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arXiv · 2608.19967

Oscillator-driven broadband femtosecond transient microspectroscopy with supercontinuum probes generated in a photonic crystal fiber

Rikuto Fukuda·Kyosuke Kishihata·Ryo Man-nami·Hiroaki Atsumi·Borja Cirera·DaeGwi Kim·Masahiro Shibuta
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Abstract

We present an oscillator-driven femtosecond transient microspectroscopy system based on supercontinuum generation in a photonic crystal fiber (PCF). The system operates at 80 MHz without pulse amplification, enabling high-sensitivity measurements with a detection sensitivity better than $10^{-4}$ while using low pulse energies suitable for microspectroscopy. Optimization of the PCF length ($\leq 50$ mm) suppresses dispersion-induced chirp, achieving nearly uniform temporal resolution below 100 fs across 450-900 nm. The high-repetition-rate operation allows rapid spectral acquisition and efficient noise reduction. The developed system provides micrometer-scale spatial resolution and supports both reflection and transmission configurations. Ultrafast carrier dynamics in multilayer and monolayer MoS$_2$ are successfully resolved, including spatially dependent relaxation within a single monolayer flake. These results demonstrate a versatile platform for probing local ultrafast dynamics in low-dimensional materials.

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Rikuto Fukuda, Kyosuke Kishihata, Ryo Man-nami, Hiroaki Atsumi, Borja Cirera, DaeGwi Kim, Masahiro Shibuta. 2026-08-20. Oscillator-driven broadband femtosecond transient microspectroscopy with supercontinuum probes generated in a photonic crystal fiber. https://arxiv.org/abs/2608.19967

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