The Promise of Plasmonics
ABSTRACT Light is a wonderful medium for carrying information. Optical fibers now span the globe, guiding light signals that convey voluminous streams of voice communications and vast amounts of data. This gargantuan capacity has led some researchers to prophesy that photonic devices--which channel and manipulate visible light and other electromagnetic waves--could someday replace electronic circuits in microprocessors and other computer chips. Unfortunately, the size and performance of photonic devices are constrained by the diffraction limit; because of interference between closely spaced light waves, the width of an optical fiber carrying them must be at least half the light's wavelength inside the material. For chip-based optical signals, which will most likely employ near-infrared wavelengths of about 1,500 nanometers (billionths of a meter), the minimum width is much larger than the smallest electronic devices currently in use; some transistors in silicon integrated circuits, for instance, have features smaller than 100 nanometers.
SourceAvailable from: Yusuke Yamauchi[Show abstract] [Hide abstract]
ABSTRACT: Mesoporous gold ( Au) films with tunable pores are expected to provide fascinating optical properties stimulated by the mesospaces, but they have not been realized yet because of the difficulty of controlling the Au crystal growth. Here, we report a reliable soft-templating method to fabricate mesoporous Au films using stable micelles of diblock copolymers, with electrochemical deposition advantageous for precise control of Au crystal growth. Strong field enhancement takes place around the center of the uniform mesopores as well as on the walls between the pores, leading to the enhanced light scattering as well as surface-enhanced Raman scattering (SERS), which is understandable, for example, from Babinet principles applied for the reverse system of nanoparticle ensembles.Nature Communications 03/2015; 6. DOI:10.1038/ncomms7608 · 10.74 Impact Factor
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ABSTRACT: A novel hybrid planar lens is proposed to engineer the far-field focusing patterns. It consists of an array of slits which are filled with phase-change material Ge2Sb2Te5 (GST). By varying the crystallization level of GST from 0% to 90%, the Fabry-Pérot resonance supported inside each slit can be spectrally shifted across the working wavelength at 1.55 µm, which results in a transmitted electromagnetic phase modulation as large as 0.56π. Based on this geometrically fixed platform, different phase fronts can be constructed spatially on the lens plane by assigning the designed GST crystallization levels to the corresponding slits, achieving various far-field focusing patterns. The present work offers a promising route to realize tunable nanophotonic components, which can be used in optical circuits and imaging applications.Scientific Reports 03/2015; 5:8660. DOI:10.1038/srep08660 · 5.08 Impact Factor
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ABSTRACT: In this report we have studied the near field and the far field plasmonic prop-erties of gold nanocylinders arranged linearly in a Fibonacci number chain and compared the results with those arranged in a conventional geometry. Assigning the radius of first two nanocylinders as 10nm, we have arranged five gold nanocylinders linearly with radii varying according to Fibonacci numbers and compared the optical properties with conventional geometry. Using FEM simulation we explored the near field distribution and the far field radiation pattern of the two geometries for various excitation angles. Our study reveals significant backscattered intensity in the far field radia-tion pattern for excitation angles along the chain for Fibonacci geometry, which was otherwise absent in conventional geometry. A systematic variation in near field enhancement is observed as a function of excitation angles which could guide us to tune Raman enhancement by changing the angle of excitation. We have obtained the maximum near field enhancement in the gap of two largest nanocylinders which is in contrast to the results obtained in the self similar chain of nanostructures. In addition we have explored the polarization dependent plasmonic properties of 1D silver nanowires and observed the strong dependence of incident polarization on propagation of surface plasmon polaritons.05/2012, Degree: M.S., Supervisor: Dr. G.V. Pavan Kumar