Frontiers in Organic Nonlinear Terahertz Crystals: Innovations in Structural Design and Optical Nonlinearity

The rapid advancement of terahertz (THz) technology has driven an increasing demand for efficient THz sources and detectors, particularly in applications such as spectroscopy, imaging, and wireless communications. Organic (NLO) crystals, renowned for their high nonlinear coefficients, tunability, and flexible molecular design, have emerged as highly promising materials for THz generation. This article highlights the latest progress in the design, synthesis, and investigation of novel organic NLO crystals demonstrating exceptional THz activity, with a focus on recent breakthroughs in ionic and molecular crystals. The discussion delves into the pivotal roles of crystal packing, molecular engineering, and functional group modification in optimizing nonlinear optical properties. Furthermore, the article explores strategies for performance enhancement through molecular engineering and functional group modification, offering insights into the mechanisms driving these advancements. Based on cutting-edge research on advanced NLO crystals, this study examines future research directions and potential applications, emphasizing the critical need for improved crystal growth techniques, refined theoretical modeling, and enhanced material stability. By providing a comprehensive review of the current state of organic THz optical crystals, this article aims to illuminate the challenges and opportunities within this rapidly evolving field, paving the way for future innovations.