Frankfurt 2006 – scientific programme

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Q: Quantenoptik und Photonik

Q 47: Photonische Kristalle III

Q 47.1: Talk

Wednesday, March 15, 2006, 17:30–17:45, HV

Superfocusing of scanning beams — •Anton Husakou and Joachim Herrmann — Max Born Institute, Max Born Str. 2a, 12489 Berlin, Germany

Overcoming the diffraction limit λ/2 of light focusing is of great importance in numerous fields. Although it can be done by near-field methods, they suffer from the required subwavelength proximity between a moving near-field element and an object. Here, we study a method to achieve subdiffraction focusing of a scanning beam without subwavelength spatial control. This method is based on the suggestion that evanescent waves can be amplified by a slab of a negative-refraction material, as confirmed by extensive theoretical and experimental work using metamaterials or photonic crystals. We have recently shown that it is possible to focus a light beam below the diffraction limit by using an element which creates seed evanescent waves, and a material with negative refraction, such as a photonic crystal, to amplify them and to form a subdiffraction spot (superfocusing). To achieve focusing of a scanning light beam to an arbitrary position, we need a light-controlled nonlinear element for the creation of seed evanescent components. Here we evaluate Kerr-like nonlinear materials as such elements, placed before the layer of a negative-refraction material. The calculations are performed both with effective-medium theory appropriate for metamaterials and by numerically solving Maxwell equations for a photonic crystal. We predict that subdiffraction focusing in the range of 0.2λ is achievable.