Micro-optical switch device based on semiconductor-to-metallic phase transition characteristics of W-doped VO₂ smart coatings

The authors have successfully fabricated planar micro-optical switch device exploiting the transmitting semiconductor (on) to the reflecting metallic (off) phase transition of thermochromic W(1.4 at. %)-doped VO₂ smart coatings and driven by an external voltage. The starting W-doped VO₂-coated Al₂O₃ exhibited infrared transmittance switching about 45%. After the microfabrication, the temperature dependence of electrical resistance of the micro-optical switch showed clearly its well-known semiconductor-to-metallic phase transition at a transition temperature of 36 °C. A reversible transmittance switching (on/off) as high as 28 dB was achieved with this device at λ=1.55 μm. In addition, the transmittance switching modulation of the device was demonstrated at 1.55 μm by switching the micro-optical switch simultaneously with dc and ac voltages.