Optimization of an optical chopper-laser beam arrangement in low-frequency applications

Optical choppers are widely used in combination with continuous wave lasers in many spectroscopic and other materials characterization techniques. However, utmost care has to be taken in the use of an optical chopper in very low frequency applications. In this paper, we have used simple calculations to demonstrate the importance of the relative position of an optical chopper with respect to the laser beam path for minimal impact of the chopper speed on the measurements. We have also demonstrated an alternative simple, low-cost and easy to fabricate electromechanical shutter instead of a chopper for single pulse generation from a continuous wave laser. Focusing of the laser beam on the chopper blade can also minimize the adverse impact of slowly moving chopper wheel.