Engaging new dimensions in nonlinear optical spectroscopy using auxiliary beams of light

Ford, Jack S., Bradshaw, David S. and Andrews, David (2014) Engaging new dimensions in nonlinear optical spectroscopy using auxiliary beams of light. In: UNSPECIFIED.

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    By applying a sufficiently intense beam of off-resonant light, simultaneously with a conventional excitation source beam, the efficiencies of one- and two-photon absorption processes may be significantly modified. The nonlinear mechanism that is responsible, known as laser modified absorption, is fully described by a quantum electrodynamical analysis. The origin of the process, which involves stimulated forward Rayleigh-scattering of the auxiliary beam, relates to higher order terms which are secured by a time-dependent perturbation treatment. These terms, usually inconsequential when a single beam of light is present, become prominent under the secondary optical stimulus – even with levels of intensity that are moderate by today’s standards. Distinctive kinds of behaviour may be observed for chromophores fixed in a static arrangement, or for solution- or gas-phase molecules whose response is tempered by a rotational average of orientations. In each case the results exhibit an interplay of factors involving the beam polarisations and the molecular electronic response. Special attention is given to interesting metastable states that are symmetry forbidden by one- or two-photon absorption. Such states may be accessible, and thus become populated, on input of the auxiliary beam. For example, in the one-photon absorption case, terms arise that are more usually associated with three-photon processes, corresponding to very different selection rules. Other kinds of metastable state also arise in the two-photon process, and measuring the effect of applying the stimulus beam to absorbances of such character adds a new dimension to the information content of the associated spectroscopy. Finally, based on these novel forms of optical nonlinearity, there may be new possibilities for quantum non-demolition measurements.

    Item Type: Conference or Workshop Item (Paper)
    Faculty \ School: Faculty of Science > School of Chemistry
    University of East Anglia > Faculty of Science > Research Groups > Physical and Analytical Chemistry
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    Depositing User: Pure Connector
    Date Deposited: 09 Jul 2014 13:00
    Last Modified: 25 Jul 2018 02:08
    URI: https://ueaeprints.uea.ac.uk/id/eprint/49396
    DOI: 10.1117/12.2051333

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