Photoautotrophic microbes present vast opportunities for sustainable lipid production, CO 2 storage and green chemistry, for example, using microalgae beds to generate biofuels. A major challenge of microalgae cultivation and other photochemical reactors is the efficiency of light delivery. In order to break even on large scale, dedicated photon management will be required across all levels of reactor hierarchy – from the harvesting of light and its efficient injection and distribution inside of the reactor to the design of optical antenna and pathways of energy transfer on molecular scale. Here, we discuss a biomimetic approach for light dilution which enables homogeneous illumination of large reactor volumes with high optical density. We show that the immersion of side-emitting optical fiber within the reactor can enhance the fraction of illuminated volume by more than two orders of magnitude already at cell densities as low as ~5 10 4 ml −1 . Using the green algae Haematococcus pluvialis as a model system, we demonstrate an increase in the rate of reproduction by up to 93%. Beyond micoralgae, the versatile properties of side-emitting fiber enable the injection and dilution of light with tailored spectral and temporal characteristics into virtually any reactor containment.