We present a theory of ultrashort-pulse second-harmonic generation (SHG) in materials with longitudinally nonuniform quasi-phase-matching (QPM) gratings. We derive an expression for the output second-harmonic field generated in an arbitrary QPM grating from an arbitrary fundamental field, valid for arbitrary material dispersion in the undepleted-pump approximation. In the case when group-veloci...

We consider a blind separation problem for undetermined mixtures of two BPSK signals in a multi-path fading channel. We use independence and frequency diversity of the two source signals to identify mixture parameters, estimate Pulse Shaping Filters (PSF) and channel responses, as well as to extract both binary sequences from only one observation. Presented method uses gradient descent algorith...

LLE Review, Volume 78 97 Laser-fusion experiments require precise control of the temporal profile of optical pulses applied to targets. An optical pulse– shaping system has been in operation on OMEGA for several years.1 During this time the demands on the precision, flexibility, and repeatability of the optical pulse–shaping system have steadily increased. To meet these new demands, a new pulse...

A rigorous analysis of ultrashort pulse shaping by the spectral filtering of dispersed frequency components is presented. Particular attention is directed toward the case of two liquid-crystal spatial light modulators used to provide programmable manipulation of both the phase and the amplitude profiles of the shaped waveform in the time domain. Different optical configurations are evaluated an...

We discuss the application of diffraction theory to the reshaping of freely propagating terahertz pulses by narrow apertures. This is accomplished by using two separate electrooptic sampling detectors. The first contains a narrow electrode geometry that does not modify the frequency content of the incident terahertz field, while the second contains a narrow gap between two large electrodes. The...

The conversion of transform-limited short laser pulses to shaped longer pulses with frequency chirp was investigated. A program was created to simulate how transform-limited short input pulse shapes can be converted into output pulses of desired temporal shape and phase. The program models both electric field and spectral intensities of the pulses, conserves energy, and accounts for spectral li...

We explore the effects of ultrafast shaped pulses for two-level systems that do not have a single photon resonance by developing a multiphoton densitymatrix approach. We take advantage of the fact that the dynamics of the intermediate virtual states are absent within our laser pulse timescales. Under these conditions, the multiphoton results are similar to the single photon and that it is possi...

We consider the problem of digital communication in a fading environment using the Multi-Carrier CDMA technology. By incorporating the effect of the pulseshaping filter in the channel estimation and signal detection modules, we develop new estimator and detector structures which significantly outperform the commonly used timedomain equalizers and matched filter detector. Our simulation results ...