Abstract: A semiconductor laser device having an active layer, a pair of cladding layers interposing the active layer and a multi-quantum barrier provided between one of the pair of cladding layers and the active layer is provided. The multi-quantum barrier includes barrier layers and well layers being alternated with each other. Thickness, energy band gap, or impurity concentration of at least one of the barrier layers and well layers in the multi-quantum barrier changes with the distance from the active layer, thereby providing a stable function of reflecting carriers overflowing from the active layer back to the active layer.

Abstract: A semiconductor laser according to the present invention includes: a semiconductor substrate; a multilayer structure provided on the semiconductor substrate, the multilayer structure including an active layer, a pair of cladding layers interposing the active layer, and current confining portion for injecting a current into a stripe-shaped predetermined region of the active layer, wherein the current confining portion includes a first current confining layer formed in regions excluding a region corresponding to the predetermined region of the active layer, the first current confining layer having an energy band gap larger than an energy band gap of the active layer and having a refractive index smaller than a refractive index of the active layer.

Abstract: A semiconductor laser device having an active layer, a pair of cladding layers interposing the active layer and a multi-quantum barrier provided between one of the pair of cladding layers and the active layer is provided. The multi-quantum barrier includes barrier layers and well layers being alternated with each other. Thickness, energy band gap, or impurity concentration of at least one of the barrier layers and well layers in the multi-quantum barrier changes with the distance from the active layer, thereby providing a stable function of reflecting carriers overflowing from the active layer back to the active layer.