Journal
OPTICS EXPRESS
Volume 18, Issue 5, Pages 4939-4947Publisher
OPTICAL SOC AMER
DOI: 10.1364/OE.18.004939
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Funding
- Center for Applied Photonics (CAP)
- Engineering and Physical Sciences Research Council [EP/H016368/1, EP/D030242/1] Funding Source: researchfish
- EPSRC [EP/H016368/1] Funding Source: UKRI
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The photo-Dember effect is a source of impulsive THz emission following femtosecond pulsed optical excitation. This emission results from the ultrafast spatial separation of electron-hole pairs in strong carrier gradients due to their different diffusion coefficients. The associated time dependent polarization is oriented perpendicular to the excited surface which is inaptly for efficient out coupling of THz radiation. We propose a scheme for generating strong carrier gradients parallel to the excited surface. The resulting photo-Dember currents are oriented in the same direction and emit THz radiation into the favorable direction perpendicular to the surface. This effect is demonstrated for GaAs and In0.53Ga0.47As. Surprisingly the photo-Dember THz emitters provide higher bandwidth than photoconductive emitters. Multiplexing of phase coherent photo-Dember currents by periodically tailoring the photoexcited spatial carrier distribution gives rise to a strongly enhanced THz emission, which reaches electric field amplitudes comparable to a high-efficiency externally biased photoconductive emitter. (C) 2010 Optical Society of America
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