P. Roussignol

Surface-mediated enhancement of optical phase conjugation in metal colloids

We show that the optical phase-conjugated reflectivity from silver and gold colloids is enhanced by several orders of magnitude. The reflectivity on resonance is comparable with that of CS(2) for metal-particle volume concentration of a few parts in 10(6). We trace this enhancement to the nonlinearities of the electrons in the metal particles and extract the value of their optical Kerr-effect coefficient.

Optical phase conjugation in semiconductor-doped glasses

Abstract We have studied optical phase conjugation in two types of semiconductor-doped glasses. Corning 3.68 and Schott OG 530 at λ = 0.532 μm using picosecond pulses. We observe a slow nonlinearity in agreement with the slow decay of luminescence. The saturation of the reflectivity is strongly correlated with the absorption saturation of these glasses and may be interpreted in terms of a three-level system model.

V Nonlinear Optics in Composite Materials: 1. Semiconductor and Metal Crystallites in Dielectrics: 1. Semiconductor and Metal Crystallites in Dielectrics

Publisher Summary This chapter discusses the nonlinear optics in composite materials. The chapter presents the different experimental and theoretical results relating to nonlinear optical properties of these materials. The preparation techniques of these materials, and the linear and nonlinear optical characterization techniques are discussed. The chapter outlines electronic motion and its coupling. The nonlinear optical properties of metal-doped glasses and colloids, and the semiconductor-doped glasses and colloids are discussed. The effects of quantum and dielectric confinements are quantum-mechanical and classical, respectively. The several drawbacks of the composite materials still compare favorably with the homogeneous nonlinear materials organics or inorganics. In addition, they show properties that are not shared by the homogeneous materials, such as robustness, adaptability, thermal resistance, and many others, and most importantly, their properties can be artificially tailored through the confinement effects to meet many demands.

Nonlinear optical properties of commercial semiconductor-doped glasses

We report new observations made on semiconductor-doped glasses commercially available. We have observed that the modulus of the Kerr susceptibility is proportional to the absorption coefficient below, across and above the gap. We have measured the phase of this susceptibility for various values of the excess energy. We have also observed a blue shift of the absorption edge following pulsed excitation and have measured the diameter of the crystallites to be ∼ 70–80 Å. The band-filling model is the most appropriate to account for the nonlinear properties of these glasses.

Quantum confinement mediated enhancement of optical kerr effect in CdS x Se1−x semiconductor microcrystallites

We first discuss theoretically the enhancement of the optical nonlinearity due to quantum confinement in semiconductor-doped glasses. This quantum confinement mediated enhancement also pertains to the figure of merit x(3)/α, in which case it is due to a decrease in the spectral width rather than in an increase of the matrix elements. We then report on frequency and size-dependent measurements which confirm the theoretically expected enhancement due to quantum confinement.

Measuring the phase of slow kerr-type nonlinearities: The role of phase modulation

Abstract We show theoretically and verify experimentally how the phase modulation of the laser pulse affects the phase of the various contributions to the nonlinear polarization in the optical phase conjugation geometry. This provides an explanation for the apparent sum rule violation observed by Jain and Lind in semiconductor-doped glasses. It also allows to define the conditions which must be fulfilled when one wants to measure the phase of a slow Kerr-type nonlinearity.

Nonlinear optical properties of commercial and experimental semiconductor-doped glasses

The nonlinear optical properties, more specifically the Kerr nonlinearity, of commercial semiconductor-doped glasses have been extensively studied. The nonlinear mechanism is mainly bulk-like since no sizeable quantum confinement effect was observed in these glasses. Quantum confinement is however clearly exhibited by experimental glasses containing smaller particles. For CdSSe, phonon broadening is observed to play an important role.

Quantum Size Effects and Photocarrier Dynamics in the Optical Nonlinearities of Semiconductor Microcrystallites

In semiconductor crystals, the electrons are delocalized over several unit cells. As a consequence many details of the interactions they are subject to are averaged out and their behavior is correctly described1 within the effective mass approximation. The averaging takes place over spherical regions of radii ae = ħ2e/mee2 and ah = ħ2e/mhe2 for electrons and holes respectively where me and mh are the corresponding effective masses and e is the permittivity of the medium. If the extension of the crystal is reduced in one or more directions close to these lengths the averaging procedure breaks down and the electron is faced with the bare interactions within the confined space and its walls. On these grounds one expects size dependent effects on their properties in general and on the optical ones in particular. Such effects, also termed quantum confinement effects, constitue an area of intensive theoretical and experimental activity. The goal is certainly the design2,3 of promising nonlinear optical materials for technological applications but these effects are of fundamental interest as well since they throw new light on some physical aspects which are suppressed in the infinitely large systems.

Spectral Hole Burning and Static Stark Effect in Quantum Confined Semiconductor Microcrystallites in Glasses

We observed spectral hole burning in very small CdSx Se1-X crystallites in a glass matrix. The results clearly show the impact of the electron-phonon broadening and crystallite size distribution and are in agreement with the special conditions of the quantum confinement. In striking agreement with later also stand the measurements of the change δα of the absorption spectrum due to a static electric field; the observed oscillations of 5a as a function of the wavelength, are well explained as a Stark effect of the quantized electronic levels.