543 research outputs found
Combinatorial synthesis and high-throughput photopotential and photocurrent screening of mixed-metal oxides for photoelectrochemical water splitting
A high-throughput method has been developed using a commercial piezoelectric inkjet printer for synthesis and characterization of mixed-metal oxide photoelectrode materials for water splitting. The printer was used to deposit metal nitrate solutions onto a conductive glass substrate. The deposited metal nitrate solutions were then pyrolyzed to yield mixed-metal oxides that contained up to eight distinct metals. The stoichiometry of the metal oxides was controlled quantitatively, allowing for the creation of vast libraries of novel materials. Automated methods were developed to measure the open-circuit potentials (Eoc), short-circuit photocurrent densities (Jsc), and current density vs. applied potential (J–E) behavior under visible light irradiation. The high-throughput measurement of Eoc is particularly significant because open-circuit potential measurements allow the interfacial energetics to be probed regardless of whether the band edges of the materials of concern are above, close to, or below the values needed to sustain water electrolysis under standard conditions. The Eoc measurements allow high-throughput compilation of a suite of data that can be associated with the composition of the various materials in the library, to thereby aid in the development of additional screens and to form a basis for development of theoretical guidance in the prediction of additional potentially promising photoelectrode compositions
Conversion of neutral nitrogen-vacancy centers to negatively-charged nitrogen-vacancy centers through selective oxidation
The conversion of neutral nitrogen-vacancy centers to negatively charged
nitrogen-vacancy centers is demonstrated for centers created by ion
implantation and annealing in high-purity diamond. Conversion occurs with
surface exposure to an oxygen atmosphere at 465 C. The spectral properties of
the charge-converted centers are investigated. Charge state control of
nitrogen-vacancy centers close to the diamond surface is an important step
toward the integration of these centers into devices for quantum information
and magnetic sensing applications.Comment: 4 pages, 3 figure
Chip-based microcavities coupled to NV centers in single crystal diamond
Optical coupling of nitrogen vacancy centers in single-crystal diamond to an
on-chip microcavity is demonstrated. The microcavity is fabricated from a
hybrid gallium phosphide and diamond material system, and supports whispering
gallery mode resonances with spectrometer resolution limited Q > 25000
Nanocavity enhanced diamond nitrogen-vacancy center zero phonon line emission
Resonantly enhanced emission of the zero phonon line of a diamond nitrogen-vacancy center in single crystal diamond is demonstrated experimentally using a hybrid whispering gallery mode nanocavity
Low-temperature tapered-fiber probing of diamond NV ensembles coupled to GaP microcavities
In this work we present a platform for testing the device performance of a
cavity-emitter system, using an ensemble of emitters and a tapered optical
fiber. This method provides high-contrast spectra of the cavity modes,
selective detection of emitters coupled to the cavity, and an estimate of the
device performance in the single- emitter case. Using nitrogen-vacancy (NV)
centers in diamond and a GaP optical microcavity, we are able to tune the
cavity onto the NV resonance at 10 K, couple the cavity-coupled emission to a
tapered fiber, and measure the fiber-coupled NV spontaneous emission decay.
Theoretically we show that the fiber-coupled average Purcell factor is 2-3
times greater than that of free-space collection; although due to ensemble
averaging it is still a factor of 3 less than the Purcell factor of a single,
ideally placed center.Comment: 15 pages, 6 figure
Sub-microsecond correlations in photoluminescence from InAs quantum dots
Photon correlation measurements reveal memory effects in the optical emission
of single InAs quantum dots with timescales from 10 to 800 ns. With above-band
optical excitation, a long-timescale negative correlation (antibunching) is
observed, while with quasi-resonant excitation, a positive correlation
(blinking) is observed. A simple model based on long-lived charged states is
presented that approximately explains the observed behavior, providing insight
into the excitation process. Such memory effects can limit the internal
efficiency of light emitters based on single quantum dots, and could also be
problematic for proposed quantum-computation schemes.Comment: 8 pages, 8 figure
Towards Integrated Optical Quantum Networks in Diamond
We demonstrate coupling between the zero phonon line (ZPL) of nitrogen-vacancy centers in diamond and the modes of optical micro-resonators fabricated in single crystal diamond membranes sitting on a silicon dioxide substrate. A more than ten-fold enhancement of the ZPL is estimated by measuring the modification of the spontaneous emission lifetime. The cavity-coupled ZPL emission was further coupled into on-chip waveguides thus demonstrating the potential to build optical quantum networks in this diamond on insulator platform
Properties of implanted and CVD incorporated nitrogen-vacancy centers: preferential charge state and preferential orientation
The combination of the long electron state spin coherence time and the optical coupling of the ground electronic states to an excited state manifold makes the nitrogen-vacancy (NV) center in diamond an attractive candidate for quantum information processing. To date the best spin and optical properties have been found in centers deep within the diamond crystal. For useful devices it will be necessary to engineer NVs with similar properties close to the diamond surface. We report on properties including charge state control and preferential orientation for near surface NVs formed either in CVD growth or through implantation and annealing
Coupling of nitrogen-vacancy centers in diamond to a GaP waveguide
The optical coupling of guided modes in a GaP waveguide to nitrogen-vacancy
(NV) centers in diamond is demonstrated. The electric field penetration into
diamond and the loss of the guided mode are measured. The results indicate that
the GaP-diamond system could be useful for realizing coupled microcavity-NV
devices for quantum information processing in diamond.Comment: 4 pages 4 figure
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