Patent ID: 7421000

Claim:
A nitride semiconductor laser device having a waveguide constructed in a stack of layers including, a first conductivity type clad layer, a first conductivity type guide layer of a refractive index n g , an active quantum well layer, a second conductivity type guide layer, and a second conductivity type clad layer deposited in this order on a substrate of GaN or AlGaN with an Al composition ratio of less than 0.02 and having a refractive index n s for laser light, wherein: said optical waveguide has an effective refractive index n e <n s , n g , said first conductivity type clad layer includes a first region, a second region, and a third region in this order in its thickness direction, said second region having an Al composition ratio larger than said first and third regions, and then said first, second and third regions all having their respective refractive indexes smaller than n e , and said first region has a thickness of d c1 , said second region has a thickness of d c2 and said third region has a thickness of d c3 , and then d c2 <d c1 , d c3 <d c1 and 1.4 μm≦d c1 +d c2 +d c3 ≦4.5 μm are satisfied.