Fig. 1. Schematic diagram of simulation model of SPPs excitation based on Kretschmann configuration

Fig. 2. Simulation result and schematic diagram of imaging system. (a) Simulation result of near-field distribution of SPPs at Au-air interface; (b) schematic diagram of SPRM 4f imaging system

Fig. 3. Simulation results of SPRM under different defocus

Fig. 4. Schematic diagram of light path of SPRM

Fig. 5. Experimental results of SPRM under different defocus

Fig. 6. Maximum fringe spacing extracted from one-dimensional field distribution of SPRM image. (a) Experimental result; (b) simulated result

Fig. 7. Comparison of maximum fringe spacing induced by defocus between experiment and simulation