A semiconductor laser device

A low reflective layer (10) is - in that order, starting on a disposed with a laser chip in contact page - from a first dielectric layer (11) having a refractive index n1 and a thickness d1, a second dielectric layer (12) with a refractive index n2 and a thickness d2, a third dielectric layer (13) having a refractive index n3 and a thickness d3, and a fourth dielectric layer (14) having a refractive index n4 and a thickness d4 formed. In particular, alumina Al