Guest Editor: Prof. Junsuk Rho, Pohang University of Science and Technology, Republic of Korea; Prof. Guangwei Hu, Nanyang Technological University, Singapore

Cover story: Wang XY, Qiu XK, Liu ML, Liu F, Li MM et al. Flat soliton microcomb source. Opto-Electron Sci 2, 230024 (2023).

The fast development of big data accelerates the continuous innovations of integrated silicon photonics. One novel innovation is the implementation of a flat spectral multi-wavelength source in the chip-integrated semiconductor platform. This type of optical source is strongly compatible with wavelength division multiplexing (WDM) systems. Optical dissipative Kerr solitons in the Complementary Metal Oxide Semiconductor (CMOS) platform is a fresh chip-scale multi-wavelength source with low noise. The introductions of chip-scale soliton source have provided new insights for connecting the big data. This type of soliton microcomb source has abundant superiorities, including the integrated optical source, WDM techniques compatibility, wide spectral region, and chip-scale optical clock.

Optical soliton with a flat spectral envelope is one perfect candidate for exploring soliton-based information processing. This soliton source could provide a higher signal-to-noise ratio under an external optical amplifier owing to the weak power differences in one larger wavelength range. Central to this innovation is the single soliton formation in the microcavity with ultra-flat integrated dispersion. The large-scale ultra-flat integrated dispersion could enlarge the flat spectral range that covers the S+C+L band. In the engineering landscape, this proposed single soliton could enable parallel high-capacity communication, optical interconnection, and high-dimensional optical computing.