Yasuo Kokubun

Bio: Yasuo Kokubun is an academic researcher from Yokohama National University. The author has contributed to research in topics: Resonator & Optical filter. The author has an hindex of 36, co-authored 249 publications receiving 5918 citations. Previous affiliations of Yasuo Kokubun include Alcatel-Lucent & Chubu University.

Antiresonant reflecting optical waveguides in SiO2‐Si multilayer structures

Abstract: A new type of optical waveguide utilizing an antiresonant reflector is described. Implementation in the SiO2‐Si system gave losses as low as 0.4 dB/cm for the TE mode. The TM mode loss is >60 dB/cm, making the device an excellent planar technology integrated optic polarizer.

Vertically coupled glass microring resonator channel dropping filters

Abstract: Air-clad glass microring resonators vertically coupled to buried channel waveguides are experimentally investigated. Ring radii of 10 /spl mu/m, and channel drop bandwidths of 5 nm are reported. Vertical coupling eliminates the need for the etching of fine features, and relaxes the alignment of the resonator with respect to the input and output bus waveguides.

An eight-channel add-drop filter using vertically coupled microring resonators over a cross grid

Abstract: An eight-channel add-drop cross-grid vertically coupled microring resonator (VCMRR) filter is proposed and demonstrated. The cross grid comprises a grid-like array of buried channel waveguides which perpendicularly cross through each other, VCMRRs at each of the cross-grid nodes serve as the wavelength selective add-drop filters. Measured crosstalk levels at the crossings are typically less than -30 dB. Rings with a nominal radius of 10 /spl mu/m are used to achieve a free-spectral range of 20 nm and optical bandwidths of 1 nm, while changes of the radii in increments of 50 nm lead to a nominal channel spacing of 5.7 nm.

Heterogeneous multi-core fibers: proposal and design principle

Abstract: A new type of optical fiber called heterogeneous multi-core fiber (heterogeneous MCF) is proposed towards future large-capacity optical-transport networks and the design principle is described. In the heterogeneous MCF, not only identical but also non-identical cores, which are single-mode in isolation of each other, are arranged so that cross-talk between any pair of cores becomes sufficiently small. As the maximum power transferred between non-identical cores goes down drastically, cores are more closely packed in definite space, compared to a conventional, homogeneous multi-core fiber (homogeneous MCF) composed of only identical cores.

Microring resonator arrays for VLSI photonics

Abstract: The analytic theory governing the complete scattering response of two-dimensional (2-D) microring resonator arrays is developed, The method is applicable to arbitrary interconnections of general four-port, single polarization nodes. An 8/spl times/8 cross-grid array of vertically coupled glass microring resonators is fabricated for test purposes.

Optical microcavities

Abstract: Microcavity physics and design will be reviewed. Following an overview of applications in quantum optics, communications and biosensing, recent advances in ultra-high-Q research will be presented.

Space-division multiplexing in optical fibres

Abstract: This Review summarizes the simultaneous transmission of several independent spatial channels of light along optical fibres to expand the data-carrying capacity of optical communications. Recent results achieved in both multicore and multimode optical fibres are documented.

Guiding and confining light in void nanostructure.

Abstract: We present a novel waveguide geometry for enhancing and confining light in a nanometer-wide low-index material. Light enhancement and confinement is caused by large discontinuity of the electric field at highindex-contrast interfaces. We show that by use of such a structure the field can be confined in a 50-nm-wide low-index region with a normalized intensity of 20 mm 22 . This intensity is approximately 20 times higher than what can be achieved in SiO2 with conventional rectangular waveguides. © 2004 Optical Society of America OCIS codes: 030.4070, 130.0130, 130.2790, 230.7370, 230.7380, 230.7390, 230.7400. Recent results in integrated optics have shown the ability to guide, bend, split, and f ilter light on chips by use of optical devices based on high-index-contrast waveguides. 1–5 In all these devices the guiding mechanism is based on total internal ref lection (TIR) in a highindex material (core) surrounded by a low-indexmaterial (cladding); the TIR mechanism can strongly confine light in the high-index material. In recent years a number of structures have been proposed to guide or enhance light in low-index materials, 6–1 1 relying on external ref lections provided by interference effects. Unlike TIR, the external ref lection cannot be perfectly unity; therefore the modes in these structures are inherently leaky modes. In addition, since interference is involved, these structures are strongly wavelength dependent. Here we show that the optical field can be enhanced and conf ined in the low-index material even when light is guided by TIR. For a high-index-contrast interface, Maxwell’s equations state that, to satisfy the continuity of the normal component of electric f lux density D, the corresponding electric field (E-field) must undergo a large discontinuity with much higher amplitude in the low-index side. We show that this discontinuity can be used to strongly enhance and confine light in a nanometer-wide region of low-index material. The proposed structure presents an eigenmode, and it is compatible with highly integrated photonics technology. The principle of operation of the novel structure can be illustrated by analysis of the slab-based structure shown in Fig. 1(a), where a low-index slot is embedded between two high-index slabs (shaded regions). The novel structure is hereafter referred to as a slot waveguide. The slot waveguide eigenmode can be seen as being formed by the interaction between the fundamental eigenmodes of the individual slab waveguides. Rigorously, the analytical solution for the transverse E-field profile Ex of the fundamental TM eigenmode of the slab-based slot waveguide is