Photonic crystals can also be dynamically modified by MEMS actuators to
create novel optical devices. A variety of different approaches has been proposed
and demonstrated. Stretchable photonic crystals [187] allow the complete crystal to
be dynamically altered. Photonic crystal waveguide devices have been modulated
through evanescent coupling [188] and by atomic force microscopy (AFM) tips
[189], and by optical carrier injection [190], and waveguide switches with electro-
static actuation have been demonstrated [191, 192]. Near-field coupling between
photonic crystals has been shown to create strong modulation as a function of small
relative displacements [193, 194], and the usefulness of this effect has been
demonstrated in displacement sensors