A light mixing apparatus and method for mixing two Gaussian profile input light beams of different frequencies to form a third, homogenized output light beam having a top hat profile. The apparatus includes a first homogenizer tube having interfaced to it a second homogenizer tube. The second homogenizer tube includes an outer tubular portion which receives inside of it a tubular subassembly having an optical element at one end. The optical element is positioned to reside within the first homogenizer tube at a 45.degree. angle relative to a longitudinal axis of the first homogenizer tube. The optical element is transmissive on one surface and on the opposite surface includes a reflective surface for reflecting light traveling through the second homogenizer tube along the longitudinal axis of the first homogenizer tube. The apparatus forms a robust yet efficient means for mixing Gaussian profile light beams of different wavelengths to produce an output light beam having a top hat profile and a desired color.