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. (© 2021 Wiley‐VCH GmbH)