Use this URL to cite or link to this record in EThOS: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.636681
Title: Some propeties of metal vapour lasers
Author: Wong, Kin Hung
Awarding Body: University College of Swansea
Current Institution: Swansea University
Date of Award: 1983
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Abstract:
This thesis is primarily concerned with the design, construction and characterization of a metal vapour laser capable of simultaneously generating three primary colours, blue, green, and red, thereby constituting a "white light" laser. The physical processes responsible for the simultaneous establishment of population inversions between eight energy levels of the cadmium ions which lead to the generation of coherent blue, green and red spectral lines are examined in detail. The essential basis of the white light laser lies in the use of a negative glow discharge in a mixture of helium gas and cadmium vapour in a hollow cathode-pin anode electrode configuration, and the energy distribution and concentrations of electrons, helium and cadmium atomic and molecular ions available in this arrangement. Following a critical review of previous relevant work on metal vapour lasers, which discloses the "white light" generating possibility of the He-Cd+ glow discharge, a discussion of glow discharges is presented with emphasis on the negative glow discharge. An account of apparatus built and the techniques used to investigate the optical and electrical characteristics of He-Cd negative glow discharges is given and the data obtained is presented. This is used together with the analysis of negative glow discharges as the basis for the development of a white light laser. The successful achievement of simultaneous blue, green and red achieved. A series of measurements of the decay of spontaneous emission red boherent beams and the operational characteristics of this laser are presented in detail. Up to 40 mW of white light were of the blue, green and red spectral line intensities in He-Cd+ negative glows is described and the decay rates related to the helium atomic and molecular and cadmium ionic concentrations. From these data the collisional processes responsible for the creation of population inversions are deduced to be direct electronic excitation and Penning effect, in the proportion of 60% to 40% for the 441.6 nm blue line, helium atomic ion charge transfer excitation for the 635.5 and 636.0 nm red lines. As for the 533.7 and 537.8 nm green lines the major excitation processes involve cascading due to stimulated and spontaneous decay of the red line upper level and charge exchange from molecular He2+ ions following atomic He+ ion destruction in a three-body collision with ground state helium atoms. This last process becomes increasingly important as the pressure is increased. Finally, new improved white light laser designs are proposed and suggestion for further work to clarify further details on the inversion mechanisms are made.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.636681  DOI: Not available
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