Suppressing longitudinal spatial hole burning with dual assisted phase shifts in pitch-modulated DFB lasers

An equivalent corrugation pitch-modulated (ECPM) distributed feedback (DFB) semiconductor laser with two equivalently assisted phase shifts (EAPS) was theoretically studied and experimentally demonstrated. The simulated results showed that the longitudinal photon density distribution of the ECPM + EAPS DFB lasers was much more uniform than that of a sole ECPM DFB laser without EAPS, and the longitudinal spatial hole burning was therefore suppressed more effectively. The results of experiment showed that good single longitudinal mode operation was achieved, with side mode suppression ratio (SMSR) being over 35 dB, and the wavelength range was from 1,559.64 to 1,563.02 nm when the operation current was from 50 to 160 mA at the temperature of 25 °C, and the SMSR increased to 46.29 dB when the injection current was 130 mA.