Optical Damage Threshold of Silicon for Ultrafast Infrared Pulses

While silicon has several properties making it an attractive material for structure-based laser-driven acceleration, its optical damage threshold, a key parameter for high-gradient acceler- ation, has been unknown. Here we present measurements of the optical damage threshold of crys- talline silicon for ultrafast pulses in the mid-infrared. The wavelengths tested span a range from the telecommunications band at 1550 nm extending longer toward the two-photon absorption thresh- old at around 2200 nm. We discuss the prevailing theories of ultrafast optical breakdown, describe the experimental setup and preliminary results, and propose a relevant performance parameter for candidate accelerator structures.