7 research outputs found
Supplementary document for Metasurface Enabled Barcoding for Compact Flow Cytometry - 6831134.pdf
Supplemental Documen
Localization of Excess Temperature Using Plasmonic Hot Spots in Metal Nanostructures: Combining Nano-Optical Antennas with the Fano Effect
It
is challenging to strongly localize temperature in small volumes
because heat transfer is a diffusive process. Here we show how to
overcome this limitation using electrodynamic hot spots and interference
effects in the regime of continuous-wave (CW) excitation. We introduce
a set of figures of merit for the localization of excess temperature
and for the efficiency of the plasmonic photothermal effect. Our calculations
show that the local temperature distribution in a trimer nanoparticle
assembly is a complex function of the geometry and sizes. Large nanoparticles
in the trimer play the role of the nano-optical antenna, whereas the
small nanoparticle in the plasmonic hot spot acts as a nanoheater.
Under the specific conditions, the temperature increase inside a nanoparticle
trimer can be localized in a hot spot region at the small heater nanoparticle
and, in this way, a thermal hot spot can be realized. However, the
overall power efficiency of local heating in this trimer is much smaller
than that of a single nanoparticle. We can overcome the latter disadvantage
by using a trimer with a nanorod. In the trimer assembly composed
of a nanorod and two spherical nanoparticles, we observe a strong
plasmonic Fano effect that leads to the concentration of optical energy
in the small heater nanorod. Therefore, the power efficiency of generation
of local excess temperature in the nanorod-based assembly greatly
increases due to the strong plasmonic Fano effect. The Fano heater
incorporating a small nanorod in the hot spot has obviously the best
performance compared to both single nanocrystals and a nanoparticle
trimer. The principles of heat localization described here can be
potentially used for thermal photocatalysis, energy conversion and
biorelated applications
Dielectric Meta-Reflectarray for Broadband Linear Polarization Conversion and Optical Vortex Generation
Plasmonic metasurfaces
have recently attracted much attention
due
to their ability to abruptly change the phase of light, allowing subwavelength
optical elements for polarization and wavefront control. However,
most previously demonstrated metasurface designs suffer from low coupling
efficiency and are based on metallic resonators, leading to ohmic
loss. Here, we present an alternative approach to plasmonic metasurfaces
by replacing the metallic resonators with high-refractive-index silicon
cut-wires in combination with a silver ground plane. We experimentally
demonstrate that this meta-reflectarray can be used to realize linear
polarization conversion with more than 98% conversion efficiency over
a 200 nm bandwidth in the short-wavelength infrared band. We also
demonstrate optical vortex beam generation using a meta-reflectarray
with an azimuthally varied phase profile. The vortex beam generation
is shown to have high efficiency over a wavelength range from 1500
to 1600 nm. The use of dielectric resonators in place of their plasmonic
counterparts could pave the way for ultraefficient metasurface-based
devices at high frequencies
Hot Electron-Based Near-Infrared Photodetection Using Bilayer MoS<sub>2</sub>
Recently, there has been much interest
in the extraction of hot electrons generated from surface plasmon
decay, as this process can be used to achieve additional bandwidth
for both photodetectors and photovoltaics. Hot electrons are typically
injected into semiconductors over a Schottky barrier between the metal
and semiconductor, enabling generation of photocurrent with below
bandgap photon illumination. As a two-dimensional semiconductor single
and few layer molybdenum disulfide (MoS<sub>2</sub>) has been demonstrated
to exhibit internal photogain and therefore becomes an attractive
hot electron acceptor. Here, we investigate hot electron-based photodetection
in a device consisting of bilayer MoS<sub>2</sub> integrated with
a plasmonic antenna array. We demonstrate sub-bandgap photocurrent
originating from the injection of hot electrons into MoS<sub>2</sub> as well as photoamplification that yields a photogain of 10<sup>5</sup>. The large photogain results in a photoresponsivity of 5.2
A/W at 1070 nm, which is far above similar silicon-based hot electron
photodetectors in which no photoamplification is present. This technique
is expected to have potential use in future ultracompact near-infrared
photodetection and optical memory devices
Nonlinear Fano-Resonant Dielectric Metasurfaces
Strong nonlinear light–matter
interaction is highly sought-after for a variety of applications including
lasing and all-optical light modulation. Recently, resonant plasmonic
structures have been considered promising candidates for enhancing
nonlinear optical processes due to their ability to greatly enhance
the optical near-field; however, their small mode volumes prevent
the inherently large nonlinear susceptibility of the metal from being
efficiently exploited. Here, we present an alternative approach that
utilizes a Fano-resonant silicon metasurface. The metasurface results
in strong near-field enhancement within the volume of the silicon
resonator while minimizing two photon absorption. We measure a third
harmonic generation enhancement factor of 1.5 Ă— 10<sup>5</sup> with respect to an unpatterned silicon film and an absolute conversion
efficiency of 1.2 × 10<sup>–6</sup> with a peak pump intensity
of 3.2 GW cm<sup>–2</sup>. The enhanced nonlinearity, combined
with a sharp linear transmittance spectrum, results in transmission
modulation with a modulation depth of 36%. The modulation mechanism
is studied by pump–probe experiments
Supplementary Material from Metasurface polarization splitter
This file contains extra details regarding metasurface simulations and fabricatio