Lecture
This lecture provides an in-depth examination of thermal detectors, focusing on their materials and sources. It begins with an introduction to the infrared spectrum and black body radiation, detailing the various regions of infrared wavelengths, including near, middle, and far infrared. The discussion progresses to infrared transmission in air, highlighting the effects of atmospheric conditions on detection capabilities. The lecture also covers the transmission properties of different window materials, such as calcium fluoride and sodium chloride, which are crucial for optimizing thermal detection. Furthermore, the instructor presents thermal infrared sources, including microfilament designs and quantum cascade lasers, emphasizing their operational principles and applications. The lecture concludes with a look at the modulation characteristics of quantum cascade lasers and their integration with quantum well infrared photodetectors, showcasing their potential for high-frequency applications. Overall, this lecture serves as a comprehensive guide to understanding the fundamental aspects of thermal detectors and their practical implementations in optical detection.