Pulse duration

About: Pulse duration is a research topic. Over the lifetime, 19429 publications have been published within this topic receiving 286507 citations.

A quantum mechanical study of predissociation dynamics of NaI excited by a femtosecond laser pulse

Abstract: This work was stimulated by the experiments of Rosker, Rose, and Zewail (RRZ) who used a pump–probe sequence of femtosecond pulses to study the predissociation of NaI. We calculate quantum mechanically the nuclear wave function created by the pump pulse and its subsequent evolution. To make contact with the experiments we assume that, depending on its wavelength, the probe pulse is absorbed by either the free sodium atoms or by the bound molecule in the neutral state, and that the measured fluorescence induced by the probe pulse is proportional to the populations of these two ‘‘species.’’ The similarity between computed populations and the observed signal confirms this conjecture. We study how various factors, such as the pulse length and shape, the initial vibrational state, the temperature, and the diabatic coupling strength affect the populations (and thus the LIF signal). We also show that the RRZ analysis based on classical trajectories and the Landau–Zener formula agrees semiquantitatively with the exact quantum results.

Broadband phase-matched difference frequency mixing of femtosecond pulses in GaSe: Experiment and theory

Abstract: Phase-matched difference frequency mixing within the broad spectrum of single 13 fs pulses from a cavity-dumped, mode-locked Ti:sapphire laser in a GaSe crystal allows the generation of femtosecond mid-infrared pulses, continuously tunable in the wavelength range from 7 to 20 μm. Pulse durations down to 95 fs at 9.3 μm are directly measured. Model calculations including the full dispersion of GaSe show that the chirp of the pump pulses allows to change both the pulse duration and conversion efficiency obtained in the nonlinear process, in agreement with the experiment.

Short-pulse grating formation in photorefractive materials

Abstract: Solutions are obtained for the refractive index grating in a photorefractive material in which the writing or erasing beams are short-pulse (less than tens of nanoseconds), high-irradiance (greater than kW/cm2) lasers. The response of the photorefractive material is modeled using the continuity equation for the charge carriers, a rate equation for the ions, a current equation, and Poisson's equation for the space charge field. Two cases are discussed in detail: 1) the time for recombination of carriers with ions is much less than the pulse length of the laser; and 2) the recombination, drift, and diffusion times are all much longer than the pulse length. The energy requirements for short-pulse writing and erasing are greater than or equal to those obtained for typical CW lasers in all cases investigated. Application to previous observations in BaTiO 3 , Bi 12 SiO 20 , and LiNbO 3 is discussed.

Superposed quadrature modulated baseband signal processor

Abstract: A signal processor for providing a continuous raised cosine output signal having no jitter or intersymbol-interference and with controllable main and side lobes. An NRZ input signal is converted to a double interval raised cosine pulse signal having an amplitude normalized to 1.0. Another single interval raised cosine pulse signal having a peak amplitude (A-1) is superposed with the former raised cosine pulse to provide the output signal.