Applications of two-photon processes in semiconductor photonic devices: invited review

Semiconductor photonics is an advanced field, both from fundamental and applicative points of view, aimed at the integration of the unique features of optical communications and quantum optics with the miniaturization and controllability of semiconductors. Many classical and quantum applications may benefit from interaction between optical signals, usually implemented by nonlinear optical processes of various orders. The efficiency of such processes in semiconductors is being constantly enhanced, assisted by the progress in ultrashort laser pulses and ultra-sensitive detectors, enabling practical devices. In this review, the lowest order of nonlinear interactions-the two-photon processes in semiconductors-are discussed, and their applications to a variety of novel classical and quantum configurations are reviewed.