John E. Debs
Australian National University
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Featured researches published by John E. Debs.
Optics Express | 2012
S S Sané; Shayne Bennetts; John E. Debs; Carlos C. N. Kuhn; Gordon McDonald; Paul Altin; John Close; Nicholas Robins
We present a narrow linewidth continuous laser source with over 11 W output power at 780 nm, based on single-pass frequency doubling of an amplified 1560 nm fibre laser with 36% efficiency. This source offers a combination of high power, simplicity, mode quality and stability. Without any active stabilization, the linewidth is measured to be below 10 kHz. The fibre seed is tunable over 60 GHz, which allows access to the D₂ transitions in ⁸⁷Rb and ⁸⁵Rb, providing a viable high-power source for laser cooling as well as for large-momentum-transfer beamsplitters in atom interferometry. Sources of this type will pave the way for a new generation of high flux, high duty-cycle degenerate quantum gas experiments.
Optics Letters | 2009
J. T. Schultz; S. Abend; D. Döring; John E. Debs; Paul Altin; J. D. White; Nicholas Robins; John Close
We observe coherent, cw, 455 nm blue-beam production via frequency upconversion in cesium vapor. Two IR lasers induce strong double excitation in a heated cesium vapor cell, allowing the atoms to undergo a double cascade and produce a coherent, collimated, blue beam copropagating with the two IR pump lasers.
New Journal of Physics | 2013
Paul Altin; Mattias Johnsson; Vladimir Negnevitsky; Graham Dennis; R. P. Anderson; John E. Debs; Stuart S. Szigeti; Kyle S. Hardman; Shayne Bennetts; Gordon McDonald; L. D. Turner; John Close; Nicholas Robins
We present a precision gravimeter based on coherent Bragg diffraction of freely falling cold atoms. Traditionally, atomic gravimeters have used stimulated Raman transitions to separate clouds in momentum space by driving transitions between two internal atomic states. Bragg interferometers utilize only a single internal state, and can therefore be less susceptible to environmental perturbations. Here we show that atoms extracted from a magneto-optical trap using an accelerating optical lattice are a suitable source for a Bragg atom interferometer, allowing efficient beamsplitting and subsequent separation of momentum states for detection. Despite the inherently multi-state nature of atom diffraction, we are able to build a Mach-Zehnder interferometer using Bragg scattering which achieves a sensitivity to the gravitational acceleration of Δg/g = 2.7 × 10-9 with an integration time of 1000 s. The device can also be converted to a gravity gradiometer by a simple modification of the light pulse sequence.
Physical Review A | 2011
John E. Debs; Paul Altin; Thomas Barter; Daniel Doering; Graham Dennis; Gordon McDonald; R. P. Anderson; John Close; Nicholas Robins
We present a cold-atom gravimeter operating with a sample of Bose-condensed {sup 87}Rb atoms. Using a Mach-Zehnder configuration with the two arms separated by a two-photon Bragg transition, we observe interference fringes with a visibility of (83{+-}6)% at T=3 ms. We exploit large momentum transfer (LMT) beam splitting to increase the enclosed space-time area of the interferometer using higher-order Bragg transitions and Bloch oscillations. We also compare fringes from condensed and thermal sources and observe a reduced visibility of (58{+-}4)% for the thermal source. We suspect the loss in visibility is caused partly by wave-front aberrations, to which the thermal source is more susceptible due to its larger transverse momentum spread. Finally, we discuss briefly the potential advantages of using a coherent atomic source for LMT, and we present a simple mean-field model to demonstrate that with currently available experimental parameters, interaction-induced dephasing will not limit the sensitivity of inertial measurements using freely falling, coherent atomic sources.
New Journal of Physics | 2012
Stuart S. Szigeti; John E. Debs; Joseph Hope; Nicholas Robins; John Close
We theoretically consider the effect of the atomic sources momentum width on the efficiency of Bragg mirrors and beamsplitters and, more generally, on the phase sensitivity of Bragg pulse atom interferometers. By numerical optimization, we show that an atomic clouds momentum width places a fundamental upper bound on the maximum transfer efficiency of a Bragg mirror pulse, and furthermore limits the phase sensitivity of a Bragg pulse atom interferometer. We quantify these momentum width effects, and precisely compute how mirror efficiencies and interferometer phase sensitivities vary as functions of Bragg order and source type. Our results and methodology allow for an efficient optimization of Bragg pulses and the comparison of different atomic sources, and will help in the design of large momentum transfer Bragg mirrors and beamsplitters for use in atom-based inertial sensors.
Physical Review Letters | 2014
Gordon McDonald; Carlos C. N. Kuhn; Kyle S. Hardman; Shayne Bennetts; P. J. Everitt; Paul Altin; John E. Debs; John Close; Nicholas Robins
We present the first realization of a solitonic atom interferometer. A Bose-Einstein condensate of 1×10(4) atoms of rubidium-85 is loaded into a horizontal optical waveguide. Through the use of a Feshbach resonance, the s-wave scattering length of the 85Rb atoms is tuned to a small negative value. This attractive atomic interaction then balances the inherent matter-wave dispersion, creating a bright solitonic matter wave. A Mach-Zehnder interferometer is constructed by driving Bragg transitions with the use of an optical lattice colinear with the waveguide. Matter-wave propagation and interferometric fringe visibility are compared across a range of s-wave scattering values including repulsive, attractive and noninteracting values. The solitonic matter wave is found to significantly increase fringe visibility even compared with a noninteracting cloud.
Physical Review A | 2013
Gordon McDonald; Carlos C. N. Kuhn; Shayne Bennetts; John E. Debs; Kyle S. Hardman; Mattias Johnsson; John Close; Nicholas Robins
We demonstrate phase sensitivity in a horizontally guided, acceleration-sensitive atom interferometer with a momentum separation of
Physics Reports | 2013
Nicholas Robins; Paul Altin; John E. Debs; John Close
80\ensuremath{\hbar}k
Physical Review A | 2011
Paul Altin; Graham Dennis; Gordon McDonald; Daniel Doering; John E. Debs; John Close; C. M. Savage; Nicholas Robins
between its arms. A fringe visibility of 7% is observed. Our coherent pulse sequence accelerates the cold cloud in an optical waveguide, an inherently scalable route to large momentum separation and high sensitivity. We maintain coherence at high momentum separation due to both the transverse confinement provided by the guide and our use of optical
Physical Review Letters | 2016
Kyle S. Hardman; P. J. Everitt; Gordon McDonald; P. Manju; P. B. Wigley; M. A. Sooriyabandara; C. C. N. Kuhn; John E. Debs; John Close; Nicholas Robins
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