Yukihiko Arai

Self-organized lightwave network based on waveguide films for three-dimensional optical wiring within boxes

This paper presents core technologies for a self-organized microoptical system (SELMOS) within optoelectronic computers; mass-productive fabrication processes of waveguide films and new types of self-organized lightwave networks (SOLNETs) for three-dimensional (3-D) optical wiring with optical Z-connections. Waveguide films are fabricated by the built-in mask method, which is reusable and can construct surface-normal mirrors/filters at one time within photolithographic accuracy. Beveled core edge walls are made by the tilted ultraviolet (UV) exposure through the built-in mask using a photodefinable material. Near- and far-field patterns reveal that the walls act as micromirrors for optical Z-connections. SOLNET is a network consisting of self-organized coupling waveguides between misaligned optical devices. The self-organization is generated in a photorefractive material by self-focusing of the two write beams from the two devices. Direct SOLNET, where wavelengths of the write beam and the signal beam are the same, is demonstrated using a laser diode. Reflective SOLNET, where one of the two write beams is replaced with a reflected write beam from the edge of the coupled device, realizes two-beam-writing SOLNET in a one-beam-writing configuration. It is especially effective when the coupled device cannot transmit write beams. The proof-of-concept is demonstrated both theoretically and experimentally. These results indicate a possibility to form 3-D optical wiring simply in SELMOS.

Three-dimensional self-organized microoptoelectronic systems for board-level reconfigurable optical interconnects-performance modeling and simulation

Self-organized microoptoelectronic system (SELMOS) built from three concepts - scalable film optical link multichip-module (S-FOLM), three-dimensional (3-D) microoptical switching system (3D-MOSS), and self-organized lightwave network (SOLNET)-is proposed. The feasibility of SELMOS for board-level reconfigurable optical interconnects is studied by the beam propagation method/finite difference time domain simulation focusing on three key issues; reducing size/cost of electrical to optical (E-O) and optical to electrical (O-E) signal conversion devices, tolerating alignment accuracy for optical coupling, and miniaturizing high-speed massive optical switching. S-FOLM, which consists of film-waveguide-based 3-D structures with embedded optoelectronic active elements and optical Z-connections for interplane links, enables drastic size/cost reduction of E-O and O-E conversion devices. 3D-MOSS, which is an S-FOLM with embedded microoptical switches, has a potentiality of 1024 /spl times/ 1024 switching with a system size of /spl sim/1.4 /spl times/ 0.6 cm/sup 2/ and an insertion loss of 29 dB. The switching rate of the 3D-MOSS is determined by the heat releasing speed to be /spl sim/2 /spl times/ 10/sup 5/ 1/s when PLZT waveguide-prism-deflector microoptical switches are used. By using advanced electrooptic materials, rates higher than 10/sup 8/ 1/s are expected. Twenty-five percent misalignment in waveguide assembly raises the insertion loss of the 3D-MOSS to 73 dB. The loss is reduced to 32 dB in SELMOS-based 3D-MOSS, where a self-organized 3-D microoptical network is implemented using SOLNET. Further loss reduction is expected by structural optimization of loss-inducing parts. Thus, SELMOS is found to be a solution of the three key issues for board-level reconfigurable optical interconnects. In addition, photolithographic packaging with selectively occupied repeated transfer (PL-Pack with SORT), which integrates different types of active elements into one substrate in desired arrangements using an all-photolithographic process, can contribute to cost and the coefficient of thermal expansion-mismatching reduction.

Coupling efficiencies in reflective self-organized lightwave network (R-SOLNET) simulated by the beam propagation method

The reflective self-organized lightwave network (R-SOLNET) enables the formation of self-aligned waveguides in the photorefractive (PR) material between misaligned optical devices by introducing a write beam. The incident write beam from one device and the reflected write beam from the second device induce self-focusing in the PR material and construct a coupling waveguide. A wavelength filter on the waveguide edge is used to facilitate the reflected beam. The beam propagation method reveals that R-SOLNET exhibits higher coupling efficiencies and better tolerances than the one-beam-writing SOLNET and the free-space coupling. The apparent usefulness of R-SOLNET is remarkable for gaps wider than 100 /spl mu/m in 8-/spl mu/m-wide waveguide circuits. For 240-/spl mu/m gap, coupling efficiency better than 50% can be achieved even when the lateral misalignment is as large as 4 /spl mu/m. The results indicate that R-SOLNET may be useful for vertical waveguide constructions of optical z-connections in three-dimensional intrachip optical interconnects and switching systems, as well as for self-aligned optical couplings with devices that cannot emit write beams such as vertical-cavity surface-emitting lasers, photodetectors, and electrooptic switches.

