Chemical structure of two oligo-(-phenylenevinylene) derivatives with 3 (3-OPV) and 5 (5-OPV) monomer units.
Experimental setup to investigate the presence of stimulated emission in the films: (1) laser; (2) inverted telescope; (3) neutral density filters; (4) cylindrical lens; (5) rectangular aperture with variable width; (6) sample; (7) optical fiber; (8) spectrometer; (9) computer. Full and dashed lines correspond to rays that are in perpendicular planes and limit, respectively, the width and length of the pump stripe over the sample.
Photoluminescence spectra of a PS film doped with 3-OPV (emission at ) and a PS film doped with 5-OPV (emission at ) for various pump intensities, both above ( and , respectively) and below ( and , respectively) the pump intensity threshold for the observation of spectral narrowing.
Evolution of the full width at half maximum (FWHM) of the emission spectra as a function of pump intensity for PS films doped with various concentrations (wt. %) of (a) 3-OPV and (b) 5-OPV.
Pump intensity threshold for the observation of spectral narrowing versus the concentration of oligomer with respect to PS (in wt. %). Thresholds are obtained from Fig. 4 as the intensities at which the FWHM decays to half of its maximum value.
Optical absorption spectra for solutions and films with a varying concentration of oligomer for: (a) 3-OPV and (b) 5-OPV.
The dependence of the full width at half maximum (FWHM) of the emission spectra on excitation length at the indicated pump intensities for a PS film doped with: (a) of 3-OPV; (b) of 5-OPV.
The dependence of emission intensity at (for 3-OPV) and at (for 5-OPV) on the excitation length at the indicated pump intensities for a PS film doped with: (a) of 3-OPV and (b) of 5-OPV. The solid lines are fits to the data using Eq. (1) with the parameters listed in Table I. The net gains of the waveguides are determined from the fits.
Parameters obtained from fits of Eq. (1) to the data in Fig. 8.
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