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 are severely restricted by the mechanical delay line (DLL). 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 polarization-multiplexing dual-comb fiber laser 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/K and a control accuracy of 0.44 Hz, denoting a significant advance in operating Hz-scale differential comb lines. This design offers a robust platform for extending non-ambiguous distance in dead-zone-free dual-comb ranging and eliminating aliasing in spectroscopy.