Semiconductor VSIS laser

An index guided semiconductor laser having the inner stripe structure comprising, as a composite,

• a substrate,
• a current blocking layer formed on said substrate,
• a V-shaped groove formed in said current blocking layer in a manner to reach said substrate,
• a p-Ga.sub.1-x A1.sub.x As first cladding layer formed on said current blocking layer,
• an active layer formed on said first cladding layer,
• a n-Ga.sub.1-x A1.sub.x As second cladding layer containing A1 and As formed on said active layer,
• a cap layer formed on said second cladding layer to form said composite, and said composite being sandwiched between electrode means, wherein said A1As mole fraction x of the first and second cladding layers is selected between about 0.45 and 0.52, wherein the cavity length of said V-channeled substrate inner stripe (VSIS) semiconductor laser is selected to be longer than about 300 .mu.m, whereby the occurrence of the mode competition noise at the normal operating temperature is minimized and wherein said semiconductor laser have a front facet and rear facet of which the reflectivities R.sub.1 and R.sub.2, respectively, satisfy the following condition:
• 0. 1.ltoreq.ln(1/R.sub.1 .multidot.R.sub.2)<1.