This book presents recent and upcoming technological advancements in millimeter-wave (mm-wave), infrared (IR) and terahertz (THz) frequency spectrums. The scope of this book includes a significantly long portion of the electromagnetic spectrum, starting from the mm-waves (i.e. 30 GHz) and extended up to the end of the near-IR spectrum (i.e. 450 THz). Most significant aspect of this portion of the electromagnetic spectrum is that it includes a frequency regime where the gradual technological transition from electronics to photonics occurred. The book especially focuses on the recent advancements and several research issues related to materials, sources, detectors, passive circuits, advanced signal processing and image processing algorithms for mm-wave, IR and THz frequency bands. The book covers a very wide range of readers from basic science to technological experts as well as research scholars.