Regensburg 2007 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 53: Ultra fast phenomena

HL 53.6: Vortrag

Freitag, 30. März 2007, 12:15–12:30, H15

Terahertz radiation from a large-area photoconductive device — •Falk Peter, Sven Nitsche, Stephan Winnerl, André Dreyhaupt, Harald Schneider, and Manfred Helm — Institute of Ion-Beam Physics and Materials Research, Forschungszentrum Dresden-Rossendorf, 01314 Dresden, Germany

We present studies of the radiation properties of a photoconductive terahertz (THz) structure [1]. It consists of an interdigitated electrode structure fabricated on GaAs. Illuminating this structure by a femtosecond laser pulses yields accelerated photocarriers, which are the source of THz radiation. For avoiding destructive interference of radiation generated in regions of opposite field direction a second metallization isolated from the first one covers every second electrode spacing. Intense THz radiation with fields of the order of 1 kV/cm is observed.

We use a photoconductive detection antenna for measuring the spatial profile. The detection antenna is placed in a distance of 13 mm from the emitter. The beam profile is resolved for spectral components in the range from 0.5 to 1.5 THz. All beam profiles have Gaussian shape. The divergence increases with decreasing frequency. For wavelengths significantly smaller than the excitation spot size, the results can be well described by Gaussian optics. However, at longer wavelength, where the paraxial approximation fails, diffraction has to be considered in a more general way.

[1] A. Dreyhaupt, S.Winnerl, M.Helm, T. Dekorsy, Opt. Lett. 31, 1546 (2006)