Ultrafast spectroscopy of non resonant third-order nonlinearities

  • Research
Published on February 3, 2023 – Updated on February 3, 2023
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The article "Nonlinear chirped interferometry for frequency-shift measurement and χ(3) spectroscopy", published in APL Photonics, has been highlighted

The framework of this study is ultrafast spectroscopy of non resonant third-order nonlinearities (χ(3)). Optical Kerr effect (OKE) spectroscopy gathers numerous experimental methods suitable to measure the χ(3) tensor, with their respective advantages and drawbacks. However, most of them require noise reduction to isolate the contribution of weak nonlinearities.
In this manuscript, we propose an original and elegant method for time-resolved χ(3) spectroscopy, which, although interferometric, is immune to phase fluctuations. The method consists in monitoring the variation of the optical group delay, rather than the phase, of a transmitted probe under the effect of a strong pump pulse, via spectral interferometry between the probe and a chirped local oscillator sampled upstream. We demonstrate both theoretically and experimentally that a complex interplay between nonlinear temporal and spectral reshaping gives rise to a transient change of the probe optical group delay.
As a result, the detection is immune to phase fluctuations and provides additional means to enhance on-demand the sensitivity.

Set-up
Set-up


Optical setup. The laser source (Pharos SP, Light Conversion) is split into three beams (pump, probe, and reference). The observable is the interference spectrum between the probe beam and the chirped reference beam as a function of pump-probe delay. The top graph features the AC peak of the Fourier Transform of the spectrogram. The spectral shifts undergone by the probe pulse on a femtosecond time scale are encoded as a change of relative group delay, measured with a high signal to noise ratio (lower graph).

Reference
Nonlinear chirped interferometry for frequency-shift measurement and χ(3) spectroscopy

E. Neradovskaia, B. Maingot, G. Chériaux, C. Claudet, N. Forget, A. Jullien

APL Photonics 7, 116103 (2022); https://doi.org/10.1063/5.0109265

Contact: Aurelie.Jullien@inphyni.cnrs.fr