Abstract:
Transmission and localization of light at subwavelength scale has direct relevance in
the nanophotonic-circuits of light. Usage of dielectric materials hampers nanophotonic
operations due to diffraction limit of light. To overcome this problem, plasmonic nanostructures
made of metals such as silver and gold have been utilized. They show unique
optical properties at subwavelength scales, such as enhanced localization of electric
fields, sub-diffraction limit light propagation, directional emission and optical antenna
effects, which can be harnessed in chip-scale integrated photonics and optoelectronics.
This has motivated research in identifying novel optical nanostructures that can
efficiently perform optical operations at sub-wavelength scale. With this hindsight, we
have experimentally developed and studied unique nanophotonic architecture: seriallycoupled
plasmonic nanowires, and observed the capability of light transmission and
polarized emission beyond diffraction limit of light. In order to control the light transmission
and emission, the geometry of coupled nanowire system were optimized. The
optimization parameters were bending angle between nanowires, excitation profile and
coupling geometry. Upon optimization, we tested the capability of routing the light as a
function of polarization of incident light and showcased the ability of polarization beam
splitting at sub-wavelength scale. In order to further understand the light emission characteristics
from such nanowire systems, it was important to develop advanced optical
microscopy methods to probe angular scattering and emission characteristics. To fulfill
this requirement, we have designed and developed an advanced dual-channel Fourier
optical microscopy and spectroscopy system to study the directional optical emission
from individual plasmonic nanowires and nanoparticle-nanowire system. An important
aspect of our microscope is the measurement of k-vector distribution of light emanating
from an individual, supported nanowire through the substrate and superstrate. I have explained
how our home-built optical microscope can probe far-field directional emission
properties of an individual nanowire and nanoparticle-coupled nanowire architectures
resting on a dielectric substrate. I have emphasized upon the ability to capture optical
images in Fourier-plane and spectroscopic signatures in real-plane through a substrate
and superstrate. Our work pushes the limit of optical characterization of nanoscale
structures, and can be utilized to address relevant questions pertaining to interaction of
