Broadband electro-optic frequency comb with electrical and optical dual-resonance enhancement in lithium niobate

The electro-optic frequency comb (EOFC) has significant applications in fields such as spectroscopy, optical communications, high-precision measurements, and quantum technology, offering a flexible free spectral range (FSR) and stable spectral characteristics. Practical implementation of the EOFC requires high power and flattened comb teeth, which depend highly on optical losses and microwave modulation strength. In this work, we propose the integration of short-circuit electrodes to form a microwave resonant cavity, thereby enhancing the microwave modulation strength. The maximum modulation enhancement factor was measured to be 2.77 at approximately 20 GHz. Furthermore, the spectral bandwidth of the electrical-resonator-enhanced electro-optic frequency comb (ERE-EOFC) generator was 71 nm, 1.7 times broader than that of a generator without resonant electrodes.