Nonlinear Optical Properties of GaN-Based Nanomaterials: A Review

Considerable research has been conducted on the nonlinear optical properties of GaN bulk crystals and thin film materials. In 2001, the Pačebutas group from Lithuania studied GaN bulk crystals using picosecond Z-scan experiments with a 527 nm laser [23]. Pump-probe and open-aperture Z-scan measurements revealed the presence of both two-photon absorption and free carrier absorption in GaN. The measured two-photon absorption coefficient was found to be in the range of 17 to 20 cm/GW. In a pioneering study, the Taheri research group from the United States measured the third-order nonlinear refractive index of GaN epitaxial thin films for the first time at 532 nm using degenerate four-wave mixing [24]. The obtained value was 1×10-12 cm2/W, indicating significant nonlinear optical effects. However, there is limited literature on the nonlinear optical absorption properties of GaN-based nanomaterials. Due to their nanoscale structure, quantum confinement effects greatly influence the band distribution of the material, leading to changes in the recovery process of photo-generated carriers and subsequently affecting their nonlinear optical properties.