Figure 1
From: Non-contact ultrasonic inspection by Gas-Coupled Laser Acoustic Detection (GCLAD)
The ultrasonic pressure field p(z, t) generates a refractive index variation in an \(x_s\)-long fluid region; the GCLAD laser beam sustains deflection and displacement in such region, propagating unperturbed afterward along a \(x_1\)-long path. The position-sensitive photodetector identifies the overall \(\varDelta z\) displacement and transduces it into a voltage.
