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Physics Seminar

Evanescent waves and their fascinating properties: from optical nano-routing to lateral optical forces

Speaker: Dr Francisco Rodriguez Fortuno (King's College London)
Date: Wednesday 15 May 2019
Time: 15:00
Venue: Queens Buildings N/3.28

Evanescent waves are embedded into classical wave theories, representing field solutions which decay exponentially in a direction, while propagating in another. In photonics, evanescent waves are present and dominant in the near field of nano-photonic structures such as waveguides. Recently, interest into optical evanescent waves has grown due to their fascinating properties, such as their polarization, which is locked to their propagation direction: evanescent waves are always elliptically polarized, with a spin that is directed transverse to the propagation direction, and the sense of rotation of the polarization is directly related to the direction of propagation of the wave - this allows controlling the propagation direction simply by tuning the polarization of a localized source, enabling optical nano-routing and nano-polarimetry. This effect is very fundamental, broadband, and robust to imperfections. The effect also implies the directional excitation of evanescent waves from localized sources, with a corresponding recoil lateral optical force, with implications on lateral Casimir forces acting on objects rotating near surfaces.