Kazahiko Oka

Bio: Kazahiko Oka is an academic researcher from Hokkaido University. The author has contributed to research in topics: Polarization (waves) & Linear polarization. The author has an hindex of 1, co-authored 1 publications receiving 51 citations.

Contour mapping of the spatiotemporal state of polarization of light.

Abstract: A novel interferometric polarimeter capable of mapping a spatiotemporal change in the state of polarization (SOP) of light is described. The polarimeter has a reference beam of light with two orthogonal linearly polarized components that interfere with the counterpart components of an elliptically polarized signal beam. The resultant interference pattern is recorded by a computer by the use of a wideband metal-oxide semiconductor video camera. The interference pattern reduces to the ellipticity and azimuth of the ellipse at an instant of time, by which the spatiotemporal change in the SOP is mapped. No optical elements are used for the control of polarization in the polarimeter, and this allows for the mapping of a rapid change in the SOP. Successful experiments are demonstrated by generating an elliptically polarized beam whose SOP varies in space and time.

Fourier-transform method of fringe-pattern analysis for computer-based topography and interferometry

Abstract: A fast-Fourier-transform method of topography and interferometry is proposed. By computer processing of a noncontour type of fringe pattern, automatic discrimination is achieved between elevation and depression of the object or wave-front form, which has not been possible by the fringe-contour-generation techniques. The method has advantages over moire topography and conventional fringe-contour interferometry in both accuracy and sensitivity. Unlike fringe-scanning techniques, the method is easy to apply because it uses no moving components.

Digital holography and its multidimensional imaging applications: a review.

Abstract: In this review, we introduce digital holographic techniques and recent progress in multidimensional sensing by using digital holography. Digital holography is an interferometric imaging technique that does not require an imaging lens and can be used to perform simultaneous imaging of multidimensional information, such as three-dimensional structure, dynamics, quantitative phase, multiple wavelengths and polarization state of light. The technique can also obtain a holographic image of nonlinear light and a three-dimensional image of incoherent light with a single-shot exposure. The holographic recording ability of this technique has enabled a variety of applications.

Polarization microscopy by use of digital holography: application to optical- fiber birefringence measurements

Abstract: We present a digital holographic microscope that permits one to image polarization state. This technique results from the coupling of digital holographic microscopy and polarization digital holography. The interference between two orthogonally polarized reference waves and the wave transmitted by a microscopic sample, magnified by a microscope objective, is recorded on a CCD camera. The off-axis geometry permits one to reconstruct separately from this single hologram two wavefronts that are used to image the object-wave Jones vector. We applied this technique to image the birefringence of a bent fiber. To evaluate the precision of the phase-difference measurement, the birefringence induced by internal stress in an optical fiber is measured and compared to the birefringence profile captured by a standard method, which had been developed to obtain high-resolution birefringence profiles of optical fibers.

Fourier fringe analysis and its application to metrology of extreme physical phenomena: a review [Invited]

Abstract: The paper reviews a technique for fringe analysis referred to as Fourier fringe analysis (FFA) or the Fourier transform method, with a particular focus on its application to metrology of extreme physical phenomena. Examples include the measurement of extremely small magnetic fields with subfluxon sensitivity by electron wave interferometry, subnanometer wavefront evaluation of projection optics for extreme UV lithography, the detection of sub-Angstrom distortion of a crystal lattice, and the measurement of ultrashort optical pulses in the femotsecond to attosecond range, which show how the advantages of FFA are exploited in these cutting edge applications.

Snapshot complete imaging polarimeter using Savart plates

Abstract: An interferometric method for measuring the two-dimensional distribution of the state of polarization (SOP) of light is presented. A pair of Savart plates, a half-wave plate, and an analyzer are inserted between the lenses of a double-diffraction imaging system, so that multiple interference fringes are generated over the video camera. The Fourier analysis of the image obtained from the video camera allows us to determine the two-dimensional distributions of the four Stokes parameters over the object plane. No mechanical or active components for polarization control are required and two dimensional distributions of any parameters related to SOP can be determined from the single image. Principle of this method is experimentally demonstrated by measuring the SOP distribution of the light transmitted by a liquid crystal cell.