A narrow linewidth laser for WDM applications using silicon waveguide technology

DBR lasers are a potential alternative to DFB lasers in applications where low chirp or narrow linewidth are required. Several groups have reported hybrid distributed Bragg reflector lasers (HDBR) realised from the coupling of a fibre Bragg grating to an optical gain element, typically an AR/HR coated Fabry-Perot laser. We report on Bookham´s planar implementation of the fibre grating laser onto the ASOC silicon platform, in particular the grating to optical amplifier alignment. ASOC technology refers to the fabrication of integrated optics components in silicon on insulator (SOI) material. The advantages offered by ASOC include low loss waveguides, mass production capability and the simple hybrid and monolithic integration of active components. The laser cavity is formed between the High Reflection (HR) coating of the optical amplifier at one end and the grating at the other. In this case the grating acts as a wavelength dependent reflector which will select a single or limited number of longitudinal cavity modes of the associated external cavity. A low split ratio coupler and photodiode are monolithically integrated to enable a power monitoring function. The fibre is secured to the ASOC chip using a passive fibre attach method that has been reported previously