Monolithically integrated wavelength-multiplexed DFB laser array with laterally coupled quarter-wave phase-shift gratings defined by interference lithography

The first monolithically integrated laterally coupled, multi-wavelength distributed feedback (DFB) laser array using first-order sidewall sampled gratings with equivalent quarter-wave phase shifts defined by interference lithography is experimentally demonstrated. The elements of the monolithic DFB laser array lase strongly monomode, with an average side mode suppression ratio of ~37.3 dB and with a uniform wavelength spacing of ~7.3 nm. The output power under 100 mA bias current ranges from 11.4 to 14.1 mW. The proposed method offers a practical and low-cost method for the fabrication of multi-wavelength monolithic DFB laser arrays without regrowth or e-beam lithography.