Abstract:
The possibility of fabricating a silicon diffractive fourlevel THz Fresnel lens by laser ablation is studied. For a microrelief to be formed on the sample surface, use is made of a femtosecond Yb:YAG laser with a high pulse repetition rate (f=200 kHz). Characteristics of the diffractive optical element are investigated in the beam of a 141-mm free-electron laser. The measured diffraction efficiency of the lens is in good agreement with the theoretical estimate.