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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Light Control using Organometallic Chromophores

Henriksson, Johan January 2006 (has links)
<p> </p><p>The interaction between light and organometallic chromophores has been investigated theoretically in a strive for fast optical filters. The main emphasis is on two-photon absorption and excited state absorption as illustrated in the Jablonski diagram. We stress the need for relativistic calculations and have developed methods to address this issue. Furthermore, we present how quantum chemical calculations can be combined with Maxwell's equations in order to simulate propagation of laser pulses through a materials doped with chromophores with high two-photon absorption cross sections. Finally, we also discuss how fast agile filters using spin-transition materials can be modeled in order to accomplish theoretical material design.</p> / Report code: LIU-TEK-LIC-2006:55. On the day of the defence date the status on article III was Manuscript, article IV was Accepted and article V was Submitted.
2

Light Control using Organometallic Chromophores

Henriksson, Johan January 2006 (has links)
The interaction between light and organometallic chromophores has been investigated theoretically in a strive for fast optical filters. The main emphasis is on two-photon absorption and excited state absorption as illustrated in the Jablonski diagram. We stress the need for relativistic calculations and have developed methods to address this issue. Furthermore, we present how quantum chemical calculations can be combined with Maxwell's equations in order to simulate propagation of laser pulses through a materials doped with chromophores with high two-photon absorption cross sections. Finally, we also discuss how fast agile filters using spin-transition materials can be modeled in order to accomplish theoretical material design. / <p>Report code: LIU-TEK-LIC-2006:55. On the day of the defence date the status on article III was Manuscript, article IV was Accepted and article V was Submitted.</p>
3

Molecular Quadratic Response Properties with Inclusion of Relativity

Henriksson, Johan January 2008 (has links)
This thesis concerns quadratic response properties and their application to properties in Jablonski diagrams such as resonant two-photon absorption and excited state absorption. Our main interest lies in optical power limiting applications, and in this context, molecules containing heavy metal atoms prove superior. Therefore, we are interested in how relativity affects these properties, and in order to assess this, a four-component relativistic framework is adopted. To properly address the molecular properties of interest, both relativistic effects and electron correlation need to be accounted for. These two properties are not additive, and, therefore, correlation needs to be incorporated into the four-component framework. We present the implementation of quadratic response properties at the four-component density functional level of theory. For second-harmonic generation, we have, with numerical examples, demonstrated that correlation and relativity are indeed not additive and that the inclusion of noncollinear magnetization is of little importance. We report that both electron correlation as well as relativity strongly affect results for second-harmonic generation. For example, relativity alone reduces the µβ-response signal by 62% and 75% for meta- and ortho-bromobenzene, respectively, and enhances the same response by 17% and 21% for meta- and ortho-iodobenzene, respectively. In the four-component framework, we present the implementations of single and double residues of the quadratic response function, which allows for the evaluation of resonant two-photon absorption cross sections and excited state properties. Using these tools, we discuss different levels of approximation to the relativistic Hamiltonian and we demonstrate that for two-photon absorption, a proper treatment of relativistic effects qualitatively alters the spectrum. For example, already for an element as light as neon, significant differences are seen between the relativistic and nonrelativistic spectra as triplet transitions acquire substantial absorption cross sections in the former case. Finally, quantum mechanics in conjunction with electrodynamics is applied to determine clamping levels in macroscopic samples. The microscopic properties of the optically active chromophores are determined by response theory, and then, electrodynamics is used to describe the interactions between the chromophores and incident laser pulses. Using this approach a series of molecules have been investigated and their performances have been compared and ranked in order to find novel materials for optical power limiting applications.

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