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Photo-physical and lasing characterisation of a polyparaphenylenevinylene (PPV) neat film

“…Assuming that the effective stimulated emission cross-section, r em,eff =r em ) r ex , at the peak amplified spontaneous emission wavelength (k TWL,max =550 nm) is equal to the to stimulated emission cross-section, r em , at this wavelength ðr em ¼ 8:6 Â 10 À17 cm 2 Þ; i.e. neglecting the excited-state absorption r ex , then the experimental laser threshold requires a gain length of ' gain ¼ 10 lm (calculated by use of Equations (11) and (12d) in Holzer et al (2001)). For a smaller effective stimulated emission cross-section the gain length has to be correspondingly longer.…”

“…The size of the luminophore, i.e. of the emitting chromophore (emitting singlet exciton) expressed by the number m em of repeat units forming a coherently emitting entity, is extracted from the ratio of the repeat unit based Strickler-Berg radiative lifetime (Strickler and Berg 1962;Birks and Dyson 1963), s rad,RU , to the experimentally determined radiative lifetime, s rad =s F // F , according to (Holzer et al 2001) m em =s rad,RU /s rad , where s F and / F are the fluorescence lifetime and the fluorescence quantum yield, respectively.…”

Optically Pumped Lasing from Single Crystals of a Cyano‐Substituted Thiophene/Phenylene Co‐Oligomer

“…In order to understand the origin of higher threshold than other organic materials, an absorption cross‐section (Figure S2(b)) was estimated by the following relationship and absorption spectrum (Figure S2(a)): τ = nσd ( τ : optical density, n : molecular density, σ : absorption cross‐section, d : crystal thickness). Although the in‐plane long molecular axis of the BP1T‐CN allows for efficient optical excitation, the effective absorption cross‐section per molecule at the pumping wavelength (<10 ‐18 cm 2 ) is smaller than the values (10 ‐17 –10 ‐16 cm 2 ) reported for other organic materials . The smaller σ gave rise to the higher threshold.…”

Subpicosecond pulses from a gain-switched polymer distributed feedback laser

“…15. The photon lifetime ph , can be expressed as a function of the group velocity and a loss factor combining absorption and scattering of photons, ph =1/͑V gr · ␣ loss ͒, where ␣ loss represents the losses from the resonator including both absorption and scattering of the photons.…”