Fig. 1. (a) Diagram of the biosensor. (b) HRTEM image of G/W heterostructure. Graphene on the top and WSe2 monolayer on the bottom. (c) Photograph of the microfluidic channel, Nd:YAG waveguide, and holder. (d) Photograph of the assembled biosensor.

Fig. 2. (a) Refractive index distribution of the Nd:YAG waveguide and the propagation mode of the guided light at the wavelength of 1064 nm. (b) Polar image of the output light power along with the polarization variation. Wavelength of the detecting light is 1064 nm. (c) Real-time signal of different concentrations of dextrose solution. (d) Absorption coefficient corresponding to air, water, and dextrose solution.

Fig. 3. (a) Emission spectrum of the output laser. Inset is the measured near-field modal profile of the emitted laser from the Nd:YAG waveguide. (b) Output power of the Nd:YAG waveguide as a function of the pumping power. Variations of (c) Pth, (d) ϕ, and (e) Pout. (f) Calculated variations of Pout per 0.01 dB in the active (red line) and passive (blue line) biosensor.

Fig. 4. (a) Real-time signal of different concentrations of dextrose solution in the active biosensor. (b) Output power of detecting light corresponding to the refractive index of the different liquid.

Fig. 5. (a) Microphotograph of the tumor cells. (b) Real-time signal of the solution of PMMA balls and tumor cells, respectively. (c) Repeatability of the active biosensor measurement. (d) Real-time signal of the mixed solution of PMMA balls and tumor cells.