DFB laser with active cavity and passive cavity alternating structure

The invention provides a DFB laser with an active cavity and passive cavity alternating structure. The DFB laser comprises a substrate layer, a lower confinement layer on the substrate layer, a lowerwaveguide layer on the lower confinement layer, an active layer on the lower waveguide layer, an upper waveguide layer on the active layer, an upper limiting layer on the upper waveguide layer, an ohmic contact layer, an insulating layer and P-surface electrodes, wherein a grating structure is arranged in the upper limiting layer; a longitudinal ridge waveguide is arranged along the upper limitinglayer; the ohmic contact layer covers the upper surface of the ridge waveguide to form a ridge strip structure; the insulating layer is positioned on the surface of the upper limiting layer and the side walls of the ridge structure; the P-surface electrodes longitudinally cover the upper surface of the ridge strip structure at intervals in a comb tooth shape, cover the side walls of the ridge strip structure and then exte