Spring constant measurement of a bent near-field optical fiber probe

We present a method to determine the spring constant of a bent near-field optical fiber probe based on resonance change. The spring constant of a cylindrical fiber cantilever is first obtained and the fiber is used to measure the mass of a sticky lump around 100 μm in size through resonance change. The known mass is then transferred to the end of a bent fiber probe and its spring constant can be obtained by the same approach. Three different masses have been employed and the spring constant is measured with a total uncertainty of around 10%. The current method has the advantage that particles of uniform sizes and densities are not required.