Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    Grains of Porous Silicon Embedded in SiO〈sub〉2〈/sub〉:Studies of Optical Gain and Electroluminescence (2004)
    s.l. ; Stafa-Zurich, Switzerland
    Solid state phenomena Vol. 99-100 (July 2004), p. 31-36 
    Details
    ISSN: 1662-9779
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Physics
    Notes: Recent reports on experimental observation of optical gain in silicon nanostructures in the visible region, performed at several laboratories all over the world, have triggered an extraordinary surge of interest in silicon lasing. However, attempts aimed at reproducing the red stimulated emission from „standard“silicon nanocrystals (sized 3-5 nm) at some other laboratories either failed, or. did not come to definite conclusions. Therefore, more detailed measurements of optical gain in a wider variety of samples containing Si nanocrystals are required in order to unravel whether or not the observation of optical gain is an intrinsic property of Si nanocrystals. We have performed a detailed study of optical gain in layers of densely packed Si nanocrystals in SiO2, prepared on the basis of porous Si, using the variable-stripe-length (VSL) method in combination with the shifted-excitation-spot (SES) method. In selected samples we have observed a distinct difference in behaviour between VSL and SES curves, indicating the occurrence of positive optical gain of ~ 24 cm-1. Preliminary reports on transport and electroluminescence measurements in thin films of SiO2 doped with porous silicon grains, prepared by spin-coating technique, are also discussed
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/26/transtech_doi~10.4028%252Fwww.scientific.net%252FSSP.99-100.31.pdf
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Degenerate and non-degenerate four-wave mixing in semiconductor quantum dots (1995)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1247-1254 
    Details
    ISSN: 0392-6737
    Keywords: Nonlinear optics ; Time-resolved optical spectroscopies and other ultrafast optical measurements in condensed matter ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary We present wave-mixing techniques which are used to determine the tensor elements of the non-linear dielectric susceptibility, the dynamics of non-linear optical effects and the transport properties of a material. These techniques are applied to CdS nanocrystallites, prepared in a SiO2 matrix by a sol-gel method. They were prepared as thin films of variable density (up to 30% of volume). By the same experimental techniques, porous silicon is studied and the results are compared to those obtained from luminescence and time-of-flight measurements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02457196
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Reverse saturable absorption in C60-doped porous glasses studied by single- and double-pulse pump–probe experiments (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 111 (1999), S. 5929-5937 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We investigate the nonlinear absorption of C60-doped porous sol-gel glasses by single- and double-pulse pump–probe experiments. We find that the reverse saturable absorption (RSA) of these samples can be explained in the frame of a five level system as it is commonly used for C60 solutions. We observe a strong saturation of the RSA at high fluences, especially if the molecules are prepared in the triplet state. In a double-pulse pump–probe experiment we measure the triplet quantum yield for C60 solutions (0.8) and doped glasses (0.25) and the singlet and triplet absorption cross sections. In the first excited singlet state (S1) lifetimes of 1 ns and 65 ps are determined in solutions and glasses, respectively. We find that the dynamics of both depopulation processes, direct S1–S0 relaxation, and intersystem crossing is faster in glasses than in the case where C60 is in solution in a liquid aromatic solvent. We tentatively explain these findings by the absence of a stabilizing solvent and a perturbation of the molecular energy levels due to interaction with the solid glass matrix. We finally determine the lifetime of the triplet states in our glass samples to 2 μs. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.479888
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Optical limiting properties and dynamics of induced absorption in C60-doped solid xerogel matrices (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 108 (1998), S. 8599-8604 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We present measurements of induced absorption and its dynamics in C60-doped solid xerogel matrices. The measurements are performed in a pump-test geometry using picosecond pulses generated from a frequency doubled mode locked Nd:YAG laser at 532 nm. We observe an induced absorption leading to optical limiting. We find outstanding optical limiting qualities for single shot excitation but some degradation above a certain threshold intensity for repetitive pulses. Below this degradation threshold, the material is stable and its limiting dynamics is studied. A decrease of the initial laser-induced absorption with a time constant of 150 ps is observed, down to a very long-lived constant level. We attribute this dynamics of induced absorption to a transition from excited singlet to triplet electronic states in the C60 molecule. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.476290
