Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1587/elex.12.20150727

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1088/0022-3727/48/38/383001

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1587/elex.12.20150574

Language：English   Publishing type：Research paper (scientific journal)  

We report CW single-wavelength emission at RT from non-grating active multi-mode interferometer laser diodes (MMI LDs) by using an asymmetric configuration. Fabricated devices showed side-mode suppression ratio (SMSR) of 31 dB (λ=1.56μm). We also present the modulation characteristics of this novel device at 1.25 Gbps for a 27−1 pseudorandom binary sequence.

Language：English   Publishing type：Research paper (scientific journal)  

We demonstrate fast and low energy all optical flip-flop devices based on asymmetric active-multimode interferometer using high-mesa waveguide structure. The implemented devices showed high speed all-optical flip-flop operation with 25ps long pulses. The rising and falling times of the output signal were 121 ps and 25 ps, respectively. The required set and reset pulse energies were only 7.1 fJ and 3.4 fJ, respectively.

DOI： 10.1364/OE.19.00B119

Language：English  

A novel principle of active multi-mode-interferometer (MMI) bi-stable laser diode (BLD), utilizing different lateral modes, has been proposed and demonstrated for optical random access memory (RAM) application. The two different propagation modes realize two different identical paths in a single active MMI cavity simultaneously, with sharing exactly same port at one facet side. This novel concept contributes to realize relatively large cross-gain saturation region between the two identical paths, which result in stable bi-stability even in a relatively compact device size. Implemented devices showed relatively low operation current of 100mA and sufficient hysteresis window of 8mA with the cavity length of only 550µm. High optical ON/OFF ratio of more than 15dB was also confirmed successfully.

Language：English   Publisher：International Exchange and Innovation Conference on Engineering & Sciences  

In the context of an aging global population, breath analysis offers a non-invasive method to assess health. One approach uses Cavity Ring-Down Spectroscopy (CRDS), where an optical amplifier compensates for feedback loop loss. However, the self-lasing phenomenon (arising when coherency is secured at a wavelength other than the sensing light) reduces device sensitivity. To mitigate this, a polarization rotator is introduced in the ring cavity, ensuring amplification benefits only the sensing light. As we develop an integrable CRDS system on a Silicon-On-Insulator (SOI) platform, we demonstrate that a 90° polarization rotation is crucial. SOI nanopixel waveguides with two converters and air holes can achieve an 86° to 94° rotation over a 20-nm wavelength range, with insertion loss manageable by the EDFA. A hole diameter of 70 nm offers a balance between reduced loss and efficient mode conversion, though larger holes may enhance mode confinement, particularly for TE10 and TM00 modes.

DOI： 10.5109/7323413

CiNii Research

Publisher：Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers  

In response to the global aging population, a photonic-integrated-circuit sensor is investigated for the detection of disease markers within human breath content. The device relies on cavity-ring-down spectroscopy with an amplifying medium and loop feedback to secure sufficient sensitivity down to ppm-order concentration detection. This configuration, however, might cause unwanted oscillation, and the polarization rotation method has been proposed to prevent this issue. We have researched a waveguide-based polarization rotator using nano-pixels. The device consists of two regions: (1) From TE00 mode TE10 modes conversion and (2) TE10 to TM00 modes conversion. As the intermediary TE10 mode quality is key to realizing polarization rotation performance, the purpose of this study is to realize high-quality TE10 by employing the mean-squared-error criterion for waveguide design optimization. A finite-difference time-domain simulation with this method reveals a TE10 mode with 1% accuracy that results in a polarization extinction ratio improved from 4.3 to 8.6 dB.

DOI： 10.35848/1347-4065/ad5299

Web of Science

Scopus

Publisher：Japanese Journal of Applied Physics  

The power splitter is one of the fundamental elements in a photonic IC. Among various power splitter structures, nano-pixel-based ones have attracted attention in recent years because of their flexible design capability. As there is no rigid design rule in nano-pixel layout, typically, inverse design algorithms are employed to realize the target function. In inverse design, general criteria are needed during the design process, and one typical criterion is the excess loss, however, there are no specific criteria for mode field evaluation. When designing a 1 × N power splitter, considering the power balance among the N output ports is crucial, therefore, we propose a correlation coefficient method to evaluate the output electric field profile. In this study, we adopted vector criteria including both an excess loss and correlation coefficient method during the inverse design process. As a result, the simulated results show all four 0th order modes and the output power to be 24.490%, 24.494%, 24.494%, and 24.490% with a low excess loss of 0.1 dB.

DOI： 10.35848/1347-4065/ad50e5

Web of Science

Scopus

Language：English  

DOI： 10.1016/j.scitotenv.2024.169908

Web of Science

PubMed

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Photonics  

The modulation bandwidth in the direct modulation of a laser diode is limited by relaxation oscillation. To achieve an even higher frequency response, photon–photon resonance has been investigated to extend this modulation bandwidth. Thus far, several reports have demonstrated a higher modulation performance being achieved when utilizing PPR; however, to our knowledge, the PPR control scheme has not been comprehensively discussed. In this paper, we discuss the theory of PPR in regard to the PPR frequency, intensity, and width control scheme. We propose to utilize waveguide configuration, specifically an active multimode interferometer, for optimization. The simulation results offer an approximately 8 GHz improvement in the frequency response.

DOI： 10.3390/photonics10121298

Web of Science

Scopus

Language：Others   Publishing type：Research paper (scientific journal)   Publisher：IEEE Photonics Technology Letters  

Power splitter is one of the fundamental elements in integrated photonic circuits. In this study, we experimentally demonstrate a highly asymmetric (9:1) power splitter based on nano-pixel waveguide. The implemented device was realized in a footprint of $3.2\times 3.4\,\,\mu \text{m}^{2}$. As an experiment result, a highly asymmetric splitting ratio of 9.4:1 with a propagation loss of 2.0 dB at 1550 nm wavelength was successfully confirmed. Additionally, a power splitting ratio deviation within 10% over 30 nm wavelength-band width was successfully demonstrated.

DOI： 10.1109/LPT.2023.3313944

Web of Science

Scopus

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY  

Power-splitter is one of the fundamental elements for photonic integrated circuits. Y-junction, multi-mode-interference (MMI), and directional coupler may have been widely used as power splitter; however, the design theory to realize precise asymmetric splitting ratio is not well established. In addition, the device length is relatively long and less robustness in general. To realize a power splitter with a desired splitting ratio, the authors used a nano-pixel structure. Nano-pixel structures consist of an array of pixels in which the rectangular waveguide region is divided into many nano-scale regions. The implemented devices were realized in an area of 3.2 mu m x 3.4 mu m. The device exhibited precise asymmetric splitting of 1.7:1 successfully at 1550 nm.

