Nonreciprocal frequency doubler of electromagnetic waves based on a photonic crystal

It is shown that an electromagnetic wave corresponding to the second harmonic transmitted through a dual periodic photonic crystal possessing chi((2)) nonlinearity exhibits a profound difference in output intensity depending on the direction of the propagation and, therefore, such a system appears to be suitable in the design of a frequency doubler of electromagnetic waves which allows propagation of the wave in one direction and forbids propagation in the opposite direction.