Efficient Smith-Purcell Radiation Sources and Enhancement Methods

Technology

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.

Problem Addressed

The Smith-Purcell Effect is a light emission method induced by free electrons coupled to the electromagnetic modes of a periodic structure that diffracts light into several wavelengths. The wavelength of radiation is dependent on the velocity of the free electrons and the geometry of the periodic structure. Smith-Purcell light sources typically use a metallic periodic structure and adjust emission wavelength through electron velocity. Unfortunately, the output of conventional light sources is too weak for realistic application due to a range of nanoscale technical issues, from phase mismatch between electrons and emitted photons to misalignment of the electron beam and the periodic structure.

Advantages

• Enhances monochromatic and directional nature of Smith-Purcell radiation through dielectric periodic structure
• Tunable emission wavelength between the visible and X-ray spectrum via FEA-based electron source
• Improves output strength, allowing for realistic applications in UV, EUV, and soft X-ray technologies

Publications

Roques-Carmes, C., et al. (2019). Towards integrated tunable all-silicon free-electron light sources. Nat Commun, 10, 3176. https://doi.org/10.1038/s41467-019-11070-7.

Massuda, A., et al. (2018). Smith–Purcell Radiation from Low-Energy Electrons. ACS Photonics, 5(9), 3513-3518. https://doi.org/10.1021/acsphotonics.8b00743.

Yang, Y., et al. (2018). Maximal spontaneous photon emission and energy loss from free electrons. Nature Physics, 14, 894–899. https://doi.org/10.1038/s41567-018-0180-2.