Refractometry with ultralow detection limit using anisotropic whispering-gallery-mode resonators

The intrinsic sensitivity of whispering-gallery-mode resonators aimed at measuring refractive index can be extremely high, although their practical performance is compromised by temperature fluctuations that masquerade as refractive-index changes. We present a triple-mode approach that delivers simultaneous and independent sensing of temperature and refractive-index changes in the same resonator. The frequency difference between two orthogonally polarized modes is used to sense temperature which is then actively stabilized to ∼1  μK over 15 minutes. We then detect a frequency difference between two modes of different wavelengths to obtain a refractive-index measurement that is free of temperature fluctuations. This triple-mode technique delivers a state-of-the-art detection limit of 8×10¯⁹ refractive-index units, despite the resonator size being 100 times larger than that typically used for sensitive refractometric sensing.Wenle Weng, James D. Anstie, and Andre N. Luite

Complex direct comb spectroscopy with a virtually imaged phased array

LetterAbstract not availableSarah K. Scholten, James D. Anstie, Nicolas Bourbeau Hébert, Richard T. White, Jérôme Genest, and Andre N. Luite

High-efficiency cross-phase modulation in a gas-filled waveguide

Strong cross-Kerr nonlinearities have been long sought after for quantum information applications. Recent work has shown that they are intrinsically unreliable in traveling-wave configurations: cavity configurations avoid this, but require knowledge of both the nonlinearity and the loss. Here we present a detailed systematic study of cross-phase modulation and absorption in an Rb vapor confined within a hollow-core photonic crystal fiber. Using a two-photon transition, we observe phase modulations of up to pi rad with a signal power of 25 mu W, corresponding to a nonlinear Kerr coefficient, n(2), of 0.8 x 10(-6) cm(2)/W, or 1.3 x 10(-6) rad per photon

High-resolution two-photon spectroscopy of rubidium within a confined geometry

We present two-photon spectroscopy of a thermal rubidium vapor confined to the hollow core of a photonic-crystal fiber. Linewidths as narrow as 10 MHz were observed on the 5S(1/2) -> 5D(5/2) transition enabling the hyperfine splitting of the excited state to be resolved. Very strong nonlinear absorption (>90%) was observed, with substantial absorption maintained over large detunings (9 GHz) from an intermediate state. These attributes make this system ideal for many frequency metrology and quantum optics applications. DOI: 10.1103/PhysRevA.87.01381

Bidirectional microwave and optical signal dissemination

Abstract not availablePhilip S. Light, Ashby P. Hilton, Richard T. White, Christopher Perrella, James D. Anstie, John G. Hartnett, Giorgio Santarelli and Andre N. Luite

Real-time dynamic atomic spectroscopy using electro-optic frequency combs

Published 25 October 2016Spectroscopy is a key technology for both fundamental and applied science. A long-held desire has been the development of a means to continuously acquire broadband spectral data with simultaneous high time and frequency resolution. Frequency-comb technology can open this door: here, we use a spectroscopic technique based on an electro-optic comb to make continuous observations of cesium vapor across a 3.2-GHz spectral bandwidth with a 2-μs time resolution and with 10-MHz frequency sampling. We use a rapidly switched pump laser to burn narrow features into the spectral line and study the response to this step perturbation. This examination allows us to see a number of unexpected effects, including the temporal evolution of the bandwidth, the amplitude, and the frequency of these burnt features. We also report on the previously unobserved effect of radiation reabsorption, which slowly produces a broad pedestal of perturbation around each feature. We present models that can explain these dynamical effects.Nicolas Bourbeau Hébert, Vincent Michaud-Belleau, Christopher Perrella, Gar-Wing Truong, James D. Anstie, Thomas M. Stace, Jérôme Genest, and Andre N. Luite

Moderate drinking before the unit: medicine and life assurance in Britain and the US c.1860–1930

This article describes the way in which “Anstie’s Limit” – a particular definition of moderate drinking first defined in Britain in the 1860s by the physician Francis Edmund Anstie (1833–1874) – became established as a useful measure of moderate alcohol consumption. Becoming fairly well-established in mainstream Anglophone medicine by 1900, it was also communicated to the public in Britain, North America and New Zealand through newspaper reports. However, the limit also travelled to less familiar places, including life assurance offices, where a number of different strategies for separating moderate from excessive drinkers emerged from the dialogue between medicine and life assurance. Whilst these ideas of moderation seem to have disappeared into the background for much of the twentieth century, re-emerging as the “J-shaped” curve, these early developments anticipate many of the questions surrounding uses of the “unit” to quantify moderate alcohol consumption in Britain today. The article will therefore conclude by exploring some of the lessons of this story for contemporary discussions of moderation, suggesting that we should pay more attention to whether these metrics work, where they work and why

Two-color rubidium fiber frequency standard

We demonstrate an optical frequency standard based on rubidium vapor loaded within a hollow-core photonic crystal fiber. We use the 5S(1/2)→5D(5/2) two-photon transition, excited with two lasers at 780 and 776 nm. The sum-frequency of these lasers is stabilized to this transition using modulation transfer spectroscopy, demonstrating a fractional frequency stability of 9.8×10(-12) at 1 s. The current performance limitations are presented, along with a path to improving the performance by an order of magnitude. This technique will deliver a compact, robust standard with potential applications in commercial and industrial environments.C. Perrella, P. S. Light, J. D. Anstie, F. N. Baynes, F. Benabid, and A. N. Luite

Optically reversible photochromism in natural pink diamond

Naturally occurring pink diamonds include defect centers with properties that differ greatly from those of commonly synthesized diamond centers. The pink diamond color-center demonstrates optically-controllable photochromism which is stable at ambient temperatures. The nature of this defect and the origin of the photochromism are yet to be explained. In this work we show that the photochromic behavior can be explained by competing photoionization processes at multiple defect centers in response to an applied optical pump. Our approach quantitatively explains the dependence of both the response rate and the resulting color on the pump wavelength. From measurements of the photochromic response we are able to extract parameters that describe the ionization cross-sections of the involved centers. © 2012 Elsevier B.V. All rights reserved.K.S. Byrne, J.D. Anstie, J.G. Chapman, A.N. Luite

Infrared microspectroscopy of natural Argyle pink diamond

Abstract not availableK.S. Byrne, J.D. Anstie, J. Chapman and A.N. Luite