J. T. Remillard

Narrow nonlinear-optical resonances in CdSSe-doped glass

We describe frequency-domain spectroscopy studies of glasses doped with CdS(1-x)Se(x) using low-power cw tunable dye lasers. The results show a narrow resonance (4.4 kHz at room temperature) in the backward nearly degenerate four-wave mixing spectrum, which we believe is determined by the phonon-mediated inverse lifetime of a deep level trap involved in the nonlinear response.

Optical phase conjugation and nonlinear optical bandpass filter characteristics in CdSSe microcrystallite-doped glass

Experimental measurements of the backward CW four-wave mixing response in semiconductor-doped glass in a regime important to applications are described. In particular, it is shown that lowering the operating temperature to 125 K yields a chi /sup 3/ approximately=2*10/sup -4/ ESU. Aberration correction through optical phase conjugation is demonstrated with a phase conjugate reflectivity of 0.3% along with a wide-angle field-of-view response. In addition, the nearly-degenerate four-wave mixing response of importance to tunable bandpass optical filters is reported. >

High resolution laser spectroscopy of relaxation and the excitation lineshape of excitons in GaAs quantum well structures

Abstract A new class of measurements on GaAs quantum well structures based on frequency domain nonlinear laser spectroscopy is described. Room temperature measurements of the excitation relaxation show an interference effect in the lineshape which is interpreted as a shift in exciton frequency. Low temperature measurements on the localized exciton provide an excitation lineshape which eliminates the effects of inhomogeneous broadening and shows the presence of spectral diffusion.

High-resolution nonlinear laser spectroscopy of room-temperature GaAs quantum-well structures: observation of interference effects

We describe frequency-domain four-wave mixing spectroscopy measurements near the fundamental band edge in room-temperature GaAs multiple quantum wells. The line-shape information gives a measure of the dynamical behavior of the material and what is to our knowledge the first observation of an interference line shape due to a dominant slow contribution to the nonlinear response.

High Resolution Nonlinear Laser Spectroscopy Measurements of Exciton Dynamics in GaAs Quantum Well Structures

The optical properties of GaAs/AlxGa1-xAs multiple quantum well structures are dominated by strong sharp excitonic resonances near the band edge which are observable in both absorption and luminescence spectra1,2. The quasi 2-dimensional excitons are confined in the GaAs layer by the AlxGa1-xAs barriers. The principal properties of the confined exciton include a binding energy which increases with decreasing well width and a blue shift in the exciton transition energy. Indeed the increase in binding energy due to confinement explains the clear observation of these resonances even at room temperature. These materials are grown by molecular beam epitaxy (MBE) methods and are important for application in high speed electronic and opto-electronic devices3. Moreover, the ability to fabricate crystals with dimensions controllable at the atomic level provides an excellent opportunity to study the basic physics giving rise to relaxation of the exciton with reduced dimensionality through the interaction of the exciton with the crystal lattice.

Frequency-domain nonlinear optical studies of relaxation mechanisms and the homogeneous line shape of excitons in GaAs/AlGaAs quantum well structures

Abstract We report high resolution nonlinear laser spectroscopy studies of excitation relaxation associated with the excitonic optical nonlinearity at room temperature and low temperature in GaAs/AlGaAs multiple quantum wells. Using a new method of cw frequency domain four wave mixing, we show that relaxation of the room temperature nonlinear optical response is characterized by free carrier recombination and ambipolar diffusion. At low temperature, the excitation relaxation for localized excitons is dominated by phonon assisted tunneling. In addition, we use four wave mixing methods to eliminate contributions to the excitation line shape from inhomogeneous broadening. The observed line shape is highly asymmetric and shows the presence of spectral diffusion due to the phonon assisted tunneling associated with the excitation relaxation.

High Resolution Nonlinear Laser Spectroscopy of Excitons in GaAs/AlGaAs Multiple Quantum Well Structures

Publisher Summary This chapter describes the high-resolution nonlinear laser spectroscopy of excitons in GaAs/AlGaAs multiple quantum well structures. Frequency domain nonlinear laser spectroscopy is a powerful method for studying resonant optical excitation in solids. It provides a means for obtaining line shapes related purely to the relaxation of optically excited states of the system. In addition, it eliminates contributions from inhomogeneous broadening and enables studies of the homogeneous line shape and the effects of spectral diffusion. The chapter discusses the measurements of excitons in a GaAs/AlGaAs multiple quantum well (MQW). GaAs MQWs are semiconductor heterostructures that are of importance to electronic and optoelectronic devices. They consist of a periodic structure of thin layers of GaAs and A1GaAs. The larger band gap of AlGaAs confines the optical excitation to the thin GaAs, resulting in the quantum confinement of the exciton and an increase in the exciton binding energy.