Abstract: A device with a cavity resonator comprises a housing (3, 4, 12) made of electrically conductive material. A reflector unit (11), a microwave unit (9) and a partially reflecting reflector unit (5) are provided inside the housing (3, 4, 12), the housing (4) having a radiation opening (13). The reflector unit (11), the microwave unit (9), the partially reflecting reflector unit (5) and the radiation opening (13) are situated on a radiation axis (14), the microwave unit (9) being placed between the reflector units (5, 11). In addition, a distance between the reflector unit (11) and the partially reflecting reflector unit (5) corresponds to half a wavelength to be generated or to be detected or to several times this half wavelength. At the same time, a measurement transversal to the radiation axis (14) is at least one fourth of the wavelength.

Abstract: A laser arrangement exhibits a laser rod or a laser tube (3) as well as a high-voltage connection (19) for generating the laser beam. This laser arrangement has, in addition to the high-voltage connection, at least one electromagnetic radiation source (25) in the region of the laser rod or laser tube, which is provided for initiating the laser. The laser exhibits the special function that it can be initiated by means of additional radiation source. Essential features are: initiation by action of external electromagnetic radiation source, for example light, x-rays, microwaves or other electromagnetic waves. What is more, the laser exhibits the special feature that in the case of a so-called mixed-light, white-light or mixed-frequency laser or maser, what is emitted in the emission of the laser or also maser is not the full spectrum but only the radiation excited by the additional radiation source.