An overmoded photonic crystal waveguide based on the three-dimensional woodpile lattice has been proposed for a highenergy
charged particle accelerator. Critical to overall accelerator efficiency is the ability to couple power into an uninterrupted
vacuum waveguide in a very small volume. We present designs and simulations of coupling to the waveguide, both
from free space and from a waveguide adjoining it at 90 degrees. We discuss details of the computation, including the use
of symmetries and extraction of the resulting transmission.
We present measurements of the optical damage threshold of crystalline silicon in air for ultrafast pulses in the near infrared.
The wavelengths tested span a range from the telecommunications band at 1550 nm, extending to 2260 nm. We discuss
the motivation for the measurements and give theoretical context. We then describe the experimental setup, diagnostics,
and procedure. The results show a breakdown threshold of 0.2 J/cm2 at 1550 nm and 1.06 ps FWHM pulse duration, and a
weak dependence on wavelength.