Atomic Faraday beam splitter for light generated from pump-degenerate four-wave mixing in a hollow-core photonic crystal fiber

Abstract

We demonstrate an atomic Faraday dichroic beam splitter suitable for spatially separating signal and idler fields from pump degenerate four-wave mixing in an atomic source. By rotating the plane of polarization of one mode ${90}^{\ensuremath{\circ}}$ with respect to the other, a subsequent polarizing beam splitter separates the two frequencies, which differ by only 13.6 GHz, and achieves a suppression of $(\ensuremath{-}26.3\ifmmode\pm\else\textpm\fi{}0.1)$ and $(\ensuremath{-}21.2\ifmmode\pm\else\textpm\fi{}0.1)$ dB in the two outputs, with a corresponding transmission of 97% and 99%, respectively. This technique avoids the necessity of using spatial separation of four-wave mixing modes and thus opens the door for enhancing the process efficiency in waveguide experiments. As a proof of principle, we generate light via four-wave mixing in $^{87}\mathrm{Rb}$ loaded into a hollow-core photonic crystal fiber and interface it with the atomic Faraday dichroic beam splitter.