ABSTRACT
In laser ionisation spectroscopy studies, for example, it is common practice to frequency double the light from a dye laser, thereby providing a tuneable source of ultraviolet radiation which is ideal for multiphoton absorption by atomic electrons to real excited states. In practice, such systems require to be manually scanned in wavelength during experiments as the intensity tends to vary due to the dye emission profile and also die to non-linearities in the frequency doubling process – an undesirable situation. Traditionally, this has involved measuring the amplitude of a small portion of the pulsed beam and maintaining the full beam intensity using a manual attenuator. An automated system would clearly be advantageous in such situations. This paper describes the construction and testing of an automated optical attenuator which was designed for use with pulsed or chopped laser beams where the intensity is subject to slowly varying fluctuations. At present, it has only been tested using a chopped He-Ne beam where variations in intensity were produced using glass plates.
