Design and Growth of Piperazine‐1,4‐diium Bis (Salicylate) Crystals Toward Efficient Third‐Order Nonlinear Optical Applications

ABSTRACT

Single crystals of Piperazine‐1,4‐diium bis (salicylate) (PSA) were grown successfully at room temperature using the slow evaporation solution method, with methanol as the solvent. The crystal structural parameters (unit cell and space group) were determined by single‐crystal XRD. Hirshfeld surface analysis was then employed to visualize and to understand the types and strengths of intermolecular interactions present in the crystal lattice. Optical properties were studied through UV–Vis NIR absorption measurements, which revealed that the crystal exhibits strong transparency in the 410–1100 nm wavelength range, and this is an important factor for optical applications. The presence of various functional groups in the PSA crystal was confirmed using Fourier‐transform infrared (FTIR) spectroscopy. Photoluminescence analysis revealed distinct emission peaks corresponding to ultraviolet (UV) light, indicating strong UV luminescence behavior. The electrical properties of the PSA crystal showed a low density of defects and a low value of dielectric loss found from the dielectric studies. Additionally, the mechanical stability of the crystal was examined using Vickers microhardness testing. The antibacterial activity of the PSA material was evaluated to explore its potential biomedical applications. To explore its potential in laser applications, the laser damage threshold (LDT) was measured using a single‐shot Nd: YAG laser at 532 nm. Moreover, third‐order nonlinear optical (NLO) parameters such as the nonlinear refractive index (n ₂ ), nonlinear absorption coefficient (β), and third‐order susceptibility (χ ^{( 3 )} ) were examined using the Z‐scan method with a continuous‐wave (CW) solid‐state laser operating at a wavelength of 632.8 nm. These findings suggest that the PSA crystals could serve as promising materials for use in photonics and nonlinear optical devices.