Laser threshold reduction in an all-spiro guest–host system

We report on stimulated emission in an all-spiro guest–host (G–H) system. Different doping concentrations of the guest molecule 2,2′,7,7′-tetrakis(2,2-diphenylvinyl)spiro-9,9′-bifluorene in the host material 2,7-bis(biphenyl-4-yl)-2′, 7′-di-tert-butyl-9,9′-spirobifluorene were investigated for amplified spontaneous emission (ASE) and distributed feedback (DFB) lasing. The ASE maximum could be shifted over 20nm by variation of the doping concentration. DFB lasing is observed in the pure host, the pure guest material, and in the G–H system. The laser wavelength can be tuned from 401.5 to 529.3nm by changing the grating period of the Bragg reflector and the doping concentration. A minimum threshold energy density of 6μJ∕cm2 was observed in second-order DFB structures for a doping concentration of 1.1%. In first-order DFB operation the threshold value could be further lowered to 320nJ∕cm2. These results render this material system an excellent candidate for stable and widely tunable lasers in the visible spectrum.