High-efficiency and broadband on-chip electro-optic frequency comb generators

Developments in integrated photonics have led to stable, compact and broadband comb generators that support a wide range of applications including communications(1), ranging(2), spectroscopy(3), frequency metrology(4), optical computing(5,6) and quantum information(7,8). Broadband optical frequency combs can be generated in electro-optical cavities, where light passes through a phase modulator multiple times while circulating in an optical resonator(9-12). However, broadband electro-optic frequency combs are currently limited by low conversion efficiencies. Here we demonstrate an integrated electro-optic frequency comb with a conversion efficiency of 30% and an optical span of 132 nm, based on a coupled-resonator platform on thin-film lithium niobate(13). We further show that, enabled by the high efficiency, the device acts as an on-chip femtosecond pulse source (336 fs pulse duration), which is important for applications in nonlinear optics, sensing and computing. As an example, in the ultrafast and high-power regime, we demonstrate a frequency comb with simultaneous electro-optic and third-order nonlinearity effects. Our device paves the way for practical optical frequency comb generators and provides a platform to investigate new regimes of optical physics that simultaneously involve multiple nonlinearities.

Automated summary

Developments in integrated photonics have led to the emergence of stable, compact and broadband comb generators. The integrated electro-optic frequency comb presented in this research demonstrates a high conversion efficiency and a wide optical span, and can serve as an on-chip femtosecond pulse source. It also enables the simultaneous effects of electro-optic and third-order nonlinearity, paving the way for practical optical frequency comb generators and exploring new regimes of optical physics.