Polarization-insensitive wavefront shaping using the Pancharatnam-Berry phase

We discuss a method to achieve a polarization-independent modulation of the electromagnetic wavefront based upon the Pancharatnam-Berry phase. When the length of the twisted anisotropic material is equal to the birefringence length (i.e., full-wave plate length), a phase delay proportional to the squared transverse derivative of the twisting angle appears. Physically, the phase delay is associated with the Kapitza effect applied to the Pancharatnam-Berry phase. Our theoretical results are confirmed by finite-difference time-domain (FDTD)-based numerical simulations.