Semiconductor laser device and fabrication method thereof

Abstract

A method of fabricating a ridge-waveguide type semiconductor laser device having a large half-value width and a high kink level is provided. First, an effective refractive index difference Δn between an effective refractive index nof the ridge and an effective refractive index nof a portion on each of both sides of the ridge is taken as Δn=n−n, and a ridge width is taken as W. On such an assumption, constants 'a', 'b', “c”, and “d” of the following three equations are set on X-Y coordinates (X-axis: W, Y-axis: Δn) The first equation is expressed by Δn≦a×W+b, where “a” and “b” are constants determining a kink level. The second equation is expressed by W≧c, where “c” is a constant specifying a minimum ridge width at the time of formation of the ridge. The third equation is expressed by Δn≧d, where “d” is a constant specified by a desired half-width value θ. Then at least either of a kind and a thickness of an insulating film, a thickness of an electrode film on the insulating film, and a kind and a thickness of a portion, located on each of both the sides of the ridge, of the upper cladding layer is set in such a manner that a combination of Δn and W satisfies the above three equations.