Modulation-frequency dependencies of the intensity and the phase delay of photoinduced absorption from conjugated polymers

2000 ◽  
Author(s):  
Yukio Furukawa
Keyword(s):  
Conjugated Polymers ◽  
Modulation Frequency ◽  
Phase Delay ◽  
Photoinduced Absorption

Absorption losses and thermal diffusivity of optical fibers investigated by photothermal methods: theory and experiments

1983 ◽  
Vol 61 (9) ◽  
pp. 1334-1346 ◽  
Author(s):  
Dominique Chardon ◽  
Serge J. Huard
Keyword(s):  
Thermal Diffusivity ◽  
Absorption Coefficient ◽  
Optical Fibers ◽  
Rayleigh Scattering ◽  
Modulation Frequency ◽  
Threshold Value ◽  
Phase Delay ◽  
Algebraic Expression ◽  
Photothermal Methods ◽  
Scattering Losses

Both the absorption coefficient and the thermal diffusivity of an optical fiber have been measured using photothermal methods: photoacoustics (P.A.) and photothermal deflection (P.D.). The amplitude of the photothermal signal is proportional to the heat density generated in the fiber core. This in turn is proportional to the light absorption coefficient β. Thus, these techniques allow one to separate the absorption and Rayleigh scattering losses. The results obtained by the two methods are in agreement. A threshold value of 10 dB km−1 mW has been determined experimentally. In both cases, the device is calibrated by replacing the fiber with a heated electric wire. Moreover, the heat must diffuse from the core to the gas so that when the light is modulated, a phase delay appears. A study of phase delay versus modulation frequency gives the thermal diffusivity of the fiber. This is required in order to improve fiber sensors.Theoretically, the cylindrical geometry of the sample permits simple calculations. The thermoelastic equations in solids and coupled thermodynamic ones in the gas have been solved without neglecting viscosity effects. Noting that silica is almost unexpansible, an algebraic expression of the signal has been obtained without any assumptions on the gas transformation processes. Finally, the P.A. and P.D. techniques are compared and some extensions are presented.

Photoinduced Charge Transfer Between Tetracyano-Anthraquino-Dimethane Derivatives and Conjugated Polymers

1999 ◽  
Vol 598 ◽  
Author(s):  
G. Zerza ◽  
M. Scharber ◽  
J. L. Segura ◽  
R. Gomez ◽  
N. Martin ◽  
...  
Keyword(s):  
Charge Transfer ◽  
Power Law ◽  
Modulation Frequency ◽  
Excited State Absorption ◽  
Photoinduced Absorption ◽  
Strong Electron ◽  
Near Ir ◽  
Alkyl Side Chains ◽  
Donor Acceptor ◽  
Two Peaks

ABSTRACTThe photo-induced charge transfer between tetracyano-anthraquino-dimethane (TCAQ) derivatives and poly(2-methoxy-5-(3,7-dimethyloctyloxy)-1,4-phenylene vinylene) MDMO-PPV was studied by means of photoinduced absorption (PIA) spectroscopy in the VIS and IR spectral region and lightinduced electron spin resonance (LESR) spectroscopy. Three different TCAQ derivatives with alkyl-side chains for increased solubility compared to TCAQ and one of them attached to a C60 molecule serve as strong electron acceptors. The photoinduced absorption in the VIS near-IR range shows a broad plateau around 1.8 eV followed by two peaks at 1.35 and 1.24eV for all three acceptors. All PIA features have a power law excitation intensity dependence with an exponent close to 0.5 as expected for bimolecular kinetics. The modulation frequency dependent excited state absorption decreases with a power law. LESR studies of all donor-acceptor combinations show one radical line at a g = 2.0028 with.H = 3.5 Gauss, originating from TCAQ anion and the polymer cation.

Nonlinear Optical Properties of Two Thiophene-Based Polyconjugated Systems: Photoinduced Absorption and Third Harmonic Generation Spectroscopy

1989 ◽  
Vol 173 ◽  
Author(s):  
R. Zamboni ◽  
C. Taliani ◽  
G. Ruani ◽  
A. J. Pal ◽  
F. Kajzar
Keyword(s):  
Optical Properties ◽  
Conjugated Polymers ◽  
Harmonic Generation ◽  
Nonlinear Optical ◽  
Third Harmonic Generation ◽  
Nonlinear Optical Properties ◽  
Photoinduced Absorption ◽  
Third Harmonic ◽  
Optical Gap ◽  
The Third

ABSTRACTNonlinear optical properties of two thiophene-based conjugated polymers (PTT and PDTB) were studied by the photoinduced absorption spectroscopy and the third harmonic generation spectroscopy. The results obtained with these two methods are used to estimate the value of χ(3) in these materials. Resonant χ(3) are (2.0 ± 0.2) × 10−11 e.s.u. and (1.0 ± 0.1) × 10−11 e.s.u. for PTT and PDTB, respectively. χ(3) is shown to be related to the width of the optical gap through a sixth-power law. In PTT a vibronic structure due to the C = C stretching mode appears in the χ(3) spectrum.

Even Parity States in Ppv, Polythiophene and Polysilanes

1993 ◽  
Vol 328 ◽  
Author(s):  
F. Guo ◽  
M. Chandross ◽  
S. Mazumdar
Keyword(s):  
Conjugated Polymers ◽  
Parity State ◽  
Photoinduced Absorption ◽  
Absorption Data ◽  
Two Photon ◽  
Bond Alternation ◽  
Theoretical Evidence ◽  
Long Chains

ABSTRACTTwo photon absorptions (TPA) in conjugated polymers with large bond alternation are reinterpreted. TPA to the 2Ag in long chains should be tiny due to cancellation effects, and therefore the observed strong, narrow TPA is to a higher even parity state. We also present the first theoretical evidence for bound biexcitons, and explain recent photoinduced absorption data.

Model of transient photoinduced absorption with an exciton polaron in conjugated polymers

1998 ◽  
Vol 57 (11) ◽  
pp. 6386-6390 ◽  
Author(s):  
V. A. Shakin ◽  
S. Abe ◽  
Y. Shimoi
Keyword(s):  
Conjugated Polymers ◽  
Photoinduced Absorption

Photoinduced absorption in a series of thiophene based conjugated polymers

1991 ◽  
Vol 41 (1-2) ◽  
pp. 579-582 ◽  
Author(s):  
A.J. Pal ◽  
G. Ruani ◽  
R. Zamboni ◽  
R. Danieli ◽  
C. Taliani
Keyword(s):  
Conjugated Polymers ◽  
Photoinduced Absorption
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