Laser-Driven Electron Lensing in Silicon Microstructures.

We demonstrate a laser-driven, tunable electron lens fabricated in monolithic silicon. The lens consists of an array of silicon pillars pumped symmetrically by two 300 fs, 1.95 µm wavelength, nJ-class laser pulses from an optical parametric amplifier. The optical near field of the pillar structure focuses electrons in the plane perpendicular to the pillar axes. With 100±10 MV/m incident laser fields, the lens focal length is measured to be 50±4 µm, which corresponds to an equivalent quadrupole focusing gradient B^{'} of 1.4±0.1 MT/m. By varying the incident laser field strength, the lens can be tuned from a 21±2 µm focal length (B^{'}>3.3 MT/m) to focal lengths on the centimeter scale.