DOI： 10.1049/ell2.12831

Web of Science

Scopus

researchmap

Publisher：28th Microoptics Conference, MOC 2023  

Integration available polarization rotator has been proposed using nano-pixel waveguide. 4.2x0.96um2 region exhibits a polarization extinction ratio of 4.6 dB with excess loss of 5.1 dB in simulation.

DOI： 10.23919/MOC58607.2023.10302739

Scopus

Publisher：2023 Opto-Electronics and Communications Conference, OECC 2023  

Multimode demultiplexer is proposed by using nano-pixel configuration in a square of 3.0 × 3.0 μm2. The simulated results demonstrate mode XT of 13.6 dB and 11.4 dB for 0th and 1st order modes, respectively.

DOI： 10.1109/OECC56963.2023.10209986

Scopus

Publisher：28th Microoptics Conference, MOC 2023  

We observe slow light effect in nano-pixel waveguide for the first time as to our knowledge. The achieved slow light effect is with a group index NG of 8.73 in 1546 nm to 1553 nm wavelength range.

DOI： 10.23919/MOC58607.2023.10302870

Scopus

Publisher：28th Microoptics Conference, MOC 2023  

Vertical field enhancement is demonstrated using nano-pixel waveguide. As a result, relatively rectangular far-field-pattern are successfully obtained.

DOI： 10.23919/MOC58607.2023.10302935

Scopus

Publisher：28th Microoptics Conference, MOC 2023  

Nano-pixel based 90 ° bending waveguide is demonstrated toward 100% reflecting in a device cavity. 90 ° angle output was successfully confirmed with excess loss of 7 dB at 1550 nm.

DOI： 10.23919/MOC58607.2023.10302893

Scopus

Publisher：28th Microoptics Conference, MOC 2023  

We verify the signal modulation possibility of active-MMI laser diode on simulation. The modulation bandwidth is extended over 90 GHz which enables over 100 bps modulation.

DOI： 10.23919/MOC58607.2023.10302836

Scopus

Publisher：28th Microoptics Conference, MOC 2023  

1 \times 4 nano-pixel power splitter is designed using field profile criteria. The finalized power splitter shows all four 0th order modes, low excess loss of 0.1 dB, and low power deviation of 0.004% among all 4 ports.

DOI： 10.23919/MOC58607.2023.10302858

Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP Publishing Ltd  

Spatial-division-multiplexing, as a promising way to enhance the fiber transmission capacity of optical networks, has been widely researched, and still suffers from the problem of device size increasing along with the space-mode order increasing. In order to solve this problem, an optical mode field compression method is needed, however, it is difficult to realize for traditional optical waveguide. To achieve a highly dense photonic integrated circuit for the transmission of higher order space-mode, a space-mode compressor using nano-pixel structure was proposed and investigated in this work. A supervised machine learning model using a deep neural network was used to design and optimize the space-mode compressor based on nano-pixel structure. As a simulated result, we achieved possible nano-pixel configurations for the purpose of mode-compression and there is a more than 50% size compression for the 0th and 1st order modes, as well as a 39.3% size compression for the 2nd and 35% for 3rd order modes.

DOI： 10.35848/1347-4065/ac7b0e

Web of Science

Scopus

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

A semiconductor optical amplifier (SOA) is wildly used as gain media in a photonic integrated circuit, as it is integrable with various devices, including wavelength filter, on the same wafer. Quantum dots (QD) have been known to realize high-temperature operation without using a thermo-cooler, the saturated output power was not high due to the limited density of state in QD. To realize high saturated output power under high temperatures, we have exploited the active multi-mode interferometer (active-MMI) configuration on QD SOA. We fabricated active-MMI SOA using a 1.31 mu m InAs/GaAs QD active layer with the design of approximately 5 times larger footprint compared to a single stripe, whereas it holds regular single transverse mode output. As a result, a significant improvement of 15 dB saturated output power at 75 degrees C was substantiated successfully.

DOI： 10.35848/1347-4065/ac6a3e

Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP Publishing Ltd  

A multi-mode interference (MMI) waveguide has been widely researched and developed to realize an optical power coupler. MMI coupler exhibits the superior performance of the "Equal intensity coupling" characteristics, however, it has a problem that excess loss occurs if the phase-matching condition is not satisfied at all of the input ports. The phase condition depends on the number of input ports, and relatively complicated phase control is required, thus, it is desired to realize an optical power coupler without complicated phase adjustment. In order to avoid the phase-control difficulty, a nano-pixel power coupler is investigated in this paper. The nano-pixel-based coupler has the merit of ultra-compact dimension which is close to the wavelength order, therefore, it is expected that less excess loss even under simple "equal" phase conditions. The structure was examined using FDTD and the simulated results show equal input (intensity and phase) coupling capabilities with a low excess loss of 0.11 dB.

DOI： 10.35848/1347-4065/ac678d

Web of Science

Scopus

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.35848/1347-4065/ac6a3e

Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP Publishing Ltd  

A 3D waveguide is attractive because it has the potential that the waveguides are arranged, not only in plane, into three-dimension. The mosquito method, in which the core and cladding material sources are liquid and will be cured using UV light, is known as one of the ways to fabricate the 3D waveguide. In this method, if multiple waveguides are fabricated, the time until UV cure is different between the first waveguide and the last one and it leads to core position shift because of gravity. To solve the problem, we considered reducing the time from the first waveguide formation to the UV cure using automatic waveguide fabrication with a camera. For the automatic waveguide fabrication, YOLO (you look only once) and OpenCV are exploited as machine learning and an image processor, respectively. As a result, a waveguide recognition time of 10 ms and image processing time of 50 ms, totally 60 ms, are realized.

DOI： 10.35848/1347-4065/ac6e57

Web of Science

Scopus

researchmap

Language：Others  

DOI： 10.23919/moc52031.2021.9598033

Language：English   Publishing type：Research paper (scientific journal)  

This paper reports a single dimensional mode based multiplexer / de-multiplexer using the slab waveguide to realize high modes multiplexing and high integration in the non-MIMO (multi-in multi-out) multimode transmission system. A sufficient mode crosstalk of -20 dB was obtained by selecting suitable parameters of the spacing between the connecting positions of each arrayed waveguide D_i, the radius slab waveguide R₀ and lateral V-parameter.

