Enhanced-sensitivity interferometry with phase-sensitive unbiased multiports

Here we introduce interferometric devices by combining optical feedback (cavities) with unbiased multiports, which, unlike traditional beam dividers, allow light to reflect back out of the port from which it originated. By replacing the traditional, directionally biased beam-splitter in a Michelson interferometer with an unbiased mul-tiport, the functional dependence of the scattering amplitudes changes. As a result, the derivative of transmittance with respect to an external phase perturbation can be made substantially large. This significantly enhances the resolution of phase measurement and allows the phase response curves to be altered in real time by tuning an externally controllable phase shift.

Automated summary

This article introduces interferometric devices that combine optical feedback (cavities) with unbiased multiports, which allows light to reflect back from the port it originated. By replacing the traditional, directionally biased beam-splitter in a Michelson interferometer with an unbiased multiport, the functional dependence of scattering amplitudes changes. This greatly enhances the resolution of phase measurement and allows real-time alteration of phase response curves by tuning an externally controllable phase shift.