3 research outputs found
Anticorrelation of Photoluminescence from Gold Nanoparticle Dimers with Hot-Spot Intensity
Bulk gold shows photoluminescence
(PL) with a negligible quantum yield of ∼10<sup>–10</sup>, which can be increased by orders of magnitude in the case of gold
nanoparticles. This bears huge potential to use noble metal nanoparticles
as fluorescent and unbleachable stains in bioimaging or for optical
data storage. Commonly, the enhancement of the PL yield is attributed
to nanoparticle plasmons, specifically to the enhancements of scattering
or absorption cross sections. Tuning the shape or geometry of gold
nanostructures (e.g., via reducing the distance between two nanoparticles)
allows for redshifting both the scattering and the PL spectra. However,
while the scattering cross section increases with a plasmonic redshift,
the PL yield decreases, indicating that the common simple picture
of a plasmonically boosted gold luminescence needs more detailed consideration.
In particular, precise experiments as well as numerical simulations
are required. Hence, we systematically varied the distance between
the tips of two gold bipyramids on the nanometer scale using AFM manipulation
and recorded the PL and the scattering spectra for each separation.
We find that the PL intensity decreases as the interparticle coupling
increases. This anticorrelation is explained by a theoretical model
where both the gold-intrinsic d-band hole recombination probabilities
as well as the field strength inside the nanostructure are considered.
The scattering cross section or the field strength in the hot-spot
between the tips of the bipyramids are not relevant for the PL intensity.
Besides, we not only observe PL supported by dipolar plasmon resonances,
but also measure and simulate PL supported by higher order plasmonic
modes
Hybrid Multilayered Plasmonic Nanostars for Coherent Random Lasing
Here,
we report that hybrid multilayered plasmonic nanostars can
be universally used as feedback agents for coherent random lasing
in polar or nonpolar solutions containing gain material. We show that
silver-enhancement of gold nanostars reduces the pumping threshold
for coherent random lasing substantially for both a typical dye (R6G)
and a typical fluorescent polymer (MEH-PPV). Further, we reveal that
the lasing intensity and pumping threshold of random lasers based
on silver-enhanced gold nanostars are not influenced by the silica
coating, in contrast to gold nanostar-based random lasers, where silica-coated
gold nanostars support only amplified spontaneous emission but no
coherent random lasing
Assessing the alignment accuracy of state-of-the-art deterministic fabrication methods for single quantum dot devices
The realization of efficient quantum light sources relies on the integration of self-assembled quantum dots (QDs) into photonic nanostructures with high spatial positioning accuracy. In this work, we present a comprehensive investigation of the QD position accuracy, obtained using two marker-based QD positioning techniques, photoluminescence (PL) and cathodoluminescence (CL) imaging, as well as using a marker-free in-situ electron beam lithography (in-situ EBL) technique. We employ four PL imaging configurations with three different image processing approaches and compare them with CL imaging. We fabricate circular mesa structures based on the obtained QD coordinates from both PL and CL image processing to evaluate the final positioning accuracy. This yields final position offset of the QD relative to the mesa center of = (-4058) nm and = (-3985) nm with PL imaging and = (-3930) nm and = (2577) nm with CL imaging, which are comparable to the offset = (2040) nm and = (-1439) nm obtained using the in-situ EBL method. We discuss the possible causes of the observed offsets, which are significantly larger than the QD localization uncertainty obtained from simply imaging the QD light emission from an unstructured wafer. Our study highlights the influences of the image processing technique and the subsequent fabrication process on the final positioning accuracy for a QD placed inside a photonic nanostructure