Tunable fiber Fabry-Perot cavities with high passive stability

We present three high finesse tunable monolithic fiber Fabry-Perot cavities (FFPCs) with passive mechanical stability. The mirrors are fixed inside slotted glass ferrules, which guarantee an inherent alignment of the resonators. An attached piezoelectric element enables fast tuning FFPC resonance frequency over entire free-spectral range for two designs. Stable locking cavity is achieved sub-Hertz feedback bandwidths, demonstrating At other limit, bandwidths up to tens kilohertz, close first resonance, can be obtained. root-mean-square fluctuations suppressed down ∼2% linewidth. Over a wide range, noise dominated by thermal limit system’s resonances. demonstrated small footprint devices used advantageously in broad applications like cavity-based sensing techniques, optical filters or quantum light-matter interfaces.