New Generation of Photoconductive Few-Cycle Terahertz Emitters

Abstract

The generation of few-cycle Terahertz radiation into the free space from a biased photoconductive gap illuminated by an ultrashort laser pulse is known more than a decade [1]. Since then, many attempts were presented to increase the generated THz power without compromising the bandwidth of the output radiation [2, 3]. In this contribution, we report on a low-temperaturegrown GaAs (LT GaAs) based photoconductive THz emitter integrated with a semiconductor based Bragg mirror. This design improves the generators THz output power by about one order of magnitude. The optical resonance and the confinement of the photogenerated carriers in the high electric field region of the LT GaAs layer are responsible for the observed enhancement of the THz emission. In addition, we have focused on an optimization of the growth temperature of the LT GaAs layer with respect to a maximum photoresponse of the material and a maximum breakdown field. It is known that annealed LT GaAs changes its properties (resistivity, carriers’ lifetime) with the growth temperature [4]. Therefore, we designed and tested a multilayer LT GaAs structure grown at an optimized temperature to increase the performance of the THz emitter. Finally, we have shown an application of the Bragg mirror based photoconductive THz antenna for the THz generation in the cavity of femtosecond Ti:Sapphire laser.KeywordsSapphire LaserGaAs LayerPhotogenerated CarrierMolecular Beam EpitaxialBragg MirrorThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.