A laser including: a gain chip; an external cavity incorporating a Bragg grating; and a baseplate; wherein a first end of the gain chip has a high reflectivity facet forming a first end of the laser cavity; a second end of the gain chip has a low reflectivity facet; and a second part of the external cavity comprises a Bragg grating, supported by the baseplate, the temperature of the baseplate being maintained through a feedback loop; wherein the optical length of the external cavity is at least an order of magnitude greater than the optical length of the gain chip; wherein the Bragg grating is physically long and occupies a majority of the length of the external cavity and is apodized to control the sidemodes of the grating reflection.

A tunable laser device comprises a multi-section distributed feedback (DFB) laser having a first Bragg section including a waveguide and a Bragg grating, a second Bragg section comprising a waveguide and a Bragg grating, and a phase section being longitudinally located between the first Bragg section and the second Bragg section. The phase section is made of a passive material, and each Bragg section has a first longitudinal end joining the phase section and a second longitudinal end opposed to the phase section. The Bragg grating of at least one Bragg section has a grating coupling coefficient which decreases from the first longitudinal end to the second longitudinal end of the at least one Bragg section.

Monolithic asymmetric optical waveguide grating resonators including an asymmetric resonant grating are disposed in a waveguide. A first grating strength is provided along a first grating length, and a second grating strength, higher than the first grating strength, is provided along a second grating length. In advantageous embodiments, the effective refractive index along first grating length is substantially matched to the effective refractive index along second grating length through proper design of waveguide and grating parameters. A well-matched effective index of refraction may permit the resonant grating to operate in a highly asymmetric single longitudinal mode (SLM). In further embodiments, an asymmetric monolithic DFB laser diode includes front and back grating sections having waveguide and grating parameters for highly asymmetric operation.

An example device in accordance with an aspect of the present disclosure includes a ring waveguide and bus waveguide. The ring waveguide has a first coupled portion associated with a first modal index, and the bus waveguide includes a second coupled portion associated with a second modal index. The second coupled portion is evanescently coupleable to the first coupled portion. A laser outcoupling and associated lasing output of the device is variable based on varying a difference between the first modal index and the second modal index to vary coupling between the first coupled portion and the second coupled portion, without varying modal indices of non-coupled portions of the ring waveguide and bus waveguide.

A distributed reflector (DR) laser may include a distributed feedback (DFB) region and a distributed Bragg reflector (DBR). The DFB region may have a length in a range from 30 micrometers (m) to 100 m and may include a DFB grating with a first kappa in a range from 100 cm.sup.1 to 150 cm.sup.1. The DBR region may be coupled end to end with the DFB region and may have a length in a range from 30-300 m. The DBR region may include a DBR grating with a second kappa in a range from 150 cm.sup.1 to 200 cm.sup.1. The DR laser may additionally include a lasing mode and a p-p resonance frequency. The lasing mode may be at a long wavelength side of a peak of a DBR reflection profile of the DBR region. The p-p resonance frequency may be less than or equal to 70 GHz.

A symmetric distributed feedback (DFB) laser that is integrated in a silicon based photonic integrated circuit can output light from both sides of the symmetric DFB laser onto waveguides. The light in the waveguides can be phase adjusted and combined using an optical coupler. The symmetric DFB laser can generate light and symmetrically output light onto different lanes of a multi-lane transmitter.

Laser diode comprises an active layer; a waveguiding region at least partially surrounding the active layer; a rear facet; a front facet designed for decoupling laser radiation, wherein the active layer extends at least partially along a first axis (X) between the rear facet and the front facet; and a grid operatively connected to the waveguiding region, wherein the grid comprises a plurality of webs and trenches designed such that an average increase of a coupling parameter P for the plurality of trenches along the grid is non-zero, wherein the coupling parameter P of a trench is defined by the formula, wherein dres is a distance of the trench to the active layer, w is a width of the trench and n is the refractive index difference between a refractive index of the trench and a refractive index of a material surrounding the trench.

An optical element includes a distributed Bragg reflector, wherein the distributed Bragg reflector includes a first-order diffraction grating of a first-order period disposed in a central region, and second-order diffraction gratings of a second-order period having a coupling coefficient smaller than a coupling coefficient of the first-order diffraction grating and disposed in both end regions between which the central region is located.

A method for producing a quantum cascade laser includes the steps of forming a laser structure including a mesa structure and a buried region embedding the mesa structure; forming a mask on the laser structure, the mask including a first pattern that defines a /4 period distribution Bragg reflector structure and a second pattern that defines a 3/4 period distribution Bragg reflector structure; and forming a first distribution Bragg reflector structure, a second distribution Bragg reflector structure, and a semiconductor waveguide structure by dry-etching the laser structure through the mask, the semiconductor waveguide structure including the mesa structure that has first and second end facets. The first distribution Bragg reflector structure is optically coupled to the first end facet. The second distribution Bragg reflector structure is optically coupled to the second end facet. Here, denotes a value of an oscillation wavelength of the quantum cascade laser in vacuum.

A two-dimensional photonic-crystal surface-emitting laser includes an active layer; and a photonic-crystal layer including a two-dimensional photonic-crystal light-amplification portion that is a first two-dimensional photonic-crystal region provided in a plate-shaped base body disposed on one side of the active layer, and includes an amplification-portion photonic band gap which is a photonic band gap formed between two photonic bands having a band edge at a predetermined point in a reciprocal lattice space, and a two-dimensional photonic-crystal light-reflection portion that is a second two-dimensional photonic-crystal region provided around the two-dimensional photonic-crystal light-amplification portion, and includes a reflection-portion photonic band gap which is a photonic band gap formed between two photonic bands having a band edge at the predetermined point of the reciprocal lattice space, wherein energy ranges of the amplification-portion photonic band gap and the reflection-portion photonic band gap partially overlap and are different.