Waveguides

A waveguide is a physical structure that confines and directs electromagnetic energy along a desired path with minimal loss. It is designed to support propagating modes and to control the distribution of the field across its cross section. Waveguides are used across a wide range of frequencies, from radio and microwave bands to infrared and visible light, and they form essential components of communication, sensing, and imaging systems.

In microwave and RF regimes, hollow metal channels such as rectangular and circular waveguides are common. The conducting walls support transverse electric and transverse magnetic modes, each with a specific cut-off frequency. Only modes with frequencies above their cut-off propagate, while the geometry and material properties influence attenuation and dispersion. These waveguides are valued for low loss at high frequencies and for shielding unwanted signals.

At optical frequencies, dielectric waveguides confine light by total internal reflection in a higher-index core surrounded by a lower-index cladding. The most familiar example is the optical fiber, where core diameter and wavelength determine the number of guided modes. Planar and ridge (or channel) waveguides enable integrated photonics and on-chip optical circuits, allowing complex routing of light in compact architectures.

Key design considerations include attenuation, dispersion, mode confinement, and fabrication tolerances. Waveguides can be single-mode or multimode, and their performance depends on material properties and geometric dimensions. Applications span fiber-optic communications, microwave and radar systems, sensors, and photonic integrated circuits, reflecting the broad utility of guiding electromagnetic energy.