Polarization Gratings in Disperse Red 1 Doped Polystyrene

Abstract

Polystyrene films containing commercially available azobenzene dye Disperse Red 1 were illuminated with interference patterns of polarized laser beams with wavelengths near the maximum of chromophore absorption. Laser induced mixed amplitude and phase gratings in this system were observed by the degenerate two-wave mixing (DTWM) and the four-wave mixing (DFWM) techniques. These experiments allowed for measurement of the gratings build-up time constants and the phase conjugate (PC) signal. We determined which of the gratings is responsible for the main contribution to the PC signal in DFWM process. The volume gratings were selectively destroyed by changing the polarization of respective incoming light beams from being parallel (full intensity modulation) to orthogonal (no intensity modulation) configuration while monitoring the PC signal. Initially apparent disagreement between the measurements and the simple model proposed by us for the whole process lead us to the hypothesis of the presence, in the studied system, of the efficient polarization gratings. This finding was confirmed by a separate two-wave mixing experiment and when taken into account could reasonably fair explain the obtained in DFWM results.