The past 20 years have witnessed the rapid growth of photonic integration circuits (PIC) technology, which has been warmly embraced by both academia and the industry. Powered by the advanced development in material growth, processing, and design capability, the PIC technology now covers multiple material platforms, including III–V (InP, GaAs), silicon, silica, lithium niobate on insulator (LNOI) polymer, etc. The integration level has evolved from a single functional device to thousands of components on-chip. The increase in the performance and the complexity of the PICs have become an energetic booster for communication and information technology.



To reflect the recent advances in the PICs, we organized a special issue on semiconductor optoelectronic integrated circuits. The special issue includes eight invited reviews and three research articles, focusing on the development of key devices and technologies in mainstream PIC platforms. Hao Sun et al. review the recent progress on integrated electro-optic frequency comb generators reported on the InP, LiNbO₂, and silicons platforms. Mengxi Tan et al. review recent work on broadband RF channelizers based on integrated optical frequency Kerr micro-combs combined with passive micro-ring resonator filters. Swapnajit Chakravarty et al. reviews the existing integration strategies of III–V materials and present a route towards hybrid integration of both III–V and ferroelectrics on the same chip. Shuai Yuan et al. review the latest developments in the LNOI platform, covering ultra-high-speed electro-optic modulators, optical frequency combs, opto-electro-mechanical system on a chip, second-harmonic generation in periodically poled LN waveguides, and efficient edge coupling for LNOI. Mengxi Tan et al. review their recent work on fixed and tunable orthogonally polarized optical single sideband (OSSB) generators as well as a dual-channel RF equalizer, based on integrated dual polarization micro-ring resonators. Three reviews are dedicated to the light sources. Jianou Huang et al. review the directly modulated laser (DML) for short-reach applications, elaborating the data rate demands and technical standards of the data centers and 5G fronthaul networks, as well as the technical routes and achievements of recent DMLs. Songtao Liu and Akhilesh Khope review the recent progress of the high-performance lasers and amplifiers on silicon-based on different technology, including ultra-narrow linewidth III–V/Si lasers, fully integrated III–V/Si/Si₃N₄ lasers, high-channel-count mode-locked quantum dot (QD) lasers, and high gain QD amplifiers. Chanchan Luo et al. review the technologies to the state-of-the-art progress of waveguide-based external cavity narrow linewidth semiconductors. Additionally, three research articles are contributed to cover the areas of integrated light sources, micro-ring-based signal generation, and high-frequency characterization techniques. Lianping Hou et al. report a low-cost manufacturing approach for fabricating monolithic multi-wavelength sources for dense wavelength division multiplexing (DWDM) systems. Yuhua Li et al. report a silicon-nanocrystal embedded high-index doped silica micro-ring resonator to increase its nonlinearity. Mengke Wang et al. report a self-referenced and ultra-wideband high-frequency characterization of a high-speed MZM and PD in an optical link based on low-speed photonic sampling.



We sincerely hope this special issue could provide a valuable overview and reference for the readers. We would like to thank all the authors for their outstanding contributions to this special issue. We are also grateful to the editorial and production staff of Journal of Semiconductors for their assistance.