Integrated microcomb system chip using heterogeneous integration

ongoing

Optical frequency combs (OFC) play an essential role in precision, timing and navigation applications. Integrated photonics facilities the development of OFC-based applications towards chip-scale miniature package. Most applications require detecting the radio frequency (RF) signals of a OFC (i.e. repetition rate and carrier-envelope offset frequency). Thus, an important step towards miniaturized complex OFC systems is to integrate the OFC generation with the auxiliaries components required for detecting its RF signals onto the same chip. This project aim to develop an integrated microcomb system chip with accessible RF signals detection using heterogeneously integrated photonic platforms. Silicon nitride (SiN) platforms have shown their superiority in comb generations using microresonators (i.e. microcomb), with octave-spanning spectrum and dispersive wave emissions that enable detection of the carrier-envelope offset frequency via f-2f self-referencing process. Thin-film lithium niobate (TFLN) platforms are advantageous in second-order nonlinear frequency conversions and electro-optics modulations, the former can be applied for the f-2f process, while the latter is widely used for frequency down-converting the high-frequency repetition rate of a microcomb. Therefore, this project will explore heterogeneous integration technique to combine the SiN microcomb generator with TFLN devices for f-2f process and frequency down-conversion on a single chip. Specially, a novel photonic molecule structure will be explored for power-efficient octave-spanning microcomb generation with strong dispersive wave emission. A broadband electro-optics frequency comb will be developed for frequency down-conversion of microcomb repetition rate. Periodically poling of TFLN waveguide will be explored for frequency doubling in f-2f process. Heterogeneous integration will bring together all these components to deliver an integrated microcomb system.