Rakchanok Rungsawang et al 2003 J. Phys. D: Appl. Phys. 36 229 doi:10.1088/0022-3727/36/3/303
Rakchanok Rungsawang, Keisuke Ohta, Keiji Tukamoto and Toshiaki Hattori
Show affiliationsStudies using a terahertz (THz) imaging system have shown that focused THz electromagnetic pulses exhibit a ring-like spatial intensity distribution. In the study, almost half-cycle THz pulses were generated from a large-aperture photoconductive antenna and focused by an off-axis parabolic mirror. Time-resolved spatial distribution of the THz electric field on the focal plane was found to form a ring before and after the time region where a single peak is formed around the time origin. On the other hand, with the delay time fixed at the origin, the field distribution was also found to exhibit a ring-like profile at positions away from the focal plane. Existence of relatively low-frequency components in the power spectrum of the THz field gives these observable phenomena. Numerical simulations using diffraction integral calculations reproduced the observed features. A simpler numerical analysis based on the Gaussian beam approximation was shown to yield the observed features and also predicted the dependence on the beam parameters.
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
42.79.Pw Imaging detectors and sensors
02.60.-x Numerical approximation and analysis
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation
Issue 3 (7 February 2003)
Received 25 September 2002
Published 15 January 2003
Rakchanok Rungsawang et al 2003 J. Phys. D: Appl. Phys. 36 229
Toshiaki Hattori et al 2004 J. Phys. D: Appl. Phys. 37 770
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