As computing systems evolve, two trends become increasingly important: the desire for ever more computing power, and the approach toward physical limits to size and speed of conventional electronic circuits. One path of exploration, as discussed here, is the use of optical circuits that address both trends. A second path opens from our developing knowledge of how biological systems work. As it turns out, synergies exist between how neurons and optical systems work, and optical systems operate millions or billions of times faster than biological systems. Research has also shown how deoxyribonucleic acid (DNA) stores information and can fold itself into structures that can be combined with optical elements to perform computing functions.

Nanophotonics is the study of uses of light in circuits at very small dimensions, sufficiently small that quantum mechanical effects come into play. Such circuits are not related to the field of quantum computers, however. Here the circuits perform functions similar to or the same as conventional electronics, such as AND gates or switches. In other applications, the circuits may be built to model structures like biological neurons, or they may operate in two dimensions, unlike conventional systems that operate essentially linearly.

This area is in its infancy. The research presented describes the exploration of building blocks that may eventually be combined to produce larger systems. It begins with a chapter on basic theory: quantum dots and near-field quantum processes and how they relate to computing device architecture. Chapters 2 to 4 discuss the use of DNA to assemble optical computing components, the use of DNA as a processor, and how to interface the macro world to the nano world with light signals. Chapter 5 digresses from optical designs to consider nanowire circuits built as binary decision diagrams, or a graph implemented directly as a grid of nanowires, with molecules or quantum dots placed at junctions that can function as memory stores or gates. Chapter 6 discusses how complementary metal–oxide–semiconductor (CMOS) imagers can detect and manipulate single photoelectrons in sub-nanosecond time.

Chapter 7, one could argue, should have followed chapter 1. It continues the theoretical introduction of the first chapter by providing more detail on quantum dots and optical energy transfer, both of which are used heavily in nano-optical systems. Following is a discussion of a hierarchical approach to interfacing nano-level components with the macro world. Chapters 8 and 9 delve into designing optical nanosystems based on what has been discovered about how biological systems work. Chapter 8 investigates neurons and how their functions can be replicated using optical systems. Chapter 9 looks at how natural systems solve problems and shows how two difficult problems can be addressed by using an optical system that in some way mimics how the natural system works. The natural example is an amoeba that both seeks food and shuns light. In balancing these two opposite goals, it provides a very good solution to the traveling salesman problem, a difficult optimization problem. The amoeba’s behavior provides clues used to build an optical system that solves SAT problems faster than the best-known conventional algorithm.

This book provides an interesting overview, offering multiple perspectives on this very new area of research. All of the chapters are clearly written technically. Although they are grouped by topic area, one does not follow from the next; they could be read out of order. In fact, reading chapter 1 followed by chapter 7 provides a good theoretical introduction for the others. Most of the diagrams, pleasantly, are in color, making them easy to comprehend. There is a fair amount of mathematics; however, its presence will not hinder less technical readers looking for an overview of the technologies. That said, this is a detailed technical presentation. Basic knowledge of quantum mechanics will help with comprehension of the material. Those interested in the theory of computation will be particularly interested in chapter 9 on problem solving (an NP-complete problem) and decision making when faced with conflicting goals.