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.