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Excitation Power (excitation + power)

Distribution by Scientific Domains
Physics and Astronomy87%

Terms modified by Excitation Power

  • excitation power density
    		•

    Selected Abstracts

    Local Heating from Silver Nanoparticles and Its Effect on the Er3+ Upconversion in Oxyfluoride Glasses

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 10 2010
    Chao Liu
    The effect of silver (Ag) nanoparticles on the upconversion emission properties of Er3+ ions in oxyfluoride glasses was investigated, and a mechanism of the energy transfer proposed. The integrated intensity ratios between 522 and 545 nm emission bands of Er3+ ions in glasses containing Ag nanoparticles were strongly dependent on the size of the Ag nanoparticles as well as on the intensity of the 800 nm excitation laser. When the absorption of Ag nanoparticles overlapped with the 2H11/2 and 4S3/2 energy levels in Er3+ ions, a strong energy transfer occurred from Er3+: 2H11/2, 4S3/2 levels to Ag nanoparticles. This energy was then converted to a temperature rise in the vicinity of Er3+ ions, eventually leading to the large increase in the integrated intensity ratios. The estimated effective temperature was approximately 200 K higher than the experimental temperature when the excitation power was 700 mW. [source]

    Experimental evidence of bistability in a semiconductor microcavity

    PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 4 2004
    M. Gurioli
    Abstract Optical bistability in a semiconductor microcavity showing normal mode coupling regime is observed by means of reflectivity and resonant Rayleigh scattering experiments. A third resonance, spectrally lying between the two normal modes, suddenly appears in the optical response when increasing the excitation power. Hysteresis loops are found when monitoring the microcavity optical response at the energy of the third peak. Our experimental findings can not be accounted for simply by exciton bleaching. We conclude that other non-linear mechanisms are relevant in explaining the presence of the third peak and the observed bistable behaviour. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    GaN/Al0.5Ga0.5N quantum dots and quantum dashes

    PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 4 2009
    Thomas Huault
    Abstract GaN/Al0.5Ga0.5N nanostructures grown on c -plane sapphire by molecular beam epitaxy using ammonia as N source have been studied. Depending on the ammonia pressure during the two dimensional , three dimensional transition of the GaN layer, the shape of the islands is strongly modified: elongated or isotropic islands are observed, leading to the formation of quantum dashes or quantum dots, respectively. This shape transition is seen as a consequence of a change in surface energy. The change of morphology of the GaN layer is clearly evidenced by photoluminescence measurements, and a large redshift in the emission peak is observed for quantum dashes as compared to quantum dots. An electric field ,3 MV/cm is estimated from the measurements at an excitation power ,20 mW/cm2. Weak photoluminescence quenching between low and room temperature for both QDs and QDashes structures is observed, indicating a strong confinement of carriers into the nanostructures. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Silicon nanowire optical Raman line shapes at cryogenic and elevated temperatures

    PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 10 2008
    H. Scheel
    Abstract We report the Raman spectra of silicon nanowires (SiNWs) in a wide temperature range, between 2 K and 850 K. At room temperature we find a strong influence on the spectrum from applied laser excitation powers. These effects can be attributed a laser heated sample, leading to an inhomogeneous temperature distribution within the laser-spot. If the laser excitation power is small (below 100 ,W) such effects are negligible, and we find a temperature dependence governed by threephonon decay processes. The results from temperature dependent measurements indicate a change of sample morphology due to heating. Raman measurements on SiNWs immersed in superfluid helium at , 2 K show very strong red-shifts, even though they still have the perfect thermal contact via the superfluid helium. Considering anharmonic effects we find massively increased Si core temperatures. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Optical characterization of Zn0.97Mn0.03Se/ZnSe0.92Te0.08 type II multiple-quantum-well structures

    PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 5 2007
    D. Y. Lin
    Abstract The optical characterization of type II Zn0.97Mn0.03Se/ZnSe0.92Te0.08 multiple-quantum-well structures have been studied using photoluminescence (PL), temperature-dependent PL, polarized PL, power-dependent PL, and photoreflectance (PR) in this study. The PL data reveal that the band alignment of the ZnMnSe/ZnSeTe system is type II. Comparing with the theoretical calculation based on the Schrodinger equation, the valence band offset is estimated to be 0.6 eV. From the power-dependent PL spectra, it is observed that the peak position of PL spectra shows a blueshift under different excitation power. The blueshift can be interpreted in terms of the band-bending effect due to spatially photoexcited carriers in a type II alignment. The thermal activation energy (EA) for quenching the PL intensity was determined from tem- perature-dependent PL spectra. The thermal activation energy was found to decrease as the thickness of ZnMnSe and ZnSeTe layers decreased. The polarized PL spectra exhibit a large in-plane polarization with the polarization degree up to 50%. The polarization does not depend on the excitation intensity as well as temperature. The large polarization is an inherent orientation of the interface chemical bonds. The higher transition features observed in PR spectra show a blueshift with the similar trend observed in the PL spectra as decreasing the thickness of ZnSeTe layer. This result provides a consistent evidence for the assumption that square-like well shapes were built in the ZnSeTe layers. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Large excitation-power dependence of pressure coefficients of InxGa1,xN/InyGa1,yN quantum wells

    PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 2 2003
    Q. Li
    Abstract Excitation-power dependence of hydrostatic pressure coefficients (dE/dP) of InxGa1,xN/InyGa1,yN multiple quantum wells is reported. When the excitation power increases from 1.0 to 33 mW, dE/dP increases from 26.9 to 33.8 meV/GPa, which is an increase by 25%. A saturation behavior of dE/dP with the excitation power is observed. The increment of dE/dP with increasing carrier density is explained by an reduction of the internal piezoelectric field due to an efficient screening effect of the free carriers on the field. [source]

    Photoluminescence study of isoelectronic traps in dilute GaAsN alloys

    PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2007
    H. Yaguchi
    Abstract We have studied photoluminescence spectra in detail to clarify the character of the isoelectronic traps in dilute GaAsN alloys. Several sharp lines have been observed at the lower energy side of the GaAs bandgap and are in good agreement with the nitrogen pair-related emission lines previously reported. In addition to the nitrogen pair-related lines, some other emission lines have been also observed. Compared with the energies of these emission lines and the nitrogen pair-related emission lines, it was found that the energy differences agree with the longitudinal optical phonon energy at the , point of GaAs, showing that the character of isoelectronic traps due to nitrogen pairs in dilute GaAsN alloys is significantly contributed from the conduction band state at the , point. The temperature dependence of the peak energy of luminescence due to nitrogen pairs also indicates that the character of isoelectronic traps in dilute GaAsN alloys is due to the conduction band edge state at the , point of GaAs. For a dilute GaAsN alloy with lower nitrogen concentration, we have observed that the intensity of an emission line increased superlinearly with excitation power . (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Silicon nanowire optical Raman line shapes at cryogenic and elevated temperatures

    PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 10 2008
    H. Scheel
    Abstract We report the Raman spectra of silicon nanowires (SiNWs) in a wide temperature range, between 2 K and 850 K. At room temperature we find a strong influence on the spectrum from applied laser excitation powers. These effects can be attributed a laser heated sample, leading to an inhomogeneous temperature distribution within the laser-spot. If the laser excitation power is small (below 100 ,W) such effects are negligible, and we find a temperature dependence governed by threephonon decay processes. The results from temperature dependent measurements indicate a change of sample morphology due to heating. Raman measurements on SiNWs immersed in superfluid helium at , 2 K show very strong red-shifts, even though they still have the perfect thermal contact via the superfluid helium. Considering anharmonic effects we find massively increased Si core temperatures. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]