Rayleigh Imaging of Graphene and Graphene Layers

We investigate graphene and graphene layers on different substrates by monochromatic and white-light confocal Rayleigh scattering microscopy. The image contrast depends sensitively on the dielectric properties of the sample as well as the substrate geometry and can be described quantitatively using the complex refractive index of bulk graphite. For few layers (<6) the monochromatic contrast increases linearly with thickness: the samples behave as a superposition of single sheets which act as independent two dimensional electron gases. Thus, Rayleigh imaging is a general, simple and quick tool to identify graphene layers, that is readily combined with Raman scattering, which provides structural identification.Comment: 8 pages, 9 figure

Model of the effective-medium approximation for nanostructured layers with the account of interparticle interactions and its ellipsometric registration

Here we discuss the deficiencies of standard Effective-Medium Approximation in the application to thin layers and propose the model, which overcomes those problems for 2-dimensional case. Ellipsometry of layers of gold nanoparticles reveals the discussed interparticle interactions in such layers

Deficiency of Standard Effective-Medium Approximation for Ellipsometry of Layers of Nanoparticles

Correct description of optical properties of layers of disordered interacting nanoparticles is the problem. Contrary to volumes of nanocomposites, when standard models of effective-medium approximations (EMA) work well, two-dimensional case of layers has intrinsic anisotropy, which influences interparticle interactions. The deficiency of standard Maxwell-Garnett model in the application to the ellipsometry of layers of gold nanoparticles is demonstrated. It demands the modification of EMA models and one way of this is considered in this paper. Contrary to existing 2D models with phenomenological parameters, the proposed Green function approach uses the same number of parameters as standard 3D EMA models for explicit calculations of effective parameters of layers of disordered nanoparticles

Magnetic Nature of Light Transmission through a 5-nm Gap

Slot antennas have been exploited as important building blocks of optical magnetism because their radiations are invoked by the magnetic fields along the axes, as vectorial Babinet principle predicts. However, optical magnetism of a few-nanometer-width slit, for which fascinating applications are found due to the colossal field enhancement but Babinet principle fails due to the nonnegligible thickness, has not been investigated. In this paper, we demonstrated that the magnetic field plays a dominant role in light transmission through a 5-nm slit on a 150-nm-thick gold film. The 5-nm slit was fabricated by atomic layer lithography, and the transmission was investigated for various incident angles by experiment and simulation at 785-nm wavelength. We found that, due to the deep subwavelength gap width, the transmission has the same incident angle dependence as the tangential magnetic field on the metal surface and this magnetic nature of a nanogap holds up to similar to 100-nm width. Our analysis establishes conditions for nanogap optical magnetism and suggests new possibilities in realizing magnetic-field-driven optical nonlinearities

Solid-Liquid Crystal Interfaces Probed by Optical Second-Harmonic Generation

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