CO2 laser pulse monitoring instrument based on PVDF pyroelectric array

This paper proposes to extend the use of low-cost, pyroelectric, polyvinylidene fluoride four-quadrant arrays, originally devoted to monitoring the beam point stability of CO₂ laser beams, to the temporal profiling of the same laser pulse providing an instrument that is not commercially available. The advantage of using a single sensor for both types of measurements can be fully exploited if the pyroelectric sensor bandwidth is made almost flat in the typical frequency range (10 Hz-20 kHz) of the signal spectrum generated by a modulated CO₂ laser. In this paper, we present the design of an active analog compensation filter aimed to improve the reconstruction accuracy of the laser pulses and its circuit implementation with a quad operational amplifier for an easy integration of the compensation filter on the same board hosting the sensor. Experimental results obtained with modulated CO₂ laser beams, at pulse repetition rates from 10 to 1000 Hz and variable duty cycle, proved accurate in the laser pulse reconstruction with sensitivity of commercial semiconductor HgCdZnTe sensors.