Abstract: A semiconductor laser device comprises: a cladding layer of a first conductivity type; an active layer provided on the cladding layer; and a cladding layer of a second conductivity type provided on the active layer. At least a part of the cladding layer of the second conductivity type has a ridge stripe. The ridge stripe includes: an upper part having substantially vertical sidewalls; and a lower portion having sidewalls inclined so that the stripe becomes wider toward the active layer.

Abstract: A semiconductor laser device comprises: a cladding layer of a first conductivity type; an active layer provided on the cladding layer; and a cladding layer of a second conductivity type provided on the active layer. At least a part of the cladding layer of the second conductivity type has a ridge stripe. The ridge stripe includes: an upper part having substantially vertical sidewalls; and a lower portion having sidewalls inclined so that the stripe becomes wider toward the active layer.

Abstract: A laser element has a first periodic structure (i.e., a diffraction grating) provided along an optical waveguide, and optical feedback is performed by the first periodic structure. Structural factors, including at least one of the width, thickness and refractive index of the optical waveguide, the composition of the laser medium, or the period of the first periodic structure is continuously changed at least in part in the axial direction of a cavity In such a manner that the continuous change provides a periodic structure of second, third or higher order.

Abstract: A periodic structure is formed along the laser medium in the axial direction of a cavity. One of the end facet of the cavity has high reflectivity and the other end facet has low reflectivity. A phase discontinuous portion of the periodic structure is disposed in position deviated from the central portion of the cavity towards the high-reflectivity end facet. The phase discontinuous portion is formed of a phase shifting portion or a phase shifting area having the same effect as the phase discontinuity. The phase shift .DELTA..PHI. of the phase shifting portion or phase shifting area is set to exceed 3.pi./4 which is represented in terms of the phase of waveguiding light (which corresponds to 3.lambda./8 when the lasing wavelength is .lambda.). Thus, the performances of high power and linearity of light output can be simultaneously achieved.

Abstract: A photoresist 12 is coated on a substrate 11, and a phase shift medium 13 is formed on the photoresist 12. The phase shift medium 13 is patterned. Thereafter, first and second laser beams 16 and 17 having asymmetric incidence angles with respect to the substrate 11 are radiated on the photoresist 12 to perform an interference exposing operation. The photoresist 12 is developed and post-baked, and the substrate 11 is etched using the photoresist 12 as a mask, thereby forming a diffraction grating having a discontinuous phase portion.

Abstract: A phase shift region is formed in a waveguide layer constituting a laser device. The phase shift region is a recess portion formed in the waveguide layer, and a periodic projection structure is formed on the surface of the waveguide layer including the recess portion. The recess portion can be formed by etching using an agent having weak etching anisotropy. Optical feedback can be performed while concentration of light in the phase shift region is suppressed.