High-coherence ultra-broadband bidirectional dual-comb fiber laser

Abstract

Dual-comb spectroscopy has emerged as an attractive spectroscopic tool for high-speed, high-resolution, and high-sensitivity broadband spectroscopy. It exhibits certain advantages when compared to the conventional Fourier-transform spectroscopy. However, the high cost of the conventional system, which is based on two mode-locked lasers and a complex servo system with a common single-frequency laser, limits the applicability of the dual-comb spectroscopy system. In this study, we overcame this problem with a bidirectional dual-comb fiber laser that generates two high-coherence ultra-broadband frequency combs with slightly different repetition rates (f rep). The two direct outputs from the single-laser cavity displayed broad spectra of > 50 nm; moreover, an excessively small difference in the repetition rate (< 1.5 Hz) was achieved with high relative stability, owing to passive common-mode noise cancellation. With this slight difference in the repetition rate, the applicable optical spectral bandwidth in dual-comb spectroscopy could attain ~479 THz (~3,888 nm). In addition, we successfully generated high-coherence ultra-broadband frequency combs via nonlinear spectral broadening and detected high signal-to-noise-ratio carrier-envelope offset frequency (f CEO) beat signals using the self-referencing technique. We also demonstrated the high relative stability between the two f CEO beat signals and tunability. To our knowledge, this is the first demonstration of f CEO detection and frequency measurement using a self-referencing technique for a dual-comb fiber laser. The developed high-coherence ultra-broadband dual-comb fiber laser with capability of f CEO detection is likely to be a highly effective tool in practical, high-sensitivity, ultra-broadband applications.

All-polarization-maintaining, polarization-multiplexed, dual-comb fiber laser with a nonlinear amplifying loop mirror

“…In this study, we develop an all-PM, polarization-multiplexed, dual-comb fiber laser with NALM, which emits two frequency combs with a small Δfrep from a single all-PM fiber laser cavity. Compared with our recent work for a bidirectional dual-comb fiber laser [23], the advantage of the all-PM dual-comb fiber laser is robustness for practical environmental instability. The experimental setup is discussed in the following section.…”

“…Recently, a dual-comb laser, which emits two optical frequency combs from a single-laser cavity with a small ∆frep value, has attracted attention owing to its common-mode noise cancellation and passive mutual coherence. Studies have been performed on dual-wavelength [20], polarization-multiplexed [21], and bidirectional [22,23] mode-locked Er-fiber lasers, an Er-doped ZBLAN chip laser [24], a Kerr-lens mode-locked bidirectional Ti:sapphire laser [25], a mode-locked integrated external-cavity surface emitting laser (MIXSEL) [26], and a microresonator [27]. Although these lasers have excellent capabilities, a dual-comb laser with high practicability and robustness is essential to extend the application of the DCS technique beyond research laboratories.…”

Combination of Adaptive Sampling Terahertz Dual-Comb Spectroscopy with a Free-Running Single-Cavity Dual-Comb Fiber Laser

“…THz-DCS systems and optical DCS systems. Recently, advances in the endeavor to generate a pair of frequency combs from a free-running single-cavity laser [22][23][24][25][26][27][28][29][30][31] have shown great potential towards this goal. By propagating through the same cavity, the dual optical combs experience almost the same disturbances, and the commonmode fluctuations thereby prevent the decline of the mutual coherence between the dual combs.…”

1 GHz dual-comb spectrometer for fast and broadband measurements

“…Broadband dual-comb spectroscopy [11][12][13] can thus be achieved in two ways: reducing ∆f r , or increasing f r . The first approach has been pursued in dual-comb systems with high-mutual coherence [14][15][16][17][18][19] with ∆f r as low as a few Hertz. Further reduction of ∆f r would require even higher-mutual coherence between the dualcomb lasers, which is challenging due to the inherent noise of laser oscillators 20 .…”