Large Crystal Growth and THz Generation Properties of 2-Amino-5-Nitrotoluene (MNA)

Despite being identified 4 decades ago as a potentially powerful organic material for intense terahertz (THz) generation, 2-amino-5-nitrotoluene (MNA) has not been extensively used as a THz source because of challenges associated with synthesizing large single crystals of the material. We report a consistent two-step process for growing large single crystals of MNA that are suitable for high intensity terahertz (THz) generation via optical rectification of IR light. Our process includes initial sublimation growth of thin sheets or needles of MNA, followed by solution phase slow evaporation growth using the sublimated crystals as seeds. To demonstrate the usefulness of MNA as a nonlinear optical crystal, we characterize the THz generation properties of MNA and compare these results to state-of-the-art organic THz generators such as OH-1, 4-N,N-dimethylamino-4′-N′-methylstilbazolium 4-methylbenzenesulfonate (DAST), and N-benzyl-2-methyl-4-nitroaniline (BNA). We further determine the dependence of THz intensity on crystal thickness and pump wavelength, determine the THz efficiency at different pump powers, and report the THz refractive index and absorption coefficient. These results demonstrate that high-quality MNA crystals provide a useful source for high intensity THz generation.