Self-pulsating semiconductor laser

A self-pulsating semiconductor laser having a refractive index distribution in a direction parallel to a p-n junction thereof and normal to the cavity lengthwise direction thereof, comprising:

• a substrate;
• a first cladding layer formed on said substrate;
• an active layer formed on said first cladding layer;
• a second cladding layer formed on said active layer;
• said second cladding layer including a mesa-type stripe portion extending above the remainder of said second cladding layer, and
• a current blocking layer formed on both sides of said mesa-type stripe portion,
• said refractive index distribution including a first refractive index portion having a first refractive index in said stripe portion, a second refractive index portion having a second refractive index lower than said first refractive index at both sides of said stripe portion, and a third refractive index portion having a third refractive index not higher than said first refractive index and higher than said second refractive index outside of said second refractive index portion.