984 research outputs found
Local Defects in colloidal quantum dot thin films measured via spatially resolved multi-modal optoelectronic spectroscopy.
The morphology, chemical composition, and electronic uniformity of thin-film solution-processed optoelectronics are believed to greatly affect device performance. Although scanning probe microscopies can address variations on the micrometer scale, the field of view is still limited to well under the typical device area, as well as the size of extrinsic defects introduced during fabrication. Herein, a micrometer-resolution 2D characterization method with millimeter-scale field of view is demonstrated, which simultaneously collects photoluminescence spectra, photocurrent transients, and photovoltage transients. This high-resolution morphology mapping is used to quantify the distribution and strength of the local optoelectronic property variations in colloidal quantum dot solar cells due to film defects, physical damage, and contaminants across nearly the entire test device area, and the extent to which these variations account for overall performance losses. It is found that macroscopic defects have effects that are confined to their localized areas, rarely prove fatal for device performance, and are largely not responsible for device shunting. Moreover, quantitative analysis based on statistical partitioning methods of such data is used to show how defect identification can be automated while identifying variations in underlying properties such as mobilities and recombination strengths and the mechanisms by which they govern device behavior.DMR-1807342 - National Science Foundation; Hopkins Extreme Materials InstituteAccepted manuscrip
Independent electrical tuning of separated quantum dots in coupled photonic crystal cavities
Systems of photonic crystal cavities coupled to quantum dots are a promising
architecture for quantum networking and quantum simulators. The ability to
independently tune the frequencies of laterally separated quantum dots is a
crucial component of such a scheme. Here, we demonstrate independent tuning of
laterally separated quantum dots in photonic crystal cavities coupled by
in-plane waveguides by implanting lines of protons which serve to electrically
isolate different sections of a diode structure.Comment: 3 pages, 3 figure
Dynamic modulation of photonic crystal nanocavities using gigahertz acoustic phonons
Photonic crystal membranes (PCM) provide a versatile planar platform for
on-chip implementations of photonic quantum circuits. One prominent quantum
element is a coupled system consisting of a nanocavity and a single quantum dot
(QD) which forms a fundamental building block for elaborate quantum information
networks and a cavity quantum electrodynamic (cQED) system controlled by single
photons. So far no fast tuning mechanism is available to achieve control within
the system coherence time. Here we demonstrate dynamic tuning by monochromatic
coherent acoustic phonons formed by a surface acoustic wave (SAW) with
frequencies exceeding 1.7 gigahertz, one order of magnitude faster than
alternative approaches. We resolve a periodic modulation of the optical mode
exceeding eight times its linewidth, preserving both the spatial mode profile
and a high quality factor. Since PCMs confine photonic and phononic
excitations, coupling optical to acoustic frequencies, our technique opens ways
towards coherent acoustic control of optomechanical crystals.Comment: 11 pages 4 figure
Single grain heating due to inelastic cotunneling
We study heating effects of a single metallic quantum dot weakly coupled to
two leads. The dominant mechanism for heating at low temperatures is due to
inelastic electron cotunneling processes. We calculate the grain temperature
profile as a function of grain parameters, bias voltage, and time and show that
for nanoscale size grains the heating effects are pronounced and easily
measurable in experiments.Comment: 4 pages, 3 figures, revtex4, extended and corrected versio
De week van ... Marjolein Thon
Ook dit keer nemen we een kijkje in het leven van een B.I.L.-lid. Dit keer vertelt Marjolein Thon over een week in februari. Marjolein heeft de bachelor Bestuurskunde afgerond. In 2011 is zij gestart met de master public administration: management van de publieke sector. deze colleges volgt zij in Den Haag. Marjolein werkt als studentassistent communicatie en marketing op de FSW. Marjolein was twee jaar geleden de Secretaris en Commissaris Bestuurskundige Berichten van de B.I.L
Tuning micropillar cavity birefringence by laser induced surface defects
We demonstrate a technique to tune the optical properties of micropillar
cavities by creating small defects on the sample surface near the cavity region
with an intense focused laser beam. Such defects modify strain in the
structure, changing the birefringence in a controllable way. We apply the
technique to make the fundamental cavity mode polarization-degenerate and to
fine tune the overall mode frequencies, as needed for applications in quantum
information science.Comment: RevTex, 7 pages, 4 figures (accepted for publication in Applied
Physics Letters
Deterministic nano-assembly of a coupled quantum emitter - photonic crystal cavity system
The interaction of a single quantum emitter with its environment is a central
theme in quantum optics. When placed in highly confined optical fields, such as
those created in optical cavities or plasmonic structures, the optical
properties of the emitter can change drastically. In particular, photonic
crystal (PC) cavities show high quality factors combined with an extremely
small mode volume. Efficiently coupling a single quantum emitter to a PC cavity
is challenging because of the required positioning accuracy. Here, we
demonstrate deterministic coupling of single Nitrogen-Vacancy (NV) centers to
high-quality gallium phosphide PC cavities, by deterministically positioning
their 50 nm-sized host nanocrystals into the cavity mode maximum with
few-nanometer accuracy. The coupling results in a 25-fold enhancement of NV
center emission at the cavity wavelength. With this technique, the NV center
photoluminescence spectrum can be reshaped allowing for efficient generation of
coherent photons, providing new opportunities for quantum science.Comment: 13 pages, 4 figure
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