Systems Overview

The new THz research facility is housed in a newly renovated 600 square-feet laboratory space in Rm. 133, Applied Sciences Complex III.  This laboratory is designed to accommodate a variety of user needs with optimal flexibility and performance.  The THz systems consist of a pulsed time-domain spectroscopy (TDS) system and a frequency-domain continuous-wave (CW) system, both manufactured by TeraView Ltd. based in Cambridge, United Kingdom.  Both systems are capable of high-speed imaging of up to 80 x 70 x 40 cm scan volume, using a three-dimensional motorized translation gantry and a turntable.  Full optical fiber coupling allows for many linear or rotational scan configurations set up in either reflection or transmission modes.

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Overview of CNDE’s THz-FTIR research facility.

 

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THz systems’ gantry (left) allows many flexible scan configurations such as (middle) pitch-catch reflection and (right) through-transmission modes

The TDS system employs the popular photoconductive antenna approach, and offers a wide spectrum from 50GHz to 4THz at 3GHz data resolution using a patented “resistor on a chip” technology.  The CW system uses the photomixing beat frequency technique to cover the frequency from 50GHz to 1.8THz at a fine 100MHz resolution in one continuous band.  Submillimeter lateral spatial resolution is achieved by employing optical focusing at 50mm and 150mm, respectively.  The gantry is also equipped with a dry air purge system to remove water vapor in the air.  As of early October 2009, all THz components have been tested and both systems are fully functional.

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(left) The THz pulsed system coupled with the motorized scan gantry; (right) the continuous-wave system connected to a separate measurement station in through-transmission mode.

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Frequency spectra of (left) the THz pulsed system and (right) the continuous-wave system.

Most recently in August 2011, the facility was further enhanced by adding a research-grade Varian (now Agilent) 680 Fourier transform infrared (FTIR) spectrometer, featuring high-end step-scan functionality, as well as capabilities in specular reflection and photo-acoustic spectroscopy.  Unlike most conventional FTIR instruments, the new spectrometer also covers frequency in the far-infrared region, starting at 20 cm-1 (0.6 THz) up to 8000 cm-1 (240THz) with typical spectral resolution better than 0.06 cm-1 (1.8GHz).  This THz-FTIR instrumental combination thus boasts an extensive electromagnetic spectrum spanning from millimeter to near-infrared, all under the same roof.

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(left) the Fourier transform infrared spectrometer, and (right) its frequency spectrum in the far-infrared range.