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Stimulated Emission (stimulated + emission)

Distribution by Scientific Domains
Physics and Astronomy70%
Polymers and Materials Science20%

Terms modified by Stimulated Emission

  • stimulated emission depletion
    		•

    Selected Abstracts

    Ultrafast Vibronic Processes in a Ru,Porphyrin Complex

    EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 31 2008
    Izumi Iwakura
    Abstract The excited-state dynamics of RuII(TPP)(CO)(acetone) (TPP = tetraphenylporphyrin) was investigated by using a sub-5-fs pulse. In previous studies, the fluorescence lifetime of RuII(TPP)(CO) could not be resolved and was reported to be <1 ps. Analysis of the six-coordinate complexes of RuII(TPP)(CO)(acetone) showed that 1Qx(,,,*) had a lifetime of 140,±,20 fs and the lifetime of 3(d,,*) was 560,±,150 fs. Stimulated emission due to a spin-forbidden transition from 3(,,,*) to the ground state was observed for the first time.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source]

    Effects of growth temperature on exciton lifetime and structural properties of ZnO films on sapphire substrate

    PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 15 2006
    S. Cho
    Abstract We report on optimization of growth conditions by studying the structural and optical properties of ZnO films grown on sapphire substrate by pulsed laser deposition at different growth temperatures. The crystallographic structure and surface morphology were studied by X-ray diffraction and atomic force microscopy, respectively. The flattest surface was observed in the sample grown at substrate temperature of 500 °C. The optical characterization was performed by steady state and time resolved photoluminescence spectroscopy. Photoluminescence of the samples was studied at low CW excitation and at high-power-density pulsed excitation in picosecond domain. Stimulated emission was observed at pulsed excitation. Carrier lifetimes were found to significantly depend on the growth temperature reaching the peak value also in the samples grown at approximately 500 °C. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Stimulated emission and leakage current in InxGa1,xN lasers

    PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 10 2005
    Elis Mon
    Abstract In this paper we calculate the temperature dependence of the transparency concentration n0 for InxGa1,xN/GaN single quantum well laser diodes. To establish the lasing mechanism existing in these lasers, this concentration is compared with that given by the Mott criterion limiting the existence of an excitonic gas or electron-hole plasma. For a typical structure with an In0.13Ga0.87N active layer n0 results higher than the critical excitonic concentration. This result indicates that the conventional electron-hole plasma instead of excitonic recombination is the dominant mechanism responsible for lasing in nitride lasers. The contribution of the diffusion leakage current density to the total threshold current density was also calculated, considering both electron and hole components. We obtain that the electron leakage current density is more than a half of the total threshold current density, confirming it is the main loss mechanism present in these lasers. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Amplified Spontaneous Emission of Poly(ladder-type phenylene)s , The Influence of Photophysical Properties on ASE Thresholds,

    ADVANCED FUNCTIONAL MATERIALS, Issue 20 2008
    Frédéric Laquai
    Abstract Amplified spontaneous emission (ASE) of a series of blue-emitting poly(ladder-type phenylene)s (LPPP)s has been studied in thin film polymer waveguide structures. The chemically well-defined step-ladder polymers consist of an increasing number of bridged phenylene rings per monomer unit starting from fully arylated poly(ladder-type indenofluorene) up to poly(ladder-type pentaphenylene). The ASE characteristics of the polymers including the onset threshold values for ASE, the gain and loss coefficients as well as the photoluminescence (PL) properties, i.e., the solid state fluorescence lifetimes, decay kinetics and solid state quantum efficiencies have been studied by time-resolved PL spectroscopy. A fully arylated polyfluorene has been synthesized and its photophysical properties were compared to the step-ladder polymers. Steady-state photoinduced absorption and ultrafast transient absorption spectroscopy have been used to study excited state absorption of singlet and triplet states and polarons present in the solid state. The results demonstrate a minimum regarding the onset threshold value of ASE for a fully arylated poly(ladder-type indenofluorene) and a successive increase of the ASE threshold for the step-ladder polymers with more bridged phenylene rings. In particular, carbazole-containing step-ladder LPPPs exhibit significantly increased ASE threshold values as compared to their carbazole-free analogues due to a pronounced overlap of stimulated emission (SE) and photoinduced absorption (PA). [source]

    Dye-Doped POSS Solutions: Random Nanomaterials for Laser Emission

    ADVANCED MATERIALS, Issue 41 2009
    Angel Costela
    New perspectives on disorder in photonic materials are opened up by polyhedral oligomeric silsesquioxanes (POSS) dispersed at a molecular level in dye-doped liquid and solid solutions. The optical homogeneity of these hybrid materials assures a coherent laser action, which is significantly enhanced by the stimulated emission multiply scattered by passive POSS centers. [source]

