Optical frequency combs, a Nobel Prize winning technology, provide a powerful tool to enable unprecedented precise measurements of frequency and time and allow for phase coherent link of optical and radio frequencies. Stable and coherent optical frequency combs represent in the time domain a unique type of mode-locked emission of optical pulses. The recent series of breakthroughs in compact optical frequency combs, particularly temporal dissipative Kerr soliton (DKS) microcombs, opened up a new way to generate high-coherence, high-repetition-rate optical frequency combs in compact microresonators, providing a promising technology to replace bulky mode-locked lasers (MLLs) and overcome the fundamental timing jitter limit of electronic analog-to-digital converters (ADCs). However, integrated soliton microcombs with high coherence, high repetition rates, and sufficient power for photonic ADCs remained largely unexplored.
To solve these challenges, the project “Sub-Terahertz Analog-to-Digital Conversion Using Integrated Soliton Microcombs (CompADC)” aimed to demonstrate integrated soliton microcomb sources with repetition rates, high coherence, and high power for the applications in photonic-assisted analog-to-digital conversion (ADC). The innovative approach planned in the CompADC project was to implement a novel photonic integrated circuit that can generate Kerr-based soliton microcombs that can satisfy the requirement for the demonstration of a high-speed microwave photonic ADC with the improved effective number of bits.
CompADC has achieved significant research output, such as fully integrated high-power soliton microcomb sources, and fully integrated single-mode, tunable lasers as optical LOs. Thes results can fundamentally solve the issues of the CompADC system but also, viewed more broadly, novel coherent communication receivers and LiDAR engines. Therefore, the CompADC project provided a venue to discover new technical challenges and has propelled the researcher and the host lab to carry out ground-breaking research results and disruptive solutions.