12 research outputs found
Efficient Single Photon Absorption by Optimized Superconducting Nanowire Geometries
We report on simulation results that shows optimum photon absorption by
superconducting nanowires can happen at a fill-factor that is much less than
100%. We also present experimental results on high performance of our
superconducting nanowire single photon detectors realized using NbTiN on
oxidized silicon.Comment: \copyright 2013 IEEE. Submitted to "Numerical Simulation of
Optoelectronic Devices - NUSOD 2013" on 19-April-201
Diamond optomechanical crystals
Cavity-optomechanical systems realized in single-crystal diamond are poised
to benefit from its extraordinary material properties, including low mechanical
dissipation and a wide optical transparency window. Diamond is also rich in
optically active defects, such as the nitrogen-vacancy (NV) and silicon-vacancy
(SiV) centers, which behave as atom-like systems in the solid state.
Predictions and observations of coherent coupling of the NV electronic spin to
phonons via lattice strain has motivated the development of diamond
nanomechanical devices aimed at realization of hybrid quantum systems, in which
phonons provide an interface with diamond spins. In this work, we demonstrate
diamond optomechanical crystals (OMCs), a device platform to enable such
applications, wherein the co-localization of ~ 200 THz photons and few to 10
GHz phonons in a quasi-periodic diamond nanostructure leads to coupling of an
optical cavity field to a mechanical mode via radiation pressure. In contrast
to other material systems, diamond OMCs operating in the resolved-sideband
regime possess large intracavity photon capacity (> 10) and sufficient
optomechanical coupling rates to reach a cooperativity of ~ 20 at room
temperature, allowing for the observation of optomechanically induced
transparency and the realization of large amplitude optomechanical
self-oscillations
Strain engineering of the silicon-vacancy center in diamond
We control the electronic structure of the silicon-vacancy (SiV) color-center in diamond by changing its static strain environment with a nano-electro-mechanical system. This allows deterministic and local tuning of SiV optical and spin transition frequencies over a wide range, an essential step towards multiqubit networks. In the process, we infer the strain Hamiltonian of the SiV revealing large strain susceptibilities of order 1 PHz/strain for the electronic orbital states. We identify regimes where the spin-orbit interaction results in a large strain susceptibility of order 100 THz/strain for spin transitions, and propose an experiment where the SiV spin is strongly coupled to a nanomechanical resonator
Habermas, democracy and civil society: Unearthing the social in transformation theory
The debate as to whether transformative learning theory takes adequate account of the social has contributed to the clarification and development of the theory. But this debate has been, to a great extent, framed within transformation theory. This paper outlines some key ideas from Jürgen Habermas - civil society, public sphere, democracy and discourse - that are crucial to unearthing the social in transformation theory