Spacetime Processing Metasurfaces: GSTC Synthesis and Prospective   Applications
  The paper presents the general concept of spacetime processing metasurfaces, synthesized by generalized sheet transition conditions (GSTCs). It is shown that such metasurfaces can perform multiple simultaneous spatio-temporal processing transformations on incident electromagnetic waves. A time-reversal space-generalized-refraction metasurface and a multi-time-space-differentiating metasurfaces are presented as applications of the general spacetime processing metasurface concept. 
Nima Chamanara, Yousef Vahabzadeh, Karim Achouri, Christophe Caloz
physics.optics