Frequency and spatial multimode beams generation and applications

A multimode beam can have a single spatial mode and multiple frequency components, or bemonochromatic and have multiple spatial modes. Recent studies have analysed analogies between frequency multimode laser source with equally spaced frequency lines, such as opticalfrequency comb and spatial multimode beams carrying orbital angular momentum. Optical frequency combs, originally conceived for absolute and precise measurement of opticalfrequencies, nowadays have kicked off a growing number of applications including frequencydivision multiplexing in optical communications. On the other side, orbital angular momentum is a degree of freedom, encoded in the spatial transverse profile of the optical beam andit can in principle take unlimited values. This unique peculiarity has attracted much interestin the quantum information and communication fields, opening the possibility to transfera wealth of information between different nodes of a network. Here we present differenttechniques to generate both optical frequency combs and orbital angular momentum beams,their analogies and their main applications.