Gallium nitride-based semiconductor laser

The gallium nitride-based semiconductor laser comprises a substrate, a lower limiting layer, a lower waveguide layer, an active layer, an upper waveguide layer and an upper limiting layer which are sequentially arranged from bottom to top, and the lower limiting layer comprises a first sub lower limiting layer, a second sub lower limiting layer and a third sub lower limiting layer which are sequentially arranged from bottom to top. The first sub lower limiting layer, the second sub lower limiting layer and the third sub lower limiting layer all have the characteristics of thermal expansion coefficient distribution, lattice constant distribution and forbidden bandwidth distribution. The thickness and component regulation and control limitation of the lower limiting layer can be relieved, the problems of cracking, bending and quality reduction are solved, meanwhile, the coupling rate from the pumping energy level to the laser energy level is increased, the yield of waste heat is reduced, the thermal stress mism