Interference filter based beam confinement for increased mechanical phase modulation

Abstract

Modulating the phase or rather the optical path difference of a laser beam is a challenging task. Not too seldom limitations in optical path modulation bandwidth and optical path stroke limit the desired application. Approaches to compensate for these restrictions typically trade one parameter for another and vice versa. To avoid this trade off between parameters, an in-place beam folding would be desirable. Here, an approach based on a wedged optical light interference-filter trap (WOLIT) allows the increase of the optical path difference while maintaining a small and fast optical path modulator. We showed that with the WOLIT acting as an opto-mechanical-gearbox, mechanical mirror movements of 10 nm are sufficient to generate an optical path difference greater than 1 ? m at a frequency of 100 kHz.