Hybrid System of Atomic Force Microscopy and Optical Spectroscopy: Photo-induced Force Microscopy

Photo-induced force microscopy(PiFM) is a variant of the multifrequency atomic force microscopy that measures the force between the sample and a tip induced by a laser. The PiFM technique uses a mechanical resonance of the probe to amplify the photo-induced force, enabling the detection of forces in the (sub-) picoNewton range under ambient conditions. Furthermore, by measuring a gradient of the force through detection at side-band frequencies background contributions are suppressed and sensitive measurements of the photo-induced gradient force can be made. When a femtosecond light source is used to illuminate the tip-sample junction, it is possible to record the nonlinear optical response of nanoscopic objects with PiFM. In this talk, we introduce the principles of PiFM and present recent results in ultrafast spectroscopy at the nanoscale that are enabled by force detection.