Label-free superresolution effect of nonlinear reverse saturation absorption thin films through difference method

Label-free superresolution effect of nonlinear reverse saturation absorption (NRSA) thin films was investigated through difference method, where a subdiffraction-limit spot signal was constructed by intensity subtraction of two spots obtained under different laser intensities. By using annealed InSb films as the NRSA thin films, we experimentally obtained the subdiffraction-limit spot signal, and the optimal reduction ratio was approximately 52.5% of the original spot. Experimental results agreed well with theoretical simulations. The simulation results of a 9-point array sample showed the capability to achieve nonfluorescence superresolution imaging using the NRSA effect.