Author
Shojiro Kawakami
Bio: Shojiro Kawakami is an academic researcher from Tohoku University. The author has contributed to research in topics: Photonic crystal & Optical fiber. The author has an hindex of 32, co-authored 154 publications receiving 4836 citations.
Topics: Photonic crystal, Optical fiber, Autocloning, Polarizer, Yablonovite
Papers published on a yearly basis
Papers
More filters
TL;DR: In this article, a super-prism phenomenon was demonstrated at optical wavelength in photonic crystals with three-dimensional-periodic structure fabricated on Si substrate, where the incident-angle dependence including negative refraction and multiple beam branching was interpreted from highly anisotropic dispersion surfaces derived by photonic band calculation.
Abstract: Extraordinary angle-sensitive light propagation, which we call a superprism phenomenon, was demonstrated at optical wavelength in photonic crystals with three-dimensional-periodic structure fabricated on Si substrate. The propagation beam was swung from $\ensuremath{-}90\ifmmode^\circ\else\textdegree\fi{}$ to $+90\ifmmode^\circ\else\textdegree\fi{}$ with a slight change in the incident angle within $\ifmmode\pm\else\textpm\fi{}12\ifmmode^\circ\else\textdegree\fi{}.$ This effect together with wavelength sensitivity is at least two orders of magnitude stronger than that of the conventional prism. The incident-angle dependence including negative refraction and multiple beam branching was interpreted from highly anisotropic dispersion surfaces derived by photonic band calculation. These phenomena will be available to fabricate microscale light circuits on Si with LSI-compatible lithography techniques.
973 citations
TL;DR: In this article, the coupling coefficients of a variational principle for the propagation constant of the waveguide-wave solution using a superposition of the uncoupled modes as a trial field were derived.
Abstract: The coupled-mode theory of parallel waveguides is derived from a variational principle for the propagation constant of the waveguide-wave solution using a superposition of the uncoupled modes as a trial field. The nonorthogonality of modes as emphasized by Hardy and Streifer is part of this formalism as well. The coupling Coefficients agree with those of Hardy and Streifer derived for TE modes of loss-free guides. For TM modes the coupling coefficients differ slightly for the simpler trial solution and agree exactly for a different trial solution. The simpler trial solution gives results closer to the exact solution. Conventional coupled-mode theory emerges from orthonormalization.
418 citations
TL;DR: In this paper, a circular metallic hollow waveguide with inner dielectric multilayers was designed with the emphasis on low-loss transmission of the HE 11 mode for the infrared.
Abstract: A circular metallic hollow waveguide with inner dielectric multilayers is designed with the emphasis on low-loss transmission of the HE 11 mode for the infrared. The effects of absorptions and variations of thickness of coated dielectric materials are discussed and are shown to be small on the minimum attainable transmission losses. Mode structure and transmission properties are also clarified for the general class of hollow waveguides by using a normalized surface impedance and admittance.
323 citations
TL;DR: In this article, the superprism phenomenon was demonstrated at optical wavelengths in photonic crystals (PC's) fabricated on Si, achieving a scanning span of 50/spl deg/ with only a 1% shift of incident wavelength.
Abstract: The superprism phenomenon, the dispersion of light 500 times stronger than the dispersion in conventional prisms, was demonstrated at optical wavelengths in photonic crystals (PC's) fabricated on Si. Drastic light-beam steering in the PC's was achieved by slightly changing the incident wavelength or angle. The scanning span reached 50/spl deg/ with only a 1% shift of incident wavelength, and reached 140/spl deg/ with only a 14/spl deg/ shift of the incident angle at wavelengths around 1 /spl mu/m. The propagation direction was quantitatively interpreted in terms of highly anisotropic dispersion surfaces derived by photonic band calculation. The physics behind this demonstration will open a novel field called photonic crystalline optics. The application of these phenomena promises to enable the fabrication of integrated microscale lightwave circuits (/spl mu/LC's) on Si with large scale integrated (LSI)-compatible lithography techniques. Such /spl mu/LC's will allow more efficient use of wavelength resources when used in wavelength multiplexers/demultiplexers or dispersion compensators by enabling lower loss and broader bandwidth.
