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2010-01-25

S 20100126

Changing matter with light: from atoms to optical chips

 

- by Jovana Petrović from the University of Oxford, UK


Ultra cold molecules, including the molecular BEC, are an optimal sample for contemporary spectroscopy, Rydberg atoms and molecules entaglement, collision research and other applications which are still in the theoretical area. The link between cold atom and short-pulsed lasers expertises in Oxford enabled a series of experiments with the aim to obtain cold molecules by femtosecond association - a method promising the best flexibility and coherent control, but least efficient. Atoms cooled in magneto-optical trap are excited by wide laser pulses, and - due to the nuclear wavefunctions interference - wave packets are generated and oscillate in non-harmonic nuclear potential. The stabilization of molecules is obtained by the implementation of another laser pulse just at the time of good overlap of the packet with a wavefuction of a low vibrating level in base state. In the scope of this lecture, I will explain the first realization of the photoassociation of molecules excited by femtosecond pulses and the theoretical-experimental work on the system dynamics.


The second part of the lecture deals with the interaction of femtosecond lasers with optical materials. Focused pulses induce multi-photon ionization of the material which leads to the generation and heating of electron plasma and to the great gradients of the temperature and pressure. During the relaxation, structural changes take part, which lead to the irreversible change of the refractive index. The similarity of the plasma density distribution, obtained by numerical solution of the nonlinear Schroedinger equation coupled with the equations of plasma generation, justifies the im0plementation of this model. The simulation of further elastical-platical modifications in the material indicates the modification out of the laser beam focus, but also to the reduced modifications due to the material relaxation which has been confirmed in the experiments with lattices in optical fibers. The possibility of the control of laser pulses and precise samples movement was used in the manufacturing of microchannels and Bragg lattices in optical fibers which could be used as sensors, while the parametric conversion has been used for the manufacturing of the precursors of integrated optical components.

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