Surface-emitting tapered unstable resonator laser with integrated focusinggrating coupler

We report on the fabrication and operation characteristics of a grating-bas ed, surface-emitting, tapered unstable resonator laser with a trumpet shape d taper and a focusing outcoupler The laser has a low threshold current den sity of 225 A/cm(2). It operates with a spatially coherent field and the ne ar-field intensity indicates stable, filamentation free behavior up to at l east 3 x the threshold current under continuous operation. At low drive cur rents the laser produces a nearly diffraction limited focused spot, With in creasing current, the focused spot size increases and multiple side-lobes d evelop at high currents. We attribute this to a change in the phase of the emitted wavefront associated with thermal effects in the gain region.