Hybrid perovskites has recently emerged as a promising material for flatland optoelectronic and nanophotonic applications. In this report, we present our initial findings about probing the microscopic emission process using back focal plane spectroscopy. Our results highlight how the growth, induced defects and morphological heterogeneity modify the photoluminescence emission in hybrid perovskite nanostructured thin films. Furthermore, we explain our findings within the framework of back focal plane imaging principles.
Researchers all over the world are competing in a technology-driven quest to develop the next generation of ultrasmall,
low-power photonic and plasmonic devices. One route to this objective involves hybrid structures that incorporate a
phase-changing material into the structure, creating a nanocomposite material in which the optical response of a
plasmonic or photonic structure is modulated by a change in phase, crystallinity or dielectric function induced by
thermal, optical or electrical stimulus. Vanadium dioxide (VO2) has been considered as a potential electro-optic
switching material for electronic and photonic applications ever since its semiconductor-to-metal transition (SMT) was
first described half a century ago. This review describes the application of vanadium dioxide as the switching element in
(i) a hybrid silicon ring resonator and (ii) a polarization-sensitive, multifunctional plasmonic modulator in the form of a
nanoscale heterodimer. As is now widely known, the SMT in VO2 is also accompanied by a structural phase transition
(SPT) from the M1 (monoclinic) to a rutile (tetragonal, R) crystalline form that was believed to prevent a fast recovery
after switching. However, recent research has shown that this picture is oversimplified, and that there is a monoclinic
metallic state that enables true ultrafast switching. That understanding, in turn, is leading to new concepts in developing
hybrid nanocomposites that incorporate VO2 in silicon photonics and plasmonic modulators, enabling the construction of
ultrafast optical switches, modulators and memory elements.
We discuss in this paper the feasibility of dynamically modulating both resonance wavelength and spectral width
of single nanostructures exhibiting plasmonic effects by cycling through a metal-insulator transition (MIT) in
vanadium dioxide (VO2). Using full-field 3D finite-difference time domain (FDTD) simulation method with
nonuniform mesh techniques, we study the effects of this modulation by varying the lateral dimensions of these
nanostructures from 40 nm to 120 nm radially and changing its configuration as well, that is VO2 nanodisk on
gold one and vice-versa. As an initial step towards fabricating those single composite nanostructures showing the
greatest modulating effect, we start by making single NPs of VO2 and single gold NPs embedded between two
60 nm layers of VO2. The samples are fabricated on 130 μm thin glass substrates by electron-beam lithography,
pulsed laser deposition of VO2 and electron-beam evaporation of gold. Using confocal extinction spectroscopy,
we hereafter provide for the first time experimental observations of spectral tuning in these lithographically
prepared single nanostructures. However, we discussed the variability in spectra obtained. Indeed, as the gold
NP size decreases, it becomes comparable to the domain sizes of the embedding VO2 and this prevent the correct
acquisition of the flat field. Hence the study of the tunability of gold particle plasmon resonance is imparted.
However, we conclude that this study will be feasible for truly hybridized NP, that is gold nanodisk stacked on
VO2 nanodisk and vice-versa. As hinted by our simulation studies and preliminary experimental results, these
hybridized composite NPs could potentially be used in the dynamic spectral tuning of plasmonic waveguides.
Previous observations on arrays of single nanoparticles (NPs) have shown that particle separation and grating
constant determine the peak extinction wavelength of the local surface plasmon resonance (LSPR). Recently, it
has been predicted that the LSPR peak extinction wavelength in arrays of nanodimers (NDs) exhibit enhanced
sensitivity to changes in the local dielectric function compared to single NPs. In order to test this prediction,
arrays of NPs, NDs and heterodimers comprising three different NP sizes were fabricated by electron-beam
lithography with various grating constants, particle diameters, and interparticle separations. Another set of
arrays were also fabricated and coated with approximately 60-nm of vanadium dioxide, which undergoes an
insulator to metal phase transition at a critical temperature near 68.C. By tuning the temperature of the
samples through the strong-correlation region around the critical temperature, we varied the effective dielectric
constant surrounding the NP arrays over a significant range. Linear extinction measurements on the arrays were
made at temperatures above and below the critical temperature, with linear polarizers placed in the incident
beam in order to distinguish between LSPR modes. Measurements show a clear dependence of LSPR sensitivity
to interparticle separation as well as the dielectric function of the surrounding medium. Finally, finite-difference
time-domain (FDTD) simulations were carried out for comparison with the experimental results.
Thin films of a conducting polymer have been grown by resonant infrared matrix-assisted pulsed-laser evaporation
(RIR-MAPLE). Properties of the thin films such as surface morphology and electrical conductivity have
been investigated as a function of laser wavelength, fluence, and pulse structure. Using a free-electron laser
whose wavelength is continuously tunable throughout the mid-infrared region (2-10 μm), we are able to deposit
polymer films from various liquid matrices by resonantly exciting selective vibrational modes of the solvent. An
Er:YAG laser operating at 2.94 μm is used to study the effects of different laser pulse durations. In the case of
poly(3,4 ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS), it is found that only specific excitation
wavelengths and pulse durations lead to the deposition of smooth and functional polymer films.
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