Optical energy and spatial filter for high local resolution Raman spectroscopy with giant pulse lasers

It is shown theoretically and verified experimentally for Raman scattering that a simple combination of a biconvex and a biconcave lens can be used as an optical energy and spatial filter to regulate the focused incident laser energy and the spatial resolution of the system simultaneously. While filtering of optical energy usually reduces the spatial resolution, the described optical filter improves the spatial resolution proportional to the square root of the energy reduction and provides a simple method to avoid gas breakdown or other disturbances of the gas state.