Laser induced birefringence in a wavelength-mismatched cascade system of   inhomogeneously broadened Yb atoms
  We report the observation of laser induced birefringence (LIB) in a wavelength-mismatched cascade system (J=0 \leftrightarrow J=1 \leftrightarrow J=0 transitions) of inhomogeneously broadened ytterbium atoms with strong pump and probe fields. We investigate the transmission spectrum of two circular polarization (\sigma_p^+ and \sigma_p^-) components of strong probe field at fixed frequency, depending on the detuning of circularly polarized (\sigma_c^-) coupling field from two-photon resonance. We find that \sigma_p^+ (\sigma_p^-) 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 coupling laser without frequency modulation. 
Tai Hyun Yoon, Chang Yong Park, and Sung Jong Park