Laser-induced birefringence in a wavelength-mismatched cascade system of inhomogeneously broadened Yb atoms

Abstract

We report the observation of laser-induced birefringence (LIB) in a wavelength-mismatched cascade system ($J=0\ensuremath{\leftrightarrow}J=1\ensuremath{\leftrightarrow}J=0$ transitions) of inhomogeneously broadened ytterbium atoms with strong pump and probe fields. We investigate the transmission spectrum of two circular polarization (${\ensuremath{\sigma}}_{p}^{+}$ and ${\ensuremath{\sigma}}_{p}^{\ensuremath{-}}$) components of strong probe field at fixed frequency, depending on the detuning of a circularly polarized $({\ensuremath{\sigma}}_{c}^{\ensuremath{-}})$ coupling field from two-photon resonance. We find that the ${\ensuremath{\sigma}}_{p}^{+}$ $({\ensuremath{\sigma}}_{p}^{\ensuremath{-}})$ polarized component exhibits a narrow electromagnetically induced absorption (transparency) spectrum. Numerical solutions of density matrix equations show qualitative agreement with experimental results. A Doppler-free dispersive LIB signal is obtained by detecting the Stokes parameter of the probe field, enabling us to stabilize the frequency of the coupling laser without frequency modulation.