Abstract: An apodizing filter is disclosed comprising two solid bodies of transparent material the first of which is struck by the incident light while the second receives the light from the first. The second body has a curve surface approaching the first body at a distance therefrom not greater than some wavelengths of the incident light. The plane tangent to the curve surface of the second body at the point of minimum distance from the first one forms with the direction of the incident light an angle greater than the limit angle of the total reflection related to the first body with respect to the medium in which the filter is sunk. The indexes of refraction of the two materials of which the two bodies are made are such that the light incidence on said tangent plane is lower than the limit angle of the total reflection. The combination is disclosed of the apoditic filter according to this invention with a mirror and an example is given of the filter application to a laser cavity.

Abstract: An interferometer wherein the deviator element, that is the means whereby the interferometer optical elements are optically coupled together, the incident beam is admitted into the interferometer, and the beams to be made to interfere with one another are extracted therefrom comprises, according to a first embodiment a prism whose faces are uncoated and according to a second embodiment a diffraction grating. Basing on the above concept various optical arrangements are described which are referable to known arrangements such for instance the Fox-Smith, the Michelson, the Petrun'kin interferometers wherein the deviator element is replaced, according to this invention by a prism or by a diffraction grating functioning as reflectors. Specifically the use is disclosed of an interferometer as an output coupler of a laser optical resonator.

Abstract: A laser having a gaseous mixture including carbon dioxide as the lasing medium, wherein the lasing medium is cooled to a temperature such that the thermal population of the lower energy level of an output lasing transition between a higher energy level and a lower energy level of the carbon dioxide molecule is reduced, and the lasing medium is initially energised to create the population inversion which results in the lasting transition at a rate such that significant thermal population of the lower energy level is avoided.