Ideas from the Metamaterials Community

What we're reading... Why we like it...
Nitrogen-doping induced self-assembly of graphene nanoribbon-based two-dimensional and three-dimensional metamaterials by TH Vo, UGE Perera, M Shekhire, MM Pour, DA Kunkel, H Lu, A Gruverman, E Sutter, M Cotlet, D Nykypanchuk, P Zahl, A Enders, A Sinitskii, and P Sutter in Nano Letters, 2015
Posted: Sep 3, 2015 		Timothy H.Vo and his colleagues present a new type of nitrogen-doped graphene nanoribbons (GNRs), which shows a great potential to create novel nanoscale both 2D and 3D metamaterials. Atomically precise bottom-up synthesis has been used on a surface and in solution in order to fabrication these planar and 3D crystalline GNRs. Technologies such as Scanning tunneling microscopy (STM), Scanning tunneling spectroscopy (STS), transmission electron microscopy (TEM), X-ray scattering as well as photoluminescence (PL) spectroscopy and UV-vis absorption spectroscopy are used to measure the performance of the structures which are outstanding, compared to other similar nanostructures. As nanoscale building blocks, the reported 8N-GNRs structure provides a rapid developing toolset to realize families of novel carbon-based materials with engineered properties.
High efficiency low-power microwave rectifier for wireless energy harvesting by S Ladan and K Wu in Microwave Symposium Digest (IMS), 2013 IEEE MTT-S International. IEEE,, 2013
Posted: Sep 3, 2015 		S. Ladan and K.Wu have designed a self-biased, highly efficient microwave rectifier circuit which operates in the K-band frequency region. By designing a self-biased rectifier, they are reducing the power consumed by the circuit and especially for Wireless power transfer, reducing the power is one of the highest priorities. The circuitry also involves no usage of lumped elements for matching purpose before the rectification of the AC signal which also adds to low loss. Since, the operating frequency is high, lower wavelengths, the form factor of the system will be very low. We could utilize the self-biasing idea on to our WPT system at C-band frequency. This also gives us motivation to work in higher frequency bands for WPT which will reduce the form factor greatly.
Distinguishing between plasmon-induced and photoexcited carriers in a device geometry by BY Zheng, H Zhao, A Manjavacas, M McClain, P Nordlander, and NJ Halas in in Nature Communications, 2015
Posted: Sep 3, 2015 		The generation of photocurrent from decaying plasmons in metal nanostructures is an interesting approach for photodetection and photovoltaics that has recently received much attention. However, there are two mechanisms that can contribute to the photocurrent: direct absorption in the metal and generation/decay of plasmons, and it has been unclear which is dominant. Zheng et al. perform careful experiments using Schottky and Ohmic junction photodetectors that allow them to conclude that plasmonic carrier generation can be the dominant mechanism over direct excitation.
Metascreen-Based Superdirective Antenna in the Optical Frequency Regime by A. Ludwig, C.D. Sarris and G.V. Eleftheriades in Phys. Rev. Letters, 2012
Posted: May 17, 2015 		Ludwig and his collaborators designed a metasurface to achieve near-field subwavelength focusing at a given frequency. Interestingly, in the vicinity of this frequency the metasurface acts as superdirective antenna in the farfield. The principle of operation of this discovery is explained and different designs are proposed in both microwave and optical regime. In our group it is very important to understand the operation principles of these devices in order to design the metamaterials that placed close to an antenna, improve its performance. We are using a similar approach to enhance the directivity of Leaky Waveguide Antennas.
Manipulating the Optical Bistability in a Nonlinear Plasmonic Nanoantenna Array with a Reflecting Surface by J. Butet, O.J.F Martin in Plasmonics, Springer , 2014
Posted: May 17, 2015 		Butet et al. theoretically investigate the influence of a reflecting surface on the optical bistability of an array of nanoantennas. They show that by varying the distance between the nanoantenna array and the reflecting surface, they can control important parameters of the nonlinear response such as threshold intensity and the area of the hysteresis cycle. They predict a switching intensity threshold of 20MW/cm2 for the ideal design, which is much lower than previously reported values for isolated nanoantennas. This design is a promising approach for realizing nanoscale optical switches.
Graphene Mode-Locked Ultrafast Laser by Z. Sun, T. Hasan, F. Torrisi, D. Popa, G. Privitera, F. Wang, F. Bonaccorso, D.M. Basko and A.C. Ferrari in ACS Nano, 2010
Posted: Mar 10, 2015 		The exceptional optoelectronic properties of graphene make it an ideal material for many applications. Here Sun et al. use a graphene-polymer composite fabricated with wet-chemistry techniques to make a wavenlength-independent saturable absorber, which they use to passively mode-lock an erbium-dope fiber laser. The resulting ultrafast laser produces pulses of several hundreds of femtoseconds at telecom wavelengths. This work could suggest using metamaterials as passive or active elements to drive the dynamics of ultrafast laser cavities.
Liquid Crystal Metamaterial Absorber Spatial Light Modulator for THz Applications by S. Salvatore, D. Shrekenhamer and W. Padilla in Advanced Optical Materials, 2014
Posted: Mar 10, 2015 		Savo et. al present the use of dynamically tuned metamaterials to create a spatial light modulator for terahertz frequencies. This research demonstrates the use of liquid crystal to adjust the resonant frequency of the metamaterials and the resultant spatial light modulation provides promise for terahertz imaging applications.
Anomalous Light Absorption around Subwavelength Apertures in Metal Films by O. Lozan, M. Perrin, B. Ea-Kim, J. M. Rampnoux, S. Dilhaire, and P. Lalanne in Physical Review Letters, 2014
Posted: Dec 2, 2014 		Lozan et al. study the heat dissipated near a subwavelength aperture on a gold surface. Contrary to the common belief that the intensity of light created by local sources exponentially decays with distance from the source, they show that the heat dissipated at the surface exhibits a constant plateau over a large spatial interval that can be as high as seventy wavelengths. This property has very important implications in plasmonics as it may offer an alternative to amplification for compensating losses in plasmonic devices.
Metasurface holograms for visible light by Xingjie Ni, Alexander V. Kildishev & Vladimir M. Shalaev in Nature Communications, 2013
Posted: Dec 2, 2014 		Ni et al. present an ultrathin method for designing holograms which can encode information through modulating both the amplitude and phase of the incident light with metamaterial elements. This design utilizes a metasurface to achieve modulation as opposed to many holography techniques which typically adjust the thickness or the index of the material from which the hologram is constructed. The plasmonic metasurface has a thickness of 30 nm, less than 1/23 of the incident wavelength of 676 nm, and successfully generates high-resolution as well as low-noise images, demonstrating the viability of this method for designing planar photonic devices.
Metamaterial Perfect Absorber Based Hot Electron Photodetection by Wei Li and Jason Valentine in Nano Letters, 2014
Posted: Dec 2, 2014 		Li and Valentine demonstrate a hot electron photodetector with a near-record photoresponsivity by using a metamaterial perfect absorber. Ordinarily, the losses in plasmonic structures are considered a burden. However, the hot electrons generated in metals during light absorption can actually be extracted, although the efficiency of this process is typically very low. In this paper the authors created a patterned Si metamaterial structure coated with a thin gold film. This structure results in all the incident light being absorbed in the 15 nm gold film, which happens to be about the diffusion length of hot electrons in gold. Generating nearly perfect absorption in such a thin metal layer allows for more hot electrons to be collected.

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