Multi-wavelength semiconductor laser device

A multi-wavelength semiconductor laser device comprising:

• first and second device sections monolithically formed on a substrate;
• a first active layer and a second active layer;
• a stripe-shaped ridge portion extending in a perpendicular direction to each of the first and second device sections, wherein current constriction is provided, wherein the stripe-shaped ridge portion consists of a first ridge portion and a second ridge portion corresponding to the first and second device sections, respectively, and wherein the first ridge portion and the second ridge portion are asymmetrical and the first ridge portion forms a first off-centered light emitting area disposed on the first active layer and the second ridge portion forms a second off-centered light emitting area disposed on the second active layer;
• a first upper electrode and a second upper electrode, wherein the first upper electrode is disposed on the upper surface of the first ridge portion and the second upper electrode is disposed on the upper surface of the second ridge portion, wherein the entirety of the first upper electrode is parallel to the first active layer and at least a portion of the second upper electrode is not parallel to the second active layer;
• and
• a rear end face film formed together on a rear end face of each of the first device section and the second device section,
• wherein the first device section is alight-emitting device section having an oscillation wavelength of λ1,
• the second device section is a light-emitting device section having an oscillation wavelength of λ2 (λ1<λ2),
• the rear end face film includes a layer in which N sets (N≧2) of layers each having the combination of a low refractive index layer having a refractive index of n1 and a high refractive index layer having a refractive index of n3 (n1<n3) as one set are laminated, and an intermediate refractive index layer having a refractive index of n2 (n1<n2<n3) in order from the rear end face of the respective device section such that the N sets of layers are disposed between the rear end face and the intermediate refractive index layer, and is constituted by a film different from an Si film, and
• the optical film thickness of each of the low refractive index layer, the high refractive index layer, and the intermediate refractive index layer is set to be λ3/4 when a wavelength between λ1 and λ2 is set to be λ3.