α-Synuclein orchestrates Th17 responses as antigen and adjuvant in Parkinson's disease.

Recently, the role of T cells in the pathology of α-synuclein (αS)-mediated neurodegenerative disorders called synucleinopathies, including Parkinson's disease (PD), dementia with Lewy bodies (DLB), and multiple system atrophy, has attracted increasing attention. Although the existence of αS-specific T cells and the immunogenicity of the post-translationally modified αS fragment have been reported in PD and DLB, the key cellular subset associated with disease progression and its induction mechanism remain largely unknown.Peripheral blood mononuclear cells (PBMCs) from synucleinopathy patients and healthy controls were cultured in the presence of the αS peptide pools.

Compact magneto-optical isolator by µ-transfer printing of magneto-optical single-crystal film on silicon waveguides.

Optical isolators provide one-way propagation and are necessary to protect laser diodes from damage and unstable operation caused by reflected light. Although magneto-optical (MO) devices can operate as isolators, achieving high-density integration using conventional direct bonding methods is difficult because a large and thick growth substrate remains on the circuits. We experimentally demonstrated a compact Mach-Zehnder interferometer-based MO isolator with Si waveguides by the µ-transfer printing of a Ce:YIG/SGGG coupon.

Inter-layer light transition in hybrid III-V/Si waveguides integrated by µ-transfer printing.

We demonstrate low-loss and broadband light transition from III-V functional layers to a Si platform via two-stage adiabatic-crossing coupler waveguides. A 900-µm-long and 2.7-µm-thick III-V film waveguide consisting of a GaInAsP core and InP cladding layers is transferred onto an air-cladding Si photonic chip by the µ-transfer printing (µ-TP) method.

Dopamine detection on activated reaction field consisting of graphene-integrated silicon photonic cavity.

Graphene is widely recognized as an outstanding and multi-functional material in various application fields such as electronics, photonics, mechanics, and life sciences. We propose a neurotransmitter sensor with ultra-small volume for detecting the photonic light-matter response. Such detection can be achieved using surface-activated monolayer graphene sheets and CMOS-compatible silicon-photonic circuits.

Evaluation of graphene optical nonlinearity with photon-pair generation in graphene-on-silicon waveguides.

We evaluate the nonlinear coefficient of graphene-on-silicon waveguides through the coincidence measurement of photon-pairs generated via spontaneous four-wave mixing. We observed the temporal correlation of the photon-pairs from the waveguides over various transfer layouts of graphene sheets. A simple analysis of the experimental results using coupled-wave equations revealed that the atomically-thin graphene sheets enhanced the nonlinearity of silicon waveguides up to ten-fold.

Quantum-critical conductivity of the Dirac fluid in graphene.

Graphene near charge neutrality is expected to behave like a quantum-critical, relativistic plasma-the "Dirac fluid"-in which massless electrons and holes collide at a rapid rate. We used on-chip terahertz spectroscopy to measure the frequency-dependent optical conductivity of clean, micrometer-scale graphene at electron temperatures between 77 and 300 kelvin. At charge neutrality, we observed the quantum-critical scattering rate characteristic of the Dirac fluid.

Mid-IR broadband supercontinuum generation from a suspended silicon waveguide.

Mid-infrared light provides numerous unexpected opportunities in scientific discoveries because this wavelength region covers the fingerprints of various molecular vibrational resonances. However, the light generation efficiency and bandwidth have been a long-standing bottleneck which has limited the development so far. Moreover, the light source that can be integrated with other components such as wavelength filters, detectors, and electronics, will be the key factor toward the future practical applications.

Optical nonlinearity enhancement with graphene-decorated silicon waveguides.

Broadband on-chip optical frequency combs (OFCs) are important for expanding the functionality of photonic integrated circuits. Here, we demonstrate a huge local optical nonlinearity enhancement using graphene. A waveguide is decorated with graphene by precisely manipulating graphene's area and position.

Single silicon wire waveguide based delay line interferometer for DPSK demodulation.

We experimentally demonstrate a high-quality phase shift keying demodulator based on a silicon photonic wire waveguide. Since the birefringence of the waveguide generates extremely huge differential group delay, an ultra-compact and high-extinction-ratio delay line interferometer is devised in TE and TM modes. We firstly calculated and simulated the requirements for propagation length and waveguide's dimensions.

Monolithic integration of a silica AWG and Ge photodiodes on Si photonic platform for one-chip WDM receiver.

On the silicon (Si) photonic platform, we monolithically integrated a silica-based arrayed-waveguide grating (AWG) and germanium (Ge) photodiodes (PDs) using low-temperature fabrication technology. We confirmed demultiplexing by the AWG, optical-electrical signal conversion by Ge PDs, and high-speed signal detection at all channels. In addition, we mounted a multichannel transimpedance amplifier/limiting amplifier (TIA/LA) circuit on the fabricated AWG-PD device using flip-chip bonding technology.

High-gain, wide-dynamic-range parametric interaction in Mg-doped LiNbO3 quasi-phase-matched adhered ridge waveguide.

With recent developments and optimizations for quasi-phase-matched adhered ridge waveguide (QPM-ARW), outstanding performances containing efficient amplification were demonstrated by difference frequency generation (DFG) and optical parametric amplification (OPA). A maximum channel conversion efficiency of +7.6 dB (570%) was achieved in a telecommunication band using a 50 mm-long device, when coupling with 160 mW pump.

Influence of carrier lifetime on performance of silicon p-i-n variable optical attenuators fabricated on submicrometer rib waveguides.

We investigated influence of carrier lifetime on performance of silicon (Si) p-i-n variable optical attenuators (VOAs) on submicrometer Si rib waveguides. VOAs were fabricated with and without intentional implantation of lattice defects into their intrinsic region. Carrier lifetime was measured by pulse responses for normal incidence of picosecond laser pulse of 775 nm to the VOA, as approximately 1 ns and approximately 7 ns for the VOAs with and without defects, respectively.