One of the most fundamental light-matter interactions is the absorption of a photon that causes an electron to move up from its ground state to an excited state. The excited state could be virtual or a quantum level in a molecule depending on the energy of the photon and the difference between the energy levels in the molecule. The interaction of light with matter and the further development of novel materials that can manipulate light are foundational for numerous applications in optics, sensing, communications, materials processing, characterization, imaging, and other technologies.

The aim of this book is to guide graduate students how to investigate and understand optoelectronic devices via exploring the light-material interactions with graphical concepts and simplified formulas. This book can be a textbook in graduate courses and a reference book in undergraduate courses. The contents in Chapters 1, 2, 3, 4, and 5 are related to electromagnetic waves, laser beams, and waveguides. The contents in Chapters 6, 7, and 8 are related to excitons and carriers in semiconductors. The contents in Chapters 9 and 10 are focused on solar cells and light-emitting diodes, respectively.