Time-varying metasurfaces and Lorentz non-reciprocity
Abstract
A cornerstone equation of optics, Snell's law, relates the angles of incidence and refraction for light passing through an interface between two media. It is built on two fundamental constrains: the conservation of tangential momentum and the conservation of energy. By relaxing the classical Snell law photon momentum conservation constrain when using space-gradient phase discontinuity, optical metasurfaces enabled an entirely new class of ultrathin optical devices. Here, we show that by eradicating the photon energy conservation constrain when introducing time-gradient phase discontinuity, we can further empower the area of flat photonics and obtain a new genus of optical devices. With this approach, classical Snell relations are developed into a more universal form not limited by Lorentz reciprocity, hence, meeting all the requirements for building magnetic-free optical isolators. Furthermore, photons experience inelastic interaction with time-gradient metasurfaces, which modifies photonic energy eigenstates and results in a Doppler-like wavelength shift. Consequently, metasurfaces with both space- and time-gradients can have a strong impact on a plethora of photonic applications and provide versatile control over the physical properties of light.
- Publication:
-
Optical Materials Express
- Pub Date:
- November 2015
- DOI:
- 10.1364/OME.5.002459
- arXiv:
- arXiv:1507.04836
- Bibcode:
- 2015OMExp...5.2459S
- Keywords:
-
- Physics - Optics;
- Condensed Matter - Mesoscale and Nanoscale Physics