A three color 'white light' laser passes through blocks of gradient index optical polymer. In a gradient index material the index of refraction is spatially varying, so for each of the blocks the index of refraction is higher on one side than it is on the other. Light passing through the block will bend towards the side with the larger index of refraction. The change in the the index of refraction is not the same for different colors, each color will bend at a different rate, causing the white laser beam to spread out into its red green and blue components. // Gradient-index (GRIN) optics bend and split laser light in the lab of University of Rochester Optical Engineering Professor Duncan Moore August 14, 2014. // photo by J. Adam Fenster / University of Rochester