Technical Insight
Tunable laser nears power of DFB lasers (Research Review)
To replace DFB lasers in DWDM systems, tunable lasers must provide the same power output. S Debrgeas and co-workers from Opto+ (Phot. Tech. Lett. 2001 13(1) 4) have demonstrated a two-section DBR laser emitter that achieves 20 mW coupled output power over a 16 nm tuning range. The device consists of a 1.45 m quaternary Bragg section to ensure a large index variation for the grating with applied current, and a 30 nm 1.45 m quaternary for the grating, separated by 120 nm of InP. This ensures a large side-mode suppression ratio of >40 dB. This region is then butt-jointed to the active region, which consists of six 8 nm thick compressively-strained quaternary layers and 10 nm barriers. The device achieves 20 mW across the 15571573 nm range, equivalent to 40 channels with 50 GHz spacing.
