Today on the archive
Thu Aug 10 08:38:04 BST 2006
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- Title: All-optical Control of the Propagation of Intense Laser Light in Condensed Media
- Authors: A. K. Dharmadhikari, K. Alti, J. A. Dharmadhikari, D. Mathur Comments: 4 figures. Submitted to PRL
- Abstract: We experimentally demonstrate optical control of filamentation that occurs during propagation of intense, ultrashort laser pulses through crystals like barium fluoride and sapphire. Control is exercised by rotating the plane of polarization of the incident laser radiation and is demonstrated by directly visualizing filamentation in the bulk via six-photon absorption-induced fluorescence and, concomitantly, by probing the spectral and spatial properties of white light that is generated.
- Comment: Filamentation occurs when an intense ultrashort pulse propagates through a medium, and results in localization of the optical energy into the region of the filament. This leads to mechanical effects such as microexplosions, opening the possibility of nanomachining within a material. This paper looks at controlling filamentation dynamics by varying the properties of the optical pulse, in this case the polarization of the pulse.
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- Title: Laser Noise Reduction in Air
- Authors: Pierre Bejot, Jerome Kasparian, Estelle Salmon, Roland Ackermann, Nicolas Gisin, Jean-Pierre Wolf Comments: 8 pages
- Journal-ref: Applied Phys. Lett. 88, 251112, 2006
- Abstract: Fluctuations of the white-light supercontinuum produced by ultrashort laser pulses in selfguided filaments (spatio-temporal solitons) in air are investigated. We demonstrate that correlations exist within the white-light supercontinuum, and that they can be used to significantly reduce the laser intensity noise by filtering the spectrum. More precisely, the fundamental wavelength is anticorrelated with the wings of the continuum, while conjugated wavelength pairs on both sides of the continuum are strongly correlated. Spectral filtering of the continuum reduces the laser intensity noise by 1.2 dB, showing that fluctuations are rejected to the edges of the spectrum.
- Comment: another article on filamentation in a medium subjected to ultrashort optical pulses, this time focussing on intensity noise reduction for supercontinuum light sources and the correlations present in supercontinuum light.
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- Title: Quantum metrology at the Heisenberg limit with ion traps
- Authors: D.A.R. Dalvit, R.L. de Matos Filho, F. Toscano
- Title: Sub-Planck phase-space structures in the Wigner function of the motional degree of freedom of a trapped ion can be used to perform weak force measurements with Heisenberg-limited sensitivity. We propose methods to engineer the Hamiltonian of the trapped ion to generate states with such small scale structures, and we show how to use them in quantum metrology applications.
- Comment: The paper discusses how to use generalised cat states of the motion of an ion to act as a weak force detector. Some useful maths about Wigner functions. The basic idea is that if you have a cat state that is a superposition of two coherent states then the Wigner function in the phase space region between the coherent states has fringes with spacing inversely proportional to the separation between the cat states, so you become sensitive to displacements on this length scale. Better sensitivity can be achieved using "compass states" consisting of superpositions of four coherent states, these are rotationally symmetric about the phase space origin.
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