A source arrangement for providing an electromagnetic radiation comprises at least one laser gain medium (2) providing the electromagnetic radiation. The arrangement further comprises at least one spectral separating first arrangement (4, 16； 4') configured to angularly separate one or more components of the electromagnetic radiation based on a frequency of the electromagnetic radiation. The arrangement further comprises at least one angularly deflecting optical second arrangement (24) that includes a pivot point, and is configured to receive the one or more components of the electromagnetic radiation to generate at least one signal associated with the one or more components. The arrangement further comprises at least one optical imaging third arrangement (20, 22) configured to directly receive from the spectral separating arrangement the one or more components of the electromagnetic radiation, and generate an image of one or more dispersive elements associated with the one or more component toward the deflecting optical arrangement. The first, second and third arrangements form a configuration that varies a mean frequency of the at least one signal over time.
