Controllable ultrabroadband slow light in a warm rubidium vapor

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We study ultrabroadband slow light in a warm rubidium vapor cell. By working between the D1 and D2 transitions, we find a several-nanometer window centered at 788:4nm in which the group index is highly uniform and the absorption is small (<1%). We demonstrate that we can control the group delay by varying the temperature of the cell, and we observe a tunable fractional delay of 18 for pulses as short as 250 fs (6:9nm bandwidth) with a fractional broadening of only 0.65 and a power leakage of 55%. We find that a simple theoretical model is in excellent agreement with the experimental results. Using this model, we discuss the impact of the pulse's spectral characteristics on the distortion it incurs during propagation through the vapor. © 2011 Optical Society of America.






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Zhang, R, JA Greenberg, MC Fischer and DJ Gauthier (2011). Controllable ultrabroadband slow light in a warm rubidium vapor. Journal of the Optical Society of America B: Optical Physics, 28(11). pp. 2578–2583. 10.1364/JOSAB.28.002578 Retrieved from

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Joel Alter Greenberg

Associate Research Professor in the Department of Electrical and Computer Engineering

Dr. Greenberg's research is in the area of computational imaging with a focus on physics-based modeling and system-level design from fundamental science through algorithm implementation.  His work spans the electromagnetic spectrum, with a focus on X-ray and visible imaging and detection systems for security and medical applications.  


Martin Fischer

Research Professor in the Department of Chemistry

Dr. Fischer’s research focuses on exploring novel nonlinear optical contrast mechanisms for molecular imaging. Nonlinear optical microscopes can provide non-invasive, high-resolution, 3-dimensional images even in highly scattering environments such as biological tissue. Established contrast mechanisms, such as two-photon fluorescence or harmonic generation, can image a range of targets (such as autofluorescent markers or some connective tissue structure), but many of the most molecularly specific nonlinear interactions are harder to measure with power levels one might be willing to put on tissue. In order to use these previously inaccessible interactions as structural and molecular image contrasts we are developing ultrafast laser pulse shaping and pulse shape detection methods that dramatically enhance measurement sensitivity. Applications of these microscopy methods range from imaging biological tissue (mapping structure, endogenous tissue markers, or exogenous contrast agents) to characterization of nanomaterials (such as graphene and gold nanoparticles). The molecular contrast mechanisms we originally developed for biomedical imaging also provide pigment-specific signatures for paints used in historic artwork. Recently we have demonstrated that we can noninvasively image paint layers in historic paintings and we are currently developing microscopy techniques for use in art conservation and conservation science.

Dr. Fischer is also the director of the Advanced Light Imaging and Spectroscopy (ALIS) facility at Duke University.

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