Optically pumped solid conjugated polymer emits blue laser light
Italian and Austrian researchers demonstrated single-mode blue laser emission from a solid conjugated polymer. They produced picosecond, 490-nm pulses from a laser cavity containing a methyl-substituted poly-(para-phenylene) type ladder polymer (m-LPPP). The lasing medium was a 500-nm-thick m-LPPP film deposited on a planar dielectric mirror with 99.8% reflectivity, which formed one end of the resonator. Output coupling was achieved through a spherical dielectric mirror at the other end with 92% reflectivity and an 8-mm radius of curvature. Cavity length was about 15 µm. The laser was optically pumped through the planar dielectric mirror with the second harmonic of a Ti:sapphire laser with chirped-pulse amplification. The planar dielectric mirror transmitted 70% of the 390-nm pump signal, which was focused onto an 80-µm-diameter spot on the polymer surface. A lasing threshold was observed at a 140-µJ/cm2 pump fluence. At 200 µJ/cm2, about 3.6 ¥ 106 pulses or one hour of operation was achieved before a 50% reduction was observed in output power. The researchers recorded time-integrated emission spectra by averaging the readings of an optical multichannel analyzer over a large number of laser pulses. Minimum pulsewidth was about 3.6 ps. Contact: Mauro Nisoli at [email protected].