Abstract: A semiconductor distributed Bragg reflector laser configured for single longitudinal mode operation, having an optical waveguide comprising an optical gain section, a first reflector being a first distributed Bragg reflector (DBR) section comprising a grating configured to produce a reflection spectrum having one or more first reflective peaks, and a second reflector, wherein the first DBR section is configured to compensate for thermal chirp that is induced inhomogeneously along the length of the DBR section, in use.

Abstract: A monolithically integrated, tunable semiconductor laser with an optical waveguide, comprising a laser chip having epitaxial layers on a substrate and having first and second reflectors bounding an optical gain section and a passive section, wherein at least one of the reflectors is a distributed Bragg reflector section comprising a grating and configured to have a tunable reflection spectrum, wherein the laser is provided with a common earth electrode, wherein control electrodes are provided on the optical waveguide in at least the optical gain section and the at least one distributed Bragg reflector section, wherein the passive section is provided with an electrode or electrical tracking on the optical waveguide, the passive section is configured not to be drivable by an electrical control signal, and no grating is present within the passive section.

Abstract: Sacrificial optical test structures are constructed upon a wafer of pre-cleaved optical chips for testing the optical functions of the pre-cleaved optical chips. The sacrificial optical structures are disabled upon the cleaving the optical chips from the wafer and the cleaved optical chips can be used for their desired end functions. The test structures may remain on the cleaved optical chips or they may be discarded.

Abstract: A monolithically integrated, tunable semiconductor laser with an optical waveguide, comprising epitaxial layers on a substrate and having first and second reflectors bounding an optical gain section and a non-driven region, wherein at least one of the reflectors is a distributed Bragg reflector section configured to have a tunable reflection spectrum, wherein control electrodes are provided to at least the optical gain section, and the distributed Bragg reflector section, and wherein the non-driven region has a length of at least 100 ?m, is without an electrical contact directly contacting onto the epitaxially grown side of the non-driven region, and the non-driven region is without a reflective Bragg grating within the epitaxial layers of the non-driven region.

Abstract: A widely tunable multi-mode semiconductor laser containing only two electrically active sections, being an optical gain section and a tunable distributed Bragg reflector section adapted to reflect at a plurality of wavelengths, wherein the gain section is bounded by the tunable distributed Bragg reflector section and a broadband facet reflector, and wherein the tunable distributed Bragg reflector section comprises a plurality of discrete segments capable of being selectively tuned, wherein the reflection spectra of one or more segments of the tunable distributed Bragg reflector section can be tuned lower in wavelength to reflect with the reflection spectrum of a further segment of the tunable distributed Bragg reflector section to provide a wavelength range of enhanced reflectivity. An optical transmitter comprising a light source that is such a widely tunable multi-mode semiconductor laser.