A method for optical characterization of a sample (64, 92) using evanescent waves, the method comprising: - detecting, with an optical detector, an optical signal interferometrically formed by: (i) first electromagnetic radiation backscattered by a nanoantenna (60, 90, 504) in response to an incident electromagnetic radiation, said nanoantenna (60, 90, 504) being controllably movable above a surface of the sample (64, 92), and (ii) second electromagnetic radiation representing a portion of said incident electromagnetic radiation, a phase difference between a phase of the second electromagnetic radiation and a phase of the first electromagnetic radiation being variable; and to form an optical data output; characterized in that the method further comprises: - processing said optical data output in time domain to extract a first portion of said optical data output that represents an electromagnetic field caused by near-field interaction between the nanoantenna (60, 90, 504) and the surface during a motion of the nanoantenna (60, 90, 504) above the sample (64, 92); and - negating a contribution of background electromagnetic radiation by irradiating the nanoantenna (60, 90, 504) with pulsed laser light only at moments corresponding to a chosen phase of a recurring motion of the nanoantenna (60, 90, 504) above the sample (64, 92), or with light from a continuous wave laser source, and detecting said optical signal only at the moments corresponding to the chosen phase of the recurring motion, wherein the motion of the nanoantenna (60, 90, 504) includes said recurring motion. - detecting, with an optical detector, an optical signal interferometrically formed by: (i) first electromagnetic radiation backscattered by a nanoantenna (60, 90, 504) in response to an incident electromagnetic radiation, said nanoantenna (60, 90, 504) being controllably movable above a surface of the sample (64, 92), and (ii) second electromagnetic radiation representing a portion of said incident electromagnetic radiation, a phase difference between a phase of the second electromagnetic radiation and a phase of the first electromagnetic radiation being variable; and to form an optical data output; (i) first electromagnetic radiation backscattered by a nanoantenna (60, 90, 504) in response to an incident electromagnetic radiation, said nanoantenna (60, 90, 504) being controllably movable above a surface of the sample (64, 92), and (ii) second electromagnetic radiation representing a portion of said incident electromagnetic radiation, a phase difference between a phase of the second electromagnetic radiation and a phase of the first electromagnetic radiation being variable; and - processing said optical data output in time domain to extract a first portion of said optical data output that represents an electromagnetic field caused by near-field interaction between the nanoantenna (60, 90, 504) and the surface during a motion of the nanoantenna (60, 90, 504) above the sample (64, 92); and - negating a contribution of background electromagnetic radiation by irradiating the nanoantenna (60, 90, 504) with pulsed laser light only at moments corresponding to a chosen phase of a recurring motion of the nanoantenna (60, 90, 504) above the sample (64, 92), or with light from a continuous wave laser source, and detecting said optical signal only at the moments corresponding to the chosen phase of the recurring motion, wherein the motion of the nanoantenna (60, 90, 504) includes said recurring motion.