Optical devices have revolutionized the modern era. These devices have made our lives much easier for communication and computation. In a certain way, it has converted the whole world into a global village. Novel nanoscale structures have shown a broad range of exclusive features and, therefore, have become very popular. New structural materials are not just used in biomedical therapy, but their nature also inspires the design of innovative optical structures. With this book, we focus on current advancements of theoretical study, designs of novel nano-photonic structures and functional materials for optical instrumentation. The chapters within this book have been contributed by renowned researchers from all over the world who work in the forefront of this field. This book is a compilation of several well researched chapters dealing with optical devices.