The millimetre-wavelength region of the electromagnetic spectrum is increasingly exploited for a wide range of commercial, industrial, and military applications. Conventionally, this region is considered as lying "above" microwaves and "below" the infrared. Hence, in practice, millimetre-wave scientists have tended to pick and mix useful techniques on an empirical basis from both these areas. Millimetre-Wave Optics, Devices and Systems describes the fundamental physics of the quasi-optical techniques, devices, and system design for instruments processing millimetre-wave signals. Relevant ideas from Gaussian beam mode theory and antenna and transmission line theory are brought together to show the underlying unity of optics and electronics. Aimed at advanced undergraduates and postgraduates as well as millimetre-wave, laser optics, antenna, and microwave engineers, this book will also be of interest to manufacturers of millimetre-wave and microwave equipment.