Achromatic optical device for generation of a broad band frequency spectrum with high frequency stability and sharp termination

We have implemented a new optical scheme to produce a broadband frequency spectrum with customizable shape and high stability. The scheme consists of the generation of a mode structure by allowing a frequency-stabilized single-mode laser to pass through an acousto-optical modulator working in the Raman-Nath regime. Diffraction yields several diffracted beams, which are shifted in frequency (Deltav(M)) by acoustic waves in the acousto-optical modulator. Then the diffracted beams are merged into one beam by means of a telescope. The scheme has worked in both the visible and the UV: Frequency spectra as wide as n Deltav(M) with n = 7 have been achieved, resulting in widths of 225 and 150 MHz for the visible and the UV spectral regions, respectively. The spectra possess the same stability as the primary single-mode laser. Their profiles may exhibit a sharp termination on one side of the spectrum, a feature that allows them to be utilized for high-efficiency laser cooling of an ion beam in a storage ring. (C) 2001 Optical Society of America.