Twistoptics: A new way to control optical nonlinearity

Engineering researchers report that they developed a new, efficient way to modulate and enhance an important type of nonlinear optical process: optical second harmonic generation — where two input photons are combined in the material to produce one photon with twice the energy — from hexagonal boron nitride through micromechanical rotation and multilayer stacking. Their work is the first to exploit the dynamically tunable symmetry of 2D materials for nonlinear optical applications.