DOI： 10.1587/transele.2020ecs6017

Language：English   Publishing type：Research paper (scientific journal)  

An optical power coupler is one of the most well-used components in integrated photonics. Although couplers with an output power ratio 1:1 have been widely studied in the past, constructing asymmetric-ration optical power couplers is still an issue that is difficult to be addressed by using traditional Y-branch waveguides. Artificial intelligence (AI) assisted design is an effective technique for realizing complex optical structures. In this work, we have designed asymmetric-ration optical power couplers by using AI assisted design. TWo couplers with the targeted splitting power ratio as 1:9 and 1:99 have been designed, respectively. In the AI assisted design, the coupler area was divided into discrete nano-pixels in the shape of circular holes with the same dimension. The AI controlled each pixel to be occupied by waveguide or air and trialed the occupation of each pixel one by one. In a 3.4 x 3.2 mu m(2) area, it took 1452 trials to obtain one optimized coupler. As a result, a splitting power ratio of 1:9.007 and 1:99.004 for the two couplers has been confirmed by using the finite-difference time-domain method. In addition, the waveguide configuration was further modified as the excess loss of the AI-designed coupler was a bit high, more than 3.50dB. The way to reduce the loss is as follows: 1) positioning optimization of the output waveguide to avoid light scattering at the boundary between the coupler and the output waveguide, and 2) widening the output waveguide width to avoid insufficient light coupling. As a result, a scattering loss reduction of 1.7 dB by position optimization, and a coupling loss reduction of 1.6dB by width widening were confirmed. The achieved design also exhibited a wide operation wavelength ranging from 1500-1600 nm in addition to sufficient fabrication tolerance of +/- 10nm (+/- 11%). (C) 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

DOI： 10.1364/OSAC.412933

Language：English   Publishing type：Research paper (scientific journal)  

A novel shuffle converter by using 3D waveguide of MCF (multi-core fiber)/SMF (single mode fiber) ribbon fan-in fan-out configuration towards over 1,000 port count optical matrix switch has been proposed. The shuffle converter enables to avoid waveguide crossing section in the optical matrix switch configuration, and the principle device showed sufficient crosstalk of less than -54.2 dB, and insertion loss of 2.1 dB successfully.

DOI： 10.1587/transele.2020ecs6002

Language：English   Publishing type：Research paper (scientific journal)  

Spot-size converter (SSC) is an essential building block for integrated photonic circuits applied as a mode transformer between optical components. One typical issue for SSC is the difficulty of broadening the vertical field profile. Herein, we propose a nanopixel SSC (1 x 2 mu m(2)) with changing hole size and density. Unlike a typical SSC, this configuration controls both the lateral and vertical field profiles relatively easily by enhancing the nanopixel density. A vertical field expansion of 1.21 mu m was obtained by enhancing the nanopixel density. In addition, we designed the optical field in the lateral direction using deep neural network (DNINO-based learning to realize a perfect circular spot for high coupling efficiency that reached -3 dB at lambda(0) = 1.572 gm when the optical field aspect ratio was adjusted to 1 after training for 200 epochs. Furthermore, the vertical expansion was increased from 1.21 to 4.9 mu m and the coupling efficiency from -3 to -0.41 dB by combining it a silicon dioxide window structure (5 x 15 x 10 mu m(3)). The 1-dB operating bandwidth of the designed SSC structure is 100 nm (1.5-1.6 mu m), while fabrication tolerance of the nanopixels and window structure length for the designed SSC structure are +/- 15 nm and +/- 250 nm when the coupling efficiency drops by 1 dB. (C) 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

DOI： 10.1364/OE.412911

Language：English   Publishing type：Research paper (scientific journal)  

DOI： https://doi.org/10.1364/OE.412911

Language：English  

Language：English  

DOI： 10.1587/transele.2020ece0001

Language：English   Publishing type：Research paper (scientific journal)  

Breath sensing is an effective tool for health monitoring. Previously, high-mesa waveguide structures have been proposed by our group for realizing a compact breath-sensing photonic circuit. By using the doped SiO2 as the waveguide core, 50% concentration CO2 has been detected. One issue of preventing parts per million (ppm)-order detection is the low portion of evanescent light (Gamma(air) = 2.2%) in the doped SiO2 waveguides. In order to realize low propagation loss a and high simultaneously, thin silicon (Si) waveguides with a Gamma(air) as high as 37.6% have been proposed and fabricated in this work. A thermal oxidation technique was applied to further reduce a, so that a was decreased from 1.45 to 0.84 and 0.29 to 0.2 dB/cm for the 0.5 and 3-mu m-wide waveguide, respectively. According to our analysis, the significantly decreased alpha is attributed to recovering the damaged Si core and smoothing the waveguide sidewalls. The high Gamma(air) air and effective loss reduction show a promising potential of applying Si high-mesa waveguides to realize ppm-order sensing. (C) 2020 Optical Society of America

DOI： 10.1364/AO.391604

Language：English  

DOI： 10.15017/2552953

Language：English   Publishing type：Research paper (other academic)  

1xN optical mode switch is newly proposed in this paper. Simulated results show all the switching under low excess loss (1.6 dB) due to the precise eigen-mode realization.

DOI： 10.15017/2552952

Language：English   Publishing type：Research paper (other academic)  

We have designed and fabricated 1 x N active multimode interferometer laser diodes to achieve two photon-photon resonances (PPRs). Very high frequency of 60 GHz in addition to 20 GHz PPR peaks were confirmed.

DOI： 10.15017/2552954

Language：English  

DOI： 10.15017/2552951

Language：Japanese  

Propagation Mode Retention at Fiber Bending Region Using Strongly Coupled Multi-Core Fiber

DOI： 10.11527/jceeek.2019.0_374

Language：Japanese   Publishing type：Research paper (other academic)  

Significant Propagation Loss Reduction on Silicon High-Mesa Waveguides Using Thermal Oxidation Technique
We have exploited thermal oxidation technique to silicon high-mesa waveguides for sensing-application. Significant propagation loss reduction from 1.45 to 0.84 dB/cm at a waveguide width of 500 nm has been achieved by the technique successfully.

DOI： 10.11527/jceeek.2019.0_373

Language：English   Publishing type：Research paper (scientific journal)  

The sol-gel method is a well-known process for SiO2 formation on top of a semiconductor-based waveguide. This method does not require expensive equipment or SiH4 gas. However, it may result in difficulty with wet-etching, which prevents proper current injection into the semiconductor layer. We have investigated the surface condition of sol-gel SiO2 on top of Si, and have confirmed that the main causes of the antietching property might be due to the formation of a polymer layer after the curing process. To improve the surface condition, plasma ashing, in addition to 700 degrees C curing, is proposed. Regular wet etching of SiO2 layer on Si with a ratio of 1800 nm min(-1) has been successfully confirmed. (C) 2019 The Japan Society of Applied Physics

DOI： 10.7567/1347-4065/ab27b2

Language：English   Publishing type：Research paper (scientific journal)  

A high-speed mode selective light source with over 40 GHz direct modulation bandwidth on both 0th and 1st order modes was demonstrated on an active multimode interferometer laser diode (active-MMI LD). By introducing multiple photon-photon resonances (PPR), the bandwidth of small signal frequency response is extremely extended. As the advantage of the active-MMI, the designed PPR frequencies are stable and do not change as the cleaving condition changes. In this work, 1 x 3 asymmetric active-MMI LD was fabricated to introduce multiple PPRs. Over 40 GHz direct modulation bandwidth has been confirmed experimentally on both 0th and 1st order modes. (C) 2019 The Japan Society of Applied Physics

