To obtain both a high power and a single mode oscillation of a semiconductor laser, the semiconductor laser includes a diffraction grating layer. The diffraction grating layer includes a ?/4 phase shift portion, and includes first and second regions. The first region has a diffraction pattern arranged therein, the diffraction pattern being formed to reflect a light beam having a Bragg wavelength and having first and second refractive index regions alternately arranged therein. The second region is provided with a first portion that reflects the light beam having the Bragg wavelength in the first region and a second portion that transmits the Bragg wavelength in the first region. The second portion is formed of the first and second refractive index regions. A total length of the first portion in a direction in which the diffraction grating layer extends is shorter than a length of the first region.

Disclosed is a Vernier effect DBR laser that has uniform laser injection current pumping along the length of the laser. The laser can include one or more tuning elements, separate from the laser injection element, and these tuning elements can be used to control the temperature or modal refractive index of one or more sections of the laser. The refractive indices of each diffraction grating can be directly controlled by temperature changes, electro optic effects, or other means through the one or more tuning elements. With direct control of the temperature and/or refractive indices of the diffraction gratings, the uniformly pumped Vernier effect DBR laser can be capable of a wider tuning range. Additionally, uniform pumping of the laser through a single electrode can reduce or eliminate interfacial reflections caused by, for example, gaps between metal contacts atop the laser ridge, which can minimize multi-mode operation and mode hopping.

A laser diode vertical epitaxial structure, comprising a transverse waveguide comprising an active layer between an n-type semiconductor layer and a p-type semiconductor layer wherein the transverse waveguide is bounded by a lower index n-cladding layer on an n-side of the transverse waveguide and a lower index p-cladding layer on a p-side of the transverse waveguide, a lateral waveguide that is orthogonal to the transverse waveguide, wherein the lateral waveguide is bounded in a longitudinal direction at a first end by a facet coated with a high reflector (HR) coating and at a second end by a facet coated with a partial reflector (PR) coating and a higher order mode suppression layer (HOMSL) disposed adjacent to at least one lateral side of the lateral waveguide and that extends in a longitudinal direction.

A semiconductor laser device having a diffraction grating is disclosed. The semiconductor laser device comprises a first diffraction grating provided on a substrate, a second diffraction grating continuous to one end of the first diffraction grating along an optical waveguide direction, and an active layer provided above the first diffraction grating. The second diffraction grating has a pitch 1.05 times or greater, or 0.95 times or smaller of the pitch of the first diffraction grating.

A III-V heterostructure laser device located in and/or on silicon, including a III-V heterostructure gain medium, a rib optical waveguide, located facing the gain medium and including a strip waveguide equipped with a longitudinal rib, the rib optical waveguide being located in the silicon, two sets (RBE-A, RBE-B) of Bragg gratings formed in the rib optical waveguide and located on either side of the III-V heterostructure gain medium, each set (RBE-A, RBE-B) of Bragg gratings including a first Bragg grating (RB1-A, RB1B) having a first pitch and formed in the rib and a second Bragg grating (RB2-A, RB2-B) having a second pitch different from the first pitch and formed on that side of the rib waveguide which is opposite the rib.

A tunable laser for tuning a lasing mode based on light beams travelling through at least one block of channel waveguides with at least two tunable combs, includes: a frequency selective optical multiplexer comprising a first terminal for receiving/transmitting light, at least one block of channel waveguides, each channel waveguide having a reflectively coated first tail and a second tail, and an optical coupling element optically coupling the first terminal with the second tails of the channel waveguides of the at least one block of channel waveguides, each of the channel waveguides having a different length; a gain element generating a broad spectrum of light, the gain element coupling the first terminal of the frequency selective optical multiplexer with a reflective element.

A synthesized grating is provided comprising a substrate/layer, and a plurality of alternating aperiodic non-uniform low and high index profiles on a surface of the substrate/layer defining a transmission/reflection spectrum for one of either single or multi-frequency operation of said grating in an optical cavity. A method is also provided for designing the synthesized grating, comprising determining a grating structure of given profiles through analysis of an optimized weighted sum and mapping the grating profile to said surface with the plurality of alternating non-uniform low and high index profiles. A distributed feedback laser is also provided having top, bottom and two sides, comprising a top electrode, a cladding layer disposed below the top electrode a bottom electrode, a substrate disposed above the bottom electrode, one of either an active or passive waveguide layer, a synthesized aperiodic grating layer providing distributed mirrors, and wherein the waveguide layer and synthesized aperiodic grating layer are disposed between said the substrate and cladding layer and are separated by a spacer layer.

A III-V heterostructure laser device located in and/or on silicon, including a III-V heterostructure gain medium, a rib optical waveguide, located facing the gain medium and including a strip waveguide equipped with a longitudinal rib, the rib optical waveguide being located in the silicon, two sets (RBE-A, RBE-B) of Bragg gratings formed in the rib optical waveguide and located on either side of the III-V heterostructure gain medium, each set (RBE-A, RBE-B) of Bragg gratings including a first Bragg grating (RB1-A, RB1B) having a first pitch and formed in the rib and a second Bragg grating (RB2-A, RB2-B) having a second pitch different from the first pitch and formed on that side of the rib waveguide which is opposite the rib.

Provided is a semiconductor laser having excellent characteristics. The semiconductor laser includes: first and second-conductivity-type semiconductor layers; first and second electrodes electrically connected to the first or second-conductivity-type semiconductor layer; a diffraction grating layer; an insulating film placed in a part of a space between the second electrode and the second-conductivity-type semiconductor layer; a mesa structure; and first and second regions in a direction in which the mesa structure stretches. A first diffraction grating region in the diffraction grating layer of the first region and a second diffraction grating region in the diffraction grating layer of the second region form a resonator. The first region has a normalized coupling coefficient higher than a normalized coupling coefficient of the second region. In the first region, an electric current supplied from the second electrode to the mesa structure per unit area is smaller than in the second region.

To provide a semiconductor laser excellent in high output characteristic and single mode oscillation, the semiconductor laser includes a substrate, an active layer, a cladding layer including a first grating layer having a first grating structure and a second grating layer having a second grating structure, and an electrode. The active layer and the cladding layer form a mesa structure, and the mesa structure includes first and second reflection regions forming a resonator in a direction in which the mesa structure extends. The second grating structure is formed in the first reflection region, and any one of the first grating structure or the second grating structure is formed in the second reflection region. A normalized coupling coefficient of the first reflection region is larger than that of the second reflection region. Mesa widths in the first reflection region and the second reflection region are different from each other.