VO2-based MEMS tunable optical shutters are demonstrated. The design consists of a VO2-based cantilever attached to a VO2-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 VO2phase 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 VO2’s phase transition. For an input current signal with fixed amplitude (
Micrometer‐sized VO2‐based devices with integrated resistive heaters of different configurations are fabricated. Quality of the VO2films is confirmed by measuring the characteristic drop in transmittance and negative differential emissivity for these films. A two‐interface model for optical transmittance, reflectance, and absorbance is presented. This method and analytic model presents an advantage over most typically used approaches in that it does not require direct measurements of the material's optical constants to estimate transmittance. By combining the substrate and the VO2film into one layer with a reduced optical admittance, the two‐interface model is reduced to a single‐layer model. Moreover, the present work demonstrates the implementation of the developed VO2‐based devices in adaptive camouflage and shape‐converting applications. Electrical pulses are used to program different emissivity states to convert geometric shapes inside a fully integrated VO2‐based electro‐optical window. This results in the reconfiguring of thermal images to either create new shapes, or shift from one to another.
more » « less- Award ID(s):
- 1744273
- NSF-PAR ID:
- 10460825
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Advanced Materials Technologies
- Volume:
- 4
- Issue:
- 4
- ISSN:
- 2365-709X
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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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 VO2along the hysteresis is obtained. -
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Abstract Mott insulator VO2exhibits an ultrafast and reversible semiconductor‐to‐metal transition (SMT) near 340 K (67 °C). In order to fulfill the multifunctional device applications, effective transition temperature (
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