Waveguides are structures that are used to guide electromagnetic waves, such as light, through a confined space. They are typically made of materials with high refractive indices, such as glass or silicon, and are used in a variety of applications, including telecommunications, sensing, and optical computing. Waveguides can be designed to contain and direct the propagation of light, allowing for efficient transmission over long distances and through complex configurations. They come in various shapes and sizes, such as rectangular, circular, or elliptical cross-sections, and can be fabricated using different techniques, such as lithography or etching. Waveguides play a crucial role in the field of photonics and are essential components in modern optical systems.