Real-Time, Two-Dimensional Terahertz Beam Imaging

We will develop a real-time, two-dimensional THz wave imaging system. The proposed THz imaging system uses Electro-optic crystals and is capable of time-domain far-infrared spectroscopy across a frequency range extending from near DC to severalTHz. Fundamentally, the imaging sensor is based on the linear Electro-optic effect (Pockeles effect) in Electro-optic crystals where a pulsed microwave signal acts as .. transient bias to induce a transient polarization in the sensor crystal. Importantly this polarization is then probed by a synchronously pulsed laser beam, and both the spatial and temporal electric-field distribution is projected onto a COD camera by the laser Previous studies of these imaging sensors have demonstrated: a diffraction-limited spatial resolution, femtosecond temporal resolution, near DC-THz bandwidth, sub-mV/cm field sensitivity, up to 100 Hz scan rate, single-shot capability, and a signal-to-noise ratio better than 100,000:1. The Electro-optic detection has a flat (nonresonant) spectral responsivity (from near DC to several THZ) , a large detector area (> 6 cm2) , and an extended dynamic range (>10,000,000). The simplicity of the detection geometry, capability for optical parallel processing, and excellent signal-to-noise ratio make this system suitable for real-time, 2-dimensional coherent far infrared imaging applications. For the first time, a video of real-time THz imaging has been demonstrated at Rensselaer. We will build a portable THz beam system for commercial applications. In particular, we will investigate the feasibility of using a chirped optical probe pulse to read THz imaging in an Electro-optic crystal which provides the measurement of a THz wave with an unprecedented data acquisition rate. BENEFITS: A scientific breakthrough that could eventually become as important as ultrasonic, x-ray and radar technologies, may soon make it possible for us to see images of electric fields, diseased tissue, the chemical composition of plants, identification of suspicious materials, and much more that is undetected by other imaging systems.