Enhancement of terahertz radiation from GaP emitters by subwavelength antireflective micropyramid structures

Subwavelength antireflective micropyramid structures, designed by rigorous coupled-wave analysis and fabricated by precision micromachining, are used to enhance the terahertz (THz) radiation output of optical rectification in GaP crystal-based emitters. An average 16% increase in the THz radiation power emitted by a 3 mm GaP crystal is experimentally demonstrated using an antireflective micropyramid grating with a period of 60 μm and a base angle of 55.5°. Optimized pyramidal-frustum gratings are shown to operate as highly efficient antireflective structures within an ultrabroadband range of 0.5-5 THz.