Co-investigators Jing Kong , Tomas Palacios
Uncooled mid-infrared (Mid-IR) detection and imaging technologies are highly desired for night vision, security surveillance, remote sensing, industrial inspection, medical, and environmental chemical sensing. Traditional mid-IR detection technologies operating at room temperature are all associated with thermal related phenomena that transfer the optical signals into electrical signals through changes of temperature on the device. Here we propose and implement a new signal transducing scheme where the energy transfer path is optical-thermal-mechanical-electrical. By combining highly sensitive strain sensors made with percolative graphene nano-flake films synthesized by Marangoni self-assembly method, and the highly efficient polymer opto-thermo-actuators, we were able to demonstrate the proof-of-concept bolometric type mid-IR detectors that could be more sensitive than state-of- the-art technologies.
Two types of photoresponse behaviors were observed in our devices: a gradual change in resistance in terms of temperature, which may be associated with the average overlap area decrease of adjacent nano-flakes; and an abrupt “switch” like response that is presumably due to the decrease of the number of conduction paths of the percolative film. Microscopic characterizations and theoretical modeling were carried on to understand such behaviors. Theoretical analysis showed that our new technology could be at least one order of magnitude more sensitive than the fundamental limit of existing uncooled mid-IR technologies.