Studies On Realization Method Of Multi-wavelength Optical Pickup Combination/Separation System And Subwavelength Grating Polarization Elements

Super-high-density and high-capacity data storage plays an important role in national economy as well as in national defence. An idea of combining the technique of multi-wavelength optical data storage with the integration, and miniaturization technologies develops a new research approach to realize the super-high-density and high-capacity optical storage. In this dissertation, an realization method of integrated multi-wavelength optical disk pickup combination/separation system and the components based on subwavelength gratings (SWGs) are studied. After analyzing and comparing different integration schemes, the planar-optics integration scheme is adopted.Based on planar optics, thin film optics and diffractive optics, a prototype of integrated multi-wavelength optical disk pickup combination/separation system is developed and tested. Multi-wavelength planar combiner, multi-wavelength polarizing beam splitter, multi-wavelength achromatic phase retarder, and color separation grating are the key elements. The feasibility and the availability of the elements and system are experimentally proved.A novel broadband polarizing beam splitter is proposed based on the form-birefringence of SWG. Using effective-medium theory and anisotropic thin-film theory, SWGs with high extinction ratios are designed over different spectrums, including wide visible range, large-interval discrete wavelengths and wide infrared range. The performance deterioration caused by fabrication and assembly errors are investigated with rigorous coupled-wave theory (RCWT). Harmonic blazed gratings are designed to couple the multi-wavelength beam into and out of the polarizing beam splitter efficiently.Based on RCWT, a combination method of multi-dimension enumeration and local (global) optimization is presented to design SWG achromatic phase retarder over broadband spectrum, such as wide spectral range, narrow spectral range or large-interval discrete wavelengths. Rectangular and sinusoidal SWGs for realizing achromatic -degree and -degree phase retardation in the full visible region are successfully designed. The performances designed are better than the achromatic phase retarder of bi-crystal. The performance of the designed SWG functioning as a -degree achromatic phase retarder over narrow spectrum has a better achromatism than other designs that ever reported.SWGs designed as achromatic phase retarders in the full visible region with rectangular and sinusoidal profiles are fabricated with the technique of the combination technology of e-beam lithography, dry (wet) etching, and interference exposure, respectively. 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 system of integrated multi-wavelength optical disk pickup combination/separation system is constructed by replacing the refractive optical elements with corresponding SWGs. The weight and volume of the system are reduced remarkably, and the integration level and reliability are improved significantly. SWG shows its advantages in the integration and miniaturization of optical systems.