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Near-infrared Light Amplification and Lasing in Luminescent Polymer Microresonators
Takeyuki Kobayashi, Martin Djiango, Grace Jordan, Manuel Ruther, Werner J. Blau, Yasuhiro Suziki and Toshikuni Kaino

We present the results of our study on light amplification and laser emission in polymer gain media containing a near-infrared emitting dye, 2-(6-(4-dimethylaminophenyl)-2, 4-neopentylene-1, 3, 5-hexatrienyl)-3-methyl-benzothiazolium perchlorat, with a view to the development of polymer amplifiers and lasers operating in the 800-nm region of the spectrum. Nanosecond gain spectroscopy is carried out by use of amplified spontaneous emission. Multimoded poly(1-vinyl-2-pyrrolidone)-base planar waveguides, 50 µm in thickness, doped with 0.5 wt% dye show a net small-signal gain of 2.6 ±0.3 cm-1 (11.3 ±1.3 dB/cm) at 820 nm for a pump fluence of 115 µJ/cm 2 (23.1 kW/cm2). Moreover, we have fabricated polymer microring resonators 200 µm in diameter with the same material composition. The moderate optical gain in the material allows lasing to occur at around 840 nm under nanosecond transversal photopumping at 532 nm. The threshold for lasing is found to be 311 ±87 µJ/cm2(62.2 ±17.3 kW/cm2).

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