Repetition-Rate-Difference Tunable Dual-Comb Fiber Laser Using Bidirectional Lyot filtering

Single cavity dual-comb fiber lasers adopting different multiplexing configurations are benefited from the natures of common-mode noise suppression and superior coherence. Particularly, repetition-rate tunable dual-combs enable non-ambiguous ranging and aliasing-free spectroscopy. However, their sampling rate and spectral resolution is severely restricted by the mechanical delay lines. In a previous work, as rapid as 500 kHz/s tuning rate was realized to address this issue, while the minimum comb frequency difference remained large under the inaccuracy of mechanical DLL. In this work, a dual-comb prototype incorporated with a thermally controlled bidirectional lyot filter is demonstrated with 870-times enhanced tuning precision compared with mechanical schemes. Linear correlation between temperature and repetition-rate-difference of this tuning mechanism is revealed. We achieve a tuning efficiency of 4.4 Hz/°C and a control accuracy of 0.44 Hz/K, denoting a significant advance in operating Hz-scale differential comb lines. This design offers an optimal playground for extending non-ambiguous distance in dead-zone-free dual-comb ranging and eliminating aliasing in spectroscopy.