Abstract: A semiconductor laser and an optical device employing the semiconductor laser are described. The semiconductor laser comprises and activating layer; first and second cladding layers for sandwiching the activating layer, the energy gaps of which are greater than that of the activating layer; a current blocking layer provided in contact with both sides of the activating layer; a first electrode electrically connected to the first cladding layer; and a second electrode electrically connected to the second cladding layer. The activating layer has a structure that the activating layer is two-dimensionally confined within the first cladding layer, the second cladding layer, and the current blocking layer, reflectivity of at least on end face of a resonator of the activating layer is less than, or equal to 5%, and loss in the resonator of the activating layer is higher than, or equal to 100 cm.sup.-3.