Multi-wavelength DFB laser based on a sidewall third-order four phase-shifted sampled Bragg grating with uniform wavelength spacing.

We present the first, to our knowledge, demonstration of a 1550 nm multi-wavelength distributed feedback (MW-DFB) laser employing a third-order, four-phase-shifted sampled sidewall grating. By utilizing linearly chirped sampled gratings and incorporating multiple true π-phase shifts within a cavity, we achieved and experimentally validated a four-wavelength laser with a channel spacing of 0.4 nm.