Infrared technologies are very important for a wide range of military, scientific and commercial applications. Devices and systems based on semiconductor heterostructure and quantum well and quantum dot structures open up a new era in infrared technologies.This book deals with various topics related to the latest achievements in the development of intersubband infrared photodetectors, reviewed by top experts in the field. It covers physical aspects of the operation of the devices as well as details of their design in different applications. The papers included in the book will be useful for researchers and engineers interested in the physics of optoelectronic devices as well as their practical design and applications.