62 research outputs found
A planar dielectric antenna for directional single-photon emission and near-unity collection efficiency
Single emitters have been considered as sources of single photons in various
contexts such as cryptography, quantum computation, spectroscopy, and
metrology. The success of these applications will crucially rely on the
efficient directional emission of photons into well-defined modes. To
accomplish a high efficiency, researchers have investigated microcavities at
cryogenic temperatures, photonic nanowires, and near-field coupling to metallic
nano-antennas. However, despite an impressive progress, the existing
realizations substantially fall short of unity collection efficiency. Here we
report on a theoretical and experimental study of a dielectric planar antenna,
which uses a layered structure for tailoring the angular emission of a single
oriented molecule. We demonstrate a collection efficiency of 96% using a
microscope objective at room temperature and obtain record detection rates of
about 50 MHz. Our scheme is wavelength-insensitive and can be readily extended
to other solid-state emitters such as color centers and semiconductor quantum
dots
Quantum Interference of Tunably Indistinguishable Photons from Remote Organic Molecules
We demonstrate two-photon interference using two remote single molecules as
bright solid-state sources of indistinguishable photons. By varying the
transition frequency and spectral width of one molecule, we tune and explore
the effect of photon distinguishability. We discuss future improvements on the
brightness of single-photon beams, their integration by large numbers on chips,
and the extension of our experimental scheme to coupling and entanglement of
distant molecules
Controlled coupling of counterpropagating whispering-gallery modes by a single Rayleigh scatterer: a classical problem in a quantum optical light
We present experiments where a single subwavelength scatterer is used to
examine and control the back-scattering induced coupling between
counterpropagating high-Q modes of a microsphere resonator. Our measurements
reveal the standing wave character of the resulting symmetric and antisymmetric
eigenmodes, their unbalanced intensity distributions, and the coherent nature
of their coupling. We discuss our findings and the underlying classical physics
in the framework common to quantum optics and provide a particularly intuitive
explanation of the central processes.Comment: accepted for publication in Pysical Review Letter
Swept source / Fourier domain polarization sensitive optical coherence tomography with a passive polarization delay unit
Polarization sensitive optical coherence tomography (PS-OCT) is a functional imaging method that provides additional contrast using the light polarizing properties of a sample. This manuscript describes PS-OCT based on ultrahigh speed swept source / Fourier domain OCT operating at 1050nm at 100kHz axial scan rates using single mode fiber optics and a multiplexing approach. Unlike previously reported PS-OCT multiplexing schemes, the method uses a passive polarization delay unit and does not require active polarization modulating devices. This advance decreases system cost and avoids complex synchronization requirements. The polarization delay unit was implemented in the sample beam path in order to simultaneously illuminate the sample with two different polarization states. The orthogonal polarization components for the depth-multiplexed signals from the two input states were detected using dual balanced detection. PS-OCT images were computed using Jones calculus. 3D PS-OCT imaging was performed in the human and rat retina. In addition to standard OCT images, PS-OCT images were generated using contrast form birefringence and depolarization. Enhanced tissue discrimination as well as quantitative measurements of sample properties was demonstrated using the additional contrast and information contained in the PS-OCT images.National Institutes of Health (U.S.) (NIH R01-EY011289-25)National Institutes of Health (U.S.) (R01-EY013178-12)National Institutes of Health (U.S.) (R01-EY013516-09)National Institutes of Health (U.S.) (R01-EY019029-04)National Institutes of Health (U.S.) (R01-EY018184-05)National Institutes of Health (U.S.) (R01-CA075289-14)National Institutes of Health (U.S.) (R01-HL095717-03)National Institutes of Health (U.S.) (R01-NS057476-05)United States. Air Force Office of Scientific Research (AFOSR FA9550-10-1-0063)United States. Dept. of Defense. Medical Free Electron Laser Program (FA9550-07-1-0101
Spontaneous emission enhancement of a single molecule by a double-sphere nanoantenna across an interface
We report on two orders of magnitude reduction in the fluorescence lifetime
when a single molecule placed in a thin film is surrounded by two gold
nanospheres across the film interface. By attaching one of the gold particles
to the end of a glass fiber tip, we could control the modification of the
molecular fluorescence at will. We find a good agreement between our
experimental data and the outcome of numerical calculations
Excitation mapping of whispering gallery modes in silica microcavities
We report the direct observation of the electromagnetic-field distribution of
whispering?gallery modes in silica microcavities (spheres and toroids). It is
revealed by their excitation efficiency with a tapered fiber coupler swept
along the meridian. The originality of this method lies in the use of the
coupler itself for the near field mapping, eliminating the need of additional
tools used in previous work. This method is successfully applied to
microspheres and microtoroid
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FloatingCanvas: quantification of 3D retinal structures from spectral-domain optical coherence tomography
Spectral-domain optical coherence tomography (SD-OCT) provides volumetric images of retinal structures with unprecedented detail. Accurate segmentation algorithms and feature quantification in these images, however, are needed to realize the full potential of SD-OCT. The fully automated segmentation algorithm, FloatingCanvas, serves this purpose and performs a volumetric segmentation of retinal tissue layers in three-dimensional image volume acquired around the optic nerve head without requiring any pre-processing. The reconstructed layers are analysed to extract features such as blood vessels and retinal nerve fibre layer thickness. Findings from images obtained with the RTVue-100 SD-OCT (Optovue, Fremont, CA, USA) indicate that FloatingCanvas is computationally efficient and is robust to the noise and low contrast in the images. The FloatingCanvas segmentation demonstrated good agreement with the human manual grading. The retinal nerve fibre layer thickness maps obtained with this method are clinically realistic and highly reproducible compared with time-domain StratusOCT™
Optical coherence tomography—current technology and applications in clinical and biomedical research
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