Theoretical and experimental studies on a semi-organic third-order nonlinear optical material for photonic and optical limiting applications

A good quality third-order nonlinear optical (NLO) single crystal of D-phenylglycine hydrochloride (DPGCL) was successfully synthesised using the solvent evaporation method. Single crystal X-ray diffraction (XRD) analysis confirmed its orthorhombic structure with the space group P2₁2₁2₁. UV–Visible spectroscopy revealed a cut-off wavelength of 228 nm and a band gap of 5.4 eV. For the first time, quantum chemical calculations, including a detailed HOMO–LUMO analysis, were conducted alongside assessments of optical parameters, illustrating excellent crystalline quality. The photoluminescence spectrum exhibited strong ultraviolet light emission. HR-SEM and EDAX analyses provided valuable insights into the crystal’s surface morphology and elemental composition. Thermal analysis indicated stability with a melting point of 286 °C, while the laser damage threshold power density was determined to be 5.46 GW/cm². The second-harmonic generation (SHG) efficiency of the material was found to be 1.3 times that of potassium dihydrogen phosphate (KDP). Furthermore, the Z-scan technique was employed for the first time to elucidate the third-order NLO properties, yielding an absorption coefficient (β) of 0.87 × 10⁻¹⁰ m/W, a saturation intensity (I_s) of 32 × 10¹¹ W/m², and an optical limiting threshold of 2.89 × 10¹² W/m², thereby demonstrating the crystal’s significant potential for nonlinear optical limiting applications. The broad transparency range, combined with exceptional crystalline quality and enhanced laser resistance, underscores the material’s potential utility in photonics applications.