Abstract: Illuminators and systems are provided that permit the production of a beam of electromagnetic radiation having selected peak wavelength, bandwidth, intensity, pulse frequency and pulse duration for a variety of analytical and therapeutic applications. Multiple beam illuminators use filter elements arranged into filter arrays, having characteristic wavelength absorption properties. By providing a series of filter arrays formed into tracks having defined wavelength offsets, radiation passing through a portion of a track can be modified to include selected peak wavelength and bandwidth. Selection of peak wavelength(s) and bandwidth can be accomplished using mechanical interrupters, mechanical shutters, or electro-optical devices including liquid crystal device. Multiple output beams permit the coordinated illumination of a target, and sensors provide feedback regarding the effects of illumination on a target.