Optical Accelerator Structures

Dielectric accelerator structures operating at optical frequencies have the potential to attain order‐of‐magnitude improvement in accelerating gradient over conventional RF structures due to high damage thresholds. Phase‐matching the electromagnetic fields to a relativistic particle beam, along with manufacturing constraints at optical lengthscales, requires novel structure geometries. We discuss recent and ongoing developments in optical structure design. The concept of photonic crystal confinement is presented, and we describe theoretical and experimental work on both three‐dimensional and fiber structures. We also discuss side‐pumped grating geometries. In addition, we present a mechanism for confining a particle beam transversely in micron‐scale structures.