Coherently averaged dual-comb spectroscopy with a low-noise and high-power free-running gigahertz dual-comb laser

Abstract

We present a new type of dual optical frequency comb source capable of scaling applications to high measurement speeds while combining high average power, ultra-low noise operation, and a compact setup. Our approach is based on a diode-pumped solid-state laser cavity which includes an intracavity biprism operated at Brewster angle to generate two spatially-separated modes with highly correlated properties. The 15-cm-long cavity uses an Yb:CALGO crystal and a semiconductor saturable absorber mirror as an end mirror to generate more than 3 W average power per comb, below 80 fs pulse duration, a repetition rate of 1.03 GHz, and a continuously tunable repetition rate difference up to 27 kHz. We carefully investigate the coherence properties of the dual-comb by a series of heterodyne measurements, revealing several important features: (1) ultra-low jitter on the uncorrelated part of the timing noise; (2) the radio frequency comb lines of the interferograms are fully resolved in free-running operation; (3) we validate that through a simple measurement of the interferograms we can determine the fluctuations of the phase of all the radio frequency comb lines; (4) this phase information is used in a post-processing routine to perform coherently averaged dual-comb spectroscopy of acetylene (C2H2) over long timescales. Our results represent a powerful and general approach to dual-comb applications by combining low noise and high power operation directly from a highly compact laser oscillator.

Study of Time-Resolved Dynamics in Turbid Medium Using a Single-Cavity Dual-Comb Laser

“…Usually, those errors are easier to correct for a high repetition difference as the higher repetition difference corresponds to a higher tracking speed. In this work, by using a mechanically robust prototype implementation of spatial multiplexing, we are able to satisfy the condition for coherent averaging at <1 kHz Δ f rep . To compensate for the relative timing jitter and relative phase shift in the measurement arm, we built a reference arm to monitor those parameters and then correct them for the measurement arm.…”

“…In recent work, we have shown that these dual combs are compatible with coherent averaging and can support repetition rates up to a gigahertz or more. 38 Leveraging these characteristics, we demonstrate a dualcomb DWS system that simultaneously measures static properties (μ s ′ and μ a ) and depth-dependent dynamics of a homogeneous turbid medium. By combining an auxiliary arm, we correct the relative timing jitter and relative carrierenvelope phase (CEP) shift for the measurement arm in postprocessing.…”

“…In this work, by using a mechanically robust prototype implementation of spatial multiplexing, we are able to satisfy the condition for coherent averaging at <1 kHz Δf rep . 38 To compensate for the relative timing jitter and relative phase shift in the measurement arm, we built a reference arm to monitor those parameters and then correct them for the measurement arm. After this, the path-dependent intensity autocorrelation is calculated by…”

“…Owing to the high SNR in the reference arm, the relative timing jitter and the relative CEP shift can easily be extracted and compensated by using the method 38 described earlier.…”

“…This approach enables low-noise dual-comb generation while benefiting from the high power and low fundamental noise properties of diode-pumped solid-state lasers. In recent work, we have shown that these dual combs are compatible with coherent averaging and can support repetition rates up to a gigahertz or more …”