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arXiv:2408.03412

Collinear Optical Two-Dimensional Coherent Spectroscopy with Fluorescence Detection at 5 kHz Repetition Rate

Stephen Revesz, Rustam Gatamov, Adolfo Misiara, Li, Hebin

Published Aug 6, 2024• 0 citations
arXivHTMLPDF

Abstract

Optical two-dimensional coherent spectroscopy (2DCS) is a powerful ultrafast spectroscopic technique that can greatly benefit from the unique features of a femtosecond laser operating at a kHz repetition rate. However, isolating specific nonlinear signal in the collinear geometry, especially with a kHz laser, presents challenges. We present an experimental implementation of optical 2DCS in a collinear geometry using a femtosecond laser operating at a 5 KHz repetition rate. The desired nonlinear signal is selectively extracted in the frequency domain by lock-in detection. Both pump-probe and optical 2DCS experiments were conducted on a rubidium vapor. The signal-to-noise ratio of pump-probe and 2DCS spectra was characterised under various experimental parameters. The study highlights the importance of the lock-in reference frequency in overcoming the limitations imposed by low repetition rates, thereby paving the way for the application of collinear optical 2DCS in material systems requiring kHz femtosecond lasers.

DOI
10.48550/arxiv.2408.03412

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Our recent work on optical two-dimensional coherent spectroscopy (2DCS) of semiconductor materials is reviewed. We present and compare two approaches that are appropriate for the study of semiconductor nanostructures. The first one is based on a non-collinear geometry, where the Four-Wave-Mixing (FWM) signal is detected in the form of a radiated optical field. This approach works for samples with translational symmetry, such as Quantum Wells (QWs), or large and dense ensembles of Quantum Dots (QDs). The second method is based on a collinear geometry, where the FWM is detected in the form of a photocurrent. This second approach enables 2DCS of samples where translational symmetry is broken, such as single QDs, nanowires, or nanotubes, and small ensembles thereof. For each method, we provide an example of experimental results obtained on semiconductor QWs. In particular, it is shown how 2DCS can reveal coherent excitonic coupling between adjacent QWs.
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