Crystal growth, optical, thermal, dielectric and mechanical, laser damage threshold, and dielectric characterizations of a novel organic third-order nonlinear optical crystal: 2,4-Dichlorobenzoic acid 4-(Dimethylamino) Benzaldehyde (DADABA)

The new third-order nonlinear optical (NLO) crystal, 2,4-Dichlorobenzoic acid 4-(Dimethylamino) Benzaldehyde (DADABA), was synthesized and grown using the slow evaporation technique, with methanol and ethanol serving as solvents. A single crystal's X-ray diffraction data revealed that the title compound crystallized in a monoclinic structure belonging to the centrosymmetric space group C2/c. The reported UV spectrum reveals two distinct absorption peaks at 331 nm and an energy gap value of Eg=3.7 eV, indicating its potential for applications in optoelectronic devices. The photoluminescence study revealed that the π–π* transitions of the C=O groups are responsible for the widening violet emission band at 414 nm. FTIR spectroscopy identified the functional groups of the grown crystal. TGA and DTA showed that the title material is thermally stable up to 121 °C. The Vickers microhardness test determined the hardening coefficient ‘n’ is found to be 2.93, which indicates that DADABA has a soft material. Dielectric loss exhibits a low value in the high-frequency region, indicating that the crystal possesses minimal defects. The measured LDT value for the grown crystal is 4.63 GW/cm². The Z-scan technique estimated the third-order nonlinear optical (NLO) properties of the grown crystal, including absorption coefficient (β ≈ 0.09 X 10⁻⁴ cm/W), refractive index (n² ≈ 5.5210 X 10⁻⁸ cm²/W), and susceptibility range values (χ(3) ≈ 3.46 X 10⁻⁶ esu), promising the material for new nonlinear optical devices.