Waveguides are a special category of transmission line that is used to guide (direct) the waves (radiation) along the length of the tube. These are typically a hollow metallic tube that acts as the medium to transfer or transmit power.
Terahertz technology refers to the use of electromagnetic waves in the terahertz region of the electromagnetic spectrum. The potential applications of terahertz radiation are numerous and diverse, ranging from security and materials science to communications and medicine.
A Gunn diode is a semiconductor device formed by only N-type material. It is also termed as a transferred electron device. As in n-type material, electrons acts as majority carriers and these are transferred from one valley to another.