The nonlinear optical spectrum signal technology is a new type of optical characterization technology owing to its non-invasiveness and good biocompatibility. This book highlights a comprehensive introduction to the Stimulated Raman scattering (SRS), Anti-Stokes Raman Spectroscopy (CARS), Two-photon Excited Fluorescence (TPEF) and Second Harmonic Generation signals (SHG) technologies. The four types of nonlinear optical signals technologies, especially two-dimensional and three-dimensional imaging, have great application potential in physics, materials science, chemistry and biomedicine. The book covers principles, theoretical calculation methods, signal measurement methods and imaging specific methods. The theoretical part starts from the basics of nonlinear optics and the relationship with strong light, and gradually transitions to theoretical calculation methods for specific optical signals. it combines the classical theory and the quantum theory to help readers develop a thorough understanding of the technologies. The book is a good reference for graduate students majored in physics and chemistry and for researchers working on optics, photonics and materials science. 

Nanophotonics and spectroscopy has advanced rapidly in recent years. Experimental research on nanophotonics is very active. In addition to experimental research on the principles and applications of nanophotonics, computational simulation research on its various physical mechanisms and phenomena is equally important. The simulation of the optical properties of molecules or crystals, such as electronic spectra (absorption and emission spectra, etc.) and vibrational spectroscopy has extraordinary guiding significance for experiments. The current computational simulation technology can also explain and analyze the physical mechanisms behind phenomena. However, among the many computational simulation software programs available, the operation methods and application scenarios are different. The barrier for new users to conduct research with computational simulation is high. Even for researchers with some experience, it is not easy to develop a comprehensive understanding of the various software programs, keywords, programming languages and auxiliary programs. This book serves as an introductory book for beginners to get started with the technology, and a handbook for experienced readers to quickly look up for commands and script usage. It is a handy reference for graduate students and researchers engaged in the study of photonics and optics.