Pierdomenico Paolino, Felipe A. Aguilar Sandoval and Ludovic Bellon, Rev. Sci. Instrum. 84, 095001 (2013)
doi: 10.1063/1.4819743
In this article, we present a deflection measurement setup for Atomic Force Microscopy (AFM). It is based on a quadrature phase differential interferometer: we measure the optical path difference between a laser beam reflecting above the cantilever tip and a reference beam reflecting on the static base of the sensor. A design with very low environmental susceptibility and another allowing cal- ibrated measurements on a wide spectral range are described. Both enable a very high resolution (down to 2.5 × 10-15 m/√Hz), illustrated by thermal noise measurements on AFM cantilevers. They present an excellent long-term stability and a constant sensitivity independent of the optical phase of the interferometer. A quick review shows that our precision is equaling or out-performing the best results reported in the literature, but for a much larger deflection range, up to a few μm.