Chao Xiang realized the heterogeneous integration of laser- soliton optical frequency combs on a single chip for the first time, which also the most superior performance of integrated low-noise lasers on a chip.
Chao Xiang focused on developing multilayer heterogeneous integration technologies during his Ph.D. study and Postdoc work to integrate materials that have disparate optical properties on a common silicon substrate using wafer bonding techniques for novel, high-performance photonic and optoelectronic devices. One direct result is to use multiple wafer bonding steps to provide high-performance III-V-based laser sources for ultra-low-loss silicon nitride platforms for the first time.
Conventionally, silicon nitride is considered a superior passive photonic platform that could provide groundbreaking technologies (e.g., soliton microcombs) for applications including metrology, communications, and sensing, but cannot be integrated with lasers, modulators, detectors that limits its application scenarios. This novel multilayer heterogeneous integration technology Xiang developed ended this history.
On the other hand, the laser noise of semiconductor lasers is now approaching or exceeding that of expensive state-of-the-art fiber lasers, thanks to the integration with ultra-low-loss silicon nitride-based cavities.
Through this demonstrated technology, Xiang enabled the first single-chip laser soliton microcomb wafer, which avoids expensive high-power lasers, amplifiers, and optical alignment packaging in soliton microcomb generation and control. This paves the way for low-cost, high-volume production of laser soliton microcombs to be used with practical values in datacenter interconnects, microwave photonics, and related fields.
The multilayer heterogeneous integration technology Xiang developed focuses on breaking the limitations of material systems and would be applied to more material groups. The target is to build complex, multi-functional, highly-integrated, and high-performance integrated photonic-electronic circuits to be used as a unified platform for ubiquitous applications.
