Nonlinear physics is a ubiquitous study that is becoming ever more prevalent as the field of applied physics increases. The displacement of a spring is proportional to the applied force that is generally illustrated and this linear effect is violated as the force increases. The invention of laser implicates a local electric field of several MeV/cm in the material as it interacts with the high power laser. Nonlinear optics study started on 1961 when P. A. Franken and his co-workers first observed the blue light emission from a quartz plate as it was impinged by a ruby laser. The theoretical work was expressed by N. Bloembergen in 1962.

　　Today both experiments and theories of nonlinear optics are well developed. Many academic and pragmatic applications are tightly interwoven and generate new nonlinear optical sources. The impetus of generating second harmonic light for non-phase matched crystals, the phase compensated crystal slices are invented. A new surface crystalline reconstruction diagnostic method implemented by surface second harmonic generation is largely utilized.

　　This book is a collection of lectures written by the author in Tsing Hua University over about twenty years. I try to succinctly elucidate nonlinear optics for undergraduate and graduate students who only have basic knowledge in electromagnets and quantum physics. Pedagogically, the primary investigators of nonlinear optics can start their experimental work after reading this book.