Ultrafast WDM logic

Ultrafast all-optical logic gates that accept optical inputs in which wavelength designates bit position within the overall byte are proposed and demonstrated. Four-wave mixing is shown to provide a conditional test function that can be used to construct any multi-input logic gate. Polarization provides the logic state for each bit. Implementations that use semiconductor optical amplifiers as the four-wave mixing medium can be monolithic and compact

Spectral logic gates for byte-wide WDM signal processing

We propose a new class of all-optical logic gates based on four-wave mixing, designed to operate on multiwavelength input signals. We demonstrate the XOR function with two 2.5-Gbit/s modulated input signals

A general resonance theory based on Mourre's inequality

We study the perturbation of bound states embedded in the continuous spectrum which are unstable by the Fermi Golden Rule. The approach to resonance theory based on spectral deformation is extended to a more general class of quantum systems characterized by Mourre's inequality and smoothness of the resolvent. Within the framework of perturbation theory it is still possible to give a definite meaning to the notion of complex resonance energies and of corresponding metastable states. The main result is a quasi-exponential decay estimate up to a controlled error of higher order in perturbation theory.Comment: 17 page

Polarization-dependent optical nonlinearities of multiquantum-well laser amplifiers studied by four-wave mixing

We present a detailed study of the polarization properties of four-wave mixing in multiquantum-well (MQW) semiconductor optical amplifiers (SOA's). In particular, the polarization selection rules relevant to all processes contributing to the generation of the four-wave mixing signal are rigorously derived and discussed. We then show the importance of these results in applications where four-wave mixing is used as a spectroscopic tool to study the optical nonlinearities of semiconductor gain media. For illustration, we demonstrate two novel applications of polarization-resolved four-wave mixing. The first is a new technique for measuring the recombination lifetime in SOA's, based on mixing of a pump wave with polarized amplified spontaneous emission noise. In the second, we use the same polarization selection rules to measure the interwell transport lifetime in alternating-strain MQW amplifiers. Finally, we also discuss the possibility of studying the dynamics of the optically induced phase coherence between spin-degenerate states