A wavelength tunable laser resonator includes first and second resonator end reflectors for reflecting a beam of electromagnetic radiation towards each other, the first and second resonator end reflectors defining a resonator having an optical path with a length, a gain medium for generating and/or amplifying and emitting the beam towards the first and second resonator end reflectors, arranged within the resonator, and a diffractive optical element within the optical path to filter a wavelength of the beam and to focus a portion of the beam towards the gain medium. One of the resonator end reflectors are movable with respect to other optical elements within the resonator for increasing or decreasing the length of the optical path. The diffractive optical element is movable with respect to other optical elements within the resonator for adapting the filtered wavelength to the increase or decrease of the optical path length.