SPECTRAL DEPENDENCE OF THE EXCITATION OF THE FORBIDDEN 2ND OPTICAL HARMONIC IN AN AQUEOUS SUSPENSION OF PURPLE MEMBRANES BY FEMTOSECOND LASER-PULSES UNDER ELECTRONIC RESONANCE CONDITIONS

The spectral dependence of the efficiency of generation of the forbidd en (in the electric-dipole approximation) second harmonic (FSH) and it s energy on the energy of the excitation pulses is investigated experi mentally in a highly disperse suspension of purple membranes containin g bacteriorhodopsin (BR) under excitation by femtosecond laser pulses into the single-photon absorption band of BR. The experimental data fo r the case of resonance excitation attest to an interference character of the interaction of optical nonlinearities of different orders in t he process leading to the formation of the FSH signal. (C) 1998 Americ an Institute of Physics.