All-fiber Fabry-Perot resonators based on microfiber Sagnac loop mirrors.

We demonstrate all fiber Fabry-Perot resonators (F-P resonators) based on Sagnac loop mirrors assembled with tellurite microfibers. As-assembled F-P resonators, with dimensions of hundreds of micrometers, show clear resonant responses with typical quality factor of about 5700, free spectral range of about 1 nm, and a maximum extinction ratio of 18 dB. The reflectivity of the loop mirror and the effective cavity length of the F-P resonator can be tuned by micromanipulation under an optical microscope. F-P resonators demonstrated here show advantages of small size, good resonance, easy fabrication, tunability, and easy integration with fiber systems.