DOI： 10.7567/1347-4065/ab1fd7

Language：Others  

DOI： 10.23919/ps.2019.8817633, 10.1587/transele.2020ecs6017_references_DOI_OOZLX5qVNJ8FkcBLenkuCbFLfLS

Language：English   Publishing type：Research paper (other academic)  

Several mode de-multiplexers base on LP mode (Linearly Polarized) have been proposed and demonstrated [1-3], however, LP mode based multiplexing, have required multi-in multi-out (MIMO) processing due to its difficulty of mode de-multiplexing caused by the mode degeneration and the mode crosstalk. In order to resolve this problem, spatial multiplexing transmission using a single dimensional spatial mode has been proposed [4-5]. We are studying a phase control type de-multiplexer using Rowland circle waveguide to de-multiplex singledimensional spatial mode [6]. In this work, we investigated the light focusing function of the Rowland circle waveguide for single dimensional spatial mode. The simulated result shows the possibility of de-multiplexing single dimensional spatial mode with this configuration.

DOI： 10.34385/proc.31.p-17

Language：English   Publishing type：Research paper (other academic)  

"Data center traffic is already estimated to become 20 ZB by the year 2021 about twice as much as in 2018 [1]. MDM (mode division multiplexing) can expand transmission capacity within data center [2]; therefore, we propose to introduce an optical network system utilizing MDM into data centers [3]. It has; however, a problem of mode crosstalk in the fiber that prevents proper preservation of individual mode transmission. One main cause of this crosstalk has been mode excitation phenomenon at the bending region of the fiber [4]. In this paper, we study and demonstrate strongly coupled MCF to verify the mode retaining capability. We simulated and estimated the transmittance of input mode by using BPM (beam propagation method) simulation and verified the results by an experiment setup involving 4-cores strongly coupled MCF. As a result, we verified the mode retention characteristics of 5dB at 80mm bending radius, compared to regular multi-mode fiber."

DOI： 10.34385/proc.31.p-15

Language：English   Publishing type：Research paper (scientific journal)  

We have proposed and demonstrated a mode selective active-MMI (multimode interferometer) laser diode as a mode selective light source so far. This laser diode features; 1) lasing at a selected space mode, and 2) high modulation bandwidth. Based on these, it is expected to enable high speed interconnection into future personal and mobile devices. In this paper, we explain the mode selection, and the high speed modulation principles. Then, we present our recent results concerning high speed frequency response of the fundamental and first order space modes.

DOI： 10.1587/transele.2018ODI0003

Language：English   Publishing type：Research paper (scientific journal)  

One-dimensional photonic crystal (1D PhC) cavities are used as ultrasensitive gas sensors due to their high sensitivity to changes in the surrounding environment. One of the issues for typical 1D PhC-based sensors is that the confined optical field does not fully overlap with analytes, which therefore leads to low sensitivity. Herein, we propose and numerically investigate a photonic crystal cavity by introducing a two tangent air hole array to improve the gas refractive index sensitivity. We also investigate the spectral feature of the proposed photonic crystal cavity for varying structure parameters and methane gas concentration. In addition, the coupling efficiency of the waveguide and the influence of the temperature on the proposed structure for sensing applications are analyzed. Theoretical analysis reveals that the proposed two tangent hole structure simultaneously achieves a high sensitivity (353 nm/RIU) and figure of merit (FOM = 1.2 x 10(4)) compared to those observed in previous studies. (C) 2019 The Japan Society of Applied Physics

DOI： 10.11470/jsapmeeting.2019.1.0_830

Language：English   Publishing type：Research paper (scientific journal)  

A high-speed mode selective light source with over 40 GHz direct modulation bandwidth on both 0th and 1st order modes was demonstrated on an active multimode interferometer laser diode (active-MMI LD). By introducing multiple photon-photon resonances (PPR), the bandwidth of small signal frequency response is extremely extended. As the advantage of the active-MMI, the designed PPR frequencies are stable and do not change as the cleaving condition changes. In this work, 1 × 3 asymmetric active-MMI LD was fabricated to introduce multiple PPRs. Over 40 GHz direct modulation bandwidth has been confirmed experimentally on both 0th and 1st order modes.

DOI： 10.7567/1347-4065/ab1fd7

Language：English   Publishing type：Research paper (scientific journal)  

One-dimensional photonic crystal (1D PhC) cavities are used as ultrasensitive gas sensors due to their high sensitivity to changes in the surrounding environment. One of the issues for typical 1D PhC-based sensors is that the confined optical field does not fully overlap with analytes, which therefore leads to low sensitivity. Herein, we propose and numerically investigate a photonic crystal cavity by introducing a two tangent air hole array to improve the gas refractive index sensitivity. We also investigate the spectral feature of the proposed photonic crystal cavity for varying structure parameters and methane gas concentration. In addition, the coupling efficiency of the waveguide and the influence of the temperature on the proposed structure for sensing applications are analyzed. Theoretical analysis reveals that the proposed two tangent hole structure simultaneously achieves a high sensitivity (353 nm/RIU) and figure of merit (FOM = 1.2 × 10⁴) compared to those observed in previous studies.

DOI： 10.7567/1347-4065/ab26ab

Language：English   Publishing type：Research paper (scientific journal)  

A cavity-ring-down spectroscopy (CRDS) system utilizing waveguide for breath sensing realizes several meter optical path integration that has possibility for ppm-order gas sensing within a compact area. We have proposed an optical amplifier assisted gas sensing system scheme to compensate waveguide propagation loss that may prevent ppm-order gas detection. The amplifier in a CRDS system, however, may result in self-lasing at specific wavelength in case of high pumping condition. Once self-lasing happens, signal light loose its gain from amplifier. The amplifier spontaneous emission that generated by an erbium-doped fiber amplifier affects the background noise level of cavity ring-down waveforms. In this work, we propose the scheme of polarization direction control so as to suspend the self-lasing, and the scheme of additional loss as to suppress ASE power. As a result, we confirmed the suppression of light intensity at a self-lasing wavelength below -50 dBm and the gain improvement of 24 dB at signal.

DOI： 10.7567/1347-4065/ab1e3d

Language：English   Publishing type：Research paper (scientific journal)  

A multi-layer stacking scheme using a sol-gel SiO
₂
fabrication technique was developed towards stacking thick layers of >0.8 µm for cladding and passivation layers of optical waveguides. The multi-layer stacking scheme, which improves the intrinsic stress problem especially in case of thick layer stacking, enables a >0.8 µm sol-gel SiO
₂
thickness without cracking and peeling issues. As a result, thick layer of 3.5 µm with high surface resistivity of >6.6 × 10
¹³
Ω/m was obtained. Furthermore, a-Si/SiO
₂
waveguide (cladding thickness: 1.9 µm) was realized to confirm the fundamental potential as a cladding layer.

