Nanophotonics & Plasmonic Device Engineering..
PLASMONIC NanoAntennas & Enhanced Light-Matter Interactions
Plasmonic nano-antennas with their unique ability to focus light far beyond the diffraction limit are at the core of a myriad of new exciting opportunities. Recently, we utilized nanoscale analogs of dipolar antennas for unprecedented enhancement of absorption signals (molecular fingerprints) from biomolecules at mid-infrared wavelengths. More recently, we proposed and demonstrated for the first time that monopole plasmonic nanoantenna elements can be fabricated in conventional planar geometries. These monopole nano-antennas, circumventing the need for three-dimensional structures, present unique opportunities as the conducting ground plane offers current isolation in planar configuration. This capability allows on-chip integration of progressively more complex nanoantennas, incorporating multiple current carrying elements with different resonance characteristics. These structures offer an ultracompact multi-wavelength resonant spectroscopic substrates for broad-band surface enhanced nanospectroscopy of biomolecules and single-molecule conformational studies. We take advantage of the strong optical forces in these structures to trap and spectroscopically investigate bioparticles.
"Fano-resonant asymmetric metamaterials for ultrasensitive spectroscopy and identification of molecular monolayer" Wu et al., Nature Materials 11 (1), 69-75 (2012)
Radiative Engineering of Quantum Emitters
Plasmonic meta-materials provide a dramatic control over the rates of radiative decay and the rates of resonance energy transfer from emitters such as fluorophores and quantum dots. Similarly, radiative engineering of plasmonic resonances allows manipulation of the efficiency and directionality of the emitted/absorbed radiation at single-photon levels. We recently pioneered an ultracompact plasmonic structure consisting of coupled nanoantennas where the multiple radiant and sub-radiant hybrid modes can be tailored independently. By coupling plasmonic modes with opposite decay characteristics (i.e., short-lived and long-lived modes) in two separate dimer structures (consisting of side/end –coupled nanoantennas), we created structurally asymmetric resonances for highly directional angular radiations from single quantum emitters. These uni-directional nanoantennas offer unique opportunities for ultrasensitive detection of quantum emitters in biotechnology applications as well as development of single-photon light sources and detectors.
"On chip plasmonic monopole nano-antennas and circuits" R Adato, AA Yanik et al., Nano letters 11 (12), 5219-5226 (2011)
"Radiative engineering of plasmon lifetimes in embedded nanoantenna arrays" R Adato, AA Yanik et al., Optics Express 18 (5), 4526-4537 (2010)
Coupled Meta-Atoms & Meta-Materials for Slow Light and Plasmonic Lasers
We have recently demonstrated multi-spectral plasmon induced transparency (PIT) effect in coupled plasmonic meta-atoms, a classical analog of the much acclaimed electromagnetically induced transparency (EIT) effect in atomic physics. Unlike previous studies that were focused on isolated meta-atoms, we succeeded in coupling multiple meta-atoms to achieve multi-spectral PIT effect. To achieve this, we experimentally created short- and longlived resonances (in an analogy to transition-allowed and -forbidden atomic orbitals) by radiative engineering of the plasmonic modes into super/sub –radiant resonances.
This platform is highly promising as it allows precise engineering of meta-atomic energy levels to obtain desired optical dispersion characteristics. In order to overcome the metallic losses, I am particularly interested in integrating dielectric materials with optical gain in between metallic structures. These meta-material devices, offering extremely large Q/Vmode ratios (Quality factor Q and cavity mode volume Vmode), can be utilized in the realization of ultra-fast and highly efficient meta-material lasers. By modifying spontaneous emission rates of embedded dye molecules using the Purcell effect and taking advantage of the large bandwidth PIT phenomena, I want to demonstrate ultra-compact, low-power, and silicon-compatible Raman lasers. These devices, reducing group velocities and confining light both at the Stokes and pump frequencies, could open the door to novel biodetection and environmental monitoring technologies by merging photonic sensing and light sources into a single photonic platform.
"Multispectral plasmon induced transparency in coupled meta-atoms" A Artar, AA Yanik et al., Nano letters 11 (4), 1685-1689 (2011)
"Directional double Fano resonances in plasmonic hetero-oligomers" A Artar, AA Yanik et al., Nano letters 11 (9), 3694-3700 (2011)
"Ultra-sensitive vibrational spectroscopy of protein monolayers with plasmonic nanoantenna arrays" R Adato, AA Yanik et al., (PNAS) 106 (46), 19227-19232 (2009)