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Microlens coupled interdigital photoconductive switch

: Matthäus, G.; Nolte, S.; Hohmuth, R.; Voitsch, M.; Richter, W.; Pradarutti, B.; Riehemann, S.; Notni, G.; Tünnermann, A.


Applied Physics Letters 93 (2008), No.9, Art. 091110, 3 pp.
ISSN: 0003-6951
ISSN: 1077-3118
Journal Article
Fraunhofer IOF ()
spectroscopy; radiation

A large-area terahertz emitter based on an interdigital finger electrode photoconductive switch on low-temperature grown GaAs attached to a hexagonal microlens array is demonstrated. The hexagonal arranged microlenses direct the incident IR excitation pulses into specified electrode gaps, resulting in constructive interference in the terahertz far field. Using a Ti:sapphire oscillator running at 80 MHz with 150 fs pulses, 6.5 mu m THz average power at 540 mW optical excitation is obtained. The maximum IR-to-terahertz conversion efficiency achieved is >= 1.35x10(-5).