Terahertz generation of BNA derivatives

N-Benzyl-2-methyl-4-nitroanaline (BNA) is currently the industry standard for terahertz generation at 800 nm using organic materials. We developed four derivatives of BNA by replacing a hydrogen atom on the benzyl substituent with either a fluorine (F-BNA), a methoxy group (MeO-BNA), a cyano group (CN-BNA), or a methyl group (Me-BNA). X-ray diffraction measurements confirmed that all derivatives were crystallized in the same space group as BNA (Pna21). The THz generation capability of F-BNA is higher than that of BNA, with the maximum Fourier amplitude increasing by an average of 14% when pumped with wavelengths of 800, 1250, and 1550 nm. The damage threshold of F-BNA was also found to be higher than that of BNA, increasing by a factor of 1.14. The phase matching of F-BNA and BNA was found to be comparable. The increased THz output is, therefore, likely due to the higher induced nonlinear polarization, molecular hyperpolarizability, and closer molecular packing of F-BNA compared to BNA.