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.
Published Version (Please cite this version)
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 https://hdl.handle.net/10161/5105.
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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.
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.
Prof. Gauthier is interested in a broad range of topics in the fields of nonlinear and quantum optics, and nonlinear dynamical systems.
In the area of optical physics, his group is studying the fundamental characteristics of highly nonlinear light-matter interactions at both the classical and quantum levels and is using this understanding to develop practical devices.
At the quantum level, his group has three major efforts in the area of quantum communication and networking. In one project, they are investigating hybrid quantum memories where one type of memory is connected to another through the optical field (so-called flying qubits). In particular, they are exploring nonlinear optical methods for frequency converting and impedance matching photons emitted from one type of quantum memory (e.g., trapped ions) to another (e.g., quantum dots).
In another project, they are exploring methods for efficiently transmitting a large number of bits of information per photon. They are encoding information on the various photon degrees of freedom, such as the transverse modes, one photon at a time, and using efficient mode sorters to direct the photons to single-photon detectors. The experiments make use of multi-mode spontaneous down conversion in a nonlinear crystal to produce quantum correlated or entangled photon pairs.
Another recent interest is the development of the world's most sensitive all-optical switch. Currently, they have observed switching with an energy density as low as a few hundred yoctoJoules per atomic cross-section, indicating that the switch should be able to operate at the single-photon level. The experiments use a quasi-one-dimensional ultra-cold gas of rubidium atoms as the nonlinear material. They take advantage of a one-dimensional optical lattice to greatly increase the nonlinear light-matter interaction strength.
In the area of nonlinear dynamics, his group is interested in the control and synchronization of chaotic devices, especially optical and radio-frequency electronic systems. They are developing new methods for private communication of information using chaotic carriers, using chaotic elements for distance sensing (e.g., low-probability-of-detection radar), using networks of chaotic elements for remote sensing, and using chaotic elements for generating truly random numbers at high data rates. Recently, the have observed 'Boolean chaos,' where complex behavior is observed in a small network of commercially-available free-running logic gates.
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