Fast-Light in a Photorefractive Crystal for Gravitational Wave Detection

We demonstrate superluminal light propagation using two frequency multiplexed pump beams to produce a gain doublet in a photorefractive crystal of Ce:BaTiO3. The two gain lines are obtained by two-wave mixing between a probe field and two individual pump fields. The angular frequencies of the pumps are symmetrically tuned from the frequency of the probe. The frequency difference between the pumps corresponds to the separation of the two gain lines; as it increases, the crystal gradually converts from normal dispersion without detuning to an anomalously dispersive medium. The time advance is measured as 0.28 sec for a pulse propagating through a medium with a 2Hz gain separation, compared to the same pulse propagating through empty space. We also demonstrate directly anomalous dispersion profile using a modfied experimental configuration. Finally, we discuss how anomalous dispersion produced this way in a faster photorefractive crystal (such as SPS: Sn2P2S6) could be employed to enhance the sensitivity-bandwidth product of a LIGO type gravitational wave detector augmented by a White Light Cavity.Comment: 14 pages, 5 figure

Kolkata Restaurant Problem as a generalised El Farol Bar Problem

Generalisation of the El Farol bar problem to that of many bars here leads to the Kolkata restaurant problem, where the decision to go to any restaurant or not is much simpler (depending on the previous experience of course, as in the El Farol bar problem). This generalised problem can be exactly analysed in some limiting cases discussed here. The fluctuation in the restaurant service can be shown to have precisely an inverse cubic behavior, as widely seen in the stock market fluctuations.Comment: 2 column RevTeX4, 4 pages, 3 eps figs; to be published in 'Econophysics of Markets and Business Networks', [Proc. Econophys-Kolkata III], Eds. A. Chatterjee, B. K. Chakrabarti, New Economic Windows Series, Springer, Milan, 2007, pp. 220-22

Strong coupling of single emitters to surface plasmons

We propose a method that enables strong, coherent coupling between individual optical emitters and electromagnetic excitations in conducting nano-structures. The excitations are optical plasmons that can be localized to sub-wavelength dimensions. Under realistic conditions, the tight confinement causes optical emission to be almost entirely directed into the propagating plasmon modes via a mechanism analogous to cavity quantum electrodynamics. We first illustrate this result for the case of a nanowire, before considering the optimized geometry of a nanotip. We describe an application of this technique involving efficient single-photon generation on demand, in which the plasmons are efficiently out-coupled to a dielectric waveguide. Finally we analyze the effects of increased scattering due to surface roughness on these nano-structures.Comment: 34 pages, 7 figure

An instructional experience for pre-service teachers: integrating simulations and hands-on activities in physics teaching

Simulations are a valuable tool in teaching modern science. We report on an experiment in a physics laboratory on electricity using both simulations as well as hands-on activities. The laboratory was implemented as part of a course for pre-service secondary school physics teachers. The 45 participants were divided into two groups, one performing first simulations and then hands-on activities, the other in the reversed order. The laboratory activities focused on DC circuits related to real-life situations, like a multiple socket or a chandelier modeled with simple wires, batteries and bulbs. The participants were asked to make predictions of the outcome before conducting each task and to compare their predictions with the observations and measurements they made during the activities. The participants were asked to make predictions of the outcome before conducting each task and to compare their predictions with the observations and measurements they made during the activities. No significant differences in performance were observed between the two groups, suggesting that in this experiment simulations did not help the pre-service teachers in transferring their conceptual knowledge to practical application