    Polarization of eigenmodes in laser diode waveguides on semipolar and nonpolar GaN

    PHYSICA STATUS SOLIDI - RAPID RESEARCH LETTERS, Issue 1-2 2010
    Jens Rass
    Abstract Recent calculations of the eigenmodes in waveguides grown on semipolar GaN suggest that the optical polarization of the emitted light as well as the optical gain depends on the orientation of the resonator. Our measurements on separate confinement heterostructures on semipolar (112) and (102) GaN show that for laser resonators along the semipolar [11] and [011] directions (i.e. the projection of the c -axis onto the plane of growth) the threshold for amplified spontaneous emission is lower than for the nonpolar direction and that the stimulated emission is linearly polarized as TE mode. For the waveguide structures along the nonpolar [100] or [110] direction on the other hand, birefringence and anisotropy of the optical gain in the plane of growth leads not only to a higher threshold but alsoto a rotation of the optical polarization which is not any more TE- or TM-polarized but influenced by the ordinary and extraordinary refractive index of the material. We observe stimulated emission into a mode which is linearly polarized in extraordinarydirection nearly parallel to the c -axis. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Electron and phonon dynamics in zincblende gallium nitride

    PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 12 2009
    R. Brazis
    Abstract This report presents new Monte Carlo simulation results revealing the ballistic stage of growth of the phonon number, electron velocity and energy upon the switching-on electric field, the shape of electron and phonon stationary distributions in high electric fields, as well as electron cooling and phonon number relaxation rates after switching-off the field in zincblende gallium nitride crystals. LO phonon band population inversion is feasible here up to the room temperature relative to the TO phonons, and below T < 80 K , relative to the LA-phonon band provided that the phonon lifetimes satisfy the conditions of , 2 ps (LO) and , 2 ns (LA). Phonon decay scenarios with the stimulated emission of infrared-range photons are discussed including phonon difference transitions. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Time-dependent evolution of crystal lattice, defects and impurities in CdIn2S4 and GaP

    PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 5 2009
    Sergei L. Pyshkin
    Abstract We demonstrate that in III-V and ternary compounds the natural stimuli for ordered distribution of impurities along crystal nodes and interstitials, host atoms and inherent vacancies in right lattice positions prevail over the others which could lead to a heterogenic distribution. The result is obtained in the crystals, prepared in 1963-1977, due to each 10-15 years monitoring of their optical and mechanical properties. Here we have summarized the results of the 2005-2008 monitoring and compare them with the earlier obtained data. We show that the partly inverse spinel CdIn2S4 turns into the perfect normal spinel, while in GaP the impurity ordering leads to the formation of a new type of crystal lattices. Periodically disposed impurities and inherent structural defects modify, improve and stabilize properties of the crystals. New luminescent phenomena of these crystals, including stimulated emission and "hot" luminescence have been discovered. The existing technologies help us to reproduce these naturally ordered structures and to apply them for new generation of optoelectronic devices. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Ultrafast intensity correlation measurements of quantum dot microcavity lasers

    PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 2 2009
    M. Aßmann
    Abstract We present an experimental technique, which allows us to determine the second order correlation function g(2) (t, t + ,) with picosecond time resolution. The method involves a streak camera which is modified such that a signal at fixed wavelength can be monitored after each pulsed laser excitation. From these measurements insight into the quantum optical properties of light emission from semiconductor nanostructures with dynamics on the sub-ns time scale can be taken. To demonstrate the possibilities of our setup, we present time resolved g(2) -measurements of quantum dot VCSEL micropillar emission. We show, that our measurement scheme enables us to determine the transition from predominantly spontaneous emission towards stimulated emission and the temporal evolution of the intensity correlation function. Additionally, we are also able to identify unexpected features like dynamical antibunching. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Conversion of an electron,hole plasma into a high density excitonic state in ZnO epitaxial thin films

    PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 4 2004
    Y. Toshine
    Abstract Time-resolved luminescence spectra of an exciton-exciton scattering process and an electron,hole plasma (EHP) were measured in ZnO epitaxial thin films by the optical Kerr gate method. At moderate excitation density below critical Mott density, stimulated emission of luminescence due to the exciton,exciton scattering process (P band) was observed. The P band shows a red shift and spectral narrowing in the first 1,2 ps after the excitation which reflects a thermal redistribution of excitons in the n = 1 excitonic state. On the other hand, at high excitation density above the critical Mott density, stimulated emission of the luminescence due to the EHP was observed. After thermalization of the EHP, the luminescence intensity of the EHP band decreases with time, and the EHP band converts to the P band after ,10 ps through a reverse Mott transition. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]