Christophe Minot

Polarization spectroscopy as a probe of Raman optical activity

Polarization‐sensitive coherent antistokes Raman spectroscopy and the Raman‐induced Kerr effect are considered as possible techniques for investigating Raman optical activity. Generalized nonlinear optical susceptibilities including both magnetic dipole and electric quadrupole interactions are derived semiclassically. These terms can be distinguished from electric dipole terms through their particular symmetry, and several polarization configurations are discussed which seem appropriate to the study of Raman optical activity. These might constitute a convenient alternative to the conventional technique of circular differential Raman scattering for measuring this property.

Microwave miniband NDC in GaInAs/AlInAs superlattices

Abstract The negative differential conductance originating from electron Bragg scattering in miniband transport is demonstrated in a series of five GaInAs/AlInAs superlattices having miniband width from 18 to 81 meV. Sharp resonances or broad-band amplification (0–55 Ghz) are obtained according to the miniband width. Experimental values of the peak velocities deduced from the microwave resonances, and, to some extent, the d.c. values, are satisfactorily compared with semi-classical theory based upon the complete Boltzmann Transport Equation.

Miniband conduction and electron heating in semiconductor superlattices through time-of-flight experiments

We investigate the nonlinear conduction mechanisms of electrons in a semiconductor superlattice miniband. Experimental results obtained from time-of-flight measurements in GaAs/AlAs superlattices are compared with analytical semiclassical approaches. It is shown that the peak velocity can be accounted for when electron heating is assumed to take place. The dynamics of electron transport is also investigated by numerically solving the time-dependent Boltzmann equation including polar optical phonon and interface roughness scattering.

GaInAs/AlInAs superlattice oscillators for optical to mm-wave conversion

Abstract A simple optical to mm-wave conversion device is reported. It is based upon a GaInAs/AlInAs superlattice designed to produce mm-wave generation through the miniband negative conductance. It is driven by a light signal modulated near the oscillator fundamental frequency in order to obtain optical injection locking. The present paper stresses different material and non-linear transport properties necessary to optimise such devices at optical communications wavelengths.

Nonlinear conduction and space charge wave generation in semiconductor superlattices

Negative differential velocity is evidenced in semiconductor superlattices through several experimental approaches: temperature dependence of the current-voltage characteristics, frequency spectrum of the microwave S-parameters, and time-resolved photocurrent induced by a short optical pulse. In particular, new experimental data for GaInAs/AlInAs superlattices matched to InP are analyzed owing to classical models. They yield the miniband width dependence of the mobility, critical field and peak velocity which describe the electron velocity laws. The latter are in fair agreement with a semiclassical model based on numerical solutions of the Boltzmann equation, i.e., a rigorous extension of the simpler Esaki-Tsu model of miniband conduction. In the dynamical experiments, the temporal evolution of the electron distribution in the superlattice structure is represented in terms of propagating space charge waves, which can give rise to amplification and oscillation. Consequences of miniband conduction regarding maximum frequency and noise of superlattice-based oscillators are also examined.

Bursts of high-frequency oscillations induced by picosecond optical pulses in GaAs/AlAs superlattices

Negative differential velocity in nonintentionally doped GaAs/A1As superlattices has been evidenced by an optoelectronic picosecond time-of-flight experiment in the temperature range from 10 K up to 300 K. In the same structures bursts of high frequency oscillations up to 61 GHz are optically induced in the same temperature range. Experimental records are correctly reproduced by numerical simulations in the classical drift- diffusion approximation. A particular design of the superlattice structure gives high yield of mm-wave/optical excitation conversion.