Tham khảo tài liệu 'laser pulse phenomena and applications part 7', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Laser Pulses Characterization with Pyroelectric Sensors 171 experimental detector pulse time response of 24 ps to a simulated 17 ps rising edge of a Nd-YAG laser pulse is shown in Figure 7. By a fitting process based on the root mean square error the model parameters can be retrieved with good accuracy . Fig. 7. Comparison of pyroelectric sensor normalized voltage response between simulated model and experimental sensor. Several single-element detectors were built which were able to follow laser pulses with rise time up to ms. Figure 8 shows an example of the time response to a CO2 laser pulse for the values reported in Table 2. Fig. 8. Pyroelectric signal in response to a pulsed CO2 laser 172 Laser Pulse Phenomena and Applications Active area of detector 9 mm2 Thickness PVDF 40 pm Gold metallisation pm Zel Ra 1 ML parallel with Cc 15 pF Pulsed laser characteristics PRF 50 Hz Duty cycle 22 Table 2. Parameter values characterising detector and laser source for the measurement shown in Figure 8 The time response is characterized by a rising time ms like that of the laser pulse and the undershot is characteristic of a rapid cut-off. The recovery time 7 ms at 1 e of Vout max is governed by the detector thermal time constant RT CT. The settling time to zero value is mainly determined by the undershoot and it is approximately 15 ms. This basic example demonstrates the feasibility of the pyrolectric PVDF film sensor technology for monitoring IR laser pulses Capineri et. al. 1992 . Another technology that has been demonstrated useful for sensor fabrication availed of a screen printed pyroelectric paste Capinerib 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 CO2 power laser systems are described in the .
