THERMOELASTIC RESPONSE OF PULSED PHOTOTHERMAL DEFORMATION OF THIN PLATES

A theoretical investigation of the dynamic thermoelastic response of pulsed photothermal deformation (PTD) deflection detections for some Q-switch laser pulses and finite thickness samples has been presented. The results show that signals can be characterized by a quasistatic process when the laser pulse rise time is on the order of 1 mus and the sample thickness is in submillimeter range (typically for semiconductor wafers). However, as the pulse rise time decreases or the sample thickness increases, the dynamic wave behavior gradually becomes apparent, and the quasistatic approximation gives only a contour curve of the dynamic time evolution. When the rise time decreases on the order of 10 ns or less for the same kind of the samples, the PTD deflection signal reflects a totally dynamic wave behavior.