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Register a new userStored light and EIT at high optical depths
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We report a preliminary experimental study of EIT and stored light in the high optical depth regime. In particular, we characterize two ways to mitigate radiation trapping, a decoherence mechanism at high atomic density: nitrogen as buffer gas, and a long, narrow cell geometry. Initial results show the promise of both approaches in minimizing radiation trapping, but also reveal problems such as optical pumping into trapped end-states. We also observe distortion in EIT lineshapes at high optical depth, a result of interference from four-wave mixing. Experimental results are in good qualitative agreement with theoretical predictions.
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We present a preliminary experimental study of the dependence on optical depth of slow and stored light pulses in Rb vapor. In particular, we characterize the efficiency of slow and stored light as a function of Rb density; pulse duration, delay and storage time; and control field intensity. Experimental results are in good qualitative agreement with theoretical calculations based on a simplified three-level model at moderate densities.
We demonstrate a single-photon stored-light interferometer, where a photon is stored in a laser-cooled atomic ensemble in the form of a Rydberg polariton with a spatial extent of $10 times1times1mu m^3$. The photon is subject to a Ramsey sequence, i.e. `split into a superposition of two paths. After a delay of up to 450 ns, the two paths are recombined to give an output dependent on their relative phase. The superposition time of 450 ns is equivalent to a free-space propagation distance of 135 m. We show that the interferometer fringes are sensitive to external fields, and suggest that stored-light interferometry could be useful for localized sensing applications.
We study experimentally the effect of diffusion of Rb atoms on Electromagnetically Induced Transparency (EIT) in a buffer gas vapor cell. In particular, we find that diffusion of atomic coherence in-and-out of the laser beam plays a crucial role in determining the EIT resonance lineshape and the stored light lifetime.
We present theoretical results of a low-loss all-optical switch based on electromagnetically induced transparency and the classical Zeno effect in a microdisk resonator. We show that a control beam can modify the atomic absorption of the evanescent field which suppresses the cavity field buildup and alters the path of a weak signal beam. We predict more than 35 dB of switching contrast with less than 0.1 dB loss using just 2 micro-Watts of control-beam power for signal beams with less than single photon intensities inside the cavity.
Detecting light is fundamental to all optical experiments and applications. At the single photon level, the quantised nature of light requires specialised detectors, which typically saturate for more than one photon, rendering the measurement of bright light impossible. Saturation can be partially overcome by multiplexing single-photon-sensitive detectors, enabling measurement up to tens of photons. However, current approaches are still far from bridging the gap to bright light levels. Here, we report on a massively-multiplexed single-photon detector, which exhibits a dynamic range of 123 dB, from optical energies as low as $mathbf{10^{-7}}$ photons per pulse to $mathbf{sim2.5times10^{5}}$ photons per pulse. This allows us to calibrate a single photon detector directly to a power meter. The use of a single-photon sensitive detector further allows us to characterise the nonclassical features of a variety of quantum states. This device will find application where high dynamic range and single-photon sensitivity are required.
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