Development of non-linear vibrational microscopy
Fluorescence microscopy is an extremely useful technique. Its main limitations are the necessity to label samples with fluorophores and the bleaching of these fluorophores. Therefore, non-linear optical microscopy techniques which generate contrast without the use of labels have lately met a lot of interest. Our group has pioneered the development of non-linear Raman microscopy which is now used by many groups worldwide and became commercially available. The special advantage of this approach is the generation of contrast with molecular specificity based on the vibrational spectra of the sample molecules. The two main approaches of this type are coherent anti-Stokes Raman scattering (CARS) microscopy and stimulated Raman scattering (SRS) microscopy. We further develop non-linear vibrational microscopy by implementing new excitation and detection schemes as well as by using new contrast mechanisms.
Application of non-linear vibrational microscopy
We apply non-linear vibrational microscopy in a variety of different samples, for which fluorescence microscopy is difficult. As an example, we have performed quantitative microscopy to study the growth of lipid droplets in human adipocytes. Since this is a slow process, it could not be followed by fluorescence microscopy. Using CARS microscopy, it was possible to continuously image living cells on the microscope for one week. This allowed us to unravel the growth mechanism of lipid droplets. In a similar manner, we use non-linear vibrational microscopy to study mixing and chemical reactions in microfluidic devices.
C. Riek, C. Kocher, P. Zirak, C. Kölbl, P. Fimpel, A. Leitenstorfer, A. Zumbusch*, D. Brida "Stimulated Raman Scattering Microscopy By Nyquist modulation of a two-branch ultrafast fiber source", Opt. Lett. , 41 (2016) 3731-3734.
R. Selm, G. Krauss, A. Leitenstorfer, A. Zumbusch, "Simultaneous second-harmonic generation, third-harmonic generation, and four-wave mixing microscopy with single sub-8 fs laser pulses", Appl. Phys. Lett., 99 (2011) 181124.
A. Zumbusch, G. R. Holtom, X. S. Xie, "Three-dimensional Vibrational Imaging by Coherent Anti-Stokes Raman Scattering" Phys. Rev. Lett. 82(1999) 4142-4145