Photoelastic Visualization of Ultrasound Generated by Pulsed Laser

We applied the dynamic photoelastic technique to visualize the ultrasound generated in a glass sample by an Nd: YAG pulsed laser. When a laser pulse was incident on the surface of the glass sample covered by thin layer of black ink, narrow pulses of longitudinal, shear, and surface acoustic waves were seen in the sample. The photoelastic picture also showed that the directivity patterns of ultrasound generated in the present case qualitatively agree with the theoretical prediction for the case of a normal surface-acting force.