Near-zone evanescent waves generated by weak scattering of light from a spatially deterministic medium

•Spectral densities of evanescent waves are derived.•Dependences of scattered spectral densities on properties of the medium are revealed.•Evanescent amplitudes can be adjusted by changing the effective radius.•Results are applicable to the near-field biomedical imaging technique.

It is commonly known that the far-zone spectrum of a scattered field can be utilized to measure the scattering potential of the medium. However, properties of evanescent fields scattered from the medium with the dielectric susceptibility being a deterministic function, to the best of our knowledge, have not been concerned so far. Assuming the scattering potential of a spatially deterministic medium suffices the Gaussian profile, integrations are derived for the near-zone evanescent field generated by the scattering of light from the medium. It is noticed that the spectral density of the scattered field decays exponentially as either the propagation distance of scattered waves or the effective radius of the scattering potential (ERSP) increases. These results are applicable to the near-field biomedical imaging where the considered tiny particles and molecules solely scatter evanescent waves in near-zone regions.