Patent ID: 7301977

Claim:
A unipolar semiconductor laser comprising: a) a semiconducting substrate having a first electrode in contact therewith; and, b) an epitaxial structure on said semiconducting substrate wherein said epitaxial structure comprises; b1) a lower cladding layer atop said semiconducting substrate; and, b2) a lower guiding layer atop said lower cladding layer; and, b3) an active region atop said lower guiding layer; and, b4) an upper guiding layer atop said active region; and, b5) an upper cladding layer atop said upper guiding layer; and wherein said semiconducting substrate and said epitaxial layer comprise doped semiconducting material of only a single conductivity type; and, wherein said epitaxial structure has the form of a waveguide ridge comprising at least two cavity sections and further comprising two or more second electrodes, each of said second electrodes in contact with a different of said at least two cavity sections; and, wherein each adjacent pair of said cavity sections is joined by a coupling section; and, wherein said unipolar semiconductor laser is capable of producing single longitudinal mode laser light tunable over a range of wavelengths.