Analysis of ridge-waveguide distributed feedback laser.

An analysis concerning the coupling efficiency and the threshold current is presented for a ridge-waveguide distributed feedback laser where the grating exists only outside the ridge region. Since only the evanescent part of the lateral field couples with the grating, the grating coupling efficiency is smaller compared to the case where the grating extends over the whole lateral region. The threshold current density and its optimization are discussed for the 1.3micron and 1.55micron InGaAsP lasers after considering the design parameters such as the ridge width and the layer thicknesses.