Quantum wells are fundamental building blocks of modern photonic devices such as semiconductor lasers, light-emitting diodes (LEDs), and optical amplifiers. Understanding their physical properties and accurately modelling their behaviour is essential for the design of advanced optoelectronic technologies. This advanced book provides a comprehensive introduction to the theory and numerical analysis of semiconductor quantum wells. It presents the physical principles governing carrier confinement, electronic band structure, and optical transitions in low-dimensional semiconductor systems, and analytical approaches are combined with numerical modelling techniques used in modern device simulations. The authors have included ready-to-use MATLAB codes that allow readers to implement key models and perform numerical calculations for quantum well structures. Designed for graduate students and researchers in semiconductor physics, photonics, and electronic engineering, this text offers a clear, practical framework for understanding and modelling quantum well devices.