Solid state ASE from an oligomer (HOTF) in polymethyl methacrylate

Solid state laser material based on oligomer 9,9,9′,9′,9″,9″-hexakis(octyl)-2,7′,2′,7″-trifluorene (HOTF) doped poly methyl methacrylate (PMMA) was fabricated. The absorption spectrum showed only one band at 355 nm with different concentration ratios (7–12 mM); thus the broad absorption band could be attributed to the α-phase formation. In addition, there was no new band detected at the end of the spectrum as the concentration increased. This indicates the absence of the β-phase formation for all concentrations used. On the other hand, HOTF exhibited two distinct emission bands at 420 and 470 nm for 7 mM concentration. When the concentration was increased to 9 mM, the intensity of the band 470 nm increased. Further increase the concentration to 12 mM, the intensity of the band at 420 nm totally vanished and there was only one band at 470 nm. Therefore, the band at 470 could be attributed to excimer state. However, the results revealed that there is a strong correlation between quantum yield of fluorescence and fluorescence life-time, absorption cross section, and emission cross section. Under pulsed laser excitation. The ASE spectrum of HOTF has been obtained using a transverse cavity configuration where the conjugated HOTF was pumped by the third-harmonic of Nd:YAG nanosecond pulsed laser (λex = 355 nm). We demonstrate that HOTF in the solid state could produce an ASE peak at 420 nm. The obtained results were compared with the HOTF and a conducting polymer poly (9,9-dioctylfluorene) (PFO)in the liquid state.