Development and characterisation of a tunable laser source in the vacuum ultraviolet

Steinmann, Christine Margarete (1999-12)

Thesis (M.Sc.) -- University of Stellenbosch, 1999.

Thesis

ENGLISH ABSTRACT: Four-wave frequency mixing in a metal vapour medium is a technique that is used to generate small bandwidth, frequency tunable coherent vacuum ultraviolet radiation for spectroscopic applications. The theory of nonlinear optics, applied to sum-frequency generation in a magnesium vapour medium at moderate input laser intensity, describes the requirements for optimal conversion efficiency accurately. The microscopic requirement - a sufficiently large third order susceptibility - is met by employing the 3s² _ 3s3d two-photon resonance of atomic magnesium to enhance the susceptibility for sum-frequency generation. The macroscopic requirement for the constructive interference of the sum-frequency contributions generated in different volume elements (termed the phase matching condition) can be met by using a two-component gaseous medium of magnesium vapour and krypton gas. In an experimental setup phase matching requires high homogeneity of the medium, very stable temperature conditions and the ability to fine tune the krypton magnesium pressure ratio. These conditions can be met in a crossed concentric heat pipe oven by relying on the properties of a dynamic liquid-vapour phase equilibrium. Results obtained with two similar experimental setups for four-wave frequency mixing in magnesium vapour confirm the theoretical predictions and show that the technically simple setup functions as an efficient laser source of tunable vacuum ultraviolet radiation.

AFRIKAANSE OPSOMMING: Vier-foton frekwensie-vermenging in 'n metaaldamp medium is 'n tegniek wat gebruik word om 'n frekwensie afstembare laserbundel met 'n smal-frekwensie bandwydte in die vakuum ultraviolet spektraalgebied te genereer. Die teoretiese beskrywing van nie-lineere optika, toegepas op die spesiale geval van somfrekwensie-opwekking in 'n magnesiumdamp medium, lewer 'n goeie beskrywing van die vereistes vir optimale omsetting. Daar word aan die mikroskopiese vereiste - dat die derde orde suseptibiliteit 'n toereikende waarde moet he - voldoen deur die 33s²-3s3d twee-foton resonans van die magnesium atome te benut. Aan die makroskopiese vereiste - dat die bydraes tot die somfrekwensie veld wat in verskillende volume-elemente van die medium opgewek is, konstruktief moet interfereer - word voldoen deur 'n twee-komponent medium bestaande uit magnesiumdamp en kriptongas te gebruik. In die eksperimentele opstelling vereis hierdie sogenaamde fase-aanpassingskondisie 'n baie homogene mengsel, 'n stabiele temperatuur en die vermoe om die kripton-magnesium drukverhouding fyn te kan instel. In 'n kruisvormige konsentriese hittepyp-oond kan daar, deur van die eienskappe van In dinamiese vloeistof-damp ewewig gebruik te maak, aan hierdie vereistes voldoen word. Eksperimentele resultate verkry met twee soortgelyke eksperimentele opstellings vir vierfoton frekwensie-vermenging in magnesiumdamp, bevestig die teoretiese voorspellings en bewys dat die tegnies eenvoudige opstelling as 'n doeltreffende frekwensie afstembare laserbron in die vakuum ultraviolet funksioneer.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/51198
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