Autler-Townes splitting via frequency upconversion at ultra-low power levels in cold 87^{87}Rb atoms using an optical nanofiber

The tight confinement of the evanescent light field around the waist of an optical nanofiber makes it a suitable tool for studying nonlinear optics in atomic media. Here, we use an optical nanofiber embedded in a cloud of laser-cooled 87Rb for near-infrared frequency upconversion via a resonant two-photon process. Sub-nW powers of the two-photon beams, at 780 nm and 776 nm, co-propagate through the optical nanofiber and generation of 420 nm photons is observed. A measurement of the Autler-Townes splitting provides a direct measurement of the Rabi frequency of the 780 nm transition. Through this method, dephasings of the system can be studied. In this work, the optical nanofiber is used as an excitation and detection tool simultaneously, and it highlights some of the advantages of using fully fibered systems for nonlinear optics with atoms

Interaction of laser-cooled 87^{87}Rb atoms with higher order modes of an optical nanofiber

Optical nanofibres are used to confine light to subwavelength regions and are very promising tools for the development of optical fibre-based quantum networks using cold, neutral atoms. To date, experimental studies on atoms near nanofibres have focussed on fundamental fibre mode interactions. In this work, we demonstrate the integration of a few-mode optical nanofibre into a magneto-optical trap for $^{87}$Rb atoms. The nanofibre, with a waist diameter of $\sim$700 nm, supports both the fundamental and first group of higher order modes and is used for atomic fluorescence and absorption studies. In general, light propagating in higher order fibre modes has a greater evanescent field extension around the waist in comparison with the fundamental mode. By exploiting this behaviour, we demonstrate that the detected signal of fluorescent photons emitted from a cloud of cold atoms centred at the nanofibre waist is larger ($\sim$6 times) when higher order guided modes are considered as compared to the fundamental mode. Absorption of on-resonance, higher order mode probe light by the laser-cooled atoms is also observed. These advances should facilitate the realisation of atom trapping schemes based on higher order mode interference.Comment: 11 pages, 8 figure

Highly efficient coupling between a monolithically integrated photonic crystal cavity and a bus waveguide

We experimentally demonstrate a new optical filter design comprising of a photonic crystal cavity and a low index bus waveguide which are monolithically integrated on a silicon-on-insulator (SOI) platform. We have fabricated oxide clad PhC cavities with a silicon nitride waveguide positioned directly above, such that there is an overlap between the evanescent tails of the two modes. We have realised an extinction ratio of 7.5dB for cavities with total Q of 50,000.Postprin

A chemical sensor based on a photonic-crystal L3 nanocavity defined in a silicon-nitride membrane

The application of a silicon-nitride based L3 optical nanocavity as a chemical sensor is explored. It is shown that by adjusting the thickness of an ultra-thin Lumogen Red film deposited onto the nanocavity surface, the fundamental optical mode undergoes a progressive red-shift as the layer-thickness increases, with the cavity being able to detect the presence of a single molecular monolayer. The optical properties of a nanocavity whose surface is coated with a thin layer of a porphyrin-based polymer are also explored. On exposure of the cavity to an acidic-vapour, it is shown that changes in the optical properties of the porphyrin-film (thickness and refractive index) can be detected through a reversible shift in the cavity mode wavelength. Such effects are described using a finite difference time-domain model

Spectroscopy, Manipulation and Trapping of Neutral Atoms, Molecules, and Other Particles using Optical Nanofibers: A Review

The use of tapered optical fibers, i.e., optical nanofibers, for spectroscopy and the detection of small numbers of particles, such as neutral atoms or molecules, has been gaining ground in recent years. In this review, we briefly introduce the optical nanofiber, its fabrication and optical mode propagation within. We discuss recent progress on the integration of optical nanofibers into laser-cooled atom and vapor systems, paying particular attention to spectroscopy, cold atom cloud characterization and optical trapping schemes. Next, a natural extension on this work to molecules will be introduced. Finally, we consider several alternatives to optical nanofibers that display some advantages for particular applications.Comment: 28 pages, 12 figures, review articl

A heat-and-pull rig for fiber taper fabrication

We describe a reproducible method of fabricating adiabatic tapers with 3-4 micron diameter. The method is based on a heat-and-pull rig, whereby a CO2 laser is continuously scanned across a length of fiber that is being pulled synchronously. Our system relies on a CO2 mirror mounted on a geared stepper motor in order to scan the laser beam across the taper region. We show that this system offers a reliable alternative to more traditional rigs incorporating galvanometer scanners. We have routinely obtained transmission losses between 0.1 and 0.3 dB indicating the satisfactory production of adiabatic tapers. The operation of the rig is described in detail and an analysis on the produced tapers is provided. The flexibility of the rig is demonstrated by fabricating prolate dielectric microresonators using a microtapering technique. Such a rig is of interest to a range of fields that require tapered fiber fabrication such as microcavity-taper coupling, atom guiding along a tapered fiber, optical fiber sensing and the fabrication of fused biconical tapered couplers.Comment: 13 pages, 6 figures Submitted to Rev. Sci. Instru

Highly efficient optical filter based on vertically coupled photonic crystal cavity and bus waveguide

We experimentally demonstrate a new optical filter design based on a vertically coupled photonic crystal (PhC) cavity and a bus waveguide monolithically integrated on the silicon-on-insulator platform. The use of a vertically coupled waveguide gives flexibility in the choice of the waveguide material and dimensions, dramatically lowering the insertion loss while achieving very high coupling efficiencies to wavelength scale resonators and thus allows the creation of PhC-based optical filters with very high extinction ratio (>10 dB).Publisher PDFPeer reviewe

The Alternative Pre-hospital Pathway team: reducing conveyances to the emergency department through patient centered Community Emergency Medicine.

BACKGROUND Internationally increasing demand for emergency care is driving innovation within emergency services. The Alternative Pre-Hospital Pathway (APP) Team is one such Community Emergency Medicine (CEM) initiative developed in Cork, Ireland to target low acuity emergency calls. In this paper the inception of the APP Team is described, and an observational descriptive analysis of the APP Team's service data presented for the first 12 months of operation. The aim of this study is to describe and analyse the APP team service. METHODS The APP Team, consisting of a Specialist Registrar (SpR) in Emergency Medicine (EM) and an Emergency Medical Technician (EMT) based in Cork, covers a mixed urban and rural population of approximately 300,000 people located within a 40-min drive time of Cork University Hospital. The team are dispatched to low acuity 112/999 calls, aiming to provide definitive care or referring patients to the appropriate community or specialist service. A retrospective analysis was performed of the team's first 12 months of operation using the prospectively maintained service database. RESULTS Two thousand and one patients were attended to with a 67.8% non-conveyance rate. The median age was 62 years, with 33.0% of patients aged over 75 years. For patients over 75 years, the non-conveyance rate was 62.0%. The average number of patients treated per shift was 7. Medical complaints (319), falls (194), drug and alcohol related presentations (193), urological (131), and respiratory complaints (119) were the most common presentations. CONCLUSION Increased demand for emergency care and an aging population is necessitating a re-design of traditional models of emergency care delivery. We describe the Alternative Pre-Hospital Pathway service, delivered by an EMT and an Emergency Medicine SpR responding to low acuity calls. This service achieved a 68% non-conveyance rate; our data demonstrates that a community emergency medicine outreach team in collaboration with the National Ambulance Service offering Alternative Pre-Hospital Pathways is an effective model for reducing conveyances to hospital