An apparatus includes a substrate transmissive of electromagnetic energy of at least a plurality of wavelengths, having a first end, a second end, a first major face, a second major face, at least one edge, a length, a width, and a thickness, at least a first nanostructure that selectively extracts electromagnetic energy of a first set of wavelengths from the substrate; and an input optic oriented and positioned to provide electromagnetic energy into the substrate via at least one of the first or the second major face of the substrate. Nanostructures can take the form of photonic crystal arrays, a plasmonic structure arrays, or holographic diffraction gratings. The apparatus may be part of a spectrometer.