Browsing by Subject "Directional emission"

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Open Access
Bright off-axis directional emission with plasmonic corrugations
(OSA - The Optical Society, 2017) Sattari, H.; Rashed, A. R.; Özbay, Ekmel; Caglayan, H.
In this work, a new plasmonic bulls-eye structure is introduced to efficiently harvest the emitted light from diamond nitrogen vacancy (NV) centers. We show that the presence of a simple metal sub-layer underneath of a conventional bulls-eye antenna, separated by a dielectric layer, results in the spontaneous emission enhancement and increment in out-coupled light intensity. High Purcell factor is accessible in such a structure, which consequently boosts efficiency of the radiated light intensity from the structure. The structure shows considerable enhancement in far-field intensity, about three times higher than that of a one-side corrugated (conventional) optimized structure. In addition, we study for the first time asymmetric structures to steer emitted beams in two-axis. Our results show that spatial off-axial steering over a cone is approachable by introducing optimal asymmetries to grooves and ridges of the structure. The steered light retains a level of intensity even higher than conventional symmetric structures. A high value of directivity of 16 for off-axis steering is reported. © 2017 Optical Society of America.
Open Access
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).