Broadband Photoconductive Terahertz Focal Plane Arrays

Terahertz (THz) imaging systems are important for many applications, including non-destructive evaluation, cancer screening, and security. The best performing THz imaging systems utilize femtosecond lasers and ultrafast photoconductive antenna (PCA) switches for optoelectronic generation and read-out of THz pulses.  To operate at high speeds, PCAs are based on sub-picosecond carrier lifetime materials such as low temperature grown gallium arsenide (LT-GaAs). A typical THz PCA sensor element is nearly a centimeter in size and large compared to sub-mm THz wavelengths.  This makes it impractical to implement an imaging focal plane array (FPA) in PCA technology. Instead, imaging in the THz range is accomplished with a single PCA element by mechanically raster scanning over a field of view. This proposal applies novel device design and processing techniques to solve the pixel size issue in PCA arrays. The proposed technology has potential to deliver 1-3 THz bandwidth, dynamic range > 30 dB, and 1 Hz frame rates in an ultra- compact and high-resolution imaging FPA more than 1 kilo pixels in size.