SVIBOR - Project code: 1-03-281

MINISTRY OF SCIENCE AND TECHNOLOGY

Strossmayerov trg 4, HR - 10000 ZAGREB
tel.: +385 1 459 44 44, fax: +385 1 459 44 69
E-mail: ured@znanost.hr

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Project code: 1-03-281


NONLINEAR INTERACTION OF A LASER PULSE


Main researcher: PERŠIN, ANTON (56105)



Assistants
Type of research: basic
Duration from: 10/07/91. to 10/07/94.

Papers on project (total): 17
Papers on project quoted in Current Contents: 2
Institution name: Centar LAIR, Institut "R. Bošković", Zagreb (1032)
Department/Institute: Rudjer Boskovic Institute Center of Laser and Atomic R&D
Address: Bijenička c. 54
City: 10000 - Zagreb, Croatia
Communication
E-mail: zorc@olimp.irb.hr
E-mail: skala@olimp.irb.hr
E-mail: dsoldo@olimp.irb.hr
Phone: 385 (0)1 424869, 272759
Fax: 385 (0)1 424869

Summary: Research of the optical bistability in thin films multilayers has been performed. Optical modelling using a personnal computer has been done. Such systems has been realised in form of thin films in a resonant cavity. The bistability parameters have been determined. The analysis of multilayers containing a simple and compound resonant cavity has been done. It has been shown that multilayers containing a compound resonant cavity have lower bistability treshold. Moreover, varying materials and their thicknesses in the resonant cavity, it is possible to tune bistable properties! Laser pulse interaction with the metal surface (Pb and Sn) has been performed. Laser induced metal plasma spectra in the region 400-700 nm have been taken. Laser pulse of 10MW per square centimeter induced excited and single ionized atoms. Due the equipment insufficience, research of this phenomena has been stopped. The two-component model of particle size distribution has been improved and applied to olygotrophic water. Introduction of this model induced significant improvements comparing to the use of the classical models. The results show much better forward scattering predictions, when applying the two-component model of scattering function. First results of the nonlinear optical behaviour of C60 molecules stimulated the work in this field. So C60 and higher fullerenes were synthesized and characterized. Using the mass spectrometry it has been shown that a UV laser pulse is responsible for the di- and trimerisation of C60 molecules. Possibilities of caries healing by using a CO2 laser have been studied. A continous CO2 laser with the CW power 1-2W has been used. The temperature increase in the tooth root during the laser exposition has been measured, and the damage treshold has been estimated.

Keywords: optical bistability, thin films, computer design, C60, fullerenes, particle distribution, sea optics, light scattering, laser ablation, plasma diagnostic, laser in stomatology

Research goals: There were orriginally three goals in the research of the nonlinear laser pulse interaction; optical bistability, physics of the laser induced plasma and interaction of a laser pulse with the scattering medium (like turbid water or biological tissue). Optical bistability has been studied on the optical multilayers with a simple and compound resonant cavity. Possibilities of the bistability treshold decrease have been studied. It had been expected that a compound resonant cavity offers a lower bistability treshold. Bistable optical component was orriginally also in function of reshaping of NdYAG laser pulse, as an active optical component instead of passive laser mirror. A NdYAG laser pulse has been used in the research of the metal plasma diagnostics of the laser ablated atoms. A complete plasma diagnostic has been expected to be done. Only a qualitative plasma composition diagnostic has been realized. This research has been stopped due the insufficiency of the diagnostic equipment. The laser pulse transmission in olygotrophic water and in the biological tissue has been studied. The two-component model of particle size distribution has been improved. A two-component model of the scattering function has been developed. The model has been applied to the laser beam transmission in water. The research of the CO2 laser transmission in a tooth resulted by the determination of the biological laser damage treshold. The laser powers beyond this treshold introduces the damage of the tooth tissue. The interesting early results in the nonlinear behaviour of the C60 molecule triggered the research in the fullerene physics.The synthesis of C60 and higher fullerenes has been done. A complete characterization of C60 and higher fullerenes has been done to confirm a succsessfull synthesis. It has been shown that a UV NdYAG laser pulse introduces the di- and- trimerization of C60 molecules.


COOPERATION - INSTITUTIONS


  1. Name of institution: Stomatološki fakultet, odjel dentalne patologije
    Type of institution: Economical/Production
    City: 10000 - Zagreb, Croatia

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Last update: 10/19/95
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