R. Schroeder et al., Excitation density and photoluminescence studies of polyfluorene excited by two-photon absorption, J PHYS-COND, 13(16), 2001, pp. L313-L320
Highly efficient photoluminescent organic materials are excellent alternati
ves to inorganic crystals for non-linear optics applications. One candidate
, polyfluorene with an absorption onset of about 3 eV, was studied in this
paper by means of transmission and photoluminescence measurements with an u
ltra-fast laser source at 1.54 eV with 250 fs pulses. We studied the two-ph
oton absorption and emission properties of polyfluorene as a function of th
e concentration in toluene solvent at 300 K. It is demonstrated that both t
he two-photon absorption and the associated emission exhibit the same satur
ation intensity, which does not depend on the concentration. It is shown th
at although we achieve excitation rates of 1 % to 10% of all repetition uni
ts, the excited units do not interfere before luminescent recombination occ
urs.