Fig. 2: Experimental setup.
A high-finesse Fabry–Pérot fiber cavity is realized by connecting an optical fiber on both ends to fibers with dielectric Bragg mirror stacks (fiber mirror, FM). To attain degenerate polarization modes, a polarization controller (PC2) is placed within the cavity, which is used to cancel any birefringence in the fiber and mirrors. Light is sent into the cavity from a tunable diode laser via an erbium-doped fiber amplifier (EDFA) with an isolator (Iso) to prevent back reflections. A variable attenuator (VA) is then used to control the power of the input light and its polarization is set by polarization controller PC1. The output of the cavity is split by a 50:50 fiber coupler and each branch is directed to photodiodes (PD) via PC3,4 and polarization beam splitters (PBS). These final PCs are used to map the cavity’s polarization states to the PBS such that the PDs each monitor a distinct polarization mode of the resonator.