269 citations
TL;DR: In this article, a novel type of optical fiber which is composed of three portions: the core, inner cladding, and outer cladding was investigated, and it is assumed that the core has the largest refractive index of the three, and the outer claddings index is the next largest.
Abstract: This paper investigates a novel type of optical fiber which is composed of three portions: the core, inner cladding, and outer cladding. It is assumed that the core has the largest refractive index of the three, and the outer cladding index is the next largest. When the index difference between the core and the inner cladding is much larger than that between the outer cladding and the inner, the new fiber has a stronger confinement property than a usual singly clad fiber in the single-mode region. It is also assumed that the inner-cladding thickness is larger than or comparable with the core radius. This confinement is the origin of the following three properties of potential importance in single-mode optical communication. 1) As compared with a singly clad fiber, the largest core area for single-mode operation is roughly twice. 2) The group delay arising from waveguide characteristics has an opposite sign against that of typical glass dispersion. (Singly clad fiber has a dispersion of the same sign.) 3) The field is much more tightly confined within the core as compared with a singly clad fiber. This minimizes extra attenuation due to absorption in the cladding.
239 citations
Cited by
More filters
[...]
TL;DR: There is, I think, something ethereal about i —the square root of minus one, which seems an odd beast at that time—an intruder hovering on the edge of reality.
Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.
Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …
33,785 citations
Proceedings Article•
[...]
TL;DR: In this paper, the authors describe photonic crystals as the analogy between electron waves in crystals and the light waves in artificial periodic dielectric structures, and the interest in periodic structures has been stimulated by the fast development of semiconductor technology that now allows the fabrication of artificial structures, whose period is comparable with the wavelength of light in the visible and infrared ranges.
Abstract: The term photonic crystals appears because of the analogy between electron waves in crystals and the light waves in artificial periodic dielectric structures. During the recent years the investigation of one-, two-and three-dimensional periodic structures has attracted a widespread attention of the world optics community because of great potentiality of such structures in advanced applied optical fields. The interest in periodic structures has been stimulated by the fast development of semiconductor technology that now allows the fabrication of artificial structures, whose period is comparable with the wavelength of light in the visible and infrared ranges.
2,722 citations
TL;DR: In this paper, a review describes the recent progress made in creating nanostructured metamaterials with a negative index at optical wavelengths, and discusses some of the devices that could result from these new materials.
Abstract: Artificially engineered metamaterials are now demonstrating unprecedented electromagnetic properties that cannot be obtained with naturally occurring materials. In particular, they provide a route to creating materials that possess a negative refractive index and offer exciting new prospects for manipulating light. This review describes the recent progress made in creating nanostructured metamaterials with a negative index at optical wavelengths, and discusses some of the devices that could result from these new materials.
2,654 citations
TL;DR: A surface plasmon polariton (SPP) is an electromagnetic excitation existing on the surface of a good metal, whose electromagnetic field decays exponentially with distance from the surface.
2,211 citations
TL;DR: In this article, a method of coupling of modes in time was proposed to simplify both the analysis and filter synthesis aspects of these devices, and the response of filters comprised of an arbitrarily large dumber of resonators may be written down by inspection, as a continued fraction.
Abstract: Microring resonators side coupled to signal waveguides provide compact, narrow band, and large free spectral range optical channel dropping filters. Higher order filters with improved passband characteristics and larger out-of-band signal rejection are realized through the coupling of multiple rings. The analysis of these devices is approached by the novel method of coupling of modes in time. The response of filters comprised of an arbitrarily large dumber of resonators may be written down by inspection, as a continued fraction. This approach simplifies both the analysis and filter synthesis aspects of these devices.
1,733 citations