Published papers

Polymer optical waveguides with nanocarbondoped cores are fabricated using the Mosquito method, and their wavelength conversion efficiency based on four-wave mixing (FWM) is investigated. Waveguides doped with carbon nanotubes (CNTs), graphene, and graphene oxide (GO) exhibit FWM in all devices. The measured conversion efficiencies are -44.0 dB for CNT, -43.0 dB for graphene, and -46.0 dB for GO, showing improvements compared with the back-to-back configuration of -46.9 dB. Waveguide length dependence is also investigated, confirming the influence of propagation loss and the limited effect of length extension on conversion efficiency. These results demonstrate the potential of nanocarbon-doped polymer waveguides as practical wavelength convertors in photonic networks.

Biosilicas that are produced in vascular plants (plant opal), such as Poaceae, have a variety of shapes and functions and are regarded as an excellent model for the architectural design of artificial amorphous materials. In this work, we studied the micro- and nanostructures and mechanical and optical functions of plant opals on the bamboo culm, which is available as an important natural material. The surface of the culm wall is totally covered with silicified epidermal cells containing silica wedges. The biogenic silicious architectures, such as silicified cell walls and wedges, are composed of nanoscale particles ~ 20–80 nm in diameter with cellulose nanofibrils. Silica wedges, which have a relatively low organic content and relatively high hardness and Young’s modulus, are initially formed on cellulose nanofibrils in an organic frame as a scaffold within a few weeks after the emergence of a bamboo shoot. Several months after the formation of the wedges, the epidermal cell walls, which protect the culm surface, are lightly silicified with cellulose nanofibrils. According to a numerical simulation, the silica wedges would have an optical function delivering sunlight to chloroplasts located under the epidermal cells.

In this paper, we report on the improvement of core dispense position accuracy (both horizontal and vertical) in polymer optical waveguides fabricated using the Mosquito method.

In this paper, we fabricate GI-core single-mode and multimode polymer optical waveguides with remarkably high Δ by applying newly developed resins with high index contrast to the Mosquito Method. The fabricated single-mode waveguides exhibit high optical confinement, achieving a mode field diameter (MFD) of less than 3μ m.

In this paper, circular graded-index (GI) core polymer optical waveguides are fabricated using the Mosquito method, applying a combination of resins with a high refractive index difference (∆) for their core and cladding materials. Optical properties of the fabricated waveguides are thoroughly evaluated. These waveguides are expected to exhibit strong optical confinement in their cores due to the synergistic effects of the high ∆ and GI refractive index profile. Notably, the experimentally fabricated multimode polymer optical waveguides achieve a bending loss of less than 0.1 dB, even under extreme conditions involving a 90° bend with a bend radius as small as 1 mm.

To expand optical fiber transmission capacity by combining mode division multiplexing (MDM) and wavelength division multiplexing (WDM), we reduce the wavelength dependence in the insertion loss of waveguide-type MUX/DEMUX devices expected to be applied to MDM. This is achieved by introducing an axial tapered core into the device.

Subminiature 1×2 branched multimode polymer optical waveguides with circular GI cores are fabricated using the Mosquito method for application as MUX devices in SWDM links. Then, we evaluate their performance, including the insertion loss dependence on the launch condition. For further dense integration of devices, subminiature 2D 1×4 branched and 3D 1×4 branched waveguides are successfully fabricated.

In this paper, we create a planar polymer optical waveguide sensor with four parallel cores. This four-core array features an optimized geometry obtained through a beam propagation method simulation. UV-curable polydimethyl siloxane is selected for the cladding, while a UV-curable acrylate resin is selected as the waveguide core. When pressure is applied to the core at different locations, precise sensing of the pressure value and location is achieved through changes in the output light intensity from the pressurized cores. The experimental results show that the sensitivities of four cores, Ch.1 to 4, in a fabricated waveguide sensor in a pressure range of 0-1.13 MPa, are 8.7 dB/MPa, 10.73 dB/MPa, 9.2 dB/MPa, and 10.88 dB/MPa, respectively. Additionally, we propose a 3D crossed core structure as a potential direction for future development. Optical waveguide structures not only demonstrate good flexibility and high sensitivity, but also have broad application potential, especially in the fields of flexible electronics and smart sensing.

This study theoretically proposes a refractive index (RI) sensor based on a polymer composite with a no-core fiber (NCF) design structure. Sensor designs with diameter variations of 125 urn, 105 urn, and 85 urn are simulated using the Wave Optics Module of COMSOL Multiphysics® software. The sensors are characterized within an analyte range of 1.470 RIU to 1.500 RIU, at intervals of 0.005 RIU. The results demonstrate effective interaction between the structure and the sensing medium. The highest recorded sensitivity is 4>10~6 (dimensionless) for the 85 um sensor, followed by 2><10~6 for the 105 um sensor, and 1>10~6 for the 125 um sensor. This study offers valuable insights, guiding the optimal design of polymer-based RI sensors for future environmental monitoring, chemistry, and biomedicine applications.

We present a unique polymer optical waveguide with circular cores fabricated by our proprietary technology, the Mosquito method. We demonstrate how to form 3D wiring patterns with perpendicularly bent cores with very small bending radii. We discuss the operability of polymer waveguides in the visible wavelength range for display applications.

