A.R. Bungay

Specular optical-activity in GaAs

We report the first experimental observation of light polarization plane rotation, of approximately 10-3 rad, on normal reflection from a [001] GaAs surface. The rotation is attributed to both surface anisotropy and bulk crystal nonlocality due to violation of time-reversibility, appearing from the importance of the electron spin-orbit interaction.

Time non-invariant linear birefringence and dichroism due to spin—orbit interaction

Evidence of time-nonreversible nonreciprocal linear birefringence and dichroism has been observed in a GaAs crystal in experiments in transmission and reflection. Time-nonreversibility is treated in terms of the quantum theory of nonlocal optical response, revealing the role of the spin-orbit interaction.

Direct measurement of carrier spin relaxation times in opaque solids using the specular inverse Faraday effect

Abstract Using a spectroscopic technique based on the transient specular inverse Faraday effect (SIFE) we found the electron spin relaxation time in bulk GaAs at room temperature to be 11 ± 1 ps. The hole spin dynamics gives a SIFE signal of the opposite sign and may be resolved in the time-domain.

Specular nonlinear anisotropic polarization effect along fourfold crystal symmetry axes

We present what is to our knowledge the first experimental observation of the specular nonlinear anisotropic polarization effect of a pump-induced polarization-plane rotation for normal-incidence reflection from the (001) surface of a cubic crystal. In GaAs, azimuth rotation of the order of 9 × 10−6 rad is seen for a pump intensity of 75 MW/cm−2 at 750 nm, from which the anisotropic component of the cubic nonlinearity |Re(χxxxx − 2χxxyy − χxyyx )| = 5 × 10−9 esu is found.

Specular optical activity and specular gyrotropic linear dichroism in semiconductors

Observations of rotation of the plane of polarisation of linearly polarised light on normal reflection and in transmission for single pass and forward-backward configurations are reported in GaAs. Spectral dependence of the rotation is measured at wavelengths close to the band gap.

Time-resolved specular inverse faraday effect: direct measurement of carrier spin relaxation times and optical nonlinearities in opaque solids

The Specular Inverse Faraday Effect (SIFE) is the nonlinear optical effect of stimulation of a medium with a strong circularly polarized pump wave, resulting in alteration of the polarization state of a liearly polarized probe wave reflected from the medium’s surface (see inset in Fig. 1). This effect has been recently demonstrated but not temporally resolved with picosecond optical pulses in various solids, including semiconductor,’.‘ diluted magnetic semiconductor: and superconducting materials4 There is no obvious limitation (except the laser pulse duration) on the time resolution of the method in the study of transient effects. Here we report on first observation of transient incoherent and coherent SIFE. In incoherent SIFE, the probe polarisation azimuth rotation in reflected light is dependent on the pump-induced difference of absorption coefficients for right and left circularly polarized light. This difference appears because of the transfer of the pump-light pulse momentum to the sample. Incoherent SIFE is directly spin-polarization sensitive. Coherent SIFE is a result of a degenerate four-wave mixing process on cubic nonlinearity in the skin layer of the crystal. It depends on the phase difference between the pump and the probe waves. Observation of the transient coherent and incoherent SIFE was performed with a bulk sample of good substrate quality GaAs crystal at room temperature. The light source used was a mode-locked Ti: sapphire laser pumped by an argon-ion laser. It produced T~ = 2 ps pulses at the wavelength A = 750 nm. GaAs is completely opaque at this wavelength with ... & more.

Specular optical activity in α-HgS

Abstract We report the first positive experimental observation of the optical activity effect on normal reflection. The experiment was performed along the optic axis in a gyrotropic crystal of α-HgS (cinnabar) in a spectral region of strong absorption.