Stuttgart 2012 – wissenschaftliches Programm
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Q: Fachverband Quantenoptik und Photonik
Q 54: Poster 3
Q 54.43: Poster
Donnerstag, 15. März 2012, 16:30–19:00, Poster.I+II
Broadband degenerate four-wave mixing of optical vortex beams — Peter Hansinger1, •Georgi Maleshkov2, Dragomir N. Neshev3, Alexander Dreischuh1,2, and Gerhard G. Paulus1,4 — 1Institut für Optik und Quantenelektronik, Friedrich-Schiller-Universität Jena, Max-Wien-Platz 1, 07743 Jena, Germany — 2Department of Quantum Electronics, Sofia University, 5 James Bourchier Blvd., Sofia-1164, Bulgaria — 3Nonlinear Physics Centre, Research School of Physics and Engineering, Australian National University, Canberra, Australia — 4Helmholtz-Institute Jena, Helmholtzweg 4, 07743 Jena, Germany
Optical vortices, also known as screw dislocations, are singular points within the phase of a light beam. The phase varies by a multiple m of 2π over the angular coordinate φ, and is therefore undefined in the center and the intensity becomes zero at this point. m is called the topological charge and corresponds to photon angular momentum, and as such is a conserved quantity. Such donut beams have become useful e.g. in optical micromanipulation as so-called optical tweezers.
We have performed experiments where vortex beams with different topological charges are interacting via degenerate four-wave mixing in a nonlinear Kerr medium. The vortices are imprinted on ultrashort laser pulses of different central wavelengths, so that both spectral broadening and topological charge mixing occurs. This leads to sum- and difference- topological charges in the spectral satellites. The cascaded mixing process is observed up to third order. Broadband simulations in the spectral domain confirm the experimental findings.