Ultrafast spectroscopy has proven to be a versatile and powerful tool for investigating transient phenomena. This book provides fundamental principle and general experimental setup of ultrafast spectroscopy techniques, basic theory of semiconductor carrier dynamics, as well as basic concepts of semiconductor nanostructures. The detailed investigations into the electronic and optical properties of various semiconductor quantum systems are presented using a variety of ultrafast techniques, including up-conversion photoluminescence, pump-probe, photon echoes and four-wave mixing on the time scales from femtoseconds to microseconds and wavelength from the UV to the infrared. The semiconductor quantum systems studied include ion implanted ZnO/ZnMgO quantum wells, InGac/Gac self-assembled quantum dots, InGac/InP quantum wells and silicon quantum dots. This book can be useful to researchers and practitioners in the fields of spectroscopy, ultrafast spectroscopy and material science. It will also benefit to advanced undergraduate students and postgraduate students in the relevant subjects.