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arXiv · 2603.24988

Pulse Breathing Dynamics in a Mode-Locked Laser measured via SHG autocorrelation

S. Kannan·S. Padmanaban·X. T. Yan·Y. S. Athreya·K. G. H. Baldwin·S. S. Hodgman·A. G. Truscott
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Abstract

Pulse-to-pulse fluctuations in mode-locked lasers fundamentally limit applications from optical frequency combs to supercontinuum generation. While timing jitter has been extensively characterized, pulse amplitude and width fluctuations remain less accessible experimentally. We present a statistical autocorrelation method that demonstrates pulse breathing dynamics through Fano factor analysis of second-harmonic generation autocorrelation. This reveals a characteristic W-shape in the enhanced Fano profile, a signature of pulse shape dynamics that is invisible to time-averaged fluctuations. Applying this method to two commercially available passively mode-locked oscillators operating at 1030 nm and 1045 nm, with different performance specifications, we measure pulse width fluctuations of 3.2(1)\,fs and 2.86(2)\,fs respectively. The two independent instruments serve as a cross-validation of the technique across different laser platforms. This diagnostic capability opens the door to identifying and suppressing specific breathing mechanisms, paving the way for the design of ultra-stable oscillators required for precision frequency metrology.

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S. Kannan, S. Padmanaban, X. T. Yan, Y. S. Athreya, K. G. H. Baldwin, S. S. Hodgman, A. G. Truscott. 2026-03-26. Pulse Breathing Dynamics in a Mode-Locked Laser measured via SHG autocorrelation. https://doi.org/10.1364/oe.600699

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