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Proceedings Paper

Independent control of function and chromatic dispersion in diffractive optical devices with metasurfaces (Conference Presentation)
Author(s): Ehsan Arbabi; Amir Arbabi; Seyedeh Mahsa Kamali; Yu Horie; Andrei Faraon
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Paper Abstract

Diffractive optical devices have many applications in various fields of optics. A fundamental property of all diffractive devices is their negative chromatic dispersion: a diffractive grating always disperses light in the opposite order compared to a refractive prism made of a material with positive (normal) dispersion. Unlike refractive devices, chromatic dispersion in diffractive devices stems from geometrical features, and cannot be controlled via the intrinsic material dispersion. In addition to the always negative sign, the amplitude of diffractive chromatic dispersion is set only by the function of the device. For instance, the angular dispersion of a grating is always given by dθ/dλ=tan⁡(θ)/λ (where θ is the deflection angle and λ is wavelength), or the focal distance dispersion of a diffractive lens is given by df/dλ=-f/λ. Therefore, the chromatic dispersion of diffractive devices has always been set by their function (e.g. by the deflection angle for a grating or the focal distance for a lens), and could not be controlled separately. Here, we present our work on breaking this fundamental relation between the function and chromatic dispersion of diffractive devices using metasurfaces providing independent control over phase and group delays. We use a reflective dielectric metasurface to experimentally demonstrate gratings and lenses that have positive, zero, and extraordinary negative chromatic dispersion. Apart from its fundamental scientific value, this concept expands the applications of diffractive devices as it enables various types of chromatic dispersions. For instance, a special case would be a dispersionless lens operating over a wide bandwidth with the same focal distance.

Paper Details

Date Published: 28 April 2017
PDF: 1 pages
Proc. SPIE 10113, High Contrast Metastructures VI, 101130P (28 April 2017); doi: 10.1117/12.2253726
Show Author Affiliations
Ehsan Arbabi, California Institute of Technology (United States)
Amir Arbabi, California Institute of Technology (United States)
Seyedeh Mahsa Kamali, California Institute of Technology (United States)
Yu Horie, California Institute of Technology (United States)
Andrei Faraon, California Institute of Technology (United States)

Published in SPIE Proceedings Vol. 10113:
High Contrast Metastructures VI
Connie J. Chang-Hasnain; Andrei Faraon; Fumio Koyama; Weimin Zhou, Editor(s)

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