Using Raman intensity dependence on laser polarization for low gas concentration measurements with giant pulse lasers

A method for controlling the anode current of photomultiplier tubes (PMT) is presented which uses Raman intensity dependence on the angle between the direction of observation and the polarization vector of the linearly polarized exciting radiation. It is shown that by varying this angle, it is possible to control the Raman signal from a molecule over a range of 5-50. The Raman intensity can be reduced at high gas concentrations below the maximum allowed anode current for the PMT by choosing an appropriate polarization angle. This makes it possible to use highly sensitive PMTs for giant-pulse measurements across a wide concentration range from the pure component down to the ppm level.