Thermal imaging and infrared scene projector based on vo2 films and scanning mirrors
Bu-Ali, Eman Mohammed
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We study the properties of Vanadium Dioxide (VO2) thin films that exhibits photo-induced insulator-metal phase transition at a temperature of ∼68 °C. In this thesis, we describe two different methods of infrared (IR) and thermal imaging. The first approach is generating rewritable patterns in the optical communications band using a combination of pump-probe technique, a scanning mirror and an infrared (IR) camera. The sample used in these experiments is composed of VO2~150 nm thick films deposited on both sides of c-plane-oriented sapphire substrates whose temperature was controlled by a thermoelectric heater/cooler stage. Illumination from a high-power laser beam is deflected by the two protected scanning mirrors towards the VO2 sample’s surface in order to generate the desired transmission patterns. Furthermore, the VO2 thin film and the obtained images are illuminated by an infrared probe light source emitting in the important optical communication band. These images can be obtained using an IR camera. On the other hand, we experimentally describe a thermal imaging approach depending on controlling the thermal emissivity of VO2\sapphire samples. We change the thermal emissivity of the VO2 sample by focusing a high-power laser beam at the VO2 film in order to develop localized heating on the sample. A similar device consisting of two vibrating mirrors contribute to deflecting the pump laser. No thermal probe beam is needed because the thermal emission of the VO2 functions as the source of thermal illumination. Heating the sample near to the phase transition temperature and scanning the sample with the pump laser result in controlled thermal emissivity of the VO2\sapphire film and updated the generated emissivity pattern. This pattern can be imaged with a thermal camera.