Growth and characterization of semi-organic, third-order nonlinear optical (NLO) phthalic acid potassium chloride (PAPC) single crystals

Abstract

The utilization of slow evaporation solutions has proven to be an effective method for obtaining single crystals of semi-organic NLO from an aqueous solution. Throughout the course of this experiment, the ambient temperature was employed. Information about the crystal’s structure was revealed through single-crystal XRD, showing that it was (PAPC) crystallized in a cubic system with space group F. Through the utilization of FT-IR analysis, the arrangement of functional groups within the developed crystal was identified. A 223 nm cut-off wavelength was determined through UV–Vis–NIR spectroscopy. Apart from linear optical properties like the extinction coefficient (K) and reflectance (R), various geometrical aspects were analyzed in this investigation. Furthermore, the crystal exhibited a significant degree of optical transparency. The analysis of the fluorescence (FL) spectrum has been employed to study the behavior of PAPC luminescence. Different frequencies ranging from 50 Hz to 200 kHz have been employed to investigate the dielectric characteristics of PAPC. The threshold value for laser-induced damage was discovered to be significantly higher when compared to KDP and other organic materials. The SEM was utilized to examine the surface morphology of the crystal for a more comprehensive understanding of its appearance. EDAX analysis was performed on the PAPC crystal to identify the elemental composition within. The electrical characteristics were determined through impedance analysis. We employed a Vickers microhardness tester to determine the brittleness index (B_i), along with the hardness (H_v), Meyer’s index (n), yield strength (σ_y), fracture toughness (K_c), and elastic stiffness constant (C₁₁). The investigation of the crystal’s third-order nonlinear optical properties was conducted utilizing the Z-scan method with a nano-pulsed Nd:YAG laser. The material displays either genuine two-photon absorption or an excited-state absorption. PAPC emerges as a potential candidate for optical limiting devices owing to its elevated nonlinear absorption coefficient (0.96 × 10^–10 m/W) and reduced onset optical limiting threshold (2.14 × 10¹² W/m²).