Dr Lifeng Li, Tsinghua University, China

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Dr Lifeng Li from Tsinghua University, Beijing, China will give a seminar entitled : "Internal mechanism of perfect-reflector-backed dielectric gratings to achieve high diffraction efficiency" on Wednesday, September 20th at 10:00 a.m. in room Pierre Cotton of Institut Fresnel.

Abstract : The work started 20 years ago [Appl. Opt. 42, 6255 (2003)] investigating the physical mechanism of multilayer dielectric reflection gratings to achieve 100% diffraction efficiency is extended to offer much deeper insight than before. How different diffraction amplitudes of the top surface corrugation contribute to the −1st order efficiency of such a grating is shown analytically using a minimum set of real parameters. The two diffraction amplitudes transmitted through the corrugation play a dominant role in enabling diffraction efficiency = 100%. The necessary and sufficient condition for 100% efficiency is derived, and very simple sufficient conditions are also given. Moreover, the role of the reflection phase of the perfect-reflector, including the contribution due to optical path between the corrugation and the reflector, is emphasized.

This is a joint seminar between the themes « Electromagnetic modeling » and « Nanophotonics & Components ».