TE modes, or transverse electric modes, are electromagnetic waves that travel through a waveguide with an electric field perpendicular to the direction of propagation. These modes only have a magnetic field in the direction of propagation, and no electric field in that direction.
TM modes, or transverse magnetic modes, are electromagnetic waves that travel through a waveguide with a magnetic field perpendicular to the direction of propagation. Unlike TE modes, TM modes have no electric field in the direction of propagation and only a magnetic field in that direction.
The cutoff frequency for TE modes in a waveguide is the frequency at which the mode can no longer propagate through the waveguide. This frequency depends on the dimensions and shape of the waveguide, and can be calculated using the waveguide's cutoff wavelength.
TE modes can be excited in a waveguide through various means, such as by using a coaxial feed, a slot, or a waveguide aperture. The specific method used depends on the type of waveguide and its dimensions.
TE modes in EM waveguides are commonly used in microwave and optical communication systems, as well as in microwave and optical sensors. They are also used in microwave and optical components such as filters, couplers, and switches.