Transverse mode

Summary

A transverse mode is a pattern of the electromagnetic field across the direction of propagation. This pattern keeps its shape as the wave travels. Modes in waveguides are classified by which field components along the axis vanish: TEM, TE, TM or hybrid. In laser beams, transverse modes are the Hermite–Gaussian or Laguerre–Gaussian beam profiles. Each mode has its own propagation constant and, in a hollow guide, its own cutoff frequency.