Polarization hole burning and self-rotation of the polarization ellipse in an acetylene-filled hollow-core photonic crystal fiber

Abstract

We report on the first experimental observation of the polarization ellipse self-rotation (PSR) and the polarization hole burning (PHB) nonlinear optical effects for the acetylene ( C 2 H 2 ) vibrational–rotational transitions in the 1520–1530 nm spectral range. The experiments were performed using a 1-m-long acetylene-filled hollow-core photonic crystal fiber cell at room temperature and gas pressure of 0.4–4 Torr. The PHB effect was experimentally observed as a photo-induced input polarization ellipticity change in the output light. Among all the investigated acetylene transitions P9, P7, P5, and P3, the maximum ellipticity change of ∼ 35 % was observed at zero detuning from the center of the P5 absorption line with the initial optical absorbance about 6. The obtained results are in good agreement with the theoretical predictions of a classical analysis based on the model of the acetylene molecules as gyrators (circular oscillators) with random orientations. For the inhomogeneously broadened acetylene absorption P5 line ( ∼ 500 M H z ), the PSR effect observed for tuning at the sides of the P5 line, as expected, proved to be by factor Δ ω i h / Δ ω h (inhomogeneous-to-homogeneous broadening ratio) lower than the maximum PHB. The PSR constant for these conditions proved to be about 0.1 m − 1 , which is about 2 orders of magnitude lower than that reported earlier for the alkali metal (K, Rb) vapors.