DOI： 10.1587/elex.15.20180783

Language：English  

DOI： 10.15017/1961297

Language：Japanese  

Preliminary Research on Spatial Single Dimensional Modes Demultiplexer by Adjusting Phase Wavefronts

DOI： 10.11527/jceeek.2018.0_401

Language：Japanese   Publishing type：Research paper (scientific journal)  

Amplifier Assisted CRDS (Cavity Ring-down Spectroscopy) toward Compact Breath Sensing
A cavity-ring-down spectroscopy (CRDS) system utilizing waveguide for breath sensing realizes several meter optical path integration that has possibility for ppm-order gas sensing within a compact area. We have proposed an optical amplifier assisted gas sensing system scheme to compensate waveguide propagation loss that may prevent ppm-order gas detection. The amplifier in a CRDS system, however, may result in selflasing at specific wavelength in case of high pumping condition. Once self-lasing happens, signal light loose its gain from amplifier. The amplifier spontaneous emission that generated by an erbium-doped fiber amplifier affects the background noise level of cavity ring-down waveforms. In this work, we propose the scheme of polarization direction control so as to suspend the self-lasing, and the scheme of additional loss as to suppress ASE power. As a result, we confirmed the suppression of light intensity at a self-lasing wavelength below -50 dBm and the gain improvement of 24 dB at signal. (C) 2019 The Japan Society of Applied Physics

DOI： 10.11527/jceeek.2018.0_403

Language：Others  

DOI： 10.1117/12.2306018, 10.1587/transele.2018odi0003_references_DOI_K2uvGi87tGC58fjfaiJknKCB1cH

Language：Japanese  

Language：English   Publishing type：Research paper (scientific journal)  

We newly propose the first lateral mode selective active multimode interferometer laser diode. The design principle is to arrange identical propagation path of different lateral mode. Thanks to multimode waveguide structure, 0th mode and 1st order mode has individual propagation path within one device. Individual lasing of fundamental mode as well as first mode was confirmed successfully.

DOI： 10.1587/transele.E100.C.775

Language：English  

DOI： 10.15017/1906119

Language：English   Publishing type：Research paper (scientific journal)  

We present dynamic mode switching characteristic by using a 2 x 2 optical mode switch based on silicon waveguide. The configuration of optical mode switch is similar to MZI where the width of input and output ports are designed to permit the combining of the fundamental mode and the first order mode. We designed the symmetrical arms with phase shifter based on p-i-n structure in one arm to generate a p-phase difference between each arm. As a result, mode switching with the injection current of 60mA (5.7 V) was successfully achieved with the mode crosstalk of -10 dB at lambda = 1550 nm. A minimum of less than 60 ns and 40 ns mode switching time for the fundamental mode to first order mode and first order mode to fundamental mode, was achieved respectively in this time.

DOI： 10.1587/transele.E100.C.782

Language：English   Publishing type：Research paper (scientific journal)  

A multi-layer vertically stacked all sol-gel fabrication technique on bulk silicon is proposed to realize vertical coupling from planar waveguides to 3-dimensional structures. The all sol-gel fabrication technique realizes the capability to stack ZnO sol-gel core layer and SiO₂ sol-gel cladding and core separation layers. A major issue with sol-gel based fabrication is the appearance of cracks on the sol-gel layer, and these were improved by a slow cooling process of 1°C/min after 500°C temperature annealing in addition to a SiO₂ surface cleaning using photoresist remover. As a result, a multi-layer vertically stacked structure with a ZnO core layer thickness of 300 nm and SiO₂ cladding/core separation layer thickness of 1.5 μm was successfully fabricated on bulk Si.

Language：English  

DOI： 10.11470/jsapmeeting.2017.2.0_979

Language：English  

DOI： 10.15017/1812436

Language：English   Publishing type：Research paper (scientific journal)  

The recent rapid growth of data traffic is leading to high-speed communication for local areas, such as the fiber-to-the-home service. A semiconductor laser is used for such a purpose; however, there is the difficulty that an even higher frequency response occurs in only carrier-photon resonance. For this reason, it is effective to use a second resonance, such as a photon-photon resonance (PPR), for enhancing the frequency response, and the active multimode interferometer laser diode (active-MMI LD) is one of the candidates for achieving a high PPR frequency. In order to obtain an even higher PPR frequency, we have investigated the control scheme of enhancing PPR. In this work, we compared two types of active-MMI waveguide structures to confirm the scheme. As a result, a 3.8 GHz enhancement of the PPR peak, resulting in a 3 dB lower frequency response of 17 GHz, has been successfully achieved by waveguide geometry modification. (C) 2016 The Japan Society of Applied Physics.

DOI： 10.7567/JJAP.55.08RD04

Language：English   Publishing type：Research paper (scientific journal)  

Electrically controlled optical-mode switch for fundamental mode and first order mode
We have proposed an optical mode switch, the principle of which is based on the partial phase shift of injected light; therefore, one important issue is to clarify the proper design criteria for the mode combiner section. We focused on the bending radius of the S-bend waveguide issue that is connected to the multi mode waveguide in the Y-junction section that acts as mode combiner. Long radius leads to undesired mode coupling before the Y-junction section, whereas a short radius causes radiation loss. Thus, we simulated this mode combiner by the beam-propagation method to obtain the proper radius. In addition, we used a trench pin structure to simplify the fabrication process into a single-step dry-etching process. As a result, we successfully fabricated an optical-mode switch with the bending radius R = 610 mu m. It showed the successful electrical mode switching and the achieved mode crosstalk was approximately % 10 dB for 1550nm wavelength with the injection current of 60mA (5.7 V). (C) 2016 The Japan Society of Applied Physics

DOI： 10.7567/jjap.55.08rb06, 10.1587/transele.e100.c.782_references_DOI_GzWIMJJFo1bI9Ublmu1A7kijR5N

Language：English   Publishing type：Research paper (scientific journal)  

We have proposed and demonstrated the principle of optical mode switch. However, the crosstalk between modes has not yet reported due to the difficulty of mode recognition and distinction. To accomplish this mode crosstalk evaluation, we integrated multimode interference (MMI) mode filter with the optical mode switch in this work. As a result, for the both TE and TM modes, the crosstalk of approximately - 10 dB has been evaluated experimentally.

