Double Refraction in Optically Oriented Spin Systems

Hussein Ghafel AL-Toki, Amin Habbeb AL-Khursan

S Pancharatnam

Transverse birefringence has been observed in an aligned spin assembly consisting of helium 4 atoms in the metastable state 2 3 S 1 . The alignment of the spins was produced by optical pumping with unpolarized light. Using a cross-beam of off-resonant radiation, for example from a helium 3 lamp, together with a suitable combination of polarizer and analyser, birefringence signals could be displayed analogous to the absorption signals conventionally used for the optical monitoring of magnetic resonance. An analysis of the phenomenon is given, showing quite generally that birefringence monitors separately the degree of alignment of the spin assembly, even when orientation is also present; the latter can be monitored by the magnetic rotation of the plane of polarization for axial light. The analysis also includes the effect of the spectral characteristics of the monitoring lamp, i.e. the central frequencies of emission and the Doppler width, on the strengths of absorption and birefringence signals displayed by optically thin samples.

G. Caimi

A. A. Fomin, M. Yu. Petrov, G. G. Kozlov +4 more

Two precessing spins that are parallel (`oriented') or antiparallel (`aligned') modulate the probe light beam at the precession or double-precession frequency, respectively. Stochastic modulation of light by a spin-system at Larmor frequency is the noise of spin orientation detected in conventional spin noise spectroscopy. Polarization modulation of the probe beam at the double Larmor frequency discovered by the authors in experiments with cesium atoms is ascribed to fluctuations of spin alignment. While the spin-orientation noise is revealed as the noise of gyrotropy, the spin-alignment noise is observed in the fluctuations of linear birefringence.

Nikolay N. Bogolubov, Tran Quang, A.S. Shumovsky

K.A. Rodríguez-Magdaleno, J.C. Martı́nez-Orozco, Isaac Rodríguez-Vargas +2 more

Abstract In the framework of the effective mass approximation and using a Thomas–Fermi‐like model for the conduction band potential energy profile, the effects of hydrostatic pressure on the linear and nonlinear intersubband optical response of an asymmetric double ‐doped quantum well are studied. In particular, the intersubband coefficients of light absorption and the relative refractive index change in the system were calculated. It is found that the pressure causes a redshift of the signal response as well as a reduction in the coefficients's amplitudes. We have also found that the asymmetry of the potential profile clearly affects the relative refractive index change because, as long as the system becomes more asymmetric, this physical property becomes diminished.