Enhanced dual electro-optic comb spectroscopy for rapid metastable helium detection

Dual-comb spectroscopy is a powerful tool for precision metrology, offering advantages such as wide spectral range and high-speed spectroscopic acquisition. In this work, we extend dual electro-optic comb (EO-comb) technology to the field of plasma diagnostics, allowing for the observation of various atomic absorption lines, which broadens its applicability across different plasma species. By setting large repetition rates difference between two EO combs, we achieve a sub-microsecond density and temperature measurement rate of metastable helium. With this high measurement rate, we observed the discharge, rise, steady-state, and quenching phases of plasma. Experimental results align closely with theoretical predictions, validating the method's accuracy. Noise analysis indicates that further improvements in density resolution can be attained through hardware optimizations. The improved signal-to-noise ratio (SNR) enables simultaneous, high-precision measurements of plasma density, temperature, and velocity, which is crucial for analyzing rapid plasma processes. More atomic transitions could be accessed by incorporating nonlinear fibers, which facilitates a comprehensive understanding of the plasma initiation and evolution processes.