Particle accelerators are central to applications ranging from high-energy physics to medical treatments. However, the cost and size of conventional accelerators operating in radio-frequencies is prohibitive for widespread proliferation. Operating at optical and near-infrared frequencies, dielectric laser accelerators (DLAs) leverage the high damage threshold of dielectric materials, advances in nanofabrication techniques, and femtosecond pulsed lasers to produce miniaturized laser-driven accelerators. Previous demonstrations of dielectric laser acceleration have utilized free-space lasers directly incident on the accelerating structure. While this is acceptable for proof-of-principle, for DLAs to become a mature technology, it is necessary to integrate the accelerators on-chip to increase scalability and robustness of the system.
Here we demonstrate the first waveguide-integrated dielectric laser accelerator. In this scheme, a grating coupler is used to couple light from femtosecond pulsed laser to a 30 μm wide waveguide, fabricated on a silicon-on-insulator platform. The waveguide is then directly interfaced with an accelerating structure that is patterned with sub-wavelength features to produce near-fields phase-matched to electrons travelling through a vacuum-channel in the device. Both the input grating coupler and accelerator structure have been designed using the inverse design optimization approach.
We have experimentally demonstrated these waveguide-integrated accelerators by showing acceleration of subrelativistic electrons of initial energy 83.5 keV. We observe a maximum energy modulation of 1.19 keV over 30 μm. These results represent a significant step toward scalable and integrable on-chip DLAs for applications in ultrafast, medical, and high-energy technologies.