SNOM device

It is also necessary to say that as far as the near-field optical devices (such as SNOM) are usually working in photon-counting mode, the signal-to-noise ration can be further improved using the methods of quantum optics, see recent paper [9] and the references therein. It is worth to stress, that the quantum-optical analysis methods can use just the same mathematical formalism, based on SVD, as for classical fields, with the only exception that the decomposition coefficients now are no longer numbers, but operators in the Hilbert space, with the predefined commuting properties. 

SNOM has been applied to map topography and photocurrent of the active layer of some organic photovoltaic devices [63, 64]. However, the reported spatial resolution was only about 200 nm. 

Evanescent fields decay rapidly in the distance of sub-microns from some localized surface and cannot be usually observed, but they are enhanced by excitation of SPs and strongly depend upon nanometric structure of ultrathin films. Recently, evanescent fields are of great interest to evaluate nanometric spatial characteristics of ultrathin films and to fabricate ultrahigh-density optical memory, nano-devices, and so on [7]-[9]. And many types of scanning near-field optics microscope (SNOM) utilizing evanescent fields have been developed [10)-[12]. 

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