Person: Kats, Mikhail A
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Kats
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Mikhail A
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Kats, Mikhail A
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Publication Optics at interfaces: ultra-thin color coatings, perfect absorbers, and metasurfaces(2014-02-25) Kats, Mikhail A; Capasso, Federico; Loncar, Marko; Aizenberg, JoannaThe vast majority of optical components and devices in use today can be grouped under the umbrella of ``bulk optics''; i.e. they generally have a non-negligible thickness compared to the wavelength of light. This is true of components from lenses to wave plates to Fabry-Perot etalons, all of which need sufficient thickness such that light waves can accumulate an appropriate amount of phase upon propagation through the structure. In this thesis, we develop and explore a variety of optical components that are thin compared to the wavelength of light and lie at the interface between two materials (i.e. a substrate and air). We explore approaches to filter, absorb, redirect, and re-shape light with flat, ultra-thin structures which are easy to fabricate with modern micro- and nanofabrication techniques.Publication Fabrication and Replication of Arrays of Single- or Multicomponent Nanostructures by Replica Molding and Mechanical Sectioning(American Chemical Society (ACS), 2010) Lipomi, Darren J.; Kats, Mikhail A; Kim, Philseok; Kang, Sung; Aizenberg, Joanna; Capasso, Federico; Whitesides, GeorgeThis paper describes the fabrication of arrays of nanostructures (rings, crescents, counterfacing split rings, cylinders, coaxial cylinders, and other structures) by a four-step process: (i) molding an array of epoxy posts by soft lithography, (ii) depositing thin films on the posts, (iii) embedding the posts in epoxy, and (iv) sectioning in a plane parallel to the plane defined by the array of posts, into slabs, with an ultramicrotome (“nanoskiving”). This work demonstrates the combination of four capabilities: (i) formation of structures that are submicrometer in all dimensions; (ii) fabrication of 3D structures, and arrays of structures, with gradients of height; (iii) patterning of arrays containing two or more materials, including metals, semiconductors, oxides, and polymers; and (iv) generation of as many as 60 consecutive slabs bearing contiguous arrays of nanostructures. These arrays can be transferred to different substrates, and arrays of gold rings exhibit plasmonic resonances in the range of wavelengths spanning 2−5 μm.Publication Generation of Two-Dimensional Plasmonic Bottle Beams(Optical Society of America, 2013) Genevet, Patrice; Dellinger, Jean; Blanchard, Romain; She, Alan; Petit, Marlene; Cluzel, Benoit; Kats, Mikhail A; de Fornel, Frederique; Capasso, FedericoBy analogy to the three dimensional optical bottle beam, we introduce the plasmonic bottle beam: a two dimensional surface wave which features a lattice of plasmonic bottles, i.e. alternating regions of bright focii surrounded by low intensities. The two-dimensional bottle beam is created by the interference of a non-diffracting beam, a cosine-Gaussian beam, and a plane wave, thus giving rise to a non-diffracting complex intensity distribution. By controlling the propagation constant of the cosine-Gauss beam, the size and number of plasmonic bottles can be engineered. The two dimensional lattice of hot spots formed by this new plasmonic wave could have applications in plasmonic trapping.Publication Patterning the Tips of Optical Fibers with Metallic Nanostructures Using Nanoskiving(American Chemical Society (ACS), 2011) Lipomi, Darren J.; Martinez, Ramses V.; Kats, Mikhail A; Kang, Sung H.; Kim, Philseok; Aizenberg, Joanna; Capasso, Federico; Whitesides, GeorgeConvenient and inexpensive methods to pattern the facets of optical fibers with metallic nanostructures would enable many applications. This communication reports a method to generate and transfer arrays of metallic nanostructures to the cleaved facets of optical fibers. The process relies on nanoskiving, in which an ultramicrotome, equipped with a diamond knife, sections epoxy nanostructures coated with thin metallic films and embedded in a block of epoxy. Sectioning produces arrays of nanostructures embedded in thin epoxy slabs, which can be transferred manually to the tips of optical fibers at a rate of approximately 2 min−1, with 88% yield. Etching the epoxy matrices leaves arrays of nanostructures supported directly by the facets of the optical fibers. Examples of structures transferred include gold crescents, rings, high-aspect-ratio concentric cylinders, and gratings of parallel nanowires.Publication Designer spoof surface plasmon structures collimate terahertz laser beams(Nature Publishing Group, 2010) Yu, Nanfang; Wang, Qi Jie; Kats, Mikhail A; Fan, Jonathan A.; Khanna, Suraj P.; Li, Lianhe; Davies, A. Giles; Linfield, Edmund H.; Capasso, FedericoSurface plasmons have found a broad range of applications in photonic devices at visible and near-infrared wavelengths. In contrast, longer-wavelength surface electromagnetic waves, known as Sommerfeld or Zenneck waves, are characterized by poor confinement to surfaces and are therefore difficult to control using conventional metallo-dielectric plasmonic structures. However, patterning the surface with subwavelength periodic features can markedly reduce the asymptotic surface plasmon frequency, leading