A broadband anti-reflection apparatus for use with terahertz radiation includes a layer having an outer surface comprising a plurality of pyramid structures having about a 30 μm to about a 110 μm period, and wherein reflectance of the terahertz radiation is reduced compared to a layer comprising a planar outer surface. Also disclosed is a method for modifying terahertz radiation which includes receiving terahertz radiation on a device having an anti-reflection layer having an outer surface comprising a plurality of pyramid structures having about a 30 μm to a 110 μm period, and modifying the terahertz radiation passing through the device or processing the terahertz radiation in the device.