Compact transform optics for spectral beam combining

A spectral beam combining system comprising:

• a multi-element transform optic including a first optical element having positive optical power in a first axis, a second optical element having negative optical power in the first axis, and a third optical element having positive optical power in the first axis, the second optical element being positioned between the first and third optical elements along the first axis;
• a diffraction grating positioned at a back focal plane of the multi-element transform optic;
• and
• a plurality of optical fibers positioned at a front focal plane of the multi-element transform optic and configured to generate a corresponding plurality of individual optical beams, the multi-element transform optic and the diffraction grating in combination being configured to spectrally overlap the plurality of individual optical beams to form a combined output beam, the first axis corresponding to a dispersion axis of the plurality of optical fibers,
• wherein an effective focal length of the multi-element transform optic is longer than an optical path length of the multi-element transform optic that extends from the front focal plane to the back focal plane.