Fig. 1. (a) The scheme of the optomechanical mass sensor. (b) The scheme of analytes acting on graphene membrane. (c) Detection of mass-induced tension increases by monitoring the resonant frequency of the optomechanical resonator.

Fig. 2. (a) Raman spectrum from the suspended multilayer graphene film measured by a 532 nm laser. The inset shows the SEM image of the resonator before etching. (b) The side view of the open optical cavity at the fiber end face under the microscope. (c) The SEM image of the trampoline-type resonant structure covering the fiber end facet.

Fig. 3. Experimental setup. (a) The optical excitation and detection system used to monitor the response of the fiber tip resonator to change in Au mass. (b) The apparatus used to acquire optical reflection spectra. EOM, electro-optic modular; VNA, vector network analyzer; PD, photodetector; BBS, broadband light source; OSA, optical-spectrum analyzer. (c) The reflection spectrum of trampoline-type graphene film resonator. (d) The device of the mass source supplied by the Au target.

Fig. 4. (a) Mechanical frequency characteristics of the sensor. Insets: the simulation of the first and second order modes of the resonator obtained through finite element method. (b), (c) Amplitude versus frequency plot of the resonator. The dotted lines are Lorentz fitting of two resonance peaks in linear coordinates.

Fig. 5. Mass sensing results. (a) Frequency characteristics of the first and second order modes of the resonator as functions of time in response to increasing masses during the sputtering process. (b), (c) Plotted results of peak searching of (a), showing shifts of resonant frequencies and variation of amplitude at these two frequencies, respectively.

Fig. 6. (a) The diagram of the silicon wafer used to measure the thickness of the added Au film. (b) The calibration result of the thickness of Au film measured using atomic force microscopy (AFM).

Fig. 7. Shifts of resonant frequencies in response to increasing masses in comparison with predictions of the simulation model. k1, k1′, k2, k2′ represent the slope of linear fits. R2 denotes the linearity of the fitting result.

Fig. 8. Experimental assessments of frequency stability. (a) Frequency stability before testing. (b) Frequency stability after testing.