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Investigation of the Saturation Mechanism of Recoil-induced Resonances. Joel A. Greenberg, Marcos Oria, and Daniel J. Gauthier Duke University 5/28/2008. Atom-filled Photonic Fibers. Pattern-forming Instabilities. Plasmonics. Sensitivity to perturbations (Dawes, Kaiser).
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Investigation of the Saturation Mechanism of Recoil-induced Resonances Joel A. Greenberg, Marcos Oria, and Daniel J. Gauthier Duke University 5/28/2008
Atom-filled Photonic Fibers Pattern-forming Instabilities Plasmonics Sensitivity to perturbations (Dawes, Kaiser) Local field enhancement (Chang et al., 2007) Large intensities over long lengths (Bajcsy, Gaeta) Motivation • Nonlinear optical (NLO) effects typically require large intensities New techniques for realizing single-photon NLO effects are being developed
Our Approach Use a ‘cold atom fiber’ 3 cm • 87Rb F=2 F’=3 • 100:1 Aspect Ratio • OD=55 (I/I0=e-OD) • Temperature= 30-50μK Anisotropic Magneto-optical Trap (MOT) Need to establish See poster R1.00075 • Can the atoms guide and confine light? • What is the nonlinear optical response of the anisotropic MOT? Greenberg et al. (2007), Vengalattore et al. (2002)
(MHz) MOT Spectra Pump beams Probe beam detector MOT Mollow Vengalattore et al. (2005)
MOT Spectra (MHz) Pump beams Recoil Induced Resonance (RIR) How does the RIR saturate? Probe beam MOT (kHz)
RIR Mechanism Weak Field Limit (Amplification) (Maxwell-Boltzmann) Courtois et al. PRL (1994)
Saturation Mechanism … … Two possibilities: 1) Saturate the narrow, “two level” transitions Isat small 2) Modify the momentum distribution Isat large (10-2mW/cm2) … …
(kHz) Intensity Experiment Pump beams Probe beam detector MOT Iout/Iin
data model Gain Saturation mW/cm2 Iout/Iin Large Isat indicates multiple scattering per atom Iprobe (mW/cm2)
data model Atom recycling dominant in saturation Resonance Broadening mW/cm2 RIR HWHM (kHz) kHz Iprobe (mW/cm2)
Conclusions/Future Work • The anisotropic MOT is a great NLO sample (i.e. large nonlinearity, difficult to saturate) • “Atom recycling” is key to the process of RIR saturation • The appearance of an effective two level atom may help direct a theoretical description of the high gain regime