VO₂-based micro-electro-mechanical tunable optical shutter and modulator

Abstract

VO 2 -based MEMS tunable optical shutters are demonstrated. The design consists of a VO 2 -based cantilever attached to a VO 2 -based optical window with integrated resistive heaters for individual mechanical actuation of the cantilever structure, tuning of the optical properties of the window, or both. Optical transmittance measurements as a function of current for both heaters demonstrates that the developed devices can be used as analog optical shutters, where the intensity of a light beam can be tuned to any value within the range of VO 2 phase transition. A transmittance drop off 30% is shown for the optical window, with tuning capabilities greater than 30% upon actuation of the cantilever. Unlike typical mechanical shutters, these devices are not restricted to binary optical states. Optical modulation of the optical window is demonstrated with an oscillating electrical input. This produces a transmittance signal that oscillates around an average value within the range off VO 2 ’s phase transition. For an input current signal with fixed amplitude ( f el = 0.28 Hz), tuned to be at the onset of the phase transition, a transmittance modulation of 14% is shown. Similarly, by modulating the DC-offset, a transmittance modulation of VO 2 along the hysteresis is obtained.