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arXiv · 2505.02940

Entangled-photon time- and frequency-resolved optical spectroscopy

Raul Alvarez-Mendoza·Lorenzo Uboldi·Ashley Lyons·Richard Cogdell·Giulio Cerullo·Daniele Faccio
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Abstract

Classical time-resolved optical spectroscopy experiments are performed using sequences of ultrashort light pulses, with photon fluxes incident on the sample which are many orders of magnitude higher than real-world conditions corresponding to sunlight illumination. Here we overcome this paradigm by exploiting quantum correlations to perform time-resolved spectroscopy with entangled photons. Starting from spontaneous parametric down-conversion driven by a continuous-wave laser, we exploit the temporal entanglement between randomly generated signal/idler pairs to obtain temporal resolution, and their spectral entanglement to select the excitation frequency. We also add spectral resolution in detection, using a Fourier transform approach which employs a common-path interferometer. We demonstrate the potential of our entangled-photon streak camera by resolving, at the single-photon level, excitation energy transfer cascades from LH2 to LH1 in the photosynthetic membrane and disentangling the lifetimes of two dyes in a mixture. We show that time-resolved spectroscopy with quantum light can be performed without compromising measurement time, recording a fluorescence time trace in less than a minute even for samples with low quantum yield, which can be reduced to sub-second times with acceptable signal-to-noise ratio. Our results provide a new approach to ultrafast optical spectroscopy, where experiments are performed under conditions comparable to real-world sunlight illumination.

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Raul Alvarez-Mendoza, Lorenzo Uboldi, Ashley Lyons, Richard Cogdell, Giulio Cerullo, Daniele Faccio. 2025-05-05. Entangled-photon time- and frequency-resolved optical spectroscopy. https://arxiv.org/abs/2505.02940

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