87 research outputs found
Optical tuning of the diamond Fermi level measured by correlated scanning probe microscopy and quantum defect spectroscopy
Quantum technologies based on quantum point defects in crystals require
control over the defect charge state. Here we tune the charge state of shallow
nitrogen-vacancy and silicon-vacancy centers by locally oxidizing a
hydrogenated surface with moderate optical excitation and simultaneous spectral
monitoring. The loss of conductivity and change in work function due to
oxidation are measured in atmosphere using conductive atomic force microscopy
(C-AFM) and Kelvin probe force microscopy (KPFM). We correlate these scanning
probe measurements with optical spectroscopy of the nitrogen-vacancy and
silicon-vacancy centers created via implantation and annealing 15-25 nm beneath
the diamond surface. The observed charge state of the defects as a function of
optical exposure demonstrates that laser oxidation provides a way to precisely
tune the Fermi level over a range of at least 2.00 eV. We also observe a
significantly larger oxidation rate for implanted surfaces compared to
unimplanted surfaces under ambient conditions. Combined with knowledge of the
electron affinity of a surface, these results suggest KPFM is a powerful,
high-spatial resolution technique to advance surface Fermi level engineering
for charge stabilization of quantum defects
Superdiffusion in a Model for Diffusion in a Molecularly Crowded Environment
We present a model for diffusion in a molecularly crowded environment. The
model consists of random barriers in percolation network. Random walks in the
presence of slowly moving barriers show normal diffusion for long times, but
anomalous diffusion at intermediate times. The effective exponents for square
distance versus time usually are below one at these intermediate times, but can
be also larger than one for high barrier concentrations. Thus we observe sub-
as well as super-diffusion in a crowded environment.Comment: 8 pages including 4 figure
Hybrid Integration of GaP Photonic Crystal Cavities with Silicon-Vacancy Centers in Diamond by Stamp-Transfer
Optically addressable solid-state defects are emerging as one of the most
promising qubit platforms for quantum networks. Maximizing photon-defect
interaction by nanophotonic cavity coupling is key to network efficiency. We
demonstrate fabrication of gallium phosphide 1-D photonic crystal waveguide
cavities on a silicon oxide carrier and subsequent integration with implanted
silicon-vacancy (SiV) centers in diamond using a stamp-transfer technique. The
stamping process avoids diamond etching and allows fine-tuning of the cavities
prior to integration. After transfer to diamond, we measure cavity quality
factors () of up to 8900 and perform resonant excitation of single SiV
centers coupled to these cavities. For a cavity with of 4100, we observe a
three-fold lifetime reduction on-resonance, corresponding to a maximum
potential cooperativity of . These results indicate promise for high
photon-defect interaction in a platform which avoids fabrication of the quantum
defect host crystal
Silicon-lattice-matched boron-doped gallium phosphide: A scalable acousto-optic platform
The compact size, scalability, and strongly confined fields in integrated
photonic devices enable new functionalities in photonic networking and
information processing, both classical and quantum. Gallium phosphide (GaP) is
a promising material for active integrated photonics due to its high refractive
index, wide band gap, strong nonlinear properties, and large acousto-optic
figure of merit. In this work we demonstrate that silicon-lattice-matched
boron-doped GaP (BGaP), grown at the 12-inch wafer scale, provides similar
functionalities as GaP. BGaP optical resonators exhibit intrinsic quality
factors exceeding 25,000 and 200,000 at visible and telecom wavelengths
respectively. We further demonstrate the electromechanical generation of
low-loss acoustic waves and an integrated acousto-optic (AO) modulator.
High-resolution spatial and compositional mapping, combined with ab initio
calculations indicate two candidates for the excess optical loss in the visible
band: the silicon-GaP interface and boron dimers. These results demonstrate the
promise of the BGaP material platform for the development of scalable AO
technologies at telecom and provide potential pathways toward higher
performance at shorter wavelengths
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