In this work, electro-thermo-optical devices were developed for near-infrared (NIR) wavelengths by exploiting the optical properties of vanadium dioxide (VO2). VO2 undergoes into an insulator-to-metal transition (IMT) in which its optical, electrical, and structural properties change abruptly as a function of its temperature. The changes in these properties show hysteretic behavior.Sol-gel deposition process was investigated for growing VO2 thin films on SiO2 and SiO2/Si substrates. Its composition and crystallization were characterized by X-ray diffraction and Raman spectroscopy. Atomic force microscopy and a 3-D surface contact profilometer were used to analyze the surface topography of the films. These thin films were compared with VO2 thin films deposited by pulsed laser deposited (PLD). VO2 thin films deposited by PLD were used to develop the devices presented in this work.In the present work, the IMT is induced thermally, using photo- or electro-thermal techniques. Two devices were developed: 1. a NIR image projector and 2. a fully electronic variable optical attenuator (VOA) to operate in the NIR region. The first device uses the inherent hysteresis in the optical properties of VO2 across its phase transition, which allowed for the programming of patterns onto the VO2 thin film. The second device emerged from the optical transition in VO2, in which the electro-optical changes in the film were induced electro-thermally (i.e. a “thermo-electro-optical device”). The strong correlation between the electrical and optical properties in VO2 enabled the implementation of a self-sensing technique, which reduced the optical hysteretic behavior and simplified the modeling and control of the attenuation.
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