“…The evanescent wave is non-propagating, non-radiative, and decaying, as defined by the e − kz term instead of e − ikz for propagating electromagnetic waves. 17 The penetration depth ( d p ) of the evanescent wave in the rarer medium (in the present setup, the rarer medium is water at the glass–water interface) is given by 27
where λ 0 is the incidence wavelength, n p and n s are the refractive index of the prism (1.515@638 nm) and water (1.330 for water), respectively (critical angle, θ c = 61.38°). The penetration depth of the EW for the present configuration ( θ ∼ 72.84°) was d p ∼ 89 nm, calculated using eqn (8).…”