Propagation of ultra-short femtosecond laser pulses in aerosols

Abstract

Propagation of ultra-short femtosecond laser pulses of a few cycles of light has many new implications in communications, satellite imaging, and remote sensing. The authors present theoretical work on solving the problem of a femtosecond laser pulse interacting with an aerosol particle. Results indicate that diffraction effects are transient and the typical diffraction rings are reduced significantly. Experimental work has been carried out where femtosecond laser pulses of 50 and 80 femtoseconds have been transmitted through aerosol clouds of approximately 4 microns average diameter. Results indicate that the frequency spread of the femtosecond laser pulse is essentially unaltered by the aerosols even through particle concentrations of over 10/sup 5/ particles per cubic centimeter. Clouds through which one would need to send optical communication information would have particle concentrations of about 100 particles per centimeter cubed. Results are presented on the use of the frequency spread in the femtosecond laser pulse to perform wavelength division multiplexing using a liquid crystal spatial light modulator. The femtosecond laser pulses are multiplexed outside of the laser cavity. Recent work investigates pump probing experiments on the propagation of 5 femtosecond pulses on water. The goal is to understand the implication of nonequilibrium dielectric constants and their values during femtosecond laser pulse propagation.