PURPOSE: To oscillate monochromatic lights of different wavelengths by matching the period of a diffraction grating to the band gap energy of an active layer, thereby forming a plurality of stripes at the prescribed interval.

CONSTITUTION: An InGaAsP [Eg(x)] active layer 2 formed on an N type InP substrate is formed to distribute its band gap energy in x direction, and an interfering pattern 4 is formed and exposed on a P type InGaAs photoguide layer 3 formed thereon. The spread of the period of this pattern 4 is synchronized with Eg(x) of the layer 2. Then, a buried hetero strip 6 is formed. Thereafter, a P type InP layer 7, an N type InP layer 8, a P type InP layer 9 are grown, a P type GaAP layer 10 is eventually formed, the N type side substrate is polished in the prescribed thickness, a P type electrode metal layer 11 is then formed. Subsequently, a mesa etching for isolating one laser is performed, an N type side is then formed, and cleaved in an array shape. Thus, a light emitting device which can produce a laser light having excellent monochromatic property over many wavelength can be formed.