High resolution mesh Fabry-Perot interferometers in experiments on free electron and gas lasers

Mesh Fabry-Perot interferometers are simplest and most adequate devices for laser spectral measurements in range 20-500 microns approximately. Main design principles of the optimal interferometers are described. Experimental instrumental functions of the devices and investigation of spectral parameters of universal gas laser, Novosibirsk powerful free electron laser and compact KAERI free electron laser are presented.