Figure 1.

Experimental set-up for the generation and measuring of acoustic plane waves in water. Short laser pulses are directed on a silicon wafer. Fast local heating due to optical absorption leads to the emission of ultrasonic waves. The ultrasound detector is held by a mounting flange, and is axially fixated with a worm screw. The length of the water path between the silicon wafer (i.e., the ultrasound emitter) and the detector can be adjusted with distance bolts between two aperture discs. The silicon wafer is pressed onto one aperture disc by another mounting flange, which is bolted to the opposite flange.