Descriptor: "*EXCITON theory" / Topic: 3 selected - Searchworks@Jio Institute Digital Library Search Results

Your search keyword '"*EXCITON theory"' showing total 4 results

Start Over Descriptor "*EXCITON theory" Topic absorption Topic absorption spectra Topic nanowires

Author: Singh, Mahi R.
Subjects: *NANOPHOTONICS, *NANOWIRES, *DIELECTRICS, *ABSORPTION spectra, *EXCITON theory
Abstract: We study a dielectric catastrophe in a new class of materials called nanophotonic quantum wires. They are made from two types of photonic crystals where one is embedded in the other. It is considered that the embedded crystal is made from nonlinear dielectric spheres. The wire is doped with an ensemble of nanoparticles which are interacting with each other via the dipole-dipole interaction. The absorption coefficient of the wire has been investigated in the presence a weak probe laser and a strong pump laser. The probe field measures the absorption spectrum and the pump field changes the refractive index of nonlinear photonic crystals due to the Kerr effect. The density matrix method is used to calculate the absorption coefficient. Numerical simulations have been performed for the dielectric constant and the photon bound states. It is found that the dielectric constant of the system has a singularity when the resonance energy of a nanoparticle lies near the bound photon states of the wire. This is known as the dielectric catastrophe. This phenomenon can be used to make all-optical switching devices. [ABSTRACT FROM AUTHOR]
Published: 2009
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Author: Yi-Fan Liu, Feng-Hua Wang, Dong-Lai Guo, Sheng-You Huang, Jian-Ping Sang, and Xian-Wu Zou
Subjects: *ABSORPTION spectra, *ABSORPTION, *NANOWIRES, *MOLECULAR spectroscopy, *EXCITON theory
Abstract: Ni–P/AAO nano-array composite structure assemblies with Ni and P grown in the pores of anodic aluminum oxide (AAO) membranes were prepared by electroless deposition. The results of SEM, TEM and SAED show that as-deposited Ni–P nanowires have an amorphous structure and a few nanocrystallites form after annealing. The optical absorption spectra reveal that, as the annealing temperature increases, the absorption band edge of the Ni–P/AAO composite structure is obviously blue shifted, which is attributed to a decrease of the internal pressure after heat treatment. Meanwhile, the annealed Ni–P/AAO nano-array composite structure exhibits the absorption behavior of a direct band gap semiconductor. Details of this behavior are discussed together with the implications for potential device applications. [ABSTRACT FROM AUTHOR]
Published: 2009
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Author: Takahashi, Yasushi, Hayamizu, Yuhei, Itoh, Hirotake, Yoshita, Masahiro, Akiyama, Hidefumi, Pfeiffer, Loren N., and West, Ken W.
Subjects: *NANOWIRES, *ABSORPTION, *ABSORPTION spectra, *SPECTRUM analysis, *EXCITON theory
Abstract: We measured the absorption spectra of T-shaped quantum wires at room temperature using waveguide-transmission spectroscopy. A strong and narrow room-temperature one-dimensional-exciton absorption peak was observed, which indicates a peak modal absorption coefficient of 160 cm-1 per 20 wires with a Γ-factor of 4.3×10-3, a width of 7.2 meV, and strong polarization anisotropy. [ABSTRACT FROM AUTHOR]
Published: 2005
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Author: Che, R. C., Peng, L.-M., and Zhou, W. Z.
Subjects: *NANOSTRUCTURED materials, *NANOWIRES, *ABSORPTION, *SPECTRUM analysis, *ABSORPTION spectra, *EXCITON theory
Abstract: Crystalline microporous Co11(HPO3)8(OH)6 nanowires have been synthesized through a soft hydrothermal reaction between red phosphor, KOH, and metal halides. These nanowires were found to have their main hexagonal channels along the long axis and a narrow distribution around 30–40 nm in diameter. The growth of the nanowires were found to initiate at Co(OH)2 nuclei. The length of the nanowires depends mainly on the hydrothermal reaction time and the amount of Co(OH)2 available at the nuclei to feed the growth of the nanowires. Blue shift of up to 85 nm was observed in UV-visible absorption spectra from the Co11(HPO3)8(OH)6 nanowires in comparing with that from the micro-size particle sample, giving an absorption edge deep in the ultraviolet region at about 255 nm or a bandgap Eg∼4.9 eV. [ABSTRACT FROM AUTHOR]
Published: 2005
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