CaF{sub 2} ablation plumes as a source of CaF molecules for harmonic generation

Journal Article · Thu Apr 15 04:00:00 EDT 2010 · Physical Review. A

DOI:https://doi.org/10.1103/PHYSREVA.81.043841· OSTI ID:21408735

Oujja, M; Nalda, R de; Castillejo, M ^[1]; Lopez-Arias, M ^[1]; Torres, R; Marangos, J P ^[2]

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1. Instituto de Quimica Fisica Rocasolano, CSIC, Serrano 119, 28006 Madrid (Spain)
2. Blackett Laboratory, Imperial College London, SW7 2 BW London (United Kingdom)

Generation of low-order harmonics (third and fifth) of the fundamental radiation of a Q-switched Nd:YAG laser (1064 nm, pulse 15 ns) was observed in a CaF{sub 2} laser ablation plume. The ablation process is triggered by a second Q-switched Nd:YAG laser operating at 532 or 266 nm. In the scheme employed, the fundamental laser beam propagates parallel to the target surface at controllable distance and temporal delay, allowing to the probing of different regions of the freely expanding plume. The intensity of the harmonics is shown to decrease rapidly as the distance to the target is increased, and for each distance, an optimum time delay between the ablating laser pulse and the fundamental beam is found. In situ diagnosis of the plume by optical emission spectroscopy and laser-induced fluorescence serves to correlate the observed harmonic behavior with the temporally and spatially resolved composition and velocity of flight of species in the plume. It is concluded that harmonics are selectively generated by CaF species through a two-photon resonantly enhanced sum-mixing process exploiting the (B {sup 2{Sigma}+}-X {sup 2{Sigma}+}, {Delta}{nu}=0) transition of the molecule in the region of 530 nm. In this work polar molecules have been shown to be the dominating species for harmonic generation in an ablation plume. Implications of these results for the generation of high harmonics in strongly polar molecules which can be aligned in the ablation plasma are discussed.

• OSTI ID: 21408735
• Journal Information: Physical Review. A, Journal Name: Physical Review. A Journal Issue: 4 Vol. 81; ISSN 1050-2947; ISSN PLRAAN
• Country of Publication: United States
• Language: English

Related Subjects

74 ATOMIC AND MOLECULAR PHYSICS
ABLATION
ALKALINE EARTH METAL COMPOUNDS
BEAMS
CALCIUM COMPOUNDS
CALCIUM FLUORIDES
CALCIUM HALIDES
EMISSION
EMISSION SPECTROSCOPY
FLUORESCENCE
FLUORIDES
FLUORINE COMPOUNDS
FREQUENCY MIXING
HALIDES
HALOGEN COMPOUNDS
HARMONIC GENERATION
HARMONICS
LASERS
LUMINESCENCE
MOLECULES
NEODYMIUM LASERS
OSCILLATIONS
PHOTON EMISSION
PLASMA
PLUMES
PULSES
SOLID STATE LASERS
SPECTROSCOPY
TIME DELAY