Design of 16-wavelength heterogeneous quantum dot laser arrays with varying silicon waveguide width and grating period

The multi-wavelength laser array is crucial for high-capacity silicon photonic systems based on (dense) wavelength division multiplexing technology. However, realizing 8-wavelength or more laser arrays is challenging solely by adjusting the grating period due to the large wavelength spacings of about 12–20 nm. In this letter, we report a 16-wavelength heterogeneously integrated quantum dot distributed feedback laser array with varying silicon waveguide width and grating period. The effective refractive index of gratings is calculated by eigenmode expansion method. Considering the power reflectivity, normalized coupling coefficient and manufacturing process of gratings, the etch depth and duty cycle of gratings are optimized to 10 nm and 0.8, respectively. When the grating period is fixed at 198 nm and the silicon waveguide widths are 560 nm, 590 nm, 615 nm, and 635 nm, respectively, the corresponding lasing wavelengths are 1310.72 nm, 1311.26 nm, 1311.80 nm, and 1312.31 nm, respectively, and the wavelength spacing of adjacent laser units is about 100 GHz (0.57 nm). Furthermore, by adjusting the grating period between 196 and 202 nm with 2 nm spacing of grating period, the number of lasing wavelengths is increased to 16, and the range of lasing wavelengths is broadened to 1298.03–1337.44 nm. This work provides an excellent solution for realizing multi-wavelength heterogeneously integrated III-V/Si distributed feedback laser arrays and expanding the number of wavelengths, thereby advancing the development of high-capacity silicon photonic systems.