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Dr. Sunil Kumar
Weizmann Institute of Science, Israel
Contolled multiphoton micro-spectroscopy for high resolution
imaging applications
22nd October, 2014 (Wednesday)
11 am
FB-382

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Dr. Sunil Kumar
Weizmann Institute of Science, Israel
Contolled multiphoton micro-spectroscopy for high resolution
imaging applications.
22nd October, 2014 (Wednesday)
11 am
FB-382

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Dr. Sita Sunder
Postdoc in Physics, IIT Kanpur
Flow shear driven instability in EMHD
16 September 2014
4 pm
Old corelab 103E Meeting Room

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Sriram Guddala
Metamaterials & Plasmonics Lab, Department of Physics, IIT Kanpur
Metal-Dielectric Periodic Photonic Structures
27 August 2014 (Wednesday)
3 pm
FB - 382
The optical field confinement in periodic metal-dielectric photonic structures has been of great interest to achieve intense localized electric field strengths due to unified properties driven from plasmonic properties of metallic nanostructures and photonic band gap properties of periodic dielectric structures [1]. Here, the metal-dielectric photonic crystals (MDPCs) and some preliminary results on metamaterial perfect optical absorbers be discussed. In the context of MDPCs, it will be shown that the confined optical fields resulted from redistributed photon density of states and their influence on enhancement of Raman scattering in metal nanoparticles impinged 3D (inverse opal structures) and 1D (multilayered microcavity) photonic crystals [2-3] . The intense optical fields are obtained on excitation of band edge (3D opals) and defect state (1D microcavity) photonic modes of photonic band gap structures and their coupling to the surface plasmon resonance properties of impinged metal nanoparticles. These intense optical fields were further probed by performing spectral and angle resolved surface enhanced Raman scattering (SERS) studies, and the enhancement of Raman scattering is understood through a novel photon-plasmon-phonon interaction mechanism. Our studies show a novel aspect of PBG influence to accomplish a highly reliable periodic metal-dielectric SERS substrate for sensing and photonic applications. At the end it will be discussed some of the recent studies on design, fabrication and characterization of novel architectures of multilayer metal-dielectric perfect optical absorbers for visible and NIR wavelengths.

References:

[1] S. Guddala, K. Shadak Alee, and D. Narayana Rao, "Fabrication of  multifunctional SnO2 and SiO2-SnO2 inverse opal structures with prominent  photonic band gap properties," Opt. Mater. Express 3, 407-417 (2013).

[2] S. Guddala, V. K. Dwivedi, G. Vijaya Prakash and D. Narayana Rao,  “Raman scattering enhancement in photon-plasmon resonance mediated  metal-dielectric microcavity,” Journal of Applied Physics, 114, 224309  (2013).

[3] S. Guddala, K. S. Alee, A. Chiappini, M. Ferrari, and D. Narayana Rao,  “Experimental investigation of photonic band gap influence on enhancement  of Raman-scattering", Journal of Applied Physics, 112, 084303 (2012).

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Dr. Ipsita Mandal
Perimeter, Waterloo
Low Energy Physics of a Non-Fermi Liquid System
20 August 2014
3 pm
FB - 382
We devise a renormalization group analysis for quantum field theories with Fermi surface to study scaling behaviour of non-Fermi liquid states in a controlled approximation. The non-Fermi liquid fixed points are identified from a Fermi surface in (m+1) spatial dimensions, while the co-dimension of Fermi surface is also extended to a generic value. We also study superconducting instability in such systems as a function of dimension and co-dimension of the Fermi surface. The key point in this whole analysis is that unlike in relativistic QFT, the Fermi momentum kF enters as a dimensionful parameter, thus modifying the naive scaling arguments. The effective coupling constants are found to be combinations of the original coupling constants and kF.