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<p>Here, we demonstrate a transient absorption spectroscopy (TAS) that enables high-sensitivity measurements by synchronizing low-speed spectroscopic acquisition with laser excitation at high repetition rates. This approach utilizes pulse accumulation, where the detector directly integrates the multiple probe pulses to enhance the signal-to-noise ratio (SNR). We systematically investigate the noise characteristics of TAS signals and find the additional factors that deviate from the Poisson distribution in the SNR improvement with pulse accumulation. According to a quantitative noise model, the deviation mainly originates from signal-dependent fixed-pattern noise (FPN) inherent in the multichannel detector, which primarily influences the spectral data rather than the kinetic traces. By using a FAPbI<sub>3</sub> perovskite thin film as a testbed sample, we demonstrate that the instrumental configuration can reliably resolve transient absorption (TA) signals as low as 1.9 × 10⁻³ ΔA under sub-nanojoule excitation. This work validates the on-chip accumulation strategy as a robust and accessible alternative for achieving high-sensitivity ultrafast measurements, particularly for optically dense samples requiring significant signal averaging.</p>

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Toward Poisson-like scaling with synchronized-clock transient absorption spectroscopy via high-repetition rate pulse accumulation

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年12月29日

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  • Myungsam Jen,
  • Jong Min Lim

摘要

Here, we demonstrate a transient absorption spectroscopy (TAS) that enables high-sensitivity measurements by synchronizing low-speed spectroscopic acquisition with laser excitation at high repetition rates. This approach utilizes pulse accumulation, where the detector directly integrates the multiple probe pulses to enhance the signal-to-noise ratio (SNR). We systematically investigate the noise characteristics of TAS signals and find the additional factors that deviate from the Poisson distribution in the SNR improvement with pulse accumulation. According to a quantitative noise model, the deviation mainly originates from signal-dependent fixed-pattern noise (FPN) inherent in the multichannel detector, which primarily influences the spectral data rather than the kinetic traces. By using a FAPbI3 perovskite thin film as a testbed sample, we demonstrate that the instrumental configuration can reliably resolve transient absorption (TA) signals as low as 1.9 × 10⁻³ ΔA under sub-nanojoule excitation. This work validates the on-chip accumulation strategy as a robust and accessible alternative for achieving high-sensitivity ultrafast measurements, particularly for optically dense samples requiring significant signal averaging.