Improving the conversion efficiency of an organic distributed feedback laser by varying solvents of the laser gain layer

Control experiments were performed to improve the slope conversion efficiency of the organic distributed feedback laser by varying the dissolution solvents of the laser gain layer, a conjugated polymer poly(2-methoxy-5-(2?-ethyl-hexyloxy)-1,4-phenylene-vinylene) (MEH-PPV) in this work. The distributed feedback configuration of the laser was prepared by holographic photopolymerisation of the polymer/liquid crystal (HPDLC) mixture. Experimental results showed that the tetrahydrofuran (THF) solvent cast laser gain layer had a lower lasing threshold (0.28 μJ/pulse) and a higher slope conversion efficiency (7.8%) than that of the xylene solvent cast laser gain layer (0.5 μJ/pulse, 4.9%). Thin film waveguide characterisation demonstrated that the THF-cast film possessed a smaller waveguide loss (5.3 cm^?1) and larger net gain (17.1 cm^?1) than the xylene-cast film (8.3 cm^?1, 15.7 cm^?1). Absorbance and photoluminescence spectra indicated that the THF-cast film showed brighter luminescence at 620 nm and larger absorbance at 532 nm, indicating that the interchain interactions of the MEH-PPV is different, which plays the vital role in improving the optical performance of our organic DFB lasers.