Polarization-control components and narrow-band filters based on subwavelength grating structures

Theoretical methods for modeling diffraction from grating structures are presented. These methods are used to investigate polarization properties and resonant effects of subwavelength-period grating structures. Applications discussed include a waveplate with high transmission, a partial polarization beamsplitter and a co-directional polarization beamsplitter used in magneto-optical data storage systems, and narrowband filters based on one-dimensional and two-dimensional gratings. Fabrication processes and measured results for the partial polarization beamsplitter and resonant grating filters are reported.; The diffraction properties of subwavelength grating structures need to be analyzed through the use of rigorous electromagnetic theory. A computationally efficient implementation of rigorous coupled-wave analysis (RCWA) is presented. Specifically, the eigenvalue problem for a one-dimensional (1-D) grating in a conical mounting is reduced to two eigenvalue problems in the corresponding nonconical mounting. This reduction yields two n x n matrices to solve for eigenvalues and eigenvectors, where n is the number of orders retained in the computation. Computation on a two-dimensional (2-D) grating is also simplified by reducing the size of the matrix in the eigenvalue problem to 2n x 2n. These simplifications reduce the computation time for the eigenvalue problem by 8 to 32 times compared to the original computation time.; Phase retardation and diffraction efficiencies of zeroth-order dielectric gratings are modeled. The investigation emphasizes the transmission properties of these structures. It is found that if a zeroth-order dielectric grating is appropriately coated the transmissions for both orthogonal polarizations can be significantly enhanced. This result is particularly important for applications involving subwavelength grating structures in waveplates and birefringent computer-generated holograms. A co-directional polarization beamsplitter which consists of a subwavelength grating modulated by a coarse grating profile is also discussed.; Subwavelength-period metallic gratings formed on transparent substrates are investigated. In particular, a partial polarization beamsplitter used in magneto-optical data storage systems is designed. Using aluminum grating structures, a device was fabricated through the use of holographic exposure and reactive ion etching; the measured results agreed with the theoretical predictions and met the basic system requirements.; Detailed analysis of resonance phenomena in diffraction from two-dimensional (2D) gratings is presented. A polarization-independent narrowband reflection filter and a dual-linewidth reflection filter were designed. A 2D-grating structure consisting of a silicon nitride layer and a photoresist grating was fabricated. A symmetric, low-sideband resonant response that is suitable for narrow-band filter applications was achieved.; One-dimensional-grating resonant filters, which consist of a silicon nitride waveguide layer and a silicon dioxide grating or a photoresist grating, were fabricated. Sub-nanometer linewidth and high efficiencies ({dollar}>{dollar}70%) were achieved.