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HL: Fachverband Halbleiterphysik

HL 5: Ultra-fast Phenomena

HL 5.3: Vortrag

Montag, 22. März 2010, 10:45–11:00, H17

The spatial structure of longitudinal and transversal fields in focussed terahertz beams — •Stephan Winnerl, Ralf Hubrich, Falk Peter, Harald Schneider, and Manfred Helm — Forschungszentrum Dresden-Rossendorf, Postfach 510119, 01314 Dresden, Germany

While for many applications the terahertz (THz) frequency range is the least technologically developed region of the electromagnetic spectrum, which is often referred to as the THz gap, this region offers unique research opportunities. For example, coherent detection of single cycle and few cycle pulses has been developed in the THz range and is now extended to the full infrared range.

Here we apply coherent detection via electro-optic sampling in ZnTe crystals of different orientation to study amplitude and phase of longitudinal and transversal field components in focused terahertz beams. The THz radiation is generated by two types of scalable photoconductive emitters. The electrode pattern is optimized for generation of linearly polarized beams in one case and radially polarized beams in the second case. We show that these beams can be described well as Bessel Gauss beams, which are solutions of the vector Helmholtz equation. Consistent with the theory we observe a larger amplitude and a smaller spot size for the longitudinal component of a radially polarized beam as compared to a similarly focused linearly polarized beam.