How long is the stationary acoustic wave in the optical element?
December 4th, 2009
Photoelastic modulators are resonant devices which produce oscillating birefringence. The optical bar shaped element vibrates along its long dimension at a frequency determined by the length of the bar and the speed of a longitudinal sound wave in the optical element material. In other words, a free standing acoustic vibration mode is used, of acoustic wavelength twice the linear dimension of the modulator element.