Acetylene frequency references in gas-filled hollow optical fiber and photonic microcells

Gas-filled hollow optical fiber references based on the P(13) transition of the ${\nu }_1+{\nu }_3$ band of ${{}^{12}\mathrm{C}}_2{\mathrm{H}}_2$ promise portability with moderate accuracy and stability. Previous realizations are corrected ($<1\sigma$) by using proper modeling of a shift due to line-shape. To improve portability, a sealed photonic microcell is characterized on the ${{}^{12}\mathrm{C}}_2{\mathrm{H}}_2$ ${\nu }_1+{\nu }_3$ P(23) transition with somewhat reduced accuracy and stability. Effects of the photonic crystal fiber, including surface modes, are explored. Both polarization-maintaining (PM) and non-PM 7-cell photonic bandgap fiber are shown to be unsuitable for kilohertz-level frequency references.