Abstract: A beam including a web with a longitudinal center line, and the web including at least a first row of plurality of apertures, in a longitudinal direction of the beam, said first row of plurality of apertures are arranged on a first longitudinal axis parallel with the longitudinal center line. A distance between centers of adjacent apertures satisfies the following condition: Dadjacent=1000 mm/(2*n), where Dadjacent is a distance between the centers of the adjacent apertures in the first row of the plurality of the apertures and n is a natural number.

Abstract: An apparatus for frequency comb generation comprises a component of second order nonlinearity, where the component is configured to interact with a laser beam or derivatives of the laser beam and thereby generate frequencies for the frequency comb. The apparatus comprises advantageously an optical manipulator, which both comprises the component but additionally is configured to introduce the beam or its derivatives in a repetitive or resonating manner to the component. The component is e.g. a monolithic or other solid optical resonator or microresonator comprising optical crystal and having said second order nonlinearity.