Reflection image (20µm)

Location of the AFM tip in the laser focus for a TAO™ (Tip Assisted Optics) experiment. The platinum-coated AFM tip is scanned through a laser focus, and the optical signal is shown here. The optical reflection signal was collected through a confocal pinhole and measured using an avalanche photodiode.  The larger scan (20µm * 20µm) shows the interference fringes from the cantilever arm, and the bright reflection from the tip.

For a typical tip-enhanced raman (TERS) experiment, the cantilever  would be scanned through the laser beam to find the position where the tip is at the centre of the focus before changing to the TAO™ sample scanner.

Data courtesy of Dr. C. Heyes and Prof. G.U. Nienhaus, University of Ulm