Browsing by Author "Akbulut, Duygu"

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    Generation of new frequencies in toroid microcavities
    (IEEE, 2008) Akbulut, Duygu; Tülek, Abdullah; Bayındır, Mehmet
    Microtoroid cavities with ultra high Q-factor have been fabricated using a combined process of photolithography and reflow technique for observing non-linear effects such as generation of new frequency components. For this purpose SiO2 material was used to form the toroidal cavity shape, and chalcogenide material of As2S3 maintaining very high nonlinear refractive index was thermally evaporated on top with varying thicknesses. Simulation results of the fabricated structure have exhibited new frequency components around the excitation window of 1520 nm produced by non-linear interactions.
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    Lasing action and supercontinuum generation in nano- and micro-structures
    (2009) Akbulut, Duygu
    Supercontinuum generation is the substantial broadening of electromagnetic radiation due to nonlinear interactions with the transporting medium. It nds application in a wide range of areas, including spectroscopy, frequency metrology, optical coherence tomography and telecommunications. Whispering gallery mode microresonators con ne light in a micron scale area via total internal re ection mechanism. Among these structures, microtoroid is especially interesting since it combines ultrahigh quality factor and chip integrability. Applications of such structures include nonlinear and quantum optics, biological and chemical sensing, telecommunications and quantum electrodynamics. In the rst part of the present work, continuum generation from a nanostructured chalcogenide glass (As2Se3) core, high temperature polymer (polyethersulfone, PES) cladding ber was experimentally investigated. Simulation results for nonlinear interactions inside a microtoroid are also provided. In the second part, polymer coated toroidal microresonators were employed for observation of laser action. Owing to high quantum e ciency of the polymer, the observed lasing threshold has a very low value of 200 pJ/pulse despite free space excitation.