Predicted insertion loss reductions achieved by implementing three-dimensional microoptical network in chip-scale optical interconnects

We simulate insertion loss reductions achieved by implementing three-dimensional (3-D) microoptical network in chip-scale optical interconnects using a model structure of 3-D microoptical switching system (3-D MOSS). 3-D MOSS for a 1024/spl times/1024 Banyan network consisting of stacked layers with embedded microoptical switches minimizes the insertion loss at a layer count of 16. The optimum is determined by balance of in-plane and vertical optical connections, whose losses change oppositely with the layer count, causing a tradeoff relationship. Loss induced by 25% waveguide misalignment is decreased to a level comparable to that for no misalignment by introducing self-organized lightwave network in the 3-D optical wiring. The remaining major losses arise from microoptical switches and microreflectors.

Simulation of cross-talk reduction in multimode waveguide-based micro-optical switching systems by use of single-mode filters

We propose a method to reduce cross talk by using single-mode filters, namely, extracting the fundamental mode from a multimode optical network (EFMON). The EFMON effect is evaluated for a three-step switching system consisting of cascade electro-optic (EO) waveguide prism deflector (WPD) micro-optical switches (MOSs) and a multimode waveguide network. The WPD MOS is optimized for single-mode operation in lead lanthanum zirconate titanate thin films as EO slab waveguides with a driving voltage of 12 V, a length of 310 microm, and a channel distance of 20 microm. Beam propagation method simulation reveals that mode disturbance, higher-order modes, and cross talk are accumulated by switching steps. A single-mode filter for EFMON in the output region of the switching system reduces cross talk to below -20 dB at a propagation length of 2000 microm in the single-mode filter and below -30 dB at 20000 microm.

Selective growth of conjugated polymer thin film with nanoscale controlling by chemical vapor depositions (CVD) toward 'Nanonics'

We present a novel polymer-chain-controlling and selective growth technique to make high-index-contrast (HIC) waveguides and photonic crystals. In the present work, poly-azomethine (poly-AM) films that are conjugated polymer were grown on substrates with surface treatment by chemical vapor deposition (CVD) using p-phenylenediamine (PPDA) and terephthalaldehyde (TPA) as reactive source monomers. For polymer chain controlling, poly-AM films were grown by CVD on SiO film, which was obliquely evaporated on a substrate tilted along the y-axis. The chains on the SiO film were found to be aligned along the y-axis. For selective growth, on a glass substrate surface, where a hydrophobic treatment was applied using hexamethyl-disilazane (HMDS), a hydrophilic SiO thin film was deposited through a metal mask by the vacuum evaporation to form a hydrophilic/hydrophobic pattern. The poly-AM thin film was found to be selectively grown on the SiO region, that is, on the hydrophilic region, without growth on the hydrophobic region. These results demonstrate a potentiality of the proposed technique to provide a wide range of three-dimensional fine structures.

Core technologies for device-embedded optical interconnects with three-dimensional self-organized lightwave network

Three core technologies for three-dimensional self-organized optoelectronic computers with stacks of device-embedded waveguide films are described; mass-productive fabrication of waveguide films with micro mirrors, resource-saving device integration, and self-organized optical Z-connection.

Architecture of 1024/spl times/1024 three-dimensional micro optical switching systems with self-organized lightwave network

A three-dimensional micro optical switching system consisting of self-organized lightwave network and stacked films with embedded micro optical switches is assessed to realize 1024/spl times/1024 switching at 10/sup 5/-1/s rate with /spl sim/1.4/spl times/0.6-cm/sup 2/ size and 32-dB insertion loss.

Simulated optimum layer count to minimize insertion loss in three-dimensional micro optical switching systems (3D-MOSS)

Three-dimensional micro optical network has a certain layer count minimizing the insertion loss, which is determined by balance of in-plane and vertical optical connections where the losses exhibit opposite changes with layer count.

Assessed performance of 3-dimensional micro optical switching system (3D-MOSS) with waveguide-prism-deflectors

Performance of 3-dimensional micro optical switching system (3D-MOSS) with waveguide-prism-deflectors is assessed for size, operation voltage, switching speed, power consumption, and insertion loss by using the BPM/FDTD simulation.