Patent ID: 8295315

Claim:
A tunable semiconductor laser, comprising: a branched optical waveguide comprising a stem waveguide section with a stem optical reflector therein and optically coupled to at least two branch waveguide sections having tunable branch optical reflectors therein; and a gain section bounded by the stem optical reflector and at least one of the tunable branch optical reflectors; wherein the stem optical reflector is a distributed Bragg reflector (DBR), wherein one of the tunable branch optical reflectors has a reflection spectrum tunable within a first wavelength range, and another of the tunable branch optical reflectors has a reflection spectrum tunable within a second wavelength range, different to the first wavelength range, the first and second wavelength ranges overlapping by less than 25% of the width of one of the wavelength ranges, and wherein, during operation a lasing cavity is formed between the stem optical reflector and at least one of the tunable branch optical reflector.