Browsing by Subject "Laser action"

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    Laser action studies of π-conjugated polymer microcavities
    (IEEE, 2008) Tülek, Abdullah; Vardeny, Z. V.
    Unidirectional laser emission was observed from φ-conjugated polymer microcavities with spiral geometry, and from microdisks containing line defects. For both type of cavities directionality contrast of the laser emission was found to be ̃ 10, with far-field lateral divergence angle of ̃ 15°. No significant increase in the laser threshold intensity was observed compared with simple microdisk cavities. In addition we also studied the emission spectra of microring polymer lasers fabricated on nylon microfibers upon application of uniaxial stress with strain up to ̃ 12%. Substantial change in the laser emission spectrum was observed when stress was applied; showing enhanced optical sensitivity to stress larger than the changes induced in the emission spectrum caused by the microfiber diameter change. We explain the enhanced sensitivity to stress as due to the induced change in the polymer refractive index dispersion, in particular at the laser emission wavelength (̃ 635 nm).
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    Ultralow threshold laser action from toroidal polymer microcavity
    (American Institute of Phycsics, 2009) Tulek, A.; Akbulut, D.; Bayındır, Mehmet
    We report laser action from a toroidal microcavity coated with π-conjugated polymer. An ultralow threshold value of ∼200 pJ/pulse is achieved by free space excitation in ambient conditions. This is the lowest threshold energy obtained in microtoroid lasers by free space excitation. The effective refractive index of the polymer, extracted from Fourier analysis of emission spectra, is 1.787, which is very close to measured value of 1.790 indicating that laser modes are located around the circumference of the cavity as whispering gallery resonances. © 2009 American Institute of Physics.