CO/sub 2/ laser pulse monitoring instrument based on PVDF pyroelectric array

Abstract

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 CO 2 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 CO 2 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 CO 2 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.

Laser Pulse Phenomena and Applications

“…Another technology that has been demonstrated useful for sensor fabrication availed of a screen printed pyroelectric paste (Capineri b et al, 2004). Both pyroelectric materials have been employed to design and build array of sensors with different configuration and size, depending on the application (Capineri et al 1998) (Capineri et al, 2005) (Mazzoni et al,2007). Some example of pyroelectric arrays used to design monitoring devices for CO 2 power laser systems are described in the following section.…”

“…The two measuring modules were: Module "BeamScan64" for the laser spatial intensity characterization, and Module "PosIRix" for the laser beam point stability and pulse shape characterization (Capineri et al 1999) (Capineri et al, 2005). The architecture can be replicated with other choices of the analog electronic components and with a microcontroller with upgraded performances.…”

“…Two new implementations were developed for the processing and visualization of signals generated by PVDF pyroelectric sensor arrays with compensation filtering (Capineri et al 2005) aimed to improve the reconstruction accuracy of CO 2 laser pulses. These implementations were especially devoted to biomedical applications for which there is a stringent demand for an accurate reproduction of both the fast and slow components of the laser pulse for the evaluation of the intensity in these two temporal regimes.…”