Low threshold distributed feedback lasers fabricated from blends of conjugated polymers: Reduced losses through Forster transfer

We report on low threshold photopumped amplified spontaneous emission (ASE) in blends of derivatives of poly (p-phenylene vinylene) and distributed feedback (DFB) lasers fabricated from the same materials. Forster energy transfer is used to spectrally shift the emission away from the absorption band, thereby reducing the optical losses. The concentration of the guest polymer in the blend determines the rate of energy transfer and, thereby, has a strong effect on the observed emission spectrum. The photoluminescence quantum efficiencies (eta(PL)) of the blends are higher than the eta(PL) of the pure emissive species (eta(PL) decreases with increasing amount of the guest polymer in the blends). The blends exhibit optical losses similar to3 cm(-1) compared to similar to85 cm(-1) in pure host. As a result, the ASE thresholds are reduced from 5000 W/cm(2) in the host to 200 W/cm(2) in the blends. The corresponding lasing threshold in the DFB structures is 100 W/cm(2). (C) 2002 American Institute of Physics.