Optical resonators – in resonance with what?
One does not have to be a linguist to answer the following question correctly: Where does the term "resonator" come from? Correct: resonance. And indeed the word "resonator" refers to exactly that, in music as well as in laser technology. An optical resonator, also called an optical cavity, is a component of a solid state laser.
It is simply an assembly consisting of two mirrors – one high reflector and one output coupler. While the high reflector reflects 100 per cent of the radiation, the output coupler has to be partially transparent.
Metal mirrors would not be able to withstand the radiation load and simply produce excess losses.
Optical resonators are found in all solid state lasers as an essential component. For example in metal processing and machining:
The lasers are used for cutting, welding, engraving, drilling, tempering, cleaning and soldering ... Solid state lasers are true all-round talents. This would not be possible without optical resonators.