Marking the Difference: Interferometric Detection vs Optical Beam Deflection in AFM

Regarding the performance of an atomic force microscope adapted to a complex task, not only its sensitivity matters e.g. to finally build a cryogenic electrostatic force microscope. While allowing a stable measurement, the instrument has to be compact to enter the cryostat, it must be easy to adjust under these conditions, and it should allow a certain flexibility in its operational modes. Furthermore, linearity of the measurement is desired at for a range that is adapted to the measurement. Under this focus, we compare an interferometric detection scheme to standard optical beam deflection. A fiber‐optical interferometric detection gains in compactness and mechanical stability relative to the optical beam deflection, but at the price of intrinsic non‐linearities. The need to adjust the interferometric cavity turns into another advantage. Three conceptually different arrangements compatible with electrostatic force microscopy are discussed that additionally allow for a sample‐independent control of the ca...