Laser-induced polarization anisotropy in In three-level system

Birger Stahlberg, Peter Jungner, Tomas Fellman +2 more

A. Le Floch, Roger Le Naour, Guy Michel Stéphan

Christian Delsart, J. Keller

We have observed the Doppler-free dichroism and birefringence induced by a linearly polarized laser beam (pump beam) by monitoring the polarization and amplitude changes of a weak probe beam through an analyzer. The effects have been observed in two-level systems and also in three-level systems of Ne I. At rather low pump power, a typical refractive-index anisotropy of 10−8 has been measured. We have shown that, when the normal resonance curve exhibits a broad background due to collisions, our method allows the elimination of this background. In addition, using a rotating analyzer, we have obtained simultaneously the dichroism and birefringence curves, i.e., the imaginary and real part of the anisotropic-induced susceptibility.

Shuangqiang Liu, Yundong Zhang

We describe the effects of incoherent pump on an atomic filter based on laser-induced optical anisotropy in a three-level ladder system interacting with a strong pump polarized circularly and a weak probe polarized linearly. According to the analysis of the numerical simulation results with some comparison, at the same time of eliminating noise, the filter can enhance the probe's transmission or even the probe gain can be achieved without population inversion. Moreover, the incoherent pumping rate and the cell temperature performance are evaluated and measures are taken to improve the filter's transmission and tunability by selecting proper parameters.

Sukesh Roy, Robert P. Lucht, James R. Gord

The effects of laser-induced anisotropy on the generation of the short-pulse laser-induced polarization spectroscopy (LIPS) signal is investigated by direct numerical integration (DNI) of the time-dependent density matrix equations. The calculations are performed in the short-pulse regime (laser pulse width τL less than characteristic collision time τC) to reduce the influence of collisions on the generation of medium anisotropies. The Zeeman-state structure of the upper and lower energy levels is included in the multistate formulation of the density matrix equations. For a P-branch transition when the isotropic ground-level population is pumped by a circularly polarized light, oriented anisotropy is mainly responsible for the LIPS signal generation; whereas, when the resonance is pumped by a linearly polarized light, aligned anisotropy is mainly responsible. For a Q-branch transition that is pumped by a circularly polarized light, the contributions to the LIPS signal from orientation and alignment are comparable. The effects of saturation on the induced anisotropy is also investigated. The magnitude of the LIPS signal increases by more than a factor of 14 for an initial right circularly polarized-oriented anisotropic distribution in the ground Zeeman states as opposed to an isotropic distribution. An understanding of the effects of anisotropy on the LIPS signal will aid the modeling of the LIPS signal-generation processes and the interpretation of experimental LIPS signals.

J.R. Bupp, C. V. Heer