Retinal nerve fiber layer retardation measurements using a polarization-sensitive fundus camera.

To measure the retardation distribution of the optic retinal nerve fiber layer (RNFL) from a single image, we have developed a new polarization analysis system that is able to detect the Stokes vector using a fundus camera. The polarization analysis system is constructed with a CCD area image sensor, a linear polarizing plate, a microphase plate array, and a circularly polarized light illumination unit. In this system, the Stokes vector expressing the whole state of polarization is detected, and the influence of the background scattering in the retina and of the retardation caused by the cornea are numerically eliminated.

Two-spherical-wave ultraviolet interferometer for making an antireflective subwavelength periodic pattern on a curved surface.

An ultraviolet two-spherical-wave interferometer was developed in order to make a subwavelength structured surface on a curved surface. The change in fringe period on the curved surface was significantly suppressed compared with the two-plane-wave interferometer. The optical setup method for suppressing the change in fringe period is described.

Numerical study on a micro prism and micro lenses with metal-dielectric multilayered structures.

A micro optical prism and micro lenses with metal-and-dielectric multilayered subwavelength structure (MDMS) are discussed. The MDMS prism has a highly dispersive optical property. Light waves do not spread out in the small prism because of the restriction of propagation direction of light.

Ray tracing of an aspherical lens with antireflective subwavelength structured surfaces.

A method of ray tracing for an aspherical lens with subwavelength periodic structured surfaces has been developed. The ray tracing in the antireflective subwavelength structure is based on the group velocity of the Bloch wave. Transmittance and phase delay for the surface structure are determined with rigorous coupled wave analysis.

Refraction and diffraction by a metal-dielectric multilayered structure.

An optical refraction prism consisting of metal and dielectric, subwavelength, periodic multilayered thin films has been proposed. The multilayered structure of metal and dielectric thin films has a cylindrical dispersion surface for TM polarized light. The light behaviors are very different from those of conventional glass prisms and photonic crystal superprisms.

Estimation method for the light extraction efficiency of light-emitting elements with a rigorous grating diffraction theory.

The light extraction efficiency of a light-emitting element with microstructured surface is analyzed with a rigorous grating diffraction theory. The grating theory reveals an improvement of extraction efficiency due to diffraction of light by the surface microstructure. The simulation results show that the improvement of extraction efficiency is due mainly to the reflected diffraction rather than to the transmitted diffraction.

Reduced wavelength-dependent quarter-wave plate fabricated by a multilayered subwavelength structure.

We developed a novel fabrication method of a reduced wavelength-dependent quarter-wave plate (QWP) based on form birefringence of a multilayered subwavelength structure. The multilayered structure was constructed by depositing a high-refractive-index thin film on a subwavelength-structured substrate with a low refractive index. The surface structure of the substrate was shallow enough to be formed by a mass replication technology.

Dynamic guided-mode resonant grating filter with quadratic electro-optic effect.

We propose a novel and simple concept of dynamic switching of guided-mode resonant grating filters with quadratic electro-optic effect within a waveguide layer modulated by external fields due to comb-shaped electrodes that also behave as a grating. As the device has subwavelength structure, the performance must be analyzed electromagnetically. We describe numerical simulation with the finite-difference time-domain method specially modified so that it can treat inhomogeneous anisotropic media such as lead lanthanum zirconate titanate.

Numerical study on an asymmetric guided-mode resonant grating with a Kerr medium for optical switching.

Optical switching effects of a guided-mode resonant grating (GMRG) with a Kerr medium have been simulated with the nonlinear finite differential time domain (FDTD) method. An asymmetric waveguide grating with a large second spatial harmonic component has been proposed for the optical switch. Resonant reflection occurs at both of the band-edge wavelengths.

Optimization of diffraction grating profiles in fabrication by electron-beam lithography.

We propose a new design method for periodic diffraction gratings to be fabricated with direct-writing electron-beam lithography. When the grating has a small period, the proximity effect of electron scattering restricts the grating profile after developing. Our design method optimizes the electron-dose profile and grating profile simultaneously to obtain the desired diffraction efficiency under the restriction of the proximity effect.

Measurement by multidirectional interferometers of the position and orientation of a positioning stage.

A multidirectional interferometer system is developed to determine the position and orientation of a stage moved in a two-dimensional (2-D) space. In this system four corner-cube prisms are mounted on the moving stage, and four laser beams are incident on the corner cubes in different directions. Moving distances in the observed directions are measured by laser interferometers.

Guided-mode resonant grating filter with an antireflection structured surface.

We describe a new structure of guided-mode resonant grating (GMRG) filters with low sideband reflectance. This GMRG filter consists of a high-index thin film on an antireflective structured surface called "moth-eye structure." Since the high-index film undulates along the surface structure, the film acts as a modulated optical waveguide.