Vibration Frequency Matching in Fiber-based Interferometer for Femtogram Measurement

We proposed a Vibration Frequency Matching (VFM) method based on the Michelson interferometer with the reference ends vibrating at a fixed frequency. By doing so, the interference signal shows envelopes with period indicating the frequency difference between two ends. This method yields the ratio of the resonant frequency shift to the reference frequency (f/f_o) as low as 1/99720 at atmosphere. The Oligonucleotide probe with fluorescence function group attached was placed on cantilever beam for mass detection. It can be detected under fluorescence microscope to verify the existence. The mass was measured to be 575 fg. The frequency resolution and mass resolution of the system proposed are about 0.15 Hz and 57 fg, respectively