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  • 1
    Electronic Resource
    Electronic Resource
    Studies of resonant and preresonant femtosecond degenerate four-wave mixing in unoriented conducting polymers (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 1896-1898 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Degenerate four-wave mixing with femtosecond time resolution is used to measure the magnitude and transient response of the third-order nonlinear optical susceptibility χ(3) (ω;ω,−ω,ω) at 620 nm in nonoriented conducting polymers including polydiacetylene, 〈m1;38p〉polyacetylene, polyaniline, polydiethynylsilane, polythiophene, and polythiophene derivatives. 〈m1;40p〉Resonant and nonresonant excitations influence the magnitude and transient response of χ(3). 〈m1;39p〉The electronic response is instantaneous for preresonant excitation, but for resonant excitation it 〈m1;38p〉has ultrafast and slow components which illustrate photoexcitation dynamics. The 〈m1;38p〉magnitude of χ(3) for all of the polymers is in the range from 10−10 to 5×10−8 esu depending on the energy difference between the laser excitation and the polymer absorption maximum.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.349469
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  • 2
    Electronic Resource
    Electronic Resource
    Double-modulation electro-optic sampling for pump-and-probe ultrafast correlation measurements (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 1257-1260 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We describe a novel electro-optic double-modulation (DM) sampling technique for ultrafast transient spectroscopy, which is characterized by a superior signal-to-noise ratio compared to that of a regular single-modulation technique. DM is achieved by a combined effect of a radio-frequency modulation, which eliminates most of the low-frequency noise, and an audio-frequency modulation, which makes use of a high-performance, low-frequency lock-in amplifier. The DM sensitivity is comparable to that of the more sophisticated schemes involving electrical mixing and the A–B noise reduction method. We show that the DM technique offers superior performance in two-beam transient pump-and-probe correlation measurements compared to the regular single frequency modulation technique and is an ideal scheme for three-beam picosecond correlation measurements. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1148792
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  • 3
    Electronic Resource
    Electronic Resource
    Femtosecond dynamics of the nonlinear optical response in polydiethynylsilane (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 1695-1697 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have measured the femtosecond dynamics of the nonlinear optical response χ(3) in polydiethynylsilane (C4H2SiBu2)x, a novel class of π-conjugated polymers incorporating Si, using degenerate four-wave mixing and photoinduced absorption techniques. In resonance conditions at 620 nm we found χ(3)=3×10−9 esu, which decays in a record time of 135 fs, followed by a slower decay component of 750 fs, without a long tail even at high laser intensities. This material is an excellent candidate for nonlinear optical devices in the sub-THz frequency range.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.105111
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  • 4
    Electronic Resource
    Electronic Resource
    Symmetric light emitting devices from poly(p-di ethynylene phenylene) (p-di phenylene vinylene) derivatives (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 3960-3962 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Light emitting devices were fabricated from 2,5-dialkoxy derivatives of poly(p-di ethynylene phenylene-p-di phenylene vinylene) (PDEPDPV) sandwiched between indium tin oxide (ITO) and Al. The current–voltage (I–V) curve, electroluminescence (EL) intensity-voltage (IEL–V) curve, and the EL spectra were identical in forward and reverse bias. The I–V curves were also symmetric under illumination, with I≈0 and V=0, suggesting a negligibly small internal electric field. At high bias voltage, carrier injection was found to be dominated by tunneling at the interfaces. At low bias voltage, tunneling among localized states at the Fermi level prevailed. The behavior is discussed in relation to Fermi-level pinning at defect states in the interfaces with the ITO and Al. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.114418
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  • 5
    Electronic Resource
    Electronic Resource
    Studies of picosecond carrier dynamics in polysilane alloys: Evidence for geminate recombination in small hydrogenated amorphous silicon clusters (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 57 (1990), S. 1215-1217 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The ultrafast photocarrier dynamics in polysilane alloys, amorphous (SiH2)n, has been studied using the picosecond photoinduced absorption (PA) technique. For excitation below the optical gap, the PA response decays exponentially and is faster at low temperatures. This is interpreted in terms of e-h geminate recombination in the small clusters (∼10 A(ring)) of a-Si:H embedded in the polysilane matrix. The PA response with above-gap excitation is similar to that of conventional a-Si:H; it decays much slower in the form of a power law t −β (β〈1), independent of spectral range between 1.4 and 2.2 eV. This shows that the e-h distance after above-gap photogeneration is larger than the size of the a-Si:H clusters.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.104228
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  • 6
    Electronic Resource
    Electronic Resource
    Amplified resonant Raman scattering in conducting polymer thin films (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 2878-2880 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Using picosecond pulsed laser excitation, we investigate the optical emission characteristics of poly(2,5-dioctyloxy-p-phenylenevinylene), (DOO-PPV), thin films at high excitation intensities (∼1–90 MW/cm2). We observe the presence of amplified resonance Raman scattering in the emission spectra of conducting polymer films. The effect results in sharp Raman lines (widths smaller than 3 Å) superimposed on a significantly broader, well known, spectrally narrowed emission band (width ∼10 nm) caused by the amplified spontaneous emission in the waveguided polymer film. At the highest used excitation intensities, Raman scattering dominates the DOO-PPV emission spectrum resulting in a highly monochromatic, single-line emission spectrum. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.122616
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  • 7
    Electronic Resource
    Electronic Resource
    Cylindrical microlasers and light emitting devices from conducting polymers (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 72 (1998), S. 2811-2813 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Substantially improved, photopumped polymer lasers are demonstrated using microrings and microdisks of various diameters D ranging from 5 to 200 μm. Various cavity-dependent laser modes were observed, which for D〈10 μm were dominated by a single longitudinal mode with linewidth of less than 1 Å. These microlasers were also characterized by Q of order 5000, low threshold excitation energy of order 100 pJ/pulse for pulse duration ranging from 100 ps to sub-μs, and an abrupt increase in the emission directionality and polarization degree. Light emitting diodes with cylindrical geometry, fully compatible with these microlasers are also demonstrated. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.121466
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  • 8
    Electronic Resource
    Electronic Resource
    Plastic microring lasers on fibers and wires (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 72 (1998), S. 1802-1804 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Photopumped, pulsed, narrow line laser emission is demonstrated using cylindrical microcavities formed by π-conjugated polymer thin films wrapped around thin glass optical fibers and metal wires with various diameters D. A variety of cavity-dependent resonant laser mode structures were observed, which for D〈10 μm contain a single resonant spectral line of less than 1 Å in width. The microring lasers are also characterized by a well-defined, very low threshold excitation intensity, at which beam directionality and polarization degree dramatically increase. These findings open up the fields of lasers and fiber optics to organic materials. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.121189
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  • 9
    Electronic Resource
    Electronic Resource
    Spectral analysis of polymer microring lasers (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 76 (2000), S. 3858-3860 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The emission spectra of microring lasers made of π-conjugated polymer films that coat glass optical fibers are analyzed with the help of a Fourier transform. This method allows for the assignment of photopumped emission lines to integral Bessel functions and a more precise determination of the laser threshold excitation intensity based on harmonic analysis. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.126801
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  • 10
    Electronic Resource
    Electronic Resource
    Formation cross-sections of singlet and triplet excitons in π-conjugated polymers (2001)
    [s.l.] : Macmillian Magazines Ltd.
    Nature 409 (2001), S. 494-497 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Electroluminescence in organic light-emitting diodes arises from a charge-transfer reaction between the injected positive and negative charges by which they combine to form singlet excitons that subsequently decay radiatively. The quantum yield of this process (the number of photons ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/35054025
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