A stripe-shaped excitation region is provided in an active layer of a double heterojunction laser device, the excitation region and the other region of the active layer being endowed with an effective refractive index difference or optical absorption coefficient difference therebetween, and a carrier injection region is provided contiguously to the excitation region, whereby the laser device exhibits a low ohmic resistance, effects a stable lower-order transverse mode oscillation and suppresses relaxation oscillations. By preventing the stripe-shaped excitation region and the carrier injection region from being exposed to reflective surfaces, the aforecited beneficial results can be realized over a wide range of operating currents, and a laser device of extremely high power density emission is achieved due to the increase of the threshold of the catastrophic optical damage on mirrors.
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