Yoshio Nishiyama

Light scattering from a birefringent cylinder, spider silk, slimmer than the wavelength approaches dipole radiation

Using a plane-polarized laser of wavelength lambda = 543.5 or 441.6 nm and spider silk, we investigated the diffraction of a transparent cylinder of diameter D approximately lambda - lambda/5 at normal incidence. The measured pattern corresponded well to the one calculated by a rigorous solution of the theory for the problem. The birefringent index and D of the sample could be determined simultaneously. The experimental data of the scattering cross section for D < lambda/4 suggested that the data approached dipole radiation.

Standard optical coaxial double fiber diameter and refractive index measurement, accuracy, and precision using light scattering at normal incidence

A plane-polarized laser wave with a wavelength of 441.6 nm illuminates a cladding optical fiber with a diameter of about 18 to 38 mum at normal incidence. A measured angular distribution of the intensity of the scattered wave corresponds well with the differential cross section of a rigorous theoretical calculation of a coaxial double cylinder over a wide range of scattering angle. The diameter and refractive index of the cladding and core of the illuminated part of a fiber have been determined accurately for each uncertainty.

Trajectory in the optical wave

A trajectory in the optical wave is presented. The trajectory is an extension of the geometrical ray and runs wherever the wave exists. The optical wave is solved for the composite of the system’s continuously varying index of refraction. The wave equation is assumed to be separable into variables, and the constants of separation are the mode parameters specifying the wave. A trajectory for the system in which the plane wave is incident upon an interface of two homogeneous media with different indices of refraction is illustrated. The trajectory runs to and fro across the interface. Shifts of the reflected and transmitted points from the incident point on the interface occur in addition to the Goos–Hanchen shift for the incident angle greater than the critical angle. A trajectory through the cylindrical Luneburg lens is shown. It passes through the lens without any reflection, as does the corresponding ray. It is deflected attractively or repulsively according to the value of the parameter. It approaches the ray in the short-wavelength limit.

Output characteristics of a stratified medium in the case of bilateral incidence of monochromatic waves

The output characteristics of a stratified medium in the case of bilateral incidence of monochromatic light waves have been investigated. If the waves are incident in such a way as a single mode is standing in the medium, an asymmetry occurs in output intensities of both sides, even if the incident intensities are equal. For a medium with some values of the refractive and attenuation index, there can be a state in which both incident waves are completely absorbed. This is discussed in detail for the case of a Fabry–Perot cavity containing a linear optical medium.

Scattering of a light wave by a thin fiber on or near a prism: experiment and analytical theory

We have performed an experiment of the scattering of the near field on a prism created by a laser wave, evanescent wave (EW), or plane wave (PW) of an incident angle slightly larger than or smaller than the critical angle, by a thin fiber of subwavelength diameter set above the prism, and we made an analytical theory of an adapted model for the experiment. We have been able to analyze the experimental data exactly by the model theory better than any other theory we have ever known. The importance of the multiple interaction of the wave between the fiber and the surface and also the close similarity of the scattering characteristics between the EW and the PW mentioned above have been acknowledged by the analysis of the data obtained.

Real part of the dielectric constant of a subwavelength-in-diameter silver pipe is positive in visible light

The complex refractive index of a silver pipe of which the diameter is subwavelength in diameter have been found to be different from those of a silver thin film for the first time. The silver pipe is made of cladding a spider silk of a half-wavelength diameter with silver. It is illuminated by a plane-polarized laser of wavelength 660 nm at normal incidence. The angular distribution of the light intensity scattered by the pipe is measured and fitted using theoretical calculations based on the corresponding model. The fitting results have led to the optimum values and uncertainty ranges of the index and the diameter of the pipe.

Measurement and analysis of scattering of an evanescent wave by a Pt-coated thin fiber on a Pt-coated prism

We have measured scattering pattern of an evanescent wave by a Pt-coated thin fiber above a Pt-coated prism. The pattern is dependent on diameter and complex refractive index of the fiber and a Pt-film of the prism, the separation distance between the fiber and the film, and on an incident angle of a laser light. This is verified by assuming a model modifying the double cylinder scattering of a laser light. The diameter and the indices have been determined independently by light scattering or attenuated total reflection method before the measurement. Some of the experimental data and the well corresponding model calculations are presented.