This book explores the utilization of terahertz technology within the realms of microwave and photonics to advance the development of next-generation communication systems. Terahertz Technology in Microwave and Photonics for Effective Communications offers a fundamental comprehension of terahertz technology and its significance in reshaping research in microwave and photonics. It delves into various cutting-edge technologies such as the application of metamaterials to harness terahertz capabilities, inter-satellite communication, next-generation optical fiber communication, and the utilization of metamaterial absorbers for secure communications. This book also deals with the advancements in multi-beam and beamforming terahertz antenna technologies, incorporating multi-user multiple-input multiple-output (MU-MIMO) features. Additionally, it elucidates on the reconfigurable capabilities and the impact of artificial intelligence, machine learning, and deep learning technologies on the evolution of the next generation of communication. This book also highlights recent attempts by researchers to utilize terahertz technology in the optical domain and discusses terahertz optical sources and detectors, optical communication, leveraging quantum technology for communication technologies, and inter-satellite optical communication. This book is intended for experts and professionals in the fields of advanced communications, computer science, networking, telecommunications, and technology policy.