Deep-ultraviolet Smith–Purcell radiation

Smith–Purcell radiation (SPR) is electromagnetic radiation generated by free electrons passing over a periodic grating. Here, having the electron beam pass through 30 nm wide slots in an Al grating greatly shortens the SPR wavelength, and a directional, ultra-broadband, tunable light source spanning λ0≈230–1100 nm is demonstrated. By adjusting the electron energy, backward SPR can be tuned over λ0=251–340 nm. This work greatly extends the wavelength of SPR from the previously reported 320 nm to 230 nm, and provides a means of realizing an integrated free-electron broadband light source covering the deep ultraviolet.