Regensburg 2007 – scientific programme

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DF: Fachverband Dielektrische Festkörper

DF 2: Internal Symposium “Nonlinearities of Photonic Materials”

DF 2.8: Talk

Monday, March 26, 2007, 12:40–13:00, H11

Measurement of linear and nonlinear band structures of 1D photonic crystals — •Detlef Kip, Jürgen Wisniewski, and Christian Rüter — Institut für Physik und Physikalische Technologien, Technische Universität Clausthal, 38678 Clausthal-Zellerfeld

Arrays consisting of parallel aligned optical channel waveguides that are evanescently coupled due to the overlap of guided modes are an example of one dimensional photonic crystals. As such they can be analysed using the Floquet-Bloch approach. Due to the periodicity the linear transmission spectrum is split into bands of allowed extended Floquet-Bloch modes divided by forbidden gaps. In a nonlinear array the propagation dynamics may be altered, and nonlinear effects like modulational instabilities of Floquet-Bloch modes and energy localization, i.e., the formation of discrete solitons, occurs. So far nonlinear one dimensional waveguide arrays have been fabricated using various materials including polymers, III/IV semiconductors, or LiNbO3 and considerable work has been accomplished to study the linear and nonlinear light propagation in these systems. Recently we demonstrated that a prism coupling method can be used to measure the linear band structure and to excite pure Floquet-Bloch modes of a one dimensional periodic medium. Here we show that in a nonlinear waveguide array this method can be applied to study the temporal evolution of the propagation constant of an excited Floquet-Bloch mode and to directly measure the band structure modified by the induced nonlinear index changes.