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Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE

Laser-induced continuum structure and third-harmonic generation in calcium

O. Faucher, Dimitrios Charalambidis, E. Koudoumas, Costas Fotakis

Published May 4, 1993• 0 citations
Publisher

Abstract

Under appropriate conditions, the smooth continuum of the atom becomes structured when a bound state is coupled by a strong field with this continuum. Performing a two-color experiment in calcium we have built a dressed continuum and probed it by third harmonic generation.
DOI
10.1117/12.144594

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Observation of laser-induced continuum structure (LICS) in sodium due to the coupling of a bound state to the continuum by a strong laser field has been reported elsewhere. Such experiments have mostly employed a single laser photon to probe the structured continuum from the ground state. Other experiments have used multiphoton (third harmonic) probe schemes, but only one of these has successfully observed LICS, in agreement with theoretical predictions. We report here a very similar experiment generating third-harmonic radiation in sodium to probe the anticipated LICS produced by coupling the 5s state to the p continuum. However, under no conditions was any continuum structure observed, in agreement with in a number of other experiments, but at variance with theoretical predictions.
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Experimental investigations of the laser-induced continuum structure in the vicinity of autoionizing states (AIS's) of Ca are reported for both ionization and third-harmonic generation. The shape of the induced structures is shown to be strongly affected by the presence of the AIS's, as well as exhibiting a detuning- and laser-intensity-dependent transition from a window resonance dip to a peak. The observed modification of the continuum is discussed in terms of interfering excitation channels.