Theory, design, and performance of extended tuning range semiconductor lasers with sampled gratings

The authors have recently demonstrated 57 nm of tuning in a monolithic semiconductor laser using conventional distributed-Bragg-reflector (DBR) technology with grating elements removed in a periodic fashion. They describe the theory and design of these so-called sampled-grating tunable lasers. They calculate sample-grating reflectivity, and present normalized design curves which quantify tradeoffs involved in a sampled-grating DBR laser with two mismatched sampled-grating mirrors. These results are applied to a design example in the InP-InGaAsP system. The design provides 70-nm tuning while maintaining >30-dB mode suppression ratio (MSR), with fractional index change Δμ/μ<0.2% in the mirrors, and only 1 mm of total sampled-grating length