51-nm Uniform-Intensity Tuning of Superstructure Grating Active-DBR Laser for 2-μm Wavelength Band

To suppress the fluctuation of light intensity during wavelength tuning, we utilized a single quantum well (SQW) inserted into the bulk core layer of distributed Bragg reflectors (DBRs), called an active DBR structure, for a 2-m-wavelength superstructure grating (SSG)-DBR laser. In this structure, parts of the injected carriers are consumed for an optical amplification in the SQW, which suppresses the optical loss induced by the carriers. The SSG-DBR laser with the active DBR structure exhibited the lasing wavelength shift of a single reflection peak of the SSG-DBR of about 8 nm when the front and rear DBRs were electrically connected and simultaneously swept from 0 to 200 mA. In addition, the reduction of light intensity under this condition was less than 2.7 dB, which is significantly smaller than that for the conventional our SSG-DBR laser, although a relatively large current was required for the wavelength shift. We also measured the lasing characteristics of 39 consecutive wavelength channels with 100-GHz spacings and found that the total quasi-continuous tuning range was 51.2 nm. Furthermore, the fluctuation of light intensity was significantly suppressed to less than 2.5 dB across the whole tuning range.