Terahertz laser based standoff imaging system

Abstract

Definition and design of a terahertz standoff imaging system has been theoretically investigated. Utilizing terahertz quantum cascade lasers for transmitter and local oscillator, a detailed analysis of the expected performance of an active standoff imaging system based on coherent heterodyne detection has been carried out. Five atmospheric windows between 0.3 THz and 4.0 THz have been identified and quantified by carrying out laboratory measurements of atmospheric transmission as a function of relative humidity. Using the approximate center frequency of each of these windows, detailed calculations of expected system performance vs target distance, pixel resolution, and relative humidity were carried out. It is shown that with 1.5 THz laser radiation, a 10m standoff distance, 1 m times 1 m target area, and a 1cm times 1cm pixel resolution, a viable imaging system should be achievable. Performance calculations for various target distances, target pixel resolution, and laser frequency are presented