Researchers demonstrate lasing in organic vertical-cavity surface-emitting laser
An organic vertical-cavity surface-emitting-laser (OVCSEL) structure has been demonstrated by researchers from the Center for Photonics and Optoelectronic Materials at Princeton University (Princeton, NJ). Investigating an alternate geometry to slab waveguide structures (see Laser Focus World, July 1997, p. 11), the grou¥fabricated the optically pumped OVCSEL by sandwiching a thin organic film between two highly reflective mirrors. The active layer consisted of 500-nm-thick organic semiconductor, tris-(8-hydroxyquinoline) aluminum (Alq3) doped with 3% (by weight) DCM laser dye, codeposited in high vacuum by thermal evaporation onto the surface of a distributed-Bragg-reflector dielectric mirror stack. A 20-nm-thick Alq3 buffer layer and a 200-nm-thick silver mirror were sequentially deposited on to¥of the active layer.
When pumped at 337 nm with a nitrogen laser generating 500-ps pulses at a 50-H¥repetition rate, the structure produced an emission of 3 W with a very narrow linewidth of 0.2 ۪.1 Å (FWHM); by changing the thickness of the active organic layers from 430 to 500 nm, the laser-emission wavelength changed from 589 nm (orange) to 635 nm (red). Threshold input energy was 300 µJ/cm2, and slow degradation of the device became apparent after 4.5 hours (8 ¥ 105 pum¥laser pulses). The grou¥believes the linewidth could potentially be narrowed further.