Tunable V-Coupled-Cavity Semiconductor Laser Monolithically Integrated with Monitoring Photodiodes Using Deeply Etched Reflective Trenches

We present a 1560-nm-band digitally wavelength tunable V-coupled-cavity semiconductor laser monolithically integrated with two waveguides based monitoring photodiodes (MPD) through deeply etched reflective trenches. The reflective trenches are designed to be 1.16 mu m wide, about three quarters of the wavelength, and are deeply etched through the waveguide with a depth larger than 4 mu m. Due to the high reflectivity of the etched trenches, a low threshold current of 19mA is achieved. Using a single electrode control, wavelength tuning of 22 channels at 100GHz spacing with SMSR above 35 dB is obtained. The relationship between the photocurrents of the two MPD at the two waveguide branches and the laser output power from the coupler side is investigated as a function of the wavelength. Since the integrated tunable laser with MPDs is very compact and does not involve any grating or epitaxial regrowth, it is suitable for low-cost multifunctional photonic applications for access and data center networks.