With the gradual waning of the Moore’s Law, the sustainable development of the semiconductor industry faces a significant challenges and opportunities. Integrating photonics into microelectronics is expected to provide new momentum for the sustainable development of the semiconductor industry. Electronics-photonics convergence combines the advantages of electronics in areas such as computation and storage with the advantages of photonics in areas such as transmission capacity and interference resistance. This convergence is expected to shape the shared future of both microelectronics and photonics.

A light source is a prerequisite for implementing any electronic-photonic system. Traditional light sources are typically independently fabricated without special optimization for electronics-photonics convergence. As integration levels and performance metrics of electronic-photonic systems continue to rise, light source integration has become a bottleneck problem limiting the practical implementation of many applications. This paper reviews the development status of integrated light source technologies geared towards various applications in the context of electronics-photonics convergence, elucidates the associated challenges and their solutions, and further summarizes and anticipates future development directions of integrated light source technologies.

Optical communication, as the most significant application field for integrated light sources, attracts most research interest and devotion. Here in this work, development in mainstream semiconductor lasers is included. The summary of integrated laser sources and corresponding modulation formats are listed in Table 1. Several important progresses are included: VCSEL transmission rates have advanced significantly. In 2024, Intel reached 64 Gb/s and 256 Gb/s in a four-channel setup. DFB lasers have also progressed in modulation rates. In 2021, Yamaoka achieved a 108 GHz bandwidth and a 256 Gb/s PAM-4 modulation rate. High transmission rates have also been achieved through external modulation techniques. Other lasers such as microring lasers, micro-LEDs, and semiconductor mode-locked lasers have also made progress. For example, in 2018, Liang Di demonstrated a mixed-integrated microring laser with a modulation rate of 14 Gb/s and a modulation bandwidth of 14.5 GHz (Fig. 2).

In other application fields, such as frequency modulation continuous wave LiDAR and optical coherence tomography, significant efforts have been devoted to improving on-chip laser source performances. In 2024, Sanghonn Chin achieved an on-chip ECL with lateral resolution of 9 μm. A Ga/Sb gain chip is integrated with SOI PIC chip as laser source for FMCW LiDAR, tunability is based on the vernier effect of double micro-ring resonators. Broad band SLED and tunable ECL are also studied for OCT purposes, they aimed to achieve larger tunable range and tuning speed.

Common challenges faced by on-chip lasers and corresponding solutions are also discussed. Narrow linewidth is an important factor for coherent communication laser sources as it directly affects signal quality. Tunable external cavity lasers with waveguide structures exhibit promising linewidth properties, but coupling issues remain a challenge. To address this, solutions such as anti-reflection coatings and evanescent wave coupling have been proposed to improve coupling efficiency, thereby enhancing performance in optical communication applications.

Efficient coupling of light from on-chip lasers to waveguides is another key challenge, particularly due to mode spot mismatches and thermal effects. Techniques like grating couplers, which use diffraction, and adiabatic couplers, which rely on gradual changes in waveguide geometry, have been developed to minimize losses. Additionally, end-face direct coupling and light lead coupling, which involve the laser directly attaching to the waveguide or using guiding structures, respectively, have shown promise in ensuring efficient light transfer.

Also, multi-wavelength lasers often have lower and non-uniform power compared to single-wavelength lasers. For mode-locked lasers, on-chip amplifiers can boost power. For Kerr-comb lasers, using pulse lasers for pumping improves energy conversion efficiency, resulting in a more powerful multi-wavelength source suitable for various applications.

Lastly, To achieve high integration level between laser sources and on-chip photonics devices, direct heterogenous epitaxial growth is prompted as an effective method, where the III?V materials such as InP or InAs can be directly deposited on silicon substrates. Although there exist some challenges like lattice, polarity, and thermal mismatches. Buffer layers can reduce lattice mismatch, while specific substrate structures can minimize polarity and thermal mismatch effects. Optimizing growth techniques, such as temperature and pressure, can further enhance laser quality. These solutions are essential for developing integrated light sources for semiconductor devices.

The review includes remarkable progress on silicon-based growth of III?V quantum dot lasers. In 2011, Wang et al. achieved pulsed lasing of InAs quantum dot lasers on a slanted Si substrate at a 1.3 μm wavelength. In 2015, Chen et al. achieved room-temperature continuous lasing of InAs quantum dot FP lasers on a slanted Si substrate with improved performance. Between 2018 and 2019, Jung and Shang et al. developed high-performance quantum dot lasers with enhanced characteristics. In 2018, Wei et al. addressed challenges related to lattice, polarity, and thermal mismatches, achieving a Si-based InAs quantum dot FP laser with good performance. In 2023, Wei et al. demonstrated the monolithic integration of on-chip III?V lasers and Si waveguides, achieving direct coupling with good performance (Fig. 8).

Emerging applications demand integrated light sources. While considerable progress has been made, further innovations in materials, processes, and techniques are required for practical use. These advancements will accelerate the adoption of electronics-photonics integrated chips and may lead to a new industrial cycle akin to Moore’s Law.

In summary, although significant advancements have been achieved, continued efforts are necessary for the full realization and widespread use of integrated light sources, potentially ushering in a new era of semiconductor industry growth.