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Khorasaninejad, Mohammadreza

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Khorasaninejad

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Mohammadreza

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Khorasaninejad, Mohammadreza
Author's Publications: search.filters.isAuthorOfPublication.551a48f2-9ff1-4c81-882b-a559d51552ba

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    High Efficiency Near Diffraction-Limited Mid-Infrared Flat Lenses Based on Metasurface Reflectarrays
    (The Optical Society, 2016) Zhang, Shuyan; Kim, Myoung-Hwan; Aieta, Francesco; She, Alan; Mansuripur, Tobias; Gabay, Ilan; Khorasaninejad, Mohammadreza; Rousso, David; Wang, Xiaojun; Troccoli, Mariano; Yu, Nanfang; Capasso, Federico
    A limiting factor in the development of mid-infrared optics is the lack of abundant materials that are transparent, low cost, lightweight, and easy to machine. In this paper, we demonstrate a metasurface device that circumvents these limitations. A flat lens based on antenna reflectarrays was designed to achieve near diffraction-limited focusing with a high efficiency (experiment: 80%; simulation: 83%) at 45o incidence angle at λ = 4.6 μm. This geometry considerably simplifies the experimental arrangement compared to the common geometry of normal incidence which requires beam splitters. Simulations show that the effect of comatic aberrations is small compared to parabolic mirrors. The use of single-step photolithography allows large scale fabrication.
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    Broadband and chiral binary dielectric meta-holograms
    (American Association for the Advancement of Science (AAAS), 2016) Khorasaninejad, Mohammadreza; Ambrosio, Antonio; Kanhaiya, Pritpal; Capasso, Federico
    Subwavelength structured surfaces, known as meta-surfaces, hold promise for future compact and optically thin devices with versatile functionalities. By revisiting the concept of detour phase, we demonstrate high-efficiency holograms with broadband and chiral imaging functionalities. In our devices, the apertures of binary holograms are replaced by subwavelength structured microgratings. We achieve broadband operation from the visible to the near infrared and efficiency as high as 75% in the 1.0 to 1.4 mm range by compensating for the inherent dispersion of the detour phase with that of the subwavelength structure. In addition, we demonstrate chiral holograms that project different images depending on the handedness of the reference beam by incorporating a geometric phase. Our de- vices’ compactness, lightness, and ability to produce images even at large angles have significant potential for impor- tant emerging applications such as wearable optics.
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    Publication
    Super-Dispersive Off-Axis Meta-Lenses for Compact High Resolution Spectroscopy
    (American Chemical Society (ACS), 2016) Khorasaninejad, Mohammadreza; Chen, W. T.; Oh, J.; Capasso, Federico
    Metasurfaces have opened a new frontier in the miniaturization of optical technology by allowing exceptional control over the wavefront. Here, we demonstrate off-axis meta-lenses that simultaneously focus and disperse light of different wavelengths with unprecedented spectral resolution. They are designed based on the geometric phase via rotated silicon nanofins and can focus light at angles as large as 80°. Due to the large angle focusing, these meta-lenses have superdispersive characteristics (0.27 nm/mrad) that make them capable of resolving wavelength differences as small as 200 pm in the telecom region. In addition, by stitching several meta-lenses together, we maintain a high spectral resolution for a wider wavelength range. The meta-lenses have measured efficiencies as high as 90% in the wavelength range of 1.1 to 1.6 μm. The planar and compact configuration together with high spectral resolution of these meta-lenses has significant potential for emerging portable/wearable optics technology.