Semiconductor laser device

A semiconductor laser device, comprising:

• a first conductivity type cladding layer having a refractive index nc1;
• an undoped first conductivity type side optical guide layer;
• an active layer;
• an undoped second conductivity type side optical guide layer;
• a second conductivity type cladding layer having a refractive index nc2;
• and
• a resonator in which laser light travels back and forth, the above layers being laminated in order on a semiconductor substrate of a first conductivity type, wherein
• an oscillation wavelength is λ;
• a structure of the device is such that a first-order or higher-order mode is allowed in a lamination direction in a cross section perpendicular to an optical axis direction of the resonator and is a broad area structure in which a first-order or higher-order mode is allowed in a direction perpendicular to the optical axis direction of the resonator and the lamination direction, the broad area structure being with a ridge shape having a ridge region and cladding regions on both sides of the ridge region;
• and
• a first conductivity type low refractive index layer having a thickness of d1 and a refractive index n1 lower than nc1 is provided between the first conductivity type side optical guide layer and the first conductivity type cladding layer or inside the first conductivity type cladding layer, a second conductivity type low refractive index layer having a thickness of d2 and a refractive index n2 lower than nc2 is provided between the second conductivity type side optical guide layer and the second conductivity type cladding layer or inside the second conductivity type cladding layer, and a relationship
• 2
• ⁢
• π
• λ
• ⁢
• n
• c
• ⁢
• 2
• 2
• -
• n
• 2
• 2
• ⁢
• d
• 2
• 2
• >
• 2
• ⁢
• π
• λ
• ⁢
• n
• c
• ⁢
• 1
• 2
• -
• n
• 1
• 2
• ⁢
• d
• 1
• 2
• is satisfied.