Coupled-wave equations of Bragg diffraction for wave packets in dispersive media

摘要

We propose a unified theory of acousto-optical diffraction in crystals and wave packet propagation in dispersive media. This formal approach is crucial for precise characterization of light dispersive delay lines performance for femtosecond laser pulses. We found that dispersive phenomena in crystals influence acousto-optical coupling of modes. Modified coupled-wave equations were developed for description of acousto-optical interaction of ultrashort laser pulses. Analysis showed that group delay between the incident and the diffracted pulse results in considerable transformation of pulse envelope and decrease of diffraction efficiency. On the contrary, the influence of phase mismatch on the diffraction efficiency is lower than it is predicted by conventional theory of Bragg diffraction. As a result, the transmission bandwidth for ultrashort wave packets increases several times compared to that for stationary waves and the side lobes of the transmission function disappear.