Method of making light converting systems using thin light absorbing and light trapping structures

A method of making a light converting optical system, comprising:

• providing a first optical layer having a first microstructured broad-area front surface and at least two edges, the first microstructured broad-area front surface comprising an array of linear grooves disposed side by side and extending along a straight line between the two edges, each of the linear grooves having a triangular cross section and being configured to reflect first light rays having first incidence angles with respect to a surface normal using a total internal reflection and deflect second light rays having second incidence angles with respect to the surface normal using refraction;
• providing a thin sheet of reflective light scattering material approximately coextensive with the first optical layer;
• positioning the thin sheet of reflective light scattering material parallel to the first optical layer;
• providing a light source configured to emit light in a visible spectrum;
• providing a second optical layer approximately coextensive with the first optical layer and having a second microstructured broad-area front surface;
• providing a continuous broad-area photoabsorptive film layer approximately coextensive with the first optical layer and having an active layer comprising a first light converting semiconductor material having a first bandgap and a second light converting semiconductor material having a second bandgap which is different than the first bandgap, wherein at least one of the first and second light converting semiconductor materials comprises quantum dots distributed within an optically transmissive material, wherein each of the first and second light converting semiconductor materials is configured to absorb light selectively such that photons with a higher energy are at least partially absorbed and photons with a lower energy are transmitted, and wherein a thickness of the active layer is less than a minimum thickness sufficient for absorbing substantially all light in the visible spectrum traversing through the continuous broad-area photoabsorptive film layer;
• positioning the continuous broad-area photoabsorptive film layer between and parallel to the first optical layer and the thin sheet of reflective material;
• and
• positioning the second optical layer on a light path between the light source and the continuous broad-area photoabsorptive film layer.