Bulletin of the American Physical Society
2013 Joint Meeting of the APS Division of Atomic, Molecular & Optical Physics and the CAP Division of Atomic, Molecular & Optical Physics, Canada
Volume 58, Number 6
Monday–Friday, June 3–7, 2013; Quebec City, Canada
Session B6: Precision Measurements: Techniques and Applications |
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Chair: Derek Kimball, California State University East Bay Room: 302 |
Tuesday, June 4, 2013 10:30AM - 10:42AM |
B6.00001: Experimental Evaluation of Chip-scale Atomic Magnetometer Sensitivity Jiayan Dai, Ethan Pratt, Svenja Knappe, John Kitching We evaluate the performance of spin-exchange relaxation free magnetometry in a $1 mm$ thick microfabricated vapor cell experimentally and compare it with theoretical predictions at the $5 \frac{fT}{\sqrt{Hz}}$ sensitivity level. The magnetometer is operated by monitoring the polarization rotation of a linearly-polarized probe beam that traverses the cell perpendicular to a circularly-polarized pump beam. Specifically, we investigate the contribution of frequency and amplitude noise of the pump laser to the magnetometer noise. [Preview Abstract] |
Tuesday, June 4, 2013 10:42AM - 10:54AM |
B6.00002: Multi-channel Chip-Scale Atomic Magnetometry Orang Alem, Tilmann H. Sander, John J. Le Blanc, Rahul Mhaskar, John Kitching, Lutz Trahms, Svenja Knappe We characterize a 25-channel microfabricated atomic magnetometry system. Each fiber-coupled sensor head contains a $(1.5 \rm mm)^3$ Rb vapor cell and is pumped and probed with a single light beam from a diode laser. The magnetic sensitivities of all sensors range between 15 and 35 $\rm fT/\sqrt{Hz}$ at 10-100 Hz. The sensors require around 70 mW of power and are optically heated through the absorption of light on the windows of the cells. The small size ($<$ 1 $\rm cm^3$) of the fiber coupled, uncooled sensor heads provides great flexibility in the placement of these sensors in conformal configurations for various imaging applications. As one example, we will present measurements of magnetoencephalography (MEG) and magnetocardiography (MCG) with this system that were taken on healthy human subjects. [Preview Abstract] |
Tuesday, June 4, 2013 10:54AM - 11:06AM |
B6.00003: Atomic Magnetometry for fetal Magnetocardiography Ibrahim A. Sulai, Thad G. Walker, Ronald T. Wakai We present results of using an array of atomic magnetometers in detecting fetal Magnetocardiograms(fMCG) . The array consists of four 87-Rb atomic magnetometers operating in the spin exchange relaxation free (SERF) regime. They have a demonstrated sensitivity of 5 - 10 $fT/\sqrt{Hz}$--limited by the Johnson noise of the magnetic shielding. We report measurements of fMCG on gestational ages as small as 21 weeks and describe the technical challenges and design features that make the measurements possible. We present a method for minimizing the impact of AC Stark Shifts on the magnetometer array performance by relying on diffusion to transport polarized atoms from a pumping region to an AC Stark shift free active region. This work was supported by the NIH. [Preview Abstract] |
Tuesday, June 4, 2013 11:06AM - 11:18AM |
B6.00004: Suppression of Spin-Exchange Relaxation Using Pulsed Parametric Resonance Anna Korver, Robert Wyllie, Brian Lancor, Thad Walker A new method of optical pumping is presented in which $^{87}$Rb atoms are fully polarized perpendicular to a large DC magnetic field by applying a transverse AC coupled pulsed field. When the repetition rate of the pulsed field matches the Larmor frequency of the DC field, decoherence due to spin exchange collisions is suppressed beyond the light narrowed regime. We will present results demonstrating this further suppression and show the improved magnetometer response over a traditional light-narrowed parametric resonance magnetometer. This work is funded by the NSF. [Preview Abstract] |
Tuesday, June 4, 2013 11:18AM - 11:30AM |
B6.00005: Ultrastable light sources in the crossover from superradiance to lasing Minghui Xu, David Tieri, Murray Holland We theoretically investigate the crossover from steady-state superradiance to optical lasing. An exact solution of the quantum master equation is difficult to obtain due to the exponential scaling of the Hilbert space dimension with system size. However, since Lindblad operators in the master equation are invariant under SU(4) transformations, we are able to reduce the exponential scaling of the problem to cubic by expanding the density matrix in terms of an SU(4) basis. In this way, we obtain exact quantum solutions of the superradiance-laser crossover. We use this theory to investigate the potential for ultrastable lasers in the millihertz linewidth regime, and find the behavior of important observables, such as intensity, linewidth, spin-correlation, and entanglement. [Preview Abstract] |
Tuesday, June 4, 2013 11:30AM - 11:42AM |
B6.00006: A Portable E1-M1 Optical Clock Emily Alden, Aaron Leanhardt The frontiers of precision time measurement are improving rapidly. The pursuit of the lowest clock stability has produced a measurement of time dilation from to an elevation change of less than a meter\footnote{C.W. Chou, D.B. Hume, T. Rosenband, and D.J. Wineland, Science 329, 1630 (2010)} and creates the potential for tabletop tests of fundamental constants. We present a new setup for an optical frequency standard that accesses the $E1$ forbidden $^1S_0 \rightarrow ^3P_0$ clock transition by a two-photon allowed $E1-M1$ clock transition along $^1S_0 \rightarrow ^3P_1 \rightarrow ^3P_0$. This pathway has the potential to permit detectable clock transitions for atoms at room temperature. Further, the transition can be driven using Doppler-free spectroscopy techniques which immediately remove the dominant broadening mechanism for single-photon clocks at room temperature. Operating with hot atoms removes the extensive state preparation required by other optical frequency standards and thus makes the clock more portable that ion or lattice systems. We present the basic components of this novel technique and progress toward a hot neutral Hg clock. [Preview Abstract] |