to ‘spoof’ surface plasmons with subwavelength confinement at infrared wavelengths and beyond, which mimic surface plasmons at much shorter wavelengths. We demonstrate that by directly sculpting designer spoof surface plasmon structures that tailor the dispersion of terahertz surface plasmon polaritons on the highly doped semiconductor facets of terahertz quantum cascade lasers, the performance of the lasers can be markedly enhanced. Using a simple one-dimensional grating design, the beam divergence of the lasers was reduced from ∼180◦ to ∼10◦ , the directivity was improved by over 10 decibels and the power collection efficiency was increased by a factor of about six compared with the original unpatterned devices. We achieve these improvements without compromising high-temperature performance of the lasers.Publication Accounting for inhomogeneous broadening in nano-optics by electromagnetic modeling based on Monte Carlo methods(Proceedings of the National Academy of Sciences, 2014) Gudjonson, Herman; Kats, Mikhail A; Liu, Kun; Nie, Zhihong; Kumacheva, Eugenia; Capasso, FedericoMany experimental systems consist of large ensembles of uncoupled or weakly interacting elements operating as a single whole; this is particularly the case for applications in nano-optics and plasmonics, including colloidal solutions, plasmonic or dielectric nanoparticles on a substrate, antenna arrays, and others. In such experiments, measurements of the optical spectra of ensembles will differ from measurements of the independent elements as a result of small variations from element to element (also known as polydispersity) even if these elements are designed to be identical. In particular, sharp spectral features arising from narrow-band resonances will tend to appear broader and can even be washed out completely. Here, we explore this effect of inhomogeneous broadening as it occurs in colloidal nanopolymers comprising self-assembled nanorod chains in solution. Using a technique combining finite-difference time-domain simulations and Monte Carlo sampling, we predict the inhomogeneously broadened optical spectra of these colloidal nanopolymers and observe significant qualitative differences compared with the unbroadened spectra. The approach combining an electromagnetic simulation technique with Monte Carlo sampling is widely applicable for quantifying the effects of inhomogeneous broadening in a variety of physical systems, including those with many degrees of freedom that are otherwise computationally intractable.Publication Large Enhancement of Nonlinear Optical Phenomena by Plasmonic Nanocavity Gratings(American Chemical Society (ACS), 2010) Genevet, Patrice; Tetienne, Jean-Philippe; Gatzogiannis, Evangelos; Blanchard, Romain; Kats, Mikhail A; Scully, Marlan O.; Capasso, FedericoEnhancing nonlinear processes at the nanoscale is a crucial step toward the development of nanophotonics and new spectroscopy techniques. Here we demonstrate a novel plasmonic structure, called plasmonic nanocavity grating, which is shown to dramatically enhance surface nonlinear optical processes. It consists of resonant cavities that are periodically arranged to combine local and grating resonances. The four-wave mixing signal generated in our gold nanocavity grating is enhanced by a factor up to ≈2000, 2 orders of magnitude higher than that previously reported.Publication Holographic Detection of the Orbital Angular Momentum of Light With Plasmonic Photodiodes(Nature Publishing Group, 2012) Genevet, Patrice; Lin, Jiao; Kats, Mikhail A; Capasso, FedericoMetallic components such as plasmonic gratings and plasmonic lenses are routinely used to convert free-space beams into propagating surface plasmon polaritons and vice versa. This generation of couplers handles relatively simple light beams, such as plane waves or Gaussian beams. Here we present a powerful generalization of this strategy to more complex wavefronts, such as vortex beams that carry orbital angular momentum, also known as topological charge. This approach is based on the principle of holography: the coupler is designed as the interference pattern of the incident vortex beam and focused surface plasmon polaritons. We have integrated these holographic plasmonic interfaces into commercial silicon photodiodes, and demonstrated that such devices can selectively detect the orbital angular momentum of light. This holographic approach is very general and can be used to selectively couple free-space beams into any type of surface wave, such as focused surface plasmon polaritons and plasmonic Airy beams.Publication Multi-Beam Multi-Wavelength Semiconductor Lasers(American Institute of Physics, 2009) Capasso, Federico; Yu, Nanfang; Kats, Mikhail A; Pflügl, Christian; Geiser, Markus; Wang, Qi Jie; Belkin, Mikhail A.; Fischer, Milan; Wittmann, Andreas; Faist, Jérôme; Edamura, Tadataka; Furuta, Shinichi; Yamanishi, Masamichi; Kan, HirofumiMultibeam emission and spatial wavelength demultiplexing in semiconductor lasers by patterning their facets with plasmonic structures is reported. Specifically, a single-wavelength laser was made to emit beams in two directions by defining on its facet two metallic gratings with different periods. The output of a dual-color laser was spatially separated according to wavelength by using a single metallic grating. The designs can be integrated with a broad range of active or passive optical components for applications such as interferometry and demultiplexing.