A light converting optical system employing a planar light trapping optical structure illuminated by a source of monochromatic light. The light trapping optical structure includes a photoresponsive layer including semiconductor quantum dots. The photoresponsive layer is configured at a relatively low thickness and located between opposing broad-area surfaces that confine and redistribute light within the light trapping structure and cause multiple transverse propagation of light through the photoresponsive layer to enhance absorption. The light trapping optical structure further incorporates optical elements configured for injecting light into the light trapping structure.