Hannover 2016 – wissenschaftliches Programm

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MO: Fachverband Molekülphysik

MO 8: Experimental Techniques

MO 8.4: Vortrag

Dienstag, 1. März 2016, 11:45–12:00, f142

Enhancement of CARS signal via tailored probing in spectral focusing — •Lukas Brückner, Tiago Buckup, and Marcus Motzkus — Physikalisch-chemisches Institut, Universität Heidelberg, Germany

In the framework of coherent anti-Stokes Raman scattering (CARS), applying the same chirp to pump and Stokes frequencies allows for focusing most of the spectral amplitude into one specific Raman line. Here, a novel approach for spectral focusing using a broadband oscillator in combination with a pulse shaper controlling phase and amplitude is presented. The flexibility of the single-beam setup allows for variable and fast adjustment of the instantaneous bandwidth to the linewidths of different Raman levels throughout the spectrum. Furthermore, by identifying the frequencies acting as pump, Stokes and probe, the high degree of control can be exploited in order to specifically and independently tailor the spectral region acting only as probe to achieve the highest signal intensity. While maintaining optimal excitation of the vibrational coherence, a significant increase in comparison with usual spectral focusing schemes is readily obtained without even nearly maxing out the applicable power of the probe before photo-damage can be observed. The signal improvement and contrast is demonstrated by imaging the lipid distribution of human skin tissue.

[1] L. Brückner, T. Buckup and M. Motzkus, Opt. Lett. 22, 5204-5207 (2015)