Realization of phase grating comb reflectors and their application to widely tunable DBR lasers

Widely tunable InP lasers often require comb reflectors as an integral part of their design. It is desirable to achieve comb reflectors with as "top-hat" like a response as possible. There are several ways to do this, but one simple and practical way is by utilizing a phase grating. Previously these have been discussed theoretically, but here we will describe the fabrication of such gratings and how they can find application as the reflectors in widely tunable InP lasers. The example devices which we will discuss show that phase-grating-based distributed Bragg reflector lasers can have tuning ranges of around 35 nm combined with excellent sidemode suppression ratio of better than 45 dB at the mode centers.