This Book is an extensive guide for researchers, engineers, and scientists in the field of photonic devices. The book explores the use of crystal investigations in developing novel photonic devices by delving into the interdisciplinary nature of crystallography, materials science, optics, photonics, quantum mechanics, and electromagnetism. The book covers a wide range of topics such as crystal growth, crystallography, crystal defects, and crystal properties, along with their impact on photonic devices. The book also provides an in-depth analysis of optical properties and their application in various photonic devices such as laser diodes, LEDs, solar cells, waveguides, modulators, and nonlinear optics. The integration of optics with various other fields is also covered, including integrated optics, optical fibers, and optical communications. Additionally, the book discusses the role of photonic crystals, metamaterials, plasmonics, nanophotonics, and surface plasmon resonance in the development of innovative photonic devices. The book also covers various sensing techniques such as biosensors, chemical sensors, gas sensors, pressure sensors, temperature sensors, strain sensors, and optical sensors. It delves into the various imaging techniques, including microscopy, holography, and 3D printing. Furthermore, the book provides a comprehensive overview of semiconductor manufacturing, crystallographic etching, thin film deposition, epitaxial growth, and the use of quantum dots, quantum wires, and quantum wells in the development of photonic devices. Overall, "Crystal Investigations for Photonic Devices" is a must-read for researchers and engineers working in the field of photonic devices. The book provides a comprehensive understanding of the complex interplay between crystallography, materials science, optics, and photonics and how it can be harnessed to develop new and innovative photonic devices.