NSF Award
9805105
*** 9805105 Stewart We propose to investigate and develop an imaging and spectroscopic.system based on ultra-wideband electric-field sensors that cover a portion of the electromagnetic spectrum that is generally inacessible by current spectroscopic techniques. The proposed device will be based on a new optoelectronic design which is capable of time-domain far-infrared spectroscopy across a frequency range extending from near DC to several THz. The electric-field sensor system employs the Pockel's effect in electro-optic crystals. A pulsed microwave signal induces a transient polarization in the sensor crystal. This polarization is then probed by a synchronously pulsed laser beam, which projects the spatial and temporal electric-field distribution is projected onto a CCD camera. Our previous studies of these imaging sensors has demonstrated a sub-wavelength spatial resolution, femtosecond temporal resolution, near DC-THz bandwidth, sub-mV/cm field sensitivity, up to 100 Hz scan rate, and a signal-to-noise ratio better than 1,000,000:1. The electro-optic detection has a flat (nonresonant) spectral responsivity (from near DC to several THz), a large detector area (> 1 cm2), and an extended dynamic range (> 1,000,000). 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-D coherent far infrared imaging applications. Potential commercial applications include industrial inspection and process control, FIR spectroscopy, electric field sensor, and medical imaging. ***
