Real-time detecting of Brillouin scattering in water with ICCD

Abstract

Brillouin scattering is a way non-touching detection by measuring frequency shift and line width of Brillouin lines. In 1980, Guagliardo got Brillouin spectrum in water using Lidar of wide band pulsed laser. But resolution was low and didn't satisfy detection requirement. Later, Dr. Dahe Liu suggested that Brillouin scattering in water with high resolution and accuracy can be achieved by using edge technique. In this paper, we put forward a new method to do real time detection Brillouin backscattering in water. An intensity CCD (ICCD) was used in our experiment. As we known, when a laser fires a pulsed into the water, the backscattering includes Rayleigh lines and Brillouin lines. The former frequency is equal to original frequency of the incoming light. The later has the different frequency with the former, it is called as Brillouin shift. The signals out from water entered our system and passed through a F-P etalon, then interference rings were imaged by ICCD. It can be seen clearly that Brillouin lines were appeared at the same side of every Rayleigh lines. From the images recorded by ICCD, the Brillouin shift, the Brillouin line width and the signal intensity of Brillouin scattering can be determined. These informations can be used further to determine some parameters of the ocean. Our investigation shows that the instrumentation with ICCD may be used in the real time remote sensing of the ocean.