1550 nm‐Band InAs/InGaAlAs Quantum Dot Distributed Feedback Lasers Grown on InP(311)B Substrate with Side‐Wall Gratings Simultaneously Fabricated with a Ridge Waveguide

A 1550 nm‐band InAs/InGaAlAs quantum dot (QD) distributed feedback (DFB) laser is fabricated, in which the side‐wall grating is formed in a simultaneous process with the ridge waveguide, and room‐temperature continuous‐wave single‐mode oscillation is achieved. A rather low‐threshold current density of about 2.2 kA cm −2 is obtained. Side‐mode suppression ratios (SMSRs) are 28 dB just above the threshold current I th and 44 dB at I / I th = 2.0. Antireflection (AR) coating suppresses the amplified spontaneous emission (ASE) and increases the slope efficiency by a factor of 1.3.