Mie scattering used to determine spherical bubble oscillations

Linearly polarized laser light is scattered from an oscillating, acoustically levitated bubble, and the scattered intensity is measured with a suitable photodetector. The output photodetector current is converted into a voltage and digitized. For spherical bubbles, the scattered intensity I(rel)(R,theta,t) as a function of radius R and angle theta is calculated theoretically by solving the boundary value problem (Mie theory) for the water-bubble interface. The inverse transfer function R(I) is obtained by integrating over the photodetector solid angle centered at some constant theta. Using R(I) as a look-up table, the radius vs time [R(t)] response is calculated from the measured intensity vs time [I(exp)(R,t)].