Dresden 2006 – wissenschaftliches Programm
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HL: Halbleiterphysik
HL 24: Ultra fast phenomena
HL 24.6: Vortrag
Dienstag, 28. März 2006, 16:30–16:45, POT 151
Efficient terahertz radiation of a large-area photoconductive device. — •André Dreyhaupt1, Stephan Winnerl1, Thomas Dekorsy2, and Manfred Helm1 — 1Institute of Ion-Beam Physics and Materials Research, Forschungszentrum Rossendorf, 01314 Dresden, Germany — 2Fachbereich Physik, Universität Konstanz, 78457 Konstanz, Germany
We present an approach of photoconductive terahertz (THz) generation providing a broad bandwidth and exceptional electric field amplitude. A large-area interdigitated two-electrode structure is applied to a GaAs substrate to offer high electric fields. Photocarriers excited by a Ti:Sapphire oscillator laser with MHz repetition rate are accelerated there, yielding an intense THz output. An appropriate binary mask covers every second electrode interval and carriers are excited in uniform electric field areas only. Hence contrary carrier acceleration and destructive interference is avoided. The maximum THz field amplitude, detected by electro-optic sampling, is 1.5 kV/cm, which is almost one order of magnitude more of what is achieved with other photoconductive oscillator-excited emitters. For an excitation spot diameter of 300 µ m, which corresponds to the central wavelength of the THz pulses, the THz generation is most efficient. An average THz power of 145 µ W is generated with a NIR-to-THz power-conversion efficiency of 2× 10−4. The THz power can be improved by a sufficient cooling system. The use of LT GaAs instead of semi insulating GaAs can result in larger THz bandwidth.