Figure - available from: Journal of Infrared, Millimeter and Terahertz Waves
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A simple THz-TDS setup with two extended hemispherical lens-integrated antennas and two off-axis parabolic reflectors. a First-order transmission (collimated). b Second-order transmission (uncollimated)
Source publication
Multiple reflections in an extended hemispherical lens are shown to exhibit distinctly different Gaussian characters. It is demonstrated that the second- and third-order bounces of the electromagnetic fields within the electrically large lens result in contributions with spot sizes and locations that are uncorrelated with the fundamental Gaussian-b...
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Citations
... The observed deviations in the beam profiles from a Gaussian beam may come from the coupling of the THz antenna and the Si lens [43][44][45]. It has been previously shown that small differences in the position of the lens with respect to the antenna can have significant effects on the profiles of the emitted radiation [43,44]. However, the antenna is positioned at the centre of the lens with an automated pick and place tool and the deviation from the central position is smaller than 20 μm. ...
... The observed deviations in the beam profiles from a Gaussian beam may come from the coupling of the THz antenna and the Si lens [43][44][45]. It has been previously shown that small differences in the position of the lens with respect to the antenna can have significant effects on the profiles of the emitted radiation [43,44]. ...
... The observed deviations in the beam profiles from a Gaussian beam may come from the coupling of the THz antenna and the Si lens [43][44][45]. It has been previously shown that small differences in the position of the lens with respect to the antenna can have significant effects on the profiles of the emitted radiation [43,44]. However, the antenna is positioned at the centre of the lens with an automated pick and place tool and the deviation from the central position is smaller than 20 µm. ...
Knowledge of the beam profiles of terahertz emitters is required for the design of terahertz instruments and applications, and in particular for designing terahertz communications links. We report measurements of beam profiles of an optoelectronic silicon lens-integrated PIN-PD emitter at frequencies between 100 GHz and 1 THz and observe significant deviations from a Gaussian beam profile. The beam profiles were found to differ between the H-plane and the E-plane, and to vary strongly with the emitted frequency. Skewed profiles and irregular side-lobes were observed. Metrological aspects of beam profile measurements are discussed and addressed.
We report the design, fabrication, and prototype demonstration of a 200-GHz polarization-resolved quasi-optical detector employing monolithically integrated zero-bias heterostructure backward diodes (HBDs). In this design, polarization resolution is achieved by orthogonally integrating the detectors with a planar dual-polarization annular-slot antenna. The detector chip was fabricated and mounted on an extended hemispherical Si lens to enhance antenna efficiency in the millimeter-wave to terahertz region. The responsivity and radiation patterns of the detector were characterized experimentally; good agreement with theoretical calculations was obtained. By measuring the outputs of two orthogonal HBDs as a function of the polarization angle of the incident wave, the planar detector detects intensity and resolves polarization. On the basis of the polarimetric measurement, we further demonstrate the polarization imaging capability of the proposed detector by using it as an imaging system. The detector is promising for developing terahertz polarimetric sensors and imaging arrays in chemical sensing, biomedical imaging, and radio astronomy applications.
