Abstract: The present invention concerns tunable distributed Bragg reflector (DBR) semiconductor lasers, in particular a DBR laser with a branched optical waveguide 5 within which a plurality of differently shaped lasing cavities may be formed, and a method of operation of such a laser. The laser may comprise a phase control section (418), gain section (420, 422), a sampled grating DBR (412) giving a comb-line spectrum and two tunable, chirped DBRs (414, 416) for broadband frequency training and a coupling section (410).

Abstract: The present invention concerns tunable distributed Bragg reflector (DBR) semiconductor lasers, in particular a DBR laser with a branched optical waveguide 5 within which a plurality of differently shaped lasing cavities may be formed, and a method of operation of such a laser. The laser may comprise a phase control section (418), gain section (420, 422), a sampled grating DBR (412) giving a comb-line spectrum and two tunable, chirped DBRs (414, 416) for broadband frequency training and a coupling section (410).

Abstract: A tuneable laser is disclosed, including a gain section with first and second comb reflectors to one side thereof. The two reflectors each provide combs with substantially uniform spacings, the spacings differing as between the combs. Each comb reflector can be tuned so as to shift the reflective peaks of the combs, thus allowing alignment of a single reflective peak at a chosen wavelength which is the same in both combs, forming a supermode. This supermode has an intensity greater than the threshold of the gain section and thus the laser produces an output at that selected wavelength.

Abstract: A tuneable laser has a gain section bounded at one end by a first reflector in the form of a distributed Bragg reflector adapted to produce a comb of reflective peaks and on the other end by a second Bragg reflector, the second Bragg reflector adapted to reflect at a plurality of wavelengths and being capable of being varied selectively through discrete segments so that one or more segments of the Bragg reflector can be tuned to a lower wavelength to reflect with a segment reflecting at that lower wavelength to enhance the reflectivity at that lower wavelength.

Abstract: A tuneable laser is disclosed, including a gain section with first and second comb reflectors to one side thereof. The two reflectors each provide combs with substantially uniform spacings, the spacings differing as between the combs. Each comb reflector can be tuned so as to shift the reflective peaks of the combs, thus allowing alignment of a single reflective peak at a chosen wavelength which is the same in both combs, forming a supermode. This supermode has an intensity greater than the threshold of the gain section and thus the laser produces an output at that selected wavelength.

Abstract: A multi-wavelength optical reflector comprises a diffraction grating structure (18) which comprises a plurality of repeat grating units (20) in which each grating unit (20) comprises a series of adjacent diffraction gratings (22, 24, 26) having the same pitch. The grating units (20) and adjacent gratings within a grating unit are separated by a phase change (28) of substantially pi (&pgr; radians). The lengths of the gratings (22, 24, 26), which are different for each grating within a grating unit, are selected so as to provide a predetermined comb reflection spectrum which comprises a plurality of reflection maxima of substantially equal reflectivity.

Abstract: The array is highly suitable for producing a spacially wide output “beam” (comprising a number of individual beams). It suffers less from problems of hotspots and filamentation since each tapered laser supports a limited number of modes, or even a single mode. Therefore it produces a semiconductor laser which is especially suitable for pumping of other lasers and to be used in materials processing.