Compact fiber-pigtailed terahertz imaging system

Abstract

Terahertz imaging has been shown to be a powerful tool for analyzing a variety of materials. From the amount of water in a leaf over time to looking at the spectroscopic species in a flame, this technique shows great potential for commercial applications. However, in order to work in a commercial environment, the present free-space optical systems must be abandoned in favor of fiber-optic delivery. To this end, we have developed a compact, fiber-pigtailed terahertz imaging system that utilizes a hermetically sealed, photoconductive, transmitter and receiver. The receiver uses an integrated amplifier to obtain a 1000:1 S/N with only 1 mW of power on both the transmitter and receiver and with a one second integration time. This system has usable energy extending from 0.04 to 2 THz and has both a rapid (20 Hz) scanner for short, 40-ps, scans as well as a long rail for scans up to 1 ns. The system hardware is contained in a 1.5 cu. ft. box with fibers feeding both the transceiver units. These units can be configured into either a transmission or reflection mode depending on the user's application. An advanced software system controls the hardware, collects the data, and does image processing.