Contents: Filtering Resonators: A Historical Perspective; Self-Filtering Unstable Resonator: A Novel Resonator Concept; Half-Confocal Resonator with Diffraction Outcoupling of Radiation, or HCR; Transverse Mode Selection by 'Fourier-Transform Resonators'; Improved Beam Quality Excimer Laser; A Review on Diffraction-Filtered Resonator in Solid State Lasers; Self-Filtering Unstable Resonator: A Review on CO2 Lasers; Applications of Diffraction Limited Copper Vapour and Copper Bromide Lasers; Generalised Diffraction Filtered Resonator (GDFR) Copper Vapour Laser and Its Applications: A Study.