Broadband and high-resolution electro-optic dual-comb interferometer with frequency agility

We propose a broadband and high-resolution dual-comb interferometer (DCI) realized with dense electro-optic frequency combs (EOFCs), which are generated with two-stage electro-optic modulation and nonlinear fiber spectral broadening. The broadband coarse comb is generated in the first-stage modulation and the space between neighboring combs is filled with a dense electrical comb in the second-stage modulation. The spectral resolution of the DCI can be flexibly changed from 10 MHz to 1 GHz easily as required, and electro-optic DCIs with 10-MHz, 100-MHz, and 1-GHz frequency resolutions are experimentally realized. Meanwhile, DCI working in the quasi-integer-ratio mode is easily implemented in this system for the increased refresh rate and improved figure of merit especially for high resolution. As a demonstration, 150000 comb lines with 10 MHz frequency interval are resolved in the experiment.