DOI： 10.1587/transele.E99.C.825

Language：English  

Language：Others  

DOI： 10.1109/moc.2015.7416394, 10.1587/transele.e100.c.782_references_DOI_P7moAv8O7ddZ91egNnqZZ138Txj

Language：English  

Active MMI devices: concept, proof, and recent progress
Multi-mode interference (MMI) couplers (waveguides) are widely studied and developed as key components of photonic integrated circuits, including power coupler/dividers, and others. Furthermore, another possibility utilizing MMI has been investigated on active devices so far. Owing to the wider area of the multi-mode waveguide section compared with that of the regular single-mode waveguide, MMI may result in higher performance (high power, low power consumption, and others) rather than conventional active devices while maintaining regular single-mode output. Thus, active multi-mode interferometer (active-MMI) devices, including laser diodes (LDs), super-luminescent light emitting diodes (SLEDs), and semiconductor optical amplifiers (SOAs) have been studied. Moreover, they have been also exploited to bi-stable LDs and single wavelength emitters, and others using the interference inside the MMI section. In this paper, we review and summarize the recent progress in active MMI devices. We provide proof of MMI phenomena in active waveguides and discuss the results.

DOI： 10.1088/0022-3727/48/38/383001, 10.7567/1347-4065/ab090f_references_DOI_RPRj6MFCJEfiJM5RxJ2vQUve0qB, 10.1587/transele.e100.c.775_references_DOI_RPRj6MFCJEfiJM5RxJ2vQUve0qB

Language：English  

Language：Others  

DOI： 10.1109/ibp.2015.7230770, 10.7567/jjap.55.08rb06_references_DOI_7HIgUD4Hb1HV69plA0IBm3ku8fa

Language：English   Publishing type：Research paper (scientific journal)  

We demonstrate low hysteresis threshold current (39 mA) bistable laser diodes (BLDs), with maintaining sufficient hysteresis window(7 mA, 18% of the hysteresis threshold), in active multimode-interferometer (MMI) using lateral-modes bistability. The sufficient cross-gain saturation effect, due to the lateral-modes bistability principle, enables wide hysteresis window. By using this principle, we could design the active-MMI BLDs with relatively short saturable-absorber length that has been one of the main causes of high hysteresis threshold current. In the actual design, we reduce the saturable-absorber region length to 25 mu m, and thus, we could achieve a low hysteresis current of 39 mA in the active MMI BLDs with maintaining sufficient hysteresis window for the first time.

DOI： 10.1109/JSTQE.2011.2156386

Event date： 2021.11

Language：English   Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2021.9

Language：Japanese   Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2021.9

Language：English   Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2021.9

Language：English   Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2021.9

Language：English  

Country：Japan  

Event date： 2021.9

Language：English   Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2021.8

Language：Japanese   Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2017.11

Language：English  

Venue：Tokyo   Country：Japan  

Active-multimode interferometer laser diode that integrates at least six oscillating cavities has been achieved successfully. Multiple cavities contribute to multiple longitudinal mode spacings as well as multiple PPR frequencies. Device aiming 100 GHz bandwidth design principle is proposed.

Event date： 2017.9

Language：English  

Venue：Gothenburg   Country：Sweden  

Multiple cavity active-Multimode Interferometer Laser Diode demonstrates multiple photon-photon resonances (8 GHz, 10 GHz, 13 GHz, 19 GHz, 23 GHz and 36 GHz) for the first time. Modulation bandwidth of at least 34 GHz was confirmed.

Event date： 2017.8

Language：English  

Venue：東京   Country：Japan  

Event date： 2017.8

Language：English  

Venue：東京   Country：Japan  

Event date： 2017.7

Language：English  

Venue：New Orleans   Country：United States  

New devices of optical mode switch and mode selective light source have been developed for mode division multiplexing especially for short distance network. Optical mode switch offers mode exchange flexibility while mode selective light source offers oscillation of individual modes. These devices may contribute to realize non-MIMO flexible network, especially for short distance, in the future.

Event date： 2016.9

Language：English  

Venue：Kobe   Country：Japan  

We newly showed lateral mode interference in the emission spectrum between 0th and 1st order modes on mode selective active multi-mode-interference laser diode that leads to single wavelength emission (SMSR=25 dB).

Event date： 2016.7

Language：English   Presentation type：Oral presentation (general)  

Venue：Niigata   Country：Japan  

Core-top etched waveguide has been proposed to realize vertical multi-mode interference (MMI) toward higher order LP mode-converter. Significant loss reduction of 3.0 dB/cm on core-top etched waveguide is achieved in this work.

Event date： 2016.7

Language：English  

Venue：Niigata   Country：Japan  

Preliminary research of MCF coupling to optical mode switch is reported. Using single lens system like conventional SMF coupling, output mode coupling is confirmed between MCF and optical mode switch with coupling loss of 9dB.

Event date： 2016.7

Language：English   Presentation type：Oral presentation (general)  

Venue：Niigata   Country：Japan  

Mode selective light source is demonstrated by using active-multimode interferometer laser diode for the first time. Individual lasing of fundamental mode and first mode is successfully confirmed.

Event date： 2016.7

Language：English   Presentation type：Oral presentation (general)  

Venue：Niigata   Country：Japan  

Dynamic mode switching is demonstrated by using optical mode switch. The switch utilizes phase shift based-on current injection. Less than 60 ns switching-time for the both 0th-to-1st and 1st-to-0th was confirmed for the first time.

Event date： 2016.3

Language：English   Presentation type：Oral presentation (general)  

Venue：福岡   Country：Japan  

Event date： 2016.3

Language：English   Presentation type：Oral presentation (general)  

Venue：福岡   Country：Japan  

Event date： 2015.10

Language：English  

Venue：Fukuoka   Country：Japan  

Event date： 2015.10

Language：English  

Venue：Fukuoka   Country：Japan  

Event date： 2015.10

Language：English  

Venue：Fukuoka   Country：Japan  

Event date： 2015.10

Language：English   Presentation type：Oral presentation (general)  

Venue：Fukuoka   Country：Japan  

Event date： 2015.10

Language：English  

Venue：Fukuoka   Country：Japan  

Event date： 2015.10

Language：English  

Venue：Fukuoka   Country：Japan  

Event date： 2015.10

Language：English  

Venue：Fukuoka   Country：Japan  

Event date： 2015.10

Language：English  

Venue：Fukuoka   Country：Japan  

Event date： 2015.10

Language：English   Presentation type：Oral presentation (general)  

Venue：大分   Country：Japan  

Event date： 2015.9

Language：English   Presentation type：Oral presentation (general)  

Venue：Florence   Country：Italy  

Event date： 2015.9

Language：English   Presentation type：Oral presentation (general)  

Venue：Sendai   Country：Japan  

Event date： 2015.9

Language：English   Presentation type：Oral presentation (general)  

Venue：Sendai   Country：Japan  

Event date： 2015.7

Language：English   Presentation type：Symposium, workshop panel (public)  

Venue：Kyoto   Country：Japan  

Event date： 2015.7

Language：English   Presentation type：Symposium, workshop panel (public)  

