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 mu m 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 mu m, 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 ism focal length (B' > 3.3 MT/m) to focal lengths on the centimeter scale.