An achromatic quarterwave-plate for visible spectrum region using the dispersion of form birefringence

摘要

Sub-wavelength gratings could function as polarization components, such as wave-plates and polarized beam splitters. Furthermore, gratings in resonate regime could act as achromatic wave-plate. Here, an achromatic quarter-wave plate of a subrnicrometer grating with sinusoidal profile is designed based on diffractive optics. Rigorous coupled wave theory (RCWT) was used to analyze the subwavelength grating made on photo-resist in ambient air. Design of a broadband form-birefringent phase retarder for 400nm to 800nm visible region is discussed. A sinusoidal sub-wavelength grating with good properties was designed. Its phase retard maintains at about 90° and maximum deviation is about 15%, which approaches normal binary waveplate.