This wavelength-tunable light emission technology enhances the monochromatic and directional nature of Smith-Purcell radiation through a dielectric periodic structure. The electron source comprises of a laser that illuminates a gated field emitter array (FEA) with light pulses, propagating free electrons as a beam. The dielectric periodic structure, situated a few wavelengths away from the electron source, interacts with the free electron beam, inducing Smith-Purcell radiation. The periodic structure defines at least one light wave that gets emitted. The technology’s light emission wavelength can be specified between the visible and X-ray range by tuning the electron source’s energy within a range of 0.5 to 40 keV.