Real-time holography by stimulated Raman and Brillouin scattering

Abstract

Experimental investigations on the quality of real image reconstruction by stimulated Brillouin scattering (SBS) and stimulated Raman scattering (SRS) are reported here. The quality of real image reconstruction under two separate experimental conditions was found to be highly dependent on (1) the amplitude modulations of the laser radiation, (2) the input laser power and (3) the position of the lens-focus. The best quality of reconstruction was observed when the lens-focus was in front of the cell and the real image of the object formed by the lens was located inside the nonlinear medium, within 3 cm of the entrance window of the cell. Also, this experimental condition reconstructed a smaller area of the illuminated object than the inside focus condition. According to existing theory, when the lens-focus is inside the nonlinear medium, the complex interference pattern near the entrance window of the cell plays the role of a real-time hologram. Real image reconstruction was also obtained by the two step in-line Fresnel holographic method using similar experimental arrangements as had been used for the real-time stimulated scattering experiments. A comparative study showed that the general trend in the quality of imaging was the same for the two methods, but the real-time holographic process was capable of producing better quality of image reconstruction. A physical reasoning has been provided for this discrepancy. From these experimental investigations an estimate of the resolving power of the real-time holographic system has been determined.