Photoacoustic pulse generation and probe-beam deflection for ultrasonic velocity measurements in liquids

We have demonstrated a noncontact, fast, and accurate method for ultrasonic measurements in liquids. A pulse laser beam produces an acoustic pulse, whose propagation is monitored by its deflection effects on two cw probe beams. All laser beams are parallel to, but displaced from, one another. The acoustic velocity can be measured to an accuracy of 5 parts in 104 in a measurement time of 100 μs. Temperature-dependent velocities are measured for ethanol, methanol, water, as well as for concentrated sulfuric acid (which has not been measured previously).