FCS workshop – talk slides

I gave a tutorial talk on “Plasmons, SERS and more”: at National Workshop on Fluorescence and Raman Spectroscopy

Below is the embedded file of the presentation

Nanowire kink as an antenna for 2D material

https://link.springer.com/article/10.1140/epjs/s11734-022-00511-y

A nanowire kink on a mirror can influence light scattering wavevectors and direct photoluminescence from a monolayer of a 2D material at sharp angles.

Shailendra, Sunny Tiwari , Asutosh from my group in collaboration with my colleague Atikur and his student Gokul show this unconventional nanowire antenna concept, experimentally.

The link to publication in European Physics Journal: Special Topics is above. This paper is part of a special issue on Photonic Materials

Arxiv link : https://arxiv.org/abs/2203.00391

58. Optothermal Pulling of colloids using Nanowire Plasmons – my talk at Compflu 2021

Linked is my recorded-talk presented at Compflu 2021 today (13th Dec) in the session : Active and Living Matter.

I discuss our recent work on optothermal pulling, trapping and assembly of micro-colloids under the influence of thermoplasmonic field of a single silver nanowire.

The talk was recorded on 2nd Dec 2021, so the reference on conclusion-slide is not updated.

57. Single nanoparticle driven thermoplasmonic tweezer : single-molecule SERS

We have a new paper published in Journal of Physical Chemistry Letters on “Single Molecule Surface Enhanced Raman Scattering in a Single Gold Nanoparticle-Driven Thermoplasmonic Tweezer”

Thanks to the fantastic effort by Sunny Tiwari, and excellent support by Utkarsh Khandelwal (former IISER-P undergrad) and Vandana Sharma from my group, we have been able to combine single molecule Raman scattering with a specialized nanoscale optical tweezer.

The uniqueness of this tweezer platform is that the optical trapping process is driven by the thermo-plasmonic potential created by a SINGLE, 150nm GOLD NANOPARTICLE. Concomitantly, the same field can be used to perform single-molecule Raman spectroscopy. Kind of “ek teer mae do shikar” strategy Smile

Using this system, not only we push the limits of optothermal trapping of a single nanoparticle (see video) at low laser powers, but also create a platform for deterministic transport of reversible colloidal assembly in a fluid.

We envisage that our nanometric plasmonic tweezer can be harnessed to trap and tweeze biological entities such as single virus and bacteria. Another possible application of our study is to create reconfigurable plasmonic metafluids in physiological and catalytic environments, and to be potentially adapted as an in vivo optothermal tweezer.

All the videos related to this study can be found on our lab’s Youtube channel : https://www.youtube.com/playlist?list=PLVIRTkGrtbrvs7BaNsaH6tjPpzLUizyMI

DoI of the published paper : https://doi.org/10.1021/acs.jpclett.1c03450

preprint version on arxiv : https://arxiv.org/abs/2109.04281

49. Optical Spin in Nanowire Plasmons

We have a new paper to appear in Applied Physics Letters

The work is about “Experimental observation of transverse spin of plasmon polaritons in a single-crystalline silver nanowire”

Circularly polarized laser beams carry spin angular momentum. Such “spinning” photons have a plethora of applications including optical spanners, optical information processing, chiro-optics, micro-gyroscopes, nonlinear dynamics of matter at micro and nanoscales, and many more.

An interesting question to ask is : can we generate spin states with surface electromagnetic waves such as surface plasmon polaritons ? Unlike freely propagating optical laser beams, surface electromagnetic waves can be harnessed for sub-wavelength optical interaction on a chip, and have risen to importance.

In this paper, we experimentally show how transverse spin can be generated by nanowire surface plasmons. Thanks to the outstanding effort of my group members Chetna Taneja and Diptabrata Paul, we were able to image and measure the spin density of such (quasi) one-dimensional surface electromagnetic waves in a single-crystalline silver nanowire.

A prospect that we are interested in is to transfer this spin angular momentum to objects such as individual nanoparticles and molecules in a trap, which can, hopefully, create some interesting (nonlinear) dynamic states.

preprint version on arxiv : https://arxiv.org/abs/2104.09303

41. New paper

A small thing to cheer during these gloomy times…

A new collaborative paper in Optics Express on modal and wavelength conversions in plasmonic nanowires

Work done by Adrian, Deepak K Sharma et al,
as part of Ifcpar Cefipra grant

We show that plasmonic nanowire-nanoparticle systems can perform nonlinear wavelength and modal conversions and potentially serve as building blocks for signal multiplexing and novel trafficking modalities. When a surface plasmon excited by a pulsed laser beam propagates in a nanowire, it generates a localized broadband nonlinear continuum at the nanowire surface as well as at active locations defined by sites where nanoparticles are absorbed (enhancement sites). The local response may couple to new sets of propagating modes enabling a complex routing of optical signals through modal and spectral conversions. Different aspects influencing the optical signal conversions are presented, including the parameters defining the local formation of the continuum and the subsequent modal routing in the nanowire.

Link to the paper: https://doi.org/10.1364/OE.421183