Tuesday, June 4, 2013 11:42AM - 11:54AM |
B6.00007: Green Astro-comb for exoplanet searches at HARPS-N David Phillips, Chih-Hao Li, Alexander Glenday, Nicholas Langellier, Gabor Furesz, Guoqing Chang, Hung-Wen Chen, Jinkang Lim, Franz Kaertner, Andrew Szentgyorgyi, Ronald Walsworth Astro-combs, a combination of a laser frequency comb, a coherent wavelength shifting mechanism (such as a doubling crystal and photonic crystal fiber), and a mode-filtering Fabry-Perot cavity, are promising tools that enable searches for Earth-like extra-solar planets (exoplanets) and the direct observation of the accelerating expansion of the universe. In this talk, We will present recent results of tests of our ``green astro-comb'' operating at the HARPS-N spectrograph in the 3.6 m Telescopio Nazionale Galileo (TNG) in the Canary Islands. The green astro-comb consists of $\sim$6000 lines equally spaced by $\sim$20 GHz in the 500 nm - 600 nm optical band and is derived from a 1-GHz Ti:Sapphire comb laser, a custom tapered photonic crystal fiber that spectrally shifts the comb lines to the visible, and two mode-filtering Fabry-Perot cavities that increase the line spacing to match the R=100,000 HARPS-N spectrograph. The green astro-comb was recently installed and tested at HARPS-N. Results from initial investigations with the green astro-comb at HARPS-N will be presented. [Preview Abstract] |
Tuesday, June 4, 2013 11:54AM - 12:06PM |
B6.00008: Impulse response of microresonators with a dual frequency comb probe Vincent Michaud-Belleau, Hugo Bergeron, Jean-Rapha\"el Carrier, Julien Roy, J\'er\^ome Genest, Claudine Allen Label-free microsphere were shown to be sensitive optical biosensors thanks to the very high quality factor up to $Q\approx 10^9$ of their whispering gallery modes (WGMs). Several resonances are available to probe the frequency response in polarizability, but the spectrum of WGMs for an elliptical resonator is more complicated, warranting further measures of light propagation. Our high resolution interferometric studies of a silica microresonator with a dual frequency comb provide both its impulse response in the time domain with $80$ fs resolution and its transmission spectrum in the frequency domain with $125$ MHz resolution, i.e. at the picometer level. We observe that a light pulse is periodically outcoupling from a $\sim 156$ $\mu$m microsphere after round trips of $\sim 2$ ps as can be expected from the group velocity. However, the structure of the full impulse response is more rich, for example showing clusters of pulses separated by roughly $\sim 50$ ps. This reveals the light pulse is not outcoupling from the slightly elliptical microresonator at each round trip because its trajectory is precessing. Finally, we see that a refractive index change at the resonator surface causes a phase delay in the impulse response corresponding to the WGM frequency shifts in the spectrum [Preview Abstract] |
Tuesday, June 4, 2013 12:06PM - 12:18PM |
B6.00009: Robust, frequency-stable and accurate mid-IR laser spectrometer based on frequency comb metrology of quantum cascade lasers up-converted in orientation-patterned GaAs Stephan Schiller, Michael Hansen, Ingo Ernsting, Sergey Vasilyev, Arnaud Grisard, Erci Lallier, Bruno Gerard We demonstrate a robust and simple method for measurement, stabilization and tuning of the frequency of cw mid-infrared (MIR, 5 - 12 $\mu$m) lasers, in particular of quantum cascade lasers, allowing implementation of flexible and ``turn-key'' spectrometers for a range of high-resolution spectroscopic tasks. The MIR laser wave is upconverted by sum-frequency generation in an orientation-patterned GaAs crystal with the output of a standard high-power cw 1.5 $\mu$m fiber laser, subsequent amplification of the sum-frequency wave, Continuous measurements of this wave's and the fiber laser's frequency by a standard Er:fiber frequency comb provide signals allowing frequency control of the MIR laser. The proof of principle is performed with a quantum cascade laser at 5.4 $\mu$m, which is upconverted to 1.2 $\mu$m. The absolute QCL frequency is determined with 100 kHz-level inaccuracy relative to an atomic frequency reference. Frequency stabilization to sub-10 kHz level, controlled frequency tuning and long-term stability are demonstrated. The whole system is nearly turn-key, requiring only short warm-up time. This is an important advantage for use of the apparatus as part of more complex experimental set-ups. Further extensions of the system are possible and will be discussed. [Preview Abstract] |
Tuesday, June 4, 2013 12:18PM - 12:30PM |
B6.00010: Superluminal Ultrasensitive Optical Gyroscope in an Inverted Double-Raman Lambda System Tony Abi-Salloum, Ye Wang, Joshua Yablon, Shih Tseng, Zifan Zhou, Selim Shahriar The probe field in an inverted double-Raman lambda atomic system experiences a gain along with a negative dispersion. We show in this talk how a critical negative dispersion can lead to a dramatic enhancement in the sensitivity to cavity length change --- induced by rotation, for example --- for a ring laser employing this gain. The critical anomalous dispersion enhances the lasing frequency shift by as much as five orders of magnitude when compared to a conventional ring laser with the same dimensions. We show how a careful selection of the experimental parameters, such as strengths of the two controlling fields, can lead to the critical dispersion of interest. We also describe how such a laser can be used to realize a superluminal ring laser gyroscope with highly enhanced sensitivity. Finally, we describe our experimental efforts toward realizing such a superluminal ring laser using a rubidium vapor cell and dual frequency Raman pumps. [Preview Abstract] |
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