rotation sensitivity by up to six orders of magnitude. Future research directions likely to be fruitful are also outlined.