Adaptive CdTe:V photo-EMF detectors for laser ultrasonic detection

ABSTRACT Preliminary results on utilization of CdTe:V photo-EMF detectors for broad-band ( 10 MHz) adaptive detection of optical phase modulation, which is necessary for laser ultrasonic applications, are reported.Unlike widely used GaAs photo-EMF detectors, devices under consideration demonstrate no remarkable electron-hole competition and ensure sensitivity necessary for detection of 2 mn surface displacement for 0.1 mW of signal beam power in simple transverse configuration without utilization of asymmetric interdigitated surface contacts. For the wavelength used (2 851 nm) dielectric cut-off frequency of typical CdTe:V detector was around 1 MHz, which, in principle, allows us monitoring of as-processed objects moving with in-plane velocity up to 10 rn/s. INTRODUCTION Laser induced ultrasonic [1] is considered as one of the most promising techniques for nondestructive testingwhen remote evaluation of different parameters of solid objects (thickness, presence of defects, rust etc.) is