Speaker
Description
Molecular specific imaging on surfaces or interfaces is crucial for understanding the structures and dynamics of many spatially inhomogeneous systems in various fields such as biology, heterogeneous catalysis, etc. A key role among the various microscopy techniques plays vibrational sum frequency generation (VSFG) microscopy due to its intrinsic sensitivity to broken centro-symmetry and its ability to detect characteristic molecular vibrations with a lateral resolution in the sub µm range. This allows for combining fast, label-free high contrast imaging with the capability to analyze the chemical composition of the observed structures.
However, it can be argued that SFG microscopes have not reached their full potential, mainly for technical reasons. First, the SFG technique typically requires that the pump beams irradiate the sample at a non-zero angle with respect to the surface normal, which makes distortion free imaging very challenging. Secondly, the implementation of an interferometric technique that yields phase resolution in a wide-field SFG micros¬cope has proven difficult. Finally, due to the small signal intensities, nonlinear wide-field microscopes typically suffer from a low signal-to-noise ratio that leads to relatively long acquisition times.
Here we present a completely new design for such a nonlinear SFG microscope that addresses all three challenges. It is based on a full collinear beam geometry and contains an innovative imaging technique that allows for the straightforward acquisition of distortion-free SFG images. The optical design of this imaging approach includes a pixel-to-pixel balanced detection scheme that we have recently developed. With this balanced wide-filed imaging technique, we were able to increase the signal-to-noise ratio by a factor of ~10, which strongly reduces the required acquisition time. The spectral resolution is obtained by performing interferometric time domain scans with the involved femtosecond laser pulses. That way phase resolved nonlinear vibrational spectra are obtained for each point on the image. Along with the new design, we present the first nonlinear images that demonstrate the performance of our microscope.
| Abstract Number (department-wise) | PC 17 |
|---|---|
| Department | PC (Wolf) |
