Blue-light-emitting polymer lasers with non-periodic circular Bragg resonators

We present single mode optically pumped lasing from a new resonator structure for polymer lasers employing non-periodic circular Bragg gratings. Our devices, using a polyfluorene derivative (BN-PFO) as gain medium, are the first blue-emitting circular grating semiconductor lasers (either organic or inorganic). They exhibit feature sizes as small as 47 nm and emit azimuthally polarized beams with a spectral linewidth approximate to 0.2 nm. We find a minimum lasing threshold energy density of 1.2 mu J/cm(2) (10 Hz, 8 ns, 355 nm Nd:YAG laser excitation). The quality factor of the resonator modal fields is found to be at least 2200 for these devices.