Extending the deflection measurement range of interferometric microcantilever arrays

This paper presents a novel technique to extend the measurement range of interferometric microcantilever arrays far beyond the 1/4 limit, while achieving a uniform resolution across the entire measurement range. It is shown that the diffraction pattern can be decomposed into a series of spatial harmonic functions, whose frequencies and phases are determined by the intercantilever distances and the cantilever deflections, respectively. Using this result, limitations of the standard interferometric methods are identified, and ways to overcome them are established. Using computer simulations, a microcantilever array that can measure deflections up to 5? unambiguously, with 0.2-nm resolution, is demonstrated.