Coherent spin dynamics of donor bound electrons in GaAs

Abstract

We report experimental studies of coherent spin dynamics of donor-bound electrons in high-purity GaAs by using transient differential transmission. The donor-bound exciton transitions, which are not visible in the linear absorption spectrum, are spectrally resolved in the nonlinear differential transmission spectra. The spin beats in the transient differential transmission response, arising from electron spin precession in an external magnetic field, are investigated with the pump and probe coupling to various donor-bound exciton transitions. The spectral dependence of the spin beats provides important information on the polarization selection rule for the underlying donor-bound exciton transitions. The polarization selection rules deduced from these experiments indicate that contributions from higher-energy donor-bound exciton transitions can severely limit the effectiveness of optical spin control using mechanisms such as polarization-dependent optical Stark shifts.

Analysis of optical differential transmission signals from co-propagating fields in a lambda system medium

“…Notably, for this paper the notion of differential transmission refers to this slow modulation of a susceptibility with continuous-wave lasers, effectively comparing two different steady-state conditions. The modulation timescale is orders of magnitude slower than the intrinsic electronic dynamics of the medium (that can be directly studied in pump-probe experiments with ultrafast pulsed lasers [6][7][8][9], sometimes called transient differential spectroscopy).…”

“…Textbooks on nonlinear spectroscopy qualitatively discuss the benefits of studying crosstalk signals from modulation techniques in saturation spectroscopy [5,10,11]. Generically, the advantages lie in enhancing the visibility of weak transitions, and it was applied in experimental work on quantum wells [8], donor centers in semiconductors [2,9], quantum dots [4,[12][13][14], and other atomic-like systems [15]. However, a detailed analysis of the differential signals is mostly not presented, despite the fact that this is essential for optimal design of these experiments, interpretation of the results, and insight into systematic errors that may occur.…”