Controlled photoluminescence in amorphous-silicon-nitride microcavities

Narrow-band and enhanced photoluminescence have been observed in hydrogenated amorphous-silicon-nitride microcavities. The distributed Bragg reflectors were fabricated using alternating layers of hydrogenated amorphous-silicon nitride and hydrogenated amorphous-silicon oxide. The microcavity resonance wavelength was designed to be at the maximum of the bulk hydrogenated amorphous-silicon-nitride luminescence spectrum. At the microcavity resonance, the phololuminescence amplitude is enhanced, while the photoluminescence linewidth is reduced with respect to the bulk hydrogenated amorphous-silicon nitride. © 2001 American Institute of Physics

Propagation of light through localized coupled-cavity modes in one-dimensional photonic band-gap structures

We report on the observation of a new type of propagation mechanism through evanescent coupled optical cavity modes in one-dimensional photonic crystals. The crystal is fabricated from alternating silicon-oxide/silicon-nitride pairs with silicon-oxide cavity layers. We achieved nearly full transmission throughout the guiding band of the periodic coupled cavities within the photonic band gap. The tight-binding (TB) parameter K is determined from experimental results, and the dispersion relation, group velocity and photon lifetime corresponding to the coupled-cavity structures are analyzed within the TB approximation. The measurements are in good agreement with transfer-matrix-method simulations and predictions of the TB photon picture

Strong enhancement of spontaneous emission in amorphous-silicon-nitride photonic crystal based coupled-microcavity structures

We investigated photoluminescence (PL) from one-dimensional photonic band gap structures. The photonic crystals, a Fabry-Perot (FP) resonator and a coupled-microcavity (CMC) structure, were fabricated by using alternating hydrogenated amorphous-silicon-nitride and hydrogenated amorphous-silicon-oxide layers. It was observed that these structures strongly modify the PL spectra from optically active amorphous-silicon-nitride thin films. Narrow-band and wide-band PL spectra were achieved in the FP microcavity and the CMC structure, respectively. The angle dependence of PL peak of the FP resonator was also investigated. We also observed that the spontaneous emission increased drastically at the coupled-cavity band edge of the CMC structure due to extremely low group velocity and long photon lifetime. The measurements agree well with the transfer-matrix method results and the prediction of the tight-binding approximation

Strong enhancement of spontaneous emission in hydrogenated amorphous silicon nitride coupled-microcavity structures

The modification of spontaneous emission from the hydrogenated amorphous silicon nitride layers in a coupled-microcavity (CMC) structure was investigated. The CMC structure was composed of alternating silicon-oxide and silicon-nitride multilayers. The results showed that the strong enhancement of spontaneous emisssion can be achieved throughout the cavity band

LC-DAD-ESI-MS/MS-assisted elucidation of the phenolic compounds in shalgams: Comparison of traditional and direct methods

PubMedID: 31606693Shalgam is a beverage which is produced by lactic acid fermentation of black carrot juice. Two commercial methods (traditional method - TM and direct method - DM) used to produce shalgams were compared with respect to their effects on the general compositions, bioactive phenolic compounds and antioxidant potentials for the first time. A total of 25 phenolic compounds comprising anthocyanins, flavonols, and phenolic acids were identified and characterized by LC-DAD-ESI/MSn. Cyanidin-3-xylosyl-galactoside and cyanidin-3-xylosyl-glucosyl-galactoside accounted for the highest amount of the total anthocyanins. Also, seven newly-identified anthocyanins including cyanidin 3-xylosyl-(caffeoyl-glucosyl)-galactoside, cyanidin 3-xylosyl-(p-hydroxybenzoyl-glucosyl)-galactoside, cyanidin 3-xylosyl-galactoside+vinylphenol, cyanidin 3-xylosyl-galactoside+vinylcatechol, cyanidin 3-xylosyl-(feruloyl-glucosyl)-galactoside+vinylcatechol, cyanidin 3-xylosyl-galactoside+ vinylguaiacol, cyanidin 3-xylosyl-(feruloyl-glucosyl)-galactoside+vinylguaiacol were found in the shalgam samples for the first time. Phenolic acids and flavonols of shalgam samples were studied for the first time. The major subclass of the chlorogenic acids was identified as 5-caffeoylquinic acid in the samples. Antioxidant capacities of the samples screened using ABTS and DPPH assays were in accordance with their total phenolic content. Principal component analysis (PCA) revealed clear discrimination between the two production methods (TM and DM). This study demonstrated that the DM provided higher phenolic and antioxidant potential than the TM in the shalgam samples. © 2019 Elsevier Ltd17332003This research was made possible through the financial support from the Adana Alparslan Turkes Science and Technology University by means of a thesis Project (No: 17332003 ). The authors achnowledge Kilikya Shalgam Company for providing raw materials for shalgam production. The authors also thank to Kukre A.S. Food Company for direct method of shalgam production. We would like to thank Dr. Muharrem Keskin from Hatay Mustafa Kemal University, Turkey for his critical reading. Appendix