A wide-range monitor system for laser beam profiles

Abstract

The system described uses an array of 50 FET switches to access the elements of either a linear array of silicon photodiodes or an array of pyroelectric detectors formed on a single sheet of PVF₂ plastic. Compensating capacitors are used to give 1% uniformity of response down the array. The two types of arrays are easily interchanged, giving a very flexible system. With suitable attenuation, the photodiode array can give a saturation signal-to-noise ratio of 100:1 in the range 0.4-1.1 mu m for all levels above 4 W m^-2 CW or 60 mJ m^-2 for 10 ns duration pulses. The pyroelectric array can give a saturation signal-to-noise ratio of 1300:1 for CW beams above 180 kW m^-2 or 260:1 for 10 ns pulses above 700 J m^-2 in the range 0.3-30 mu m. These figures are achieved without the prescanning usually necessary with other systems.