Transmittance and near-field characterization of sub-wavelength tapered optical fibers

We have produced high transmission sub-wavelength tapered optical fibers for the purpose of whispering gallery mode coupling in fused silica microcavities at 780 nm. A detailed analysis of the fiber transmittance evolution during tapering is demonstrated to reflect precisely the mode coupling and cutoff in the fiber. This allows to control the final size, the number of guided modes and their effective index. These results are checked by evanescent wave mapping measurements on the resulting taper

Probing the degree of coherence through the full 1D to 3D crossover

We experimentally study a gas of quantum degenerate 87Rb atoms throughout the full dimensional crossover, from a one-dimensional (1D) system exhibiting phase fluctuations consistent with 1D theory to a three-dimensional (3D) phase-coherent system, thereby smoothly interpolating between these distinct, well-understood regimes. Using a hybrid trapping architecture combining an atom chip with a printed circuit board, we continuously adjust the system’s dimensionality over a wide range while measuring the phase fluctuations through the power spectrum of density ripples in time-of-flight expansion. Our measurements confirm that the chemical potential μ controls the departure of the system from 3D and that the fluctuations are dependent on both μ and the temperature T. Through a rigorous study we quantitatively observe how inside the crossover the dependence on T gradually disappears as the system becomes 3D. Throughout the entire crossover the fluctuations are shown to be determined by the relative occupation of 1D axial collective excitations

Fiber-coupled single ion as an efficient quantum light source

We have realized a compact system to efficiently couple the fluorescent light emitted by a single trapped ion to two opposing optical fibers. The fibers are tightly integrated in the center electrodes of a miniature endcap trap. They capture light from the ion with a numerical aperture of 0.34 each, corresponding to 6% of the solid angle in total. The high collection efficiency and high signal-to-background ratio make the setup an ideal quantum light source. We have observed strong antibunching of the photons emitted from the two fibers. The system has a range of applications from single-ion state detection in quantum information processing to strong coupling cavity-QED with ions.Comment: 4 figure

An environmental monitoring network for quantum gas experiments and devices

Quantum technology is approaching a level of maturity, recently demonstrated in space-borne experiments and in-field measurements, which would allow for adoption by non-specialist users. Parallel advancements made in microprocessor-based electronics and database software can be combined to create robust, versatile and modular experimental monitoring systems. Here, we describe a monitoring network used across a number of cold atom laboratories with a shared laser system. The ability to diagnose malfunction, unexpected or unintended behavior and passively collect data for key experimental parameters, such as vacuum chamber pressure, laser beam power, or resistances of important conductors, significantly reduces debugging time. This allows for efficient control over a number of experiments and remote control when access is limited

Neodymium Photoluminescence in Whispering Gallery Modes of Toroidal Microcavities.

We report on light emission from high-Q neodymium-implanted silica microtoroids. After description of the fabrication process of microtoroids, Neodymium light emission is analysed. This emission is coupled to various modes of the cavity. Using evanescent wave detection, we achieve selective detection of Whispering Gallery Modes of a microtoroid

Silica microspheres as high-Q microcavities for semiconductor quantum-dot lasers.

We report an experiment where InAs/GaAs self-organized Quantum Dots (QD) are coupled to the evanescent field of very-high-Q Whispering Gallery Modes (WGM) in a silica microsphere. The high performance of these microcavity and nanoemitters allowed to achieve very low threshold (200 \\\\mu W) laser operation at room temperature, involving a few thousands of QD. We show that such a low threshold relies heavily on WGM deconfinement and reconstruction in the micromesa etched in GaAs sample. Next, we present some prospects on further experiments involving various semiconductor nanostructures coupled to microspheres or to silica microtoroids integrated on a Si chip (as recently introduced by K.J. Vahala and coworkers at Caltech)

Neodymium Photoluminescence in Whispering Gallery Modes of Toroidal Microcavities.

We report on light emission from high-Q neodymium-implanted silica microtoroids. After description of the fabrication process of microtoroids, Neodymium light emission is analysed. This emission is coupled to various modes of the cavity. Using evanescent wave detection, we achieve selective detection of Whispering Gallery Modes of a microtoroid