Calculation, optimisation, and measurements of optical resonator parameters of the Novosibirsk terahertz free-electron laser

A simple analytical method for calculating open stable laser cavities suggested earlier by the author is used for calculating losses and for performing efficient optimisation of an open optical resonator of the Novosibirsk terahertz free-electron laser. The gain and cavity losses are measured at various wavelengths. Good agreement between theory and experiment is observed. Optimisation of useful losses is considered and a correct expression is derived for their calculations in lasers with uniform saturation of the active medium. Possible potential modernisation of the laser resonator is considered, which may provide greater than twice the output power.