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Large-area microlens emitters for powerful THz emission

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


Applied Physics. B 96 (2009), Nr.2-3, S.233-235
ISSN: 0340-3793
ISSN: 0721-7269
ISSN: 0946-2171
ISSN: 1432-0649
Fraunhofer IOF ()
generation; laser

A microlens coupled large-area emitter based on low-temperature grown GaAs is presented. A hexagonal microlens array directs the incident pump light into every second gap of a finger electrode structure. Consequently, an unidirectional photocurrent at high acceleration field strengths (50 kV/cm) is achieved, which generates constructively superposed THz emission. Using a Ti:Sapphire oscillator with a maximum average power of about 3 W at a repetition rate of 80 MHz, a net IR-to-THz conversion efficiency up to 1.3x10(-4) and a THz average power of 280 mu W is achieved.