Nonlinear Chemical Imaging
Nonlinear Chemical Imaging
Research Group Alexander Fellows
Research Group Alexander Fellows

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Welcome to the Nonlinear Chemical Imaging Group

Our group focusses on characterising the heterogeneity in chemical structure at interfaces using ultrafast nonlinear microscopy techniques, with the aim to connect these lateral microscopic variations to the macroscopic physical properties.

    Latest News:

    Group Trip to the Xmas Market
    Dec 2025
    To celebrate a successful year, the group enjoyed a nice Glühwein at the Christmas markets in Berlin. Merry Xmas everyone and happy new year!
    New Group Member: Tao Yang
    Jul 2025
    We would like to welcome Dr Tao Yang who has just joined as a postdoc in our group. He will be working on the development of a phase-resolved SHG microscope and its application to 2D excitonic materials and thin molecular films.
    New Archive Paper: Multipole Contributions in SFG
    May 2025
    We have a new archive paper led by the group of Roland Netz wherein we disentangle the electric and magnetic multipole contributions to the SFG spectra from the air-water interface. This work shows the importance of including electric quadrupole and magnetic dipole contributions for the correct assignment of the spectral line-shapes. You can read more here.
    New Archive Paper: Molecular Twisting in Interfacial Water
    May 2025
    We have a new archive paper wherein we revise the current understanding of the molecular structure at the air-water interface by demonstrating that the molecular twist angle is just as important as the tilt angle in defining the preferential molecular orientation. This is achieved by applying depth-resolved SFG-DFG spectroscopy in combination with MD simulations performed by the group of Roland Netz to probe the H-O-H bending mode and characterise the layer-dependent structural motifs at the interface. You can read more here.
    Our Work Presented at ECONOS 2025
    Apr 2025
    Our recent collaborative work on using SFG microscopy to image CVD-grown hexagonal Boron Nitride (hBN) monolayers was presented at ECONOS 2025 in Meudon, France. It was great to see a wide range of talks and posters and have thrilling discussions with our colleagues in the nonlinear optical spectroscopy community from all across Europe.