Investigating the plane-dependent nonlinear optical behaviour of ADP crystal
摘要
Third-order nonlinear optical (NLO) properties of ammonium dihydrogen phosphate (ADP) single crystals were investigated along the (100) and (101) crystallographic planes. High-quality ADP crystals were grown under optimized conditions, and their structural and optical characteristics were analyzed using the Z-scan technique and UV–Visible spectroscopy. The study was further supported by density functional theory calculations to provide theoretical insight into the observed optical behaviour. Z-scan measurements were carried out using a continuous wave laser to determine key NLO parameters. The nonlinear refractive index (n2) was found to be 6.171 × 10−4 cm/W for the (100) plane and 6.583 × 10−4 cm/W for the (101) plane. The nonlinear absorption coefficient (β) was measured as 0.024 × 10−6 esu for the (100) orientation and 0.028 × 10−6 esu for the (101) orientation. The dielectric constants were evaluated to understand the anisotropic optical response in different crystallographic directions. The variation in the third-order NLO properties is attributed to the inherent differences in electronic distribution and local structural arrangement between the planes. These findings provide valuable insight into the orientation-dependent optical behaviour of ADP crystals and demonstrate their relevance in the field of nonlinear photonics. The results confirm the potential of ADP crystals for applications in photonic and optoelectronic devices such as optical limiters, modulators, and switches, where control over nonlinear response is critical.