Determination of a cantilever's mechanical impedance using photon momentum

We report the use of photon momentum as a means to measure the mechanical impedance of a mechanical oscillator with traceability to the International System of Units (SI). The optical power of a fiber coupled superluminous light emitting diode is modulated at a rms optical power of 6.5 mW, driving the cantilever at a rms value of over 10 nm on resonance in vacuum (10−3 Pa). The experimentally determined mechanical impedance of the oscillator is fit to a damped harmonic oscillator response, and the stiffness is found to be in excellent agreement with the value obtained from an SI-traceable nanoindenter.