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arXiv · 1103.3334

Phase-coherent detection of an optical dipole force by Doppler velocimetry

M. J. Biercuk·H. Uys·J. W. Britton·A. P. VanDevender·J. J. Bollinger
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Abstract

We report phase-coherent Doppler detection of optical dipole forces using large ion crystals in a Penning trap. The technique is based on laser Doppler velocimetry using a cycling transition in $^{9}$Be$^{+}$ near 313 nm and the center-of-mass (COM) ion motional mode. The optical dipole force is tuned to excite the COM mode, and measurements of photon arrival times synchronized with the excitation potential show oscillations with a period commensurate with the COM motional frequency. Experimental results compare well with a quantitative model for a driven harmonic oscillator. This technique permits characterization of motional modes in ion crystals; the measurement of both frequency and phase information relative to the driving force is a key enabling capability -- comparable to lockin detection -- providing access to a parameter that is typically not available in time-averaged measurements. This additional information facilitates discrimination of nearly degenerate motional modes.

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M. J. Biercuk, H. Uys, J. W. Britton, A. P. VanDevender, J. J. Bollinger. 2011-03-18. Phase-coherent detection of an optical dipole force by Doppler velocimetry. https://doi.org/10.1364/oe.19.010304

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