Fig. 1. Dispersion relationship curves of light propagating in free space, dielectric and SPs

Fig. 2. Schematic of intensity detection mechanism based on optical surface wave

Fig. 3. Schematic of angle detection mechanism based on optical surface wave

Fig. 4. Schematic of wavelength detection mechanism based on optical surface wave

Fig. 5. Contrast schematic of angle detection mechanism and phase detection mechanism based on optical surface wave

Fig. 6. Propagation direction of SPR surface waves excited by different SPR. (a) Kretschmann structure or Otto structure; (b) focusing structure of high numerical aperture objective lens

Fig. 7. Images of epidermal cells[46]. (a) Images obtained by ordinary optical microscopy; (b) images obtained by SPRI; (c) stereoscopic images of refractive index distribution obtained by SPRI

Fig. 8. SPR imaging of single cell[112]. (a) Schematic; (b) SPR image and phase contrast image; (c) line scanning map of SPR images

Fig. 9. Acoustic signal detection system based on SPR sensing[113]. (a) Schematic of detection system; (b) contrast curves of bandwidth between designed system and different ultrasonic transducers; (c) photoacoustic image of melanoma cells; (d) relation diagram between refractive index response and sound pressure signal based on SPR

Fig. 10. Gas flow velocity measurement system based on graphene surface wave[119]. (a) Schematic of measurement system; (b) flow direction diagram; (c) time-resolved voltage signals for gas flow direction

Fig. 11. Schematic of NO2 content measurement based on graphene surface wave structure adsorption[120]. (a) Principle diagram of optical gas sensor; (b) schematic of gas control and sensor unit measurement system for NO2 sensing; (c) detection results of different NO2 contents; (d) slop curves of different concentrations in different periods

Fig. 12. System for measuring the refractive index of cell surface based on graphene surface wave[125]. (a) Schematic of the system structure; (b) schematic of polarization analysis; (c0)-(c4) mitosis process of cells

Fig. 13. Microscopic system for measuring acoustic signals based on graphene surface wave[127]. (a) Principle diagram of photoacoustic attenuated total reflection sensing based on graphene; (b) spectral profiles of the photoacoustic pressure system; (c) relationship curve between imaging signal-to noise ratio and penetration depth; (d) angiograms of mouse ear

Table 1. Comparison of sensor measurement parameters based on different detection mechanisms[77]

Table 2. SPR imaging resolutions based on total internal reflection structure