Nonlinear photonic crystal

Nonlinear photonic crystals (PCs) are periodic structures used as quasi-phase-matching materials, available in one-dimensional, two-dimensional, or three-dimensional configurations. These structures exhibit optical responses dependent on the intensity of incoming light, granting them unique functionalities beyond linear PCs. Key properties include tunability, achieved through mechanisms like electric fields or temperature changes, though intrinsic nonlinearities are essential for high-speed operations required in advanced communication systems due to their rapid response.

Characteristics of nonlinear crystals include nonlinearity (refractive index varies with intensity), periodic lattice structure, optical anisotropy, sensitivity to temperature and pressure, a high nonlinear coefficient for efficient photon generation, high optical damage threshold to withstand intense light, transparency within the pump beam's wavelength range, and high optical quality with low absorption to minimize energy loss. These features are crucial for applications in nonlinear optics, such as generating entangled photons.