Low threshold blue conjugated polymer lasers with first- and second-order distributed feedback

We report on the fabrication of low threshold distributed feedback (DFB) polymer lasers based on a polyfluorene derivative containing statistical binaphthyl units (BN-PFO). First- and second-order feedback lasers have been realized. The emission was tuned in the wavelength range from 438 to 459 nm by varying the grating period and the film thickness. A threshold energy of 280 pJ/pulse was observed in second-order DFB structures, which could be further reduced to 160 pJ/pulse by employing first-order feedback in electron beam lithographically patterned structures with a period of 140 nm. In these first-order structures, laser oscillation at both edges of the photonic stop band was observed. These very low threshold values render BN-PFO a very promising material for future electrically pumped organic semiconductor laser diodes. (c) 2006 American Institute of Physics.