The lowest-order transverse electromagnetic mode of a resonator, a smooth round beam that is brightest at the center and falls off as a Gaussian. It has the smallest divergence and focuses to the smallest spot, with M-squared equal to 1. Higher-order modes add lobes, rings and nodes, and lasers are made to run TEM00 by sizing an aperture or gain region to the fundamental mode.
Profile looks TEM00 on the camera now, the aperture fixed it, and M-squared is reading 1.08.
Also heard as
- fundamental mode
- single transverse mode
Do not mix it up with
- Longitudinal mode: Longitudinal modes are frequencies along the cavity axis; TEM00 is a transverse mode describing the beam's cross-section.
Related terms
Gaussian beam
A beam whose intensity falls off from the center as a bell curve, the shape of an ideal single-mode laser.
M-squared
The beam quality factor: how many times worse a beam focuses and diverges than an ideal Gaussian of the same wavelength.
Doughnut mode
A ring-shaped laser mode with a dark center, usually a sign of misalignment or overheating in a TEM00 laser.
Longitudinal mode
One of the discrete frequencies at which a standing wave fits a whole number of half-wavelengths into the resonator.