Generation and Applications of an Ultrafine and Ultraflat Electro-Optic Frequency Comb

Optical frequency combs (OFCs) provide a powerful tool for high-resolution spectroscopic measurements. However, their practical implementation is often hindered by large mode spacing and insufficient individual comb tooth power. To overcome these limitations, we present an ultrafine and ultraflat electro-optic frequency comb (EOFC) based on optimized multi-frequency phase modulation. The proposed EOFC comprises 6561 comb teeth with a 1 MHz spacing, exhibiting a power uniformity over 1.4 dB and power stability within 0.5 dB. The system delivers a total output power of 10 W, with each individual comb tooth exceeding 1 mW, demonstrating superior performance in both flatness and individual comb tooth power. This EOFC achieves the highest flatness, individual-tooth power, and narrowest spacing among frequency comb lasers with thousands of teeth. Furthermore, we validate its capability in high-precision real-time absorption spectroscopy by successfully resolving the fine absorption spectrum of helium (He), demonstrating its potential for advanced spectroscopic and sensing applications.