1 MHz-resolution dual electro-optic frequency comb spectroscopy via multi-frequency small-signal modulation

What is believed to be a new method for generating high-resolution, high-flatness electro-optic frequency combs (EOFCs) based on multi-frequency small-signal modulation with a Single-driver Mach-Zehnder modulator (MZM) biased at its minimum-transmission point. This approach suppresses the optical carrier and even-order sidebands while minimizing the distortion from higher-order odd sidebands. Two EOFCs with repetition rates of 1 MHz and 1.000025 MHz were generated, each containing approximately 8000 comb lines with <1 dB local flatness (40 MHz optical spectral span). These combs were employed in a dual-comb spectroscopy system to measure the molecular absorption near P (10) rotational transition of the H¹³C¹⁴N. In addition, the proposed EOFC was applied to the measurement of stimulated Brillouin scattering (SBS) in a single-mode optical fiber, demonstrating its capability for high-resolution spectral characterization. The experimental results confirmed the effectiveness and versatility of the proposed EOFC scheme for precision spectroscopic applications.