Narrow Linewidth Tunable Semiconductor Laser

A full-C band tunable laser equipped with an air-gap suspended waveguide structure for efficient thermal heater tuning is described. It is shown that the monolithic tunable laser can simultaneously meet the requirements for the output power, side-mode suppression ratio, and spectral linewidth for 16-QAM coherent communication system. Together with an optimized design for the Bragg grating and a reduced optical loss for thermally-tuned un-doped waveguide, a high SMSR of 54.5 dB, an output power of 19 dBm, and 80 kHz linewidth over 103 channels across the C-band were achieved. A possibility for further reduction of the heater tuning power is also discussed.