Amplified wavelength–time transformation for real-time spectroscopy

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Real-time spectroscopy provides invaluable information about the evolution of dynamical processes, especially non-repetitive phenomena. Unfortunately, the continuous acquisition of rapidly varying spectra represents an extremely difficult challenge. One method, wavelength–time mapping, chirps the spectrum so that it can be measured using a single-shot oscilloscope1,2,3,4. Here, we demonstrate a method that overcomes a fundamental problem that has previously plagued wavelength–time spectroscopy: fine spectral resolution requires large dispersion, which is accompanied by extreme optical loss. The present technique uses an optically amplified wavelength–time transformation to beat the dispersion-loss trade-off and facilitate high-resolution, broadband, real-time applications. We show that this distributed amplification process can even be pumped by broadband noise, generating a wide gain bandwidth using a single pump source. We apply these techniques to demonstrate real-time stimulated Raman spectroscopy. Amplified wavelength–time Raman spectroscopy creates new opportunities for the study of chemical and physical dynamics in real time.

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Figure 1: Schematic of the CWEETS set-up used to measure the SRS spectrum in a silicon waveguide.
Figure 2: Single-shot SRS spectra of silicon measured with CWEETS.
Figure 3: Sequence of silicon Raman movie frames acquired in a continuous measurement using an unstable supercontinuum probe.
Figure 4: Demonstration of the amplified wavelength–time transformation in spectroscopy.


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We thank P. Koonath for helpful discussions.

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Correspondence to D. R. Solli.

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Solli, D., Chou, J. & Jalali, B. Amplified wavelength–time transformation for real-time spectroscopy. Nature Photon 2, 48–51 (2008) doi:10.1038/nphoton.2007.253

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