Browsing by Subject "Microcavity"
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Item Open Access Characteristic equations for the lasing Modes of infinite periodic chain of quantum wires(IEEE, 2008-06) Byelobrov, V. O.; Benson, T. M.; Altıntaş, Ayhan; Nosich, A.I.In this paper, we study the lasing modes of a periodic open optical resonator. The resonator is an infinite chain of active circular cylindrical quantum wires standing in tree space. Characteristic equations for the frequencies and associated linear thresholds of lasing are derived. These quantities are considered as eigenvalues of specific electromagnetic-field problem with "active" imaginary part of the cylinder material's refractive index - Lasing Eigenvalue Problem (LEP). ©2008 IEEE.Item Open Access Coupled optical microcavities in one-dimensional photonic bandgap structures(Institute of Physics Publishing, 2001) Bayındır, Mehmet; Kural, C.; Özbay, EkmelWe present a detailed theoretical and experimental study of the evanescent coupled optical microcavity modes in one-dimensional photonic bandgap structures. The coupled-cavity samples are fabricated by depositing alternating hydrogenated amorphous silicon nitride and silicon oxide layers. Splitting of the eigenmodes and formation of a defect band due to interaction between the neighbouring localized cavity modes are experimentally observed. Corresponding field patterns and the transmission spectra are obtained by using transfer matrix method (TMM) simulations. A theoretical model based on the classical wave analogue of the tight-binding (TB) picture is developed and applied to these structures. Experimental results are in good agreement with the predictions of the TB approximation and the TMM simulations.Item Open Access Fabrication and characterization of amorphous silicon microcavities(1999) Tanriseven, SelimIn this thesis, planar amorphous silicon microcavities were fabricated and characterized at room temperature. Microcavities were realized by embedding the active amorphous silicon layer between distributed Bragg reflectors, which are composed of alternating silicon oxide and silicon nitride layers. All of the layers were grown by plasma enhanced chemical vapor deposition on silicon substrates. By tuning the cavity mode to emission maximum of amorphous silicon, a narrow and enhanced emission line is obtained. Device characterization was done by means of photoluminescence, and reflectance measurements. The experimental results compare favorably with the theoretical calculations performed by transfer matrix method.Item Open Access Large and dynamical tuning of a chalcogenide Fabry-Perot cavity mode by temperature modulation(Optical Society of America, 2010) Yaman, M.; Kondakci, H. E.; Bayındır, MehmetTe-enriched chalcogenide glass Ge15As25Se15Te45 (GAST) is synthesized, thermo-optically characterized and used to fabricate a one dimensional photonic crystal cavity mode that is dynamically and reversibly tuned by temperature modulation. The optical cavity mode is designed using GAST and As2S3 glasses after fully determining their temperature dependence of the complex refractive indices in the visible and near infrared spectrum using spectroscopic ellipsometry. By making use of the very large thermo-optic coefficient (dn/dT = 4x10(-4)/degrees C) of GAST glass at 1.2 mu m, the cavity mode of the multilayer was tuned reversibly more than 16 nm, which is, to the best of our knowledge, an order of magnitude larger for this kind of cavity modulation. Wide and dynamical spectral tuning of low bandgap chalcogenide glasses via temperature modulation can be utilized in photonic crystal based integrated optics, quantum dot resonance matching, solid state and gas laser components, and infrared photonic crystal fibers. (C) 2010 Optical Society of AmericaItem 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).Item Open Access Lasing modes of infinite periodic chain of quantum wires(IEEE, 2009-06-07) Byelobrov, V. O.; Benson, T. M.; Sewell, P.; Altıntaş, Ayhan; Nosich, A. I.In this paper, we study the scattering and eigenvalue problems for a periodic open optical resonator that is an infinite chain of active circular cylindrical quantum wires standing in free space. The scattering problem is solved by the method of partial separation of variables. The eigenvalue problem differs from the first one by the absence of the incident field and presence of "active properties" of cylinders and yields the frequencies and thresholds of lasing. ©2009 IEEE.Item Open Access Microcavity effects in the photoluminescence of hydrogenated amorphous silicon nitride(SPIE, 1998) Serpengüzel, Ali; Aydınlı, Atilla; Bek, AlpanFabry-Perot microcavities are used for the alteration of photoluminescence in hydrogenated amorphous silicon nitride grown with and without ammonia. The photoluminescence is red-near-infrared for the samples grown without ammonia, and blue-green for the samples grown with ammonia. In the Fabry- Perot microcavities, the amplitude of the photoluminescence is enhanced, while its linewidth is reduced with respect to the bulk hydrogenated amorphous silicon nitride. The microcavity was realized by a metallic back mirror and a hydrogenated amorphous silicon nitride - air or a metallic front mirror. The transmittance, reflectance, and absorbance spectra were also measured and calculated. The calculated spectra agree well with the experimental spectra. The hydrogenated amorphous silicon nitride microcavity has potential for becoming a versatile silicon based optoelectronic device such as a color flat panel display, a resonant cavity enhanced light emitting diode, or a laser.Item Open Access Stable and low ‐ threshold optical gain in CdSe/CdS quantum dots: an all ‐ colloidal frequency up ‐ converted laser(Wiley-VCH Verlag, 2015) Güzeltürk, B.; Keleşemur, Y.; Güngor, K.; Yeltik, A.; Akgül, M. Z.; Wang, Y.; Chen R.; Dang, C.; Sun, H.; Demir, Hilmi VolkanAn all-solution processed and all-colloidal laser is demonstrated using tailored CdSe/CdS core/shell quantum dots, which exhibit highly stable and low-threshold optical gain owing to substantially suppressed non-radiative Auger recombination.