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.
Overview of CNDE’s THz-FTIR research facility.
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.
(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.
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.
(left) the Fourier transform infrared spectrometer, and (right) its frequency spectrum in the far-infrared range.