Grating-free single-mode laser integrated with asymmetric vertically coupled structure

We propose a single-mode InGaAsP/InP Fabry-Pérot (FP) laser integrated with an asymmetric vertically coupled (AVC) structure without the use of a grating. The single longitudinal mode is achieved through the narrow-band filtering effect of the twin-waveguide vertically coupled structure. The laser's central wavelength is determined by material gain, FP cavity resonance characteristics, and filtering effect. The transmission characteristics of the structure are theoretically investigated to achieve a high side-lobe suppression ratio based on the transmission matrix model. In this demonstration, the AVC laser achieves an output power exceeding 5 mW, a side-mode suppression ratio of up to 40.4 dB, and a minimum intrinsic linewidth of 178.5 kHz.