We demonstrate room temperature laser activity of optically pumped GaN/GalnN-DFB-lasers. The ridge-waveguide DFB lasers were realized on GaN/GalnN double heterostructures grown by low-pressure metal-organic vapor phase epitaxy. The best laser threshold we achieved is 1.9 MW/cm2.
By varying the grating period, the laser emission wavelength could be tuned from 399 to 415 nm. This allows to determine the dispersion relation of the effective refractive index n
eff(λ) and the spectral dependence of the pump power density at the laser threshold P
th(λ) over the whole emission range. Furthermore, the shift of the emission wavelength with temperature of the DFB-lasers is investigated and is found to be small compared to the emission wavelength shift of the gain maximum.