Tailoring the pulse train of an optical frequency comb with a magnetized atomic medium

Abstract

Selecting specific modes from the complete pulse train of optical frequency comb (OFC) is helpful in ultra-narrow linewidth laser preparation. Here, the mode selector for a commercial OFC based on the magnetized atomic medium is demonstrated in both theory and experiment. Only the comb modes with specific frequencies experience polarization rotation because of the Faraday effect, thus the mode tailoring can be realized by eliminating unchanged OFC modes via polarization selection. The theory study demonstrates the rich tunability of this device, and three specifically chosen operating conditions validate the system’s characteristics. The selected pulse group is distinguished in both optical and frequency spectrum, where spectral differences and bandwidth can be observed accordingly. Further, the selected pulse group and a continuous-wavelength laser stimulate an electromagnetically induced transparency spectrum in the hyperfine Paschen–Back regime to show the pulse group characteristics in detail. The method proposed provides the experimental foundation for producing narrow linewidth lasers from a polychromatic source with tailored results retaining the excellent characteristics of the original.