Continuous phase control of nonlinear polarizability in harmonic   generations
  We prescribe a novel approach for continuously tailoring the local phase of the nonlinear polarizability which can lead to an arbitrary phase profile for harmonic generations. The introduced phase of the nonlinear polarizability is inherently a geometric Berry phase arising from the spin rotation coupling of light in the nonlinear regime. This approach provides new routes for controlling the optical nonlinear processes. 
Guixin Li, Shumei Chen, Nitipat Pholchai, Polis Wing Han Wong, Edwin   Yue Bun Pun, KokWai Cheah, Thomas Zentgraf, and Shuan...
physics.optics