Polarization Sensitive Bias-Selectable Dual-band Quantum Dot Detectors

The proposed innovation will prove the feasibility of developing a spectral tunable and polarization sensitive quantum dot (QD) based detector for the 2-14 micron range. The aim is to satisfy the U.S. Air Force (USAF) requirements for passive spectral and polarization sensing in the infrared range without external filtering components and polarizers. The approach is to start with a bias selectable multi-band QD structure. The basic detector structure will consist of QD layer (InAs/GaAs), and double barrier layer (undoped GaAs) for tunneling. This detector is integrated with a surface plasmon/grid polarizer based light coupling layer to obtain the desired polarization sensitivity. Different grid orientations will be used on adjacent pixels to allow the determination of the linear polarization. The proposed detector will allow the development of new polarization sensitive systems which will not require external polarizers or filters for wavelength selection. This will reduce the weight requirements in sensor systems making them more widely applicable. BENEFIT: In addition to potential in the defense arena, these IR detectors will be useful in surveillance, geology, agriculture, disaster relief, and drug enforcement. Gas sensing applications will benefit from these devices since gases such as CO2, H2O, CO and SO2 have signatures in the 2-14 micron range. In the medical field the monitoring of gases such as CO2, N2O, and NH3 would be invaluable. For a patient in surgery or on a ventilator, the amount of N2O, (used as anesthesia) and CO2 content could be monitored using a single dual-band detector operating at ~7.7 micron and ~4.3 micron, thus allowing for monitoring of anesthesia flow/metabolism rate, in a single detector, while preventing the chances of hypoxia or oxygen toxicity. NH3 could be monitored to detect renal failure. Weather satellites will benefit from this type of detectors due to the 2-14 micron spectral range. In Astronomy, 2-14 micron imaging will be helpful to understand structure of planetary nebulae. The polarization sensitivity is useful in remote sensing, e. g. gas clouds and the proposed research could lead to new sensors for pollution monitoring.