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 acceleration, has been unknown. Here we present measurements of the optical damage threshold of crystalline 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 threshold 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. The following article has been submitted to 12th Advanced Accelerator Concepts Workshop (AAC 2006), Lake Geneva, WI, July 10–15, 2006. After it is published, it will be found at http://proceedings.aip.org/proceedings.