A Time Mode Pulse Interleaver in a Silicon-on-Insulator Platform for Optical Analog-to-Digital Converters.

We propose and demonstrate a novel on-chip optical sampling pulse interleaver based on time mode interleaving. The designed pulse interleaver was fabricated on a 220 nm silicon-on-insulator (SOI) platform, utilizing only one S-shaped delay waveguide. Interleaving is achieved by the relative time delay between different optical modes in the waveguide, eliminating the need for any active tuning. The total length of the delay waveguide is 5620.5 µm, which is reduced by a factor of 46.3% compared with previously reported time-wavelength interleaver schemes. The experimental results indicate that the device can convert an optical pulse into a 40 GHz pulse sequence composed of four pulses with a root mean square (RMS) timing error of 0.9 ps, making it well suited for generating high-frequency sampling pulses for optical analog-to-digital converters.

Monolithically integrated 128-channel hybrid mode/polarization/wavelength (de)multiplexer on silicon-on-insulator.

In this paper, we proposed a 128-channel hybrid mode/polarization/wavelength (de)multiplexer by monolithically integrating four 16-wavelength-channel (de)multiplexers based on bi-directional MRRs arrays and an 8-channel hybrid mode/polarization (de)multiplexer. The hybrid mode/polarization (de)multiplexer consists of a polarization beam splitter (PBS) and cascaded six asymmetric directional couplers (ADCs). The present 128-channel hybrid (de)multiplexer utilizes four modes, dual polarizations, and sixteen wavelengths to improve the data transmission capacity of optical communication systems. For the fabricated hybrid (de)multiplexer, the channel spacing is 1.4 nm, and we used thermal tuning electrodes with a tuning efficiency of 0.45 nm/mW to calibrate resonance wavelengths. The measurement results show the insertion loss is 3∼8.5 dB, the inter-mode crosstalk is -7∼-23 dB, and the inter-wavelength crosstalk is-8∼-20 dB. The proposed (de)multiplexer is a promising approach to enhance the transmission capacity and has great potential in high-speed data transmission.

Metal 3D nanoprinting with coupled fields.

Metallized arrays of three-dimensional (3D) nanoarchitectures offer new and exciting prospects in nanophotonics and nanoelectronics. Engineering these repeating nanoarchitectures, which have dimensions smaller than the wavelength of the light source, enables in-depth investigation of unprecedented light-matter interactions. Conventional metal nanomanufacturing relies largely on lithographic methods that are limited regarding the choice of materials and machine write time and are restricted to flat patterns and rigid structures. Herein, we present a 3D nanoprinter devised to fabricate flexible arrays of 3D metallic nanoarchitectures over areas up to 4 × 4 mm2 within 20 min. By suitably adjusting the electric and flow fields, metal lines as narrow as 14 nm were printed. We also demonstrate the key ability to print a wide variety of materials ranging from single metals, alloys to multimaterials. In addition, the optical properties of the as-printed 3D nanoarchitectures can be tailored by varying the material, geometry, feature size, and periodic arrangement. The custom-designed and custom-built 3D nanoprinter not only combines metal 3D printing with nanoscale precision but also decouples the materials from the printing process, thereby yielding opportunities to advance future nanophotonics and semiconductor devices.

A Novel Silicon Forward-Biased PIN Mach-Zehnder Modulator with Two Operating States.

In this paper, we demonstrate a silicon forward-biased positive intrinsic negative (PIN) Mach-Zehnder modulator (MZM), which has two operating states of high efficiency and high speed. The two operating states are switched by changing the position where the electric signal is loaded. The modulator incorporates a PIN phase shifter integrated with the passive resistance and capacitance (RC) equalizer (PIN-RC), which expands the electro-optic (E-O) bandwidth by equalizing it with modulation efficiency. The fabricated modulator exhibits a low insertion loss of 1.29 dB in two operating states and a compact design with a phase shifter length of 500 µm. The modulation efficiencies are 0.0088 V·cm and 1.43 V·cm, and the corresponding 3 dB E-O bandwidths are 200 MHz and 7 GHz, respectively. The high-speed modulation performance of the modulator is confirmed by non-return-to-zero (NRZ) modulation with a data rate of 15 Gbps without any pre-emphasis or post-processing. The presented modulator shows functional flexibility, low insertion loss, and a compact footprint, and it can be suitable for applications like optical switch arrays and analog signal processing.

Silicon nitride assisted tri-layer edge coupler on lithium niobate-on-insulator platform.

Lithium niobate-on-insulator (LNOI) is a promising integration platform for various applications, such as optical communication, microwave photonics, and nonlinear optics. To make Lithium niobate (LN) photonic integrated circuits (PICs) more practical, low-loss fiber-chip coupling is essential. In this Letter, we propose and experimentally demonstrate a silicon nitride (SiN) assisted tri-layer edge coupler on LNOI platform. The edge coupler consists of a bilayer LN taper and an interlayer coupling structure composed of an 80 nm-thick SiN waveguide and an LN strip waveguide. The measured fiber-chip coupling loss for the TE mode is 0.75 dB/facet at 1550 nm. Transition loss between the SiN waveguide and LN strip waveguide is ∼0.15 dB. In addition, the fabrication tolerance of the SiN waveguide in the tri-layer edge coupler is high.

Photonic sampled and quantized analog-to- digital converters on thin-film lithium niobate platform.