In this article, optical waveguides are designed for ultrasensitive tactile sensing with fast response and high sensitivity. We create a polymer-based optical waveguide sensor that has been innovatively developed to address the limitations of conventional optical fiber-based sensors, particularly their flexibility and tactile capabilities. The principle of the sensor is output light intensity variation due to core bending. Our optical waveguides consist of polydimethylsiloxane (PDMS) as the cladding. An acrylate resin (XCL-02) is used for the core by dispensing its monomer into the PDMS (cladding) monomer using the Mosquito method. We demonstrate that there is a nearly linear relationship between the extra pressure and the insertion loss of the waveguide. The PDMS-based sensor exhibits high repeatability in the measurement pressure range. The sensor shows a sensitivity of 9.12 dB/MPa and a measurement range of 0–2.3 MPa, with a core diameter of approximately 100 μm and a light wavelength of 850 nm. This investigation sheds light on crucial factors influencing the sensor’s performance and response to the applied forces. We believe that this sensor can be applied in various fields, such as medical applications, wearable devices, and robotic tactile systems.

In this paper, we fabricate polymer optical waveguides doped with CdSe/ZnS quantum dots by applying the Mosquito method. The dependence of insertion loss and fluorescence intensity on the doping concentration is evaluated, and the potential application of these waveguides to optical amplifier devices is investigated.

Steeply bent core single-mode polymer optical waveguides are fabricated by varying the bending radius and core diameter using the Mosquito method. Then, we confirm that the small bending radius contributes to satisfy the singlemode condition even when the waveguide has high Δ. The bending loss under 1-mm bending radius can be reduced by designing slightly larger core size as 8.0 μ m.

© 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement We design graded-index (GI) circular-core waveguides to realize low-loss light coupling via 45-degree mirrors using a ray-trace simulator. The waveguide’s structural parameters, which determine the insertion loss of the waveguides with 45-degree mirrors, are the cladding thickness, the core size, the refractive index of materials, and the mirror angle. The optimum waveguide structural parameters are determined, and the GI circular-core waveguide with the appropriate structural parameters which is actually fabricated exhibits much lower total link loss than step-index (SI) core waveguides. The tight optical confinement of the GI-core contributes to the reduction of loss increment due to the mirror structure.

In this paper, propagating mode analysis is performed to optimize the core cross-sectional shape of polymer optical waveguide to be applied to a low loss adiabatic coupler to Si photonics chips when it is fabricated using the Mosquito method.

We design subminiature multimode 1x2 and 1x4 branched polymer optical waveguides with circular cores, and then applying a new needle-scan path to the Mosquito method to experimentally fabricate low-loss waveguide couplers.

We demonstrate multimode interference (MMI)-based Y-branch single-mode step-index (SI) core polymer optical waveguide splitter for the development of optical circuitry. This polymer waveguide splitter consists of a single input and multiple (six) outputs realized with organic-inorganic hybrid polymer materials. We set the core width for input and outputs of this polymer waveguide splitter as a single-mode, where the core width is particularly 6.5 mumathrm{m}. We design and demonstrate this Y-branch waveguide splitter using the beam propagation method at 1550-nm wavelength following the self-imaging principle. The power efficiency of this MMI-based Y-branch polymer waveguide splitter is 71%, and the excess loss is 1.4 dB.

In this paper, a novel structure for a multimode Y-branched polymer waveguide type multiplexer (MUX) device for mode division multiplexing (MDM) is proposed. Since the insertion loss of GI core Y-branched waveguides remains low even with the tilted launch beam or a small size of cross-sectional core, we have proposed asymmetric Y-branched MUX device which has different core size at the end of two-port arm. In this paper, we investigate the optimum structure of the asymmetric Y-branched waveguides MDM MUX device using a beam propagation simulation.

In this paper, polymer optical waveguides with 90-degree bent GI cores are fabricated using the Mosquito method. Material combinations that allow the formation of GI cores even with a diameter as large as 70 ?m are screened. By further adjusting the interim time, the desired parabolic GI core can be fabricated to realize a low-loss coupling device.

In this paper, in order to apply to optical connection components such as fan-in-fan-out (FIFO) devices for multicore fibers (MCFs), we design polymer optical waveguides with circular cores satisfying the single-mode condition, which are fabricated using the Mosquito method, and experimentally demonstrate that the optimum S-shape bent core waveguide can be fabricated as designed. The Mosquito method is a technique we have developed to form circular cores in both multimode and single-mode waveguides using a commercially available microdispenser and multi-axis syringe scanning robot. We have demonstrated that single-mode waveguides fabricated by the Mosquito method can be coupled with SMF with low loss. However, in order to realize a waveguide type FIFO device for MCFs by the Mosquito method, it is necessary to maintain micron-order positioning accuracy for the cores while three dimensionally aligning multiple cores in FIFO patterns. Since the pitch between the cores on the MCF side is very narrow, the core position is likely to deviate from the design value due to the liquid monomer flow caused by needle scan. We statistically confirm the possible amount of deviation from the design position by needle scan and feed it back to the program of needle scan path for the FIFO. We successfully fabricate a four-core FIFO with a desired core pitch. It is experimentally confirmed that the insertion loss is 1.4 dB on average. From these investigations, we confirm that the Mosquito method has an ability to fabricate small and low-loss FIFO devices.