Regensburg 2007 – wissenschaftliches Programm
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DF: Fachverband Dielektrische Festkörper
DF 2: Internal Symposium “Nonlinearities of Photonic Materials”
DF 2.4: Vortrag
Montag, 26. März 2007, 11:20–11:40, H11
On the way to µJ THz pulses by optical rectification — •Eberhard Riedle1, Balázs Bartal2, Ida Z. Kozma1, Andrei Stepanov3, Gábor Almási4, Jürgen Kuhl5, and János Hebling2 — 1LMU München, Germany — 2Dept. of Exp. Physics, Univ. of Pécs, Hungary — 3Inst. of Spectroscopy, Russian Acad. of Science, Troitsk, Russia — 4Dept. of Informatics in Physics, Univ. of Pécs, Hungary — 5MPI for Solid State Research, Stuttgart, Germany
We investigate the energy scaling of sub-ps THz pulses generated by tilted pulse front excitation. With 150fs-long 500µJ pump pulses at 800nm THz energies up to 240nJ were achieved [1]. For a 1.2mm2 pump area, the conversion efficiency of pump to THz energy had a maximum of 5x10−4 at 300µJ pump energy. This amounts already to a quantum efficiency of above 10%. For comparison, the maximum attainable THz pulse energy was limited to 2.1nJ at 32µJ pump energy in a line focusing geometry. To illustrate the very different type of development of the THz pulse inside the electro-optical crystal, model calculations were performed for both geometries and found to be in good agreement with the experiments. Comprehensive simulations predict that the tilted pulse front excitation allows further up-scaling of the THz pulse energy by using a larger pump spot size, still stronger pump pulses and cooling of the nonlinear crystal [2]. These measures should increase the THz energy into the µJ regime and the quantum efficiency to 50%. We also find an optimal pulse duration and crystal length for maximum resulting electric field and the potential for simple tuning of the THz center frequency.
[1] A. G. Stepanov, et al. Opt. Express 13, 5762-5768 (2005).
[2] B. Bartal et al., Appl. Phys. B (2006) DOI: 10.1007/s00340-006-2512-7