Quantitative Determination of the Complex Polarizability of Individual Nanoparticles by Scanning Cavity Microscopy

The complex polarizability describes the complete optical properties of a nanoobject in Rayleigh limit, including its absorption, scattering, and dispersion. A large range applications would benefit from capability to infer on single-particle level; however, it requires two complementary measurements fully determine this quantity, smallness signals makes highly challenging. Here we use signal enhancement tunable high finesse fiber cavity apply noise-rejecting differential measurement techniques simultaneously obtain extinction cross section dispersion individual gold nanospheres, which allows us quantitatively real imaginary part with precision. We achieve detection limit for sections 1.8 nm2 α/ϵ0 = (28 000 + 200i) nm3. Our method opens way full characterization nanosystems, ranging nanomaterial science biology.