Robert H. Giles

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The radar cross section of spherical retroreflectors operating at terahertz frequencies is investigated. Several spherical retroreflectors with diameters ranging from 2 mm to 8 mm were fabricated and their radar cross section was measured at 100 GHz, 160 GHz, and 350 GHz. A frequency selective surface was applied to the retroreflectors to demonstrate proof(More)
As short range, ground based, surveillance systems operating at terahertz frequencies continue to evolve, increasing attention is being directed towards the behavior of dielectric materials at terahertz frequencies as well as the behavior of optical components used to control terahertz radiation. This work provides an overview of several terahertz optical(More)
BACKGROUND AND OBJECTIVE Continuous wave terahertz imaging has the potential to offer a safe, noninvasive medical imaging modality for delineating human skin cancers. Terahertz pulse imaging (TPI) has already shown that there is contrast between basal cell carcinoma and normal skin. Continuous-wave imaging offers a simpler, lower cost alternative to TPI.(More)
We demonstrate that a short hollow dielectric tube can act as a dielectric waveguide and transform the multimode, highly diverging terahertz quantum cascade laser beam into the lowest order dielectric waveguide hybrid mode, EH(11), which then couples efficiently to the free-space Gaussian mode, TEM(00). This simple approach should enable terahertz quantum(More)
In response to the growing interest in developing terahertz imaging systems for concealed weapons detection, the Submillimeter-Wave Technology Laboratory (STL) at the University of Massachusetts Lowell has produced full-body terahertz imagery using coherent active radar measurement techniques. The proof-of-principle results were readily obtained utilizing(More)
Continuous wave terahertz imaging has the potential for diagnosing and delineating skin cancers. While contrast has been observed between cancerous and normal tissue at terahertz frequencies, the source mechanism behind this contrast is not clearly understood.Transmission measurements of 240μm thick sections of nonmelanoma skin cancer were taken at two(More)
This paper reports on the effect of random Gaussian roughness with rms roughness values of 5-20 microm on the terahertz reflection spectra of metallic aluminum surfaces using Fourier transform IR spectroscopy. By comparing experimental data with a theoretical model based on the Kirchhoff approximation, the rms roughness of a surface is accurately(More)
A simple analog locking circuit was shown to stabilize the beat signal between a 2.408 THz quantum cascade laser and a CH(2)DOH THz CO(2) optically pumped molecular laser to 3-4 kHz (FWHM). This is approximately a tenth of the observed long-term (t approximately sec) linewidth of the optically pumped laser showing that the feedback loop corrects for much of(More)
Attenuation characteristics of hollow, flexible, metal and metal/dielectric coated polycarbonate waveguides were investigated using an optically pumped far infrared (FIR) laser at 215 µm. The bending loss of silver coated polycarbonate waveguides were measured as a function of various bending angles, bending radii, and bore diameters. Minimal propagation(More)