Broadband achromatic phase retarder by subwavelength grating

摘要

A broadband achromatic phase retarder in the full visible region (wavelength λ∈ [400, 800 nm]) using subwave-length grating (SWG) is designed, fabricated and tested. For the first time, it is experimentally proved that the achromatic phase retarder in the full visible region can be realized by SWG. An improved method combining enumeration with optimization for designing the achromatic phase retarder with rectangular and sinusoidal SWG is presented. Rigorous coupled wave theory (RCWT) is applied to calculate the diffraction performances. Examples show that the designed phase retarders perform broadband achromatic phase retardation successfully. Compared with the previous methods, the improved method shows the advantages of good versatility and flexibility.