A method of generating pulsed coherent radiation, comprises the step of generating high harmonic pulses by an interaction of laser light pulses with a non-linear medium contained in a resonant cavity, wherein the non-linear medium is arranged in an environment of reduced pressure. Furthermore, a radiation source of generating pulsed coherent radiation is described, comprising a laser pulse source for generating laser light pulses, a resonant cavity including a non-linear medium for generating high harmonic pulses by an interaction of the laser light pulses with the non-linear medium, wherein the non-linear medium is arranged in an environment of reduced pressure.