The science of photonics includes the generation, emission, transmission, modulation, signal processing, switching, amplification, detection and sensing of light. Starting from the basics, this book discusses the advanced topics highlighting the research works done in the field. The topics like radiometry, optical processes in semiconductors, light emitting diodes, photodetectors, solar cells and holography, are explained logically and are well-supported with the figures and illustrations. The book is designed for the undergraduate students of Photonics and opto electronics.