Document Details

Document Type : Thesis 
Document Title :
Theoretical Study on The Ultra Fast Mechanisms Associated with the Break Down of Water Induced by Short Pulses of Laser Radiation
دراسة نظرية عن الآليات فائقة السرعة المصاحبة لانهيار الماء المستحث بواسطة نبضات قصيرة من أشعة الليزر
 
Subject : Girls' College of Education in Jeddah 
Document Language : Arabic 
Abstract : In the present work a theoretical study is carried out on the phenomenon of water breakdown induced by ultra short pulses of laser radiation as well as the associated mechanical mechanisms. In doing so, we applied two models namely; the classical breakdown model and the moving breakdown model . The first one takes into account only the temporal variation of the laser intensity in the focal volume, while the second model consider its the influence of both the temporal and spatial variations . Computations are performed under the experimental conditions given by Noack and Vogel (1999) to determine the threshold intensity of water breakdown plasma formation under the influence of different laser wavelengths (532 nm, 800 nm, 1064 nm) with a wide range of pulse duration varies from 10 fs to 10 ns .The results of calculations showed a reasonable agreement between the calculated threshold intensities and the experimentally measured ones. Moreover, a comparison is under taken for the obtained results using these Tow models to study the effect of the laser parameters on the shape of the formed plasma, the role played by the loss processes and the temporal and spatial variation of the electron density during laser irradiation in the focal volume . On the other hand, Calculations are carried out to study the effect of the propagation of laser pulse in the focal volume using a femto second laser source . This was done by applying a femto second breakdown model given by Fan et al. 2001 to interpret the experimental measurements which carried out by Vogel et al (1999) for the determination of the threshold intensity of water breakdown at laser wavelength 580 nm and pulse durations 100 fs and 300 fs .A reasonable agreement is obtained between the calculated thresholds and the measured ones for each pulse duration . In addition, the result of computations clarified also, the effect of pulse length and in turn its propagation length on the temporal variation of the electron density as well as the spatial distribution of both laser intensity and shape of the formed plasma in the focal volume. For completeness of this study, computations are carried out to determine the dynamics of cavity bubble and shock wave generation in water plasma by 40 fs and 170 ps laser pulses of wavelength 800 nm under the experimental conditions given by El kamhwy (2006).In addition, a study is performed on the effect of pulse length on the plasma shielding since it is one of the important parameters which plays a principal role for laser medical application (i.e) microsurgery in ophthalmology. 
Supervisor : Prof. Dr. Yosr .E.Gamal 
Thesis Type : Doctorate Thesis 
Publishing Year : 1430 AH
2009 AD 
Added Date : Sunday, January 17, 2010 

Researchers

Researcher Name (Arabic)Researcher Name (English)Researcher TypeDr GradeEmail
ليلى حسين جعبورJaabour, Layla HResearcherMaster 

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