Brookhaven physicists have demonstrated that charged particle beams can be detected by the electro-optical effect induced in optical crystals.

This ultrafast mode of particle detection is based on birefringence produced in an optical medium by an electrical field: the anisotropy of refractive index in the medium means that for orthogonal components of polarization, the velocity of propagation is different - a phase difference will develop, such that light that was originally linearly polarized will now appear elliptically polarized.

Using a photodiode, the researchers traced the modulation of transmitted laser light in an LiNbO3 crystal and measured the induced ellipticity as a 1 mm diameter 45 MeV electron beam, carrying up to 1 nC in 10 ps bursts, passed within a few millimetres of the crystal. The ellipticity can then be directly related to the electric field of the charged particle beam.

The team suggest these results will lead to the construction of beam profile detectors with excellent time resolution based on parallel rows of LiNbO3 crystals, and that even single particle detection could be achieved with this technology.
Nucl. Inst. Meth. A