Venue：Kyoto   Country：Japan  

Event date： 2015.7

Language：English   Presentation type：Symposium, workshop panel (public)  

Venue：Kyoto   Country：Japan  

Event date： 2015.6 - 2015.7

Language：English   Presentation type：Oral presentation (general)  

Venue：Shanghai   Country：China  

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：福岡   Country：Japan  

Language：Others   Presentation type：Oral presentation (general)  

Country：Other  

Language：Others   Presentation type：Oral presentation (general)  

Country：Other  

Language：Others   Presentation type：Oral presentation (general)  

Country：Other  

Language：Others   Presentation type：Oral presentation (general)  

Country：Belgium  

Language：Others   Presentation type：Oral presentation (general)  

Country：Other  

Language：Others   Presentation type：Oral presentation (general)  

Country：United States  

Language：Others   Presentation type：Oral presentation (general)  

Country：Other  

Language：Others   Presentation type：Oral presentation (general)  

Country：Other  

Language：Others   Presentation type：Oral presentation (general)  

Country：Austria  

Language：Others   Presentation type：Oral presentation (general)  

Country：Other  

Language：Others   Presentation type：Oral presentation (general)  

Country：Other  

Language：Others   Presentation type：Oral presentation (general)  

Country：China  

Language：Others   Presentation type：Oral presentation (general)  

Country：Other  

Language：Others   Presentation type：Oral presentation (general)  

Country：Other  

Language：Others   Presentation type：Oral presentation (general)  

Country：Other  

Language：Others   Presentation type：Oral presentation (general)  

Country：Other  

Language：Others   Presentation type：Oral presentation (general)  

Country：United States  

Language：Others   Presentation type：Oral presentation (general)  

Country：Other  

Language：Others   Presentation type：Oral presentation (general)  

Country：Other  

Language：Others   Presentation type：Oral presentation (general)  

Country：Other  

Language：Others   Presentation type：Oral presentation (general)  

Country：Other  

Language：Others   Presentation type：Oral presentation (general)  

Country：Other  

Language：Others   Presentation type：Oral presentation (general)  

Country：Other  

Language：Others   Presentation type：Oral presentation (general)  

Country：Germany  

Language：Others   Presentation type：Oral presentation (general)  

Country：Taiwan, Province of China  

Language：Others   Presentation type：Oral presentation (general)  

Country：Switzerland  

Language：Others   Presentation type：Oral presentation (general)  

Country：Other  

Language：Others   Presentation type：Oral presentation (general)  

Country：Other  

Language：Others   Presentation type：Oral presentation (general)  

Country：Other  

Language：Others   Presentation type：Oral presentation (general)  

Country：Other  

Language：Others   Presentation type：Oral presentation (general)  

Country：Other  

Language：Others   Presentation type：Oral presentation (general)  

Country：Other  

Language：English   Presentation type：Oral presentation (general)  

Venue：アメリカ   Country：United States  

Language：Japanese   Presentation type：Oral presentation (general)  

Country：Japan  

Language：Japanese   Presentation type：Oral presentation (general)  

Country：Japan  

Language：Japanese   Presentation type：Oral presentation (general)  

Country：Japan  

Language：English  

Country：Japan  

Language：Japanese   Presentation type：Oral presentation (general)  

Country：Japan  

Language：Japanese   Presentation type：Oral presentation (general)  

Country：Japan  

Language：Japanese   Presentation type：Oral presentation (general)  

Country：Japan  

Language：English   Presentation type：Oral presentation (general)  

Country：Indonesia  

Language：Japanese   Presentation type：Oral presentation (general)  

Country：Japan  

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：大分   Country：Japan  

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：大分   Country：Japan  

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：大分   Country：Japan  

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：福岡   Country：Japan  

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：福岡   Country：Japan  

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：福岡   Country：Japan  

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：大分   Country：Japan  

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：福岡   Country：Japan  

Event date： 2023.9

Language：English   Presentation type：Oral presentation (general)  

Venue：Seagaia Convention Center, Miyazaki   Country：Japan  

Event date： 2023.9

Language：English   Presentation type：Oral presentation (general)  

Venue：Seagaia Convention Center, Miyazaki   Country：Japan  

Event date： 2023.9

Language：English   Presentation type：Oral presentation (general)  

Venue：Seagaia Convention Center, Miyazaki   Country：Japan  

Event date： 2023.9

Language：English   Presentation type：Oral presentation (general)  

Venue：Seagaia Convention Center, Miyazaki   Country：Japan  

Event date： 2023.7

Language：English   Presentation type：Oral presentation (general)  

Venue：Shanghai   Country：China  

Event date： 2022.9

Language：English   Presentation type：Oral presentation (general)  

Venue：Online   Country：Japan  

Event date： 2022.9

Language：English   Presentation type：Oral presentation (general)  

Venue：Online   Country：Japan  

Event date： 2021.11

Language：English   Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2021.9

Language：English   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Japan  

Event date： 2021.9

Language：Japanese   Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2021.9

Language：English   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Japan  

Event date： 2021.6 - 2021.9

Language：English   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Japan  

Event date： 2021.3

Language：Japanese   Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2021.3

Language：English   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Japan  

Event date： 2021.3

Language：English   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Japan  

Event date： 2021.3

Language：English   Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2020.10

Language：English   Presentation type：Oral presentation (general)  

Venue：オンライン発表   Country：Japan  

Event date： 2020.10

Language：English   Presentation type：Oral presentation (general)  

Venue：オンライン発表   Country：Japan  

Event date： 2020.10

Language：English   Presentation type：Oral presentation (general)  

Venue：Web開催   Country：Japan  

Event date： 2020.10

Language：English   Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2020.9

Language：English   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Japan  

Event date： 2020.9

Language：English   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Japan  

Event date： 2020.9

Language：English   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Japan  

Event date： 2020.9

Language：English   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Japan  

Event date： 2020.6

Language：English   Presentation type：Oral presentation (general)  

Venue：オンライン発表   Country：Japan  

Event date： 2020.3

Language：English   Presentation type：Oral presentation (general)  

Venue：日本   Country：Japan  

Event date： 2020.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：日本   Country：Japan  

Event date： 2020.3

Language：English   Presentation type：Oral presentation (general)  

Venue：日本   Country：Japan  

Event date： 2019.12

Language：English  

Venue：早稲田大学   Country：Japan  

Event date： 2019.12

Language：English  

Venue：早稲田大学   Country：Japan  

Event date： 2019.11

Language：English  

Venue：富山   Country：Japan  

Event date： 2019.11

Language：English   Presentation type：Oral presentation (general)  

Venue：富山   Country：Japan  

Event date： 2019.10

Language：English   Presentation type：Oral presentation (general)  

