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.
Benefit: The proposed compact terahertz focal plane array technology would enable significant progress toward making a high sensitivity, low cost THz imaging system. Deployment of these newly developed detector devices would result in successful implementation of important applications in scientific R&D, biomedical, non-destructive testing, molecular spectroscopy, defense and security imaging, semiconductor device testing, and communications. Thz radiation is non-ionizing and non-destructive, which makes it ideal for probing structural and material defects in airframes or bridges, such as from manufacturing or fatigue factors. It is also ideal for biomedical diagnostics, such as cancer screening. Regular high sensitivity diagnostic screening of cancer is of high clinical importance for repeated assessments, patient monitoring and follow-up. Cancer is rapidly advancing as the second leading cause of death. Common examples are stomach cancer and colon cancer. High accuracy and resolution THz imaging would be an invaluable tool in early detection and monitoring of these and other types of cancers. The development of the proposed technology would also be able to satisfy an unmet medical need to accurately image the cornea. Providing this diagnostic capability is of clinical importance. End stage endothelial dysfunction results in corneal transplantation. Nearly 30,000 corneal transplants were performed in the U.S. alone in 2014 for endothelial dysfunction. Dry eyes are a common affliction and represent a $3.5 billion market of diagnostics and treatments (many elective) globally. Inflammation of the cornea, i.e. keratitis, results in nearly a million clinic or ER visits a year with direct health expenditures costing an estimated $175 million. Reducing need for corneal transplantations reduces patient morbidities and potential cost savings of up to $10,000-$15,000 per transplant.
Keywords: imaging, imaging, Frame Rate, photoconductive switch, Dynamic Range, focal plane array, Broadband, terahertz, Compact