In this paper, an on-chip photonic sampled and quantized analog-to-digital converter (ADC) on thin-film lithium niobate platform is experimentally demonstrated. Using two phase modulators as a sampler and a 5×5 multimode interference (MMI) coupler as a quantizer, a 1 GHz sinusoidal analog input signal was successfully converted to a digitized output with a 20 GSample/s sampling rate. To evaluate the system performance, the quantization curves together with the transfer function of the ADC were measured. The experimental effective number of bits (ENOB) was 3.17. The demonstrated device is capable of operating at a high frequency over 67 GHz, making it a promising solution for on-chip ultra-high speed analog-to-digital conversion.

In Situ Growth of Nanosilver on Fabric for Flexible Stretchable Electrodes.

Flexible sensing can disruptively change the physical form of traditional electronic devices to achieve flexibility in information acquisition, processing, transmission, display, and even energy, and it is a core technology for a new generation of the industrial internet. Fabric is naturally flexible and stretchable, and its knitted ability makes it flexibility and stretchability even more adjustable. However, fabric needs to be electrically conductive to be used for flexible sensing, which allows it to carry a variety of circuits. The dip-coating technique is a common method for preparing conductive fabrics, which are made conductive by attaching conductive fillers to the fabrics. However, the adhesion of the conductive fillers on the surface of such conductive fabrics is weak, and the conductive property will decay rapidly because the conductive filler falls off after repeated stretching, limiting the lifespan of flexible electronic devices based on conductive fabric. We chose multifunctional nanosilver as a conductive filler, and we increased the adhesion of nanosilver to fabric fiber by making nanosilver grow in situ and cover the fiber, so as to obtain conductive fabric with good conductivity. This conductive fabric has a minimum square resistance of 9 Ω/sq and has better electrical conductivity and more stable electrical properties than the conductive fabric prepared using the dip-coating process, and its square resistance did not increase significantlyafter 60 stretches.

The Variation of Duck RIG-I-Mediated Innate Immune Response Induced by Different Virulence Avian Influenza Viruses.

In recent years, the emerging highly pathogenic avian influenza (HPAI) A(H5N8) virus has been reported with features of widely spread, an expanding host range, and cross-species transmission, attracting wide attention. The domestic duck plays a major role in the epidemiological cycle of the HPAI H5N8 virus, but little is known concerning innate immune responses during influenza infection in duck species. In this study, we used two wild-bird-origin viruses, H5N8 and H4N6, to conduct duck infection experiments, and detect the load of the two viruses, and retinoic acid-inducible gene I (RIG-I) and interferon ß (IFN-ß) in the host's natural immune response. Through comparison, it is found that the expression levels of RIG-I and IFN-ß are both fluctuating. The innate immunity starts rapidly within 6 h after infection and is inhibited by the virus to varying degrees. The expression of RIG-I and IFN-ß decreased on 1-2 days post-infection (dpi). The HPAI H5N8 virus has a stronger inhibitory effect on RIG-I than the low pathogenic avian influenza (LPAI) H4N6 virus and is the strongest in the lungs. After infection with HPAI H5N8 virus, 2 dpi, viral RNA replicates in large amounts in the lungs. It has been proven that RIG-I and IFN-ß play an important role in the innate immune response of ducks to HPAI H5N8 virus infection, especially in the lungs. The main battlefield of RIG-I and IFN-ß after infection with the LPAI H4N6 virus is in the rectum. Both viruses have been effectively controlled after 7 dpi. These results will help to understand the transmission mechanisms of avian influenza virus in wild ducks and help effectively prevent and control avian influenza.

Asymmetric Hysteresis for Probing Dzyaloshinskii-Moriya Interaction.

The interfacial Dzyaloshinskii-Moriya interaction (DMI) is intimately related to the prospect of superior domain-wall dynamics and the formation of magnetic skyrmions. Although some experimental efforts have been recently proposed to quantify these interactions and the underlying physics, it is still far from trivial to address the interfacial DMI. Inspired by the reported tilt of the magnetization of the side edge of a thin film structure, we here present a quasi-static, straightforward measurement tool. By using laterally asymmetric triangular-shaped microstructures, it is demonstrated that interfacial DMI combined with an in-plane magnetic field yields a unique and significant shift in magnetic hysteresis. By systematic variation of the shape of the triangular objects combined with a droplet model for domain nucleation, a robust value for the strength and sign of interfacial DMI is obtained. This method gives immediate and quantitative access to DMI, enabling a much faster exploration of new DMI systems for future nanotechnology.

Thickness dependence of the interfacial Dzyaloshinskii-Moriya interaction in inversion symmetry broken systems.

In magnetic multilayer systems, a large spin-orbit coupling at the interface between heavy metals and ferromagnets can lead to intriguing phenomena such as the perpendicular magnetic anisotropy, the spin Hall effect, the Rashba effect, and especially the interfacial Dzyaloshinskii-Moriya (IDM) interaction. This interfacial nature of the IDM interaction has been recently revisited because of its scientific and technological potential. Here we demonstrate an experimental technique to straightforwardly observe the IDM interaction, namely Brillouin light scattering. The non-reciprocal spin wave dispersions, systematically measured by Brillouin light scattering, allow not only the determination of the IDM energy densities beyond the regime of perpendicular magnetization but also the revelation of the inverse proportionality with the thickness of the magnetic layer, which is a clear signature of the interfacial nature. Altogether, our experimental and theoretical approaches involving double time Green's function methods open up possibilities for exploring magnetic hybrid structures