Venue：九州大学 筑紫キャンパス   Country：Japan  

Event date： 2019.10

Language：English  

Venue：九州大学 筑紫キャンパス   Country：Japan  

Event date： 2019.10

Language：English   Presentation type：Oral presentation (general)  

Venue：九州大学 筑紫キャンパス   Country：Japan  

Event date： 2019.10

Language：English   Presentation type：Oral presentation (general)  

Venue：九州大学 筑紫キャンパス   Country：Japan  

Event date： 2019.10

Language：English   Presentation type：Oral presentation (general)  

Venue：九州大学 筑紫キャンパス   Country：Japan  

Event date： 2019.10

Language：English   Presentation type：Oral presentation (general)  

Venue：九州大学 筑紫キャンパス   Country：Japan  

Event date： 2019.10

Language：English   Presentation type：Oral presentation (general)  

Venue：鹿児島   Country：Japan  

Event date： 2019.10

Language：English   Presentation type：Oral presentation (general)  

Venue：鹿児島   Country：Japan  

Event date： 2019.10

Language：English   Presentation type：Oral presentation (general)  

Venue：鹿児島   Country：Japan  

Event date： 2019.10

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：鹿児島   Country：Japan  

Event date： 2019.9

Language：English   Presentation type：Oral presentation (general)  

Venue：九州工業大学   Country：Japan  

Event date： 2019.9

Language：English   Presentation type：Oral presentation (general)  

Venue：九州工業大学   Country：Japan  

Event date： 2019.9

Language：English   Presentation type：Oral presentation (general)  

Venue：九州工業大学   Country：Japan  

Event date： 2019.9

Language：English   Presentation type：Oral presentation (general)  

Venue：九州工業大学   Country：Japan  

Event date： 2019.9

Language：English   Presentation type：Oral presentation (general)  

Venue：大阪大学 豊中キャンパス   Country：Japan  

Event date： 2019.9

Language：English   Presentation type：Oral presentation (general)  

Venue：大阪大学 豊中キャンパス   Country：Japan  

Event date： 2019.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：大阪大学 豊中キャンパス   Country：Japan  

Event date： 2019.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：大阪大学 豊中キャンパス   Country：Japan  

Event date： 2019.7

Language：English  

Venue：Fukuoka   Country：Japan  

Slit structure is proposed to achieve stable I^st order mode emission for mode selective LD. As a result, 3.6dB improvement in mode XT is confirmed in the actually implemented device, compared to those without slit one.

Event date： 2019.7

Language：English  

Venue：Fukuoka   Country：Japan  

We are studying a space mode multiplexer / de-multiplexer using Rowland circle waveguide for multiplex / de-multiplex single dimensional spatial mode. The simulated result shows the possibility of de-multiplexing single dimensional spatial mode.

Event date： 2019.7

Language：English  

Venue：Fukuoka   Country：Japan  

We have exploited thermal oxidation technique to silicon high-mesa waveguides for sensing-application. Significant propagation loss reduction from 1.45 to 0.84 dB/cm at a waveguide width of 500 nm has been achieved by the technique successfully.

Event date： 2019.7

Language：English  

Venue：Fukuoka   Country：Japan  

1xN optical mode switch is newly proposed in this paper. Simulated results show all the switching under low excess loss (1.6 dB) due to the precise eigen-mode realization.

Event date： 2019.7

Language：English  

Venue：Fukuoka   Country：Japan  

Strongly coupled MCF is studied in propagation mode retaining capability as regular multimode fiber has an issue of mode crosstalk. As a result, mode retention characteristics of 5dB at 80 mm bending radius has been confirmed successfully.

Event date： 2019.7

Language：English   Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2019.7

Language：English   Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2019.7

Language：English   Presentation type：Oral presentation (general)  

Country：Taiwan, Province of China  

Event date： 2019.7

Language：English   Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2019.7

Language：Japanese   Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2019.7

Language：Japanese   Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2019.7

Language：English   Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2019.7

Language：English   Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2019.7

Language：Japanese   Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2019.7

Language：Japanese   Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2019.7

Language：Japanese   Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2019.7

Language：English   Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2019.7

Language：English   Presentation type：Oral presentation (general)  

Country：Taiwan, Province of China  

Event date： 2019.7

Language：English   Presentation type：Oral presentation (general)  

Country：Korea, Republic of  

Event date： 2019.7

Language：English   Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2019.7

Language：English   Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2019.7

Language：English   Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2019.7

Language：English   Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2019.7

Language：English  

Country：Japan  

Event date： 2019.7

Language：English  

Country：Taiwan, Province of China  

Event date： 2019.7

Language：English   Presentation type：Oral presentation (general)  

Country：Taiwan, Province of China  

Event date： 2019.5

Language：English   Presentation type：Oral presentation (general)  

Venue：伊勢   Country：Japan  

Event date： 2019.5

Language：English   Presentation type：Oral presentation (general)  

Venue：伊勢   Country：Japan  

Event date： 2019.3

Language：English   Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2019.1

Language：Japanese   Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2018.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：金沢大学   Country：Japan  

Event date： 2018.4

Language：English  

Venue：Strasbourg   Country：France  

Photon-photon resonance (PPR) has been researched to achieve high modulation frequency bandwidth in direct modulation laser diode (LD). The phenomena of PPR, which has the potential of having a resonance peak at a higher frequency rather than carrier-photon resonance (CPR, namely, regular resonance), is based on different internal oscillation in a laser chip, therefore, it is essential to involve plural different internal optical paths in a laser diode chip. One biggest issue is to achieve flat frequency response as the frequency response normally deteriorate at a higher frequency region than CPR. To mitigate this issue, we have demonstrated multiple PPR by using active-MMI configuration, and have proved more than 40 GHz band-width so far successfully. In this paper, we discuss about the recent progress of the active-MMI laser diode which enables to realize this multiple PPR phenomena, and the recent results. We hope and believe that this approach will contribute to realize over Tbps direct modulation laser diode, which will be integrated in the high-speed interconnection on board in the future.

Event date： 2018.3

Language：English  

Venue：San Diego   Country：United States  

Mode selective active multimode interferometer laser diode demonstrated high speed modulation capacity. Over 40 GHz direct modulation bandwidth was confirmed for the both 0th and 1st order modes.

Event date： 2015.10

Language：English  

Venue：Fukuoka   Country：Japan  

Photon-photon resonance (PPR) peak enhancement on active multimode interferometer laser diode is demonstrated. 3.8 GHz enhancement of PPR peak that results in 3 dB-down frequency response of 17 GHz has been successfully achieved by waveguide geometry modification.

Event date： 2015.10

Language：English  

Venue：Fukuoka   Country：Japan  

The design criteria that achieve the excess loss of less than 1.0 dB in entire C-band has been clarified for MMI mode converter. As a result, we have confirmed that MMI width in addition to access waveguide width ratio over MMI width are the important design criteria.