Laser-induced excited state and ultrasonic wave gratings: Amplitude and phase grating contributions to diffraction

Abstract

A detailed analysis of diffraction from laser-induced gratings is presented. The changes which occur in both the real and imaginary parts of the index of refraction are accounted for when excited states are created. These lead to phase and amplitude grating contributions, respectively, to the diffraction from a laser-induced excited state grating. Experimental confirmation of the predicted wavelength dependence of these contributions is presented. Diffraction from laser-induced excited state gratings, ultrasonic wave gratings, and mixed excited state and acoustic gratings is analyzed with the phase and amplitude contributions to each accounted for. The results permit the interpretation of mixed grating data and predict conditions under which density-dependent absorption spectral shifts and excited state-phonon interactions can be measured.