Micro-Fabry-Pérot Interferometer With High Contrast Based on an In-Fiber Ellipsoidal Cavity

We present a high-contrast extrinsic Fabry-Pérot interferometer (HCEFPI) with an in-fiber ellipsoidal cavity. The ellipsoidal air-microcavity is formed by splicing together a single-mode fiber and a photonic crystal fiber with the simple arc-discharge technique. The propagation loss in the cavity can be very low due to the confocal cavity and very short cavity. Experiments have shown that the HCEFPI has a fringe contrast of ~ 30 dB. Temperature insensitivity, high contrast, and high robustness make it appropriate for high-resolution and long-range sensing without temperature compensation.