Patent ID: 7656920

Claim:
A semiconductor laser device comprising: a GaAs substrate; a GaAsP active layer that emits light and has a thickness; first and second InGaP guide layers having respective thicknesses and between which said GaAsP active layer is interposed; and first and second AlGaInP cladding layers having respective thicknesses and between which said InGaP guide layers and said GaAsP active layer are interposed, wherein said first AlGaInP cladding layer is disposed on said GaAs substrate, said semiconductor laser produces light including a TM-polarized light component and a TE-polarized light component, and a product produced by multiplying (i) the thickness of said GaAsP active layer by (ii) a sum of thicknesses of said first and second InGaP guide layers and said first and second AlGaInP cladding layers is less than 36.0 nm·μm, whereby polarization ratio, which is a ratio of light intensity of the TM-polarized light component to light intensity of the TE-polarized light component, is greater than 0 and less than 2.3.