Contaminant-Free End-Capped And Single-Mode Acetylene Photonic Microcell For Sub-Doppler Spectroscopy

We report on the development of an acetylene-filled photonic microcell based on an assembly process that is contaminant free and requires no helium buffer gas nor gluing procedure. The microcell consists of a 7-m-long and. 30 mu m core-diameter inhibited-coupling guiding hollow-core photonic crystal fiber filled with acetylene gas at a pressure in the range of 80 mu bar, sealed by capping its ends with fusion-collapsing a glass-tube sleeve, and mounted on FC connectors for integration. The microcell shows a robust single-mode behavior and a total insertion loss of similar to 1.5 dB. The spectroscopic merit of the formed microcell is tested by generating electromagnetic induced transparency and saturated absorption on R13 and P9 absorption lines, respectively. The sub-Doppler transparencies show a close to transit time limited linewidth of 17 +/- 3 MHz. The latter was monitored for over 3 months. As a demonstration, the microcell was used to frequency stabilize a laser with fractional frequency instability improvement by a factor 50 at 100 s integration time compared to free running laser operation. (C) 2021 Optical Society of America