Vertical Bridgman growth of 2-methoxy benzoic acid single crystal: A promising approach for nonlinear optical applications

Abstract

Organic optical crystals hold a pivotal role in the field of nonlinear optical (NLO) applications. This research paper focuses on the exploration of 2-methoxy benzoic acid (2MBA) (CH₃OC₆H₄CO₂H) as a potential NLO candidate. We explored the vertical Bridgman technique to grow a 2MBA organic single crystal. The multi-nucleation was arrested by the small bend made at the bottom of the ampoule. Through rigorous optimization procedures, the ampoule geometry and the furnace’s thermal profile were meticulously tailored to achieve optimal conditions for crystal growth. A good optical quality single crystal has been grown successfully. The lattice parameters of the crystal have been investigated by single crystal XRD measurement. The crystal phase was determined by Powder X-ray Diffraction (PXRD) analysis. Fourier transform infrared spectroscopy (FTIR) analysis was conducted to determine the functional groups of the 2MBA molecule. The optical transmittance has been examined by UV–visible-NIR spectroscopy. The grown crystal shows more than 85 % transmittance in the visible region. The cut-off wavelength of the grown crystal is 340 nm, and the optical band gap energy of 2MBA was found to be 3.5 eV. A photoluminescence (PL) study was conducted to determine the emission spectrum of the grown crystal. The thermal stability of the 2MBA crystal was investigated by TGA-DTA analysis, revealing the melting point of 108 °C. The photocurrent study indicates that 2MBA exhibits positive photoconductivity. Third-order nonlinear parameters were obtained using the Z-scan technique, with the calculated value of $\begin{array}{c}\left({\chi }^{\left(3\right)}\right)\end{array}$ being 1.013 × 10⁻⁸ $\text{esu}$. The outcomes of the tests conducted confirm that the grown 2MBA has exceptional capability for nonlinear optical applications.