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Time-resolved energy transfer and absorption bleaching measurements in CuCl microcrystallites (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 2748-2751 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: By degenerate pump and test measurements, we determine the coherence time and the lifetime of excitons in CuCl quantum dots. We show the importance of the induced recombination of coherent exciton states, excited in microcrystallites by two-photon absorption.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354675
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Picosecond dynamics of absorption bleaching in polycrystalline ZnCdTe films (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 5729-5736 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The spectral and temporal behavior of absorption bleaching and of self-diffraction in ZnxCd1−xTe polycrystalline films with a nominal composition x=0.87 have been investigated. It has been found that the optical transmission increases 15 times at a wavelength of 575 nm for a laser light intensity of 0.2 GW/cm2. In a pump and test experiment, the buildup and the relaxation times T1 of the bleaching were measured. Their values, between 10 and 40 and 20 and 45 ps, respectively, depend on the wavelengths of the pump and the test beams. The saturation intensity Is was also determined (between 1.5 and 6 GW/cm2). This absorption saturation effect can be related to the high density of crystallite grain surface states as well as to other imperfections in the polycrystalline films studied. The high density of these states can explain the large linear absorption and the ultrafast relaxation of the photogenerated carriers. Then, in self-diffraction experiments, the phase relaxation time T2=(10±5) ps of the localized surface states has been determined. The long duration of T2 and the short energy lifetime T1 indicate that elastic scattering processes are highly suppressed in polycrystalline material when compared to monocrystals, while their coherence time is increased.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354190
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Dynamics of optical nonlinearities induced by strong light illumination in CdS nanocrystallites (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 3586-3591 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Light induced grating experiments have been performed at room temperature in CdS nanocrystallites of 2.5 nm radius embedded in sol-gel glass films of different semiconductor volume concentration. The dynamics of the photogenerated carriers at the lowest transition peak has been shown to depend on the excitation intensity. No spatial diffusion is observed up to a nanocrystallite volume concentration of 35%. Below a few MW/cm2 the carriers relax in each nanocrystallite, either radiatively in ∼150 ps or by trapping the electrons 15 meV below their excitation transition. For higher intensities of excitation, a saturation of the excited states occurs which allows the electrons to be trapped in the glass matrix, inducing a permanent grating by the creation of a static electric field. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.364995
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Carrier diffusion in porous silicon studied by transient laser-induced grating spectroscopy (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 2481-2486 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report laser-induced transient grating experiments performed at room temperature on self-supporting p-type porous silicon films with different porosities. With this technique the diffusion of the photocarriers can be studied with a time resolution of some tens of picoseconds. The gratings were created by two interfering pulses of the second-harmonic radiation from an Nd3+:yttrium-aluminum-garnet YAG laser (2.3 eV) and their decay in time was studied by a time-delayed pulse of the fundamental YAG laser frequency (1.15 eV). The observed grating decay time is very fast (hundreds of picoseconds) and shortens with decreasing porosity. Diffusion constants D=45, 24, and 5 cm2 s−1 have been found for the porosities of 64%, 68%, and 73%, respectively. To explain these high values of D we consider a simple kinetic model which takes into account two different types of carriers, delocalized and trapped ones. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361177
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Degenerate four-wave mixing experiments on GaN in the quasistationary regime (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 74 (1999), S. 1436-1438 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In order to determine the third order of the nonlinear susceptibility χ(3) of GaN, we perform degenerate four-wave mixing measurements in a two-beam configuration at low temperature on a GaN epilayer on sapphire substrate. We measure the excitation spectrum of χ(3) close to the exciton resonances. Besides the χ(3) contribution, higher orders of the nonlinear susceptibility show already up around 10 kW cm−2, leading to a saturation of the signal. Results are complemented by a study of the influence of a band-to-band excitation ((h-dash-bar)ωP=4.02 eV) on the nonlinear susceptibility. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.123574
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    Response to "Comment on ‘Enhancement of the optical gain of semiconductors embedded in three-dimensional photonic crystals' " [Appl. Phys. Lett. 73, 550 (1997)] (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 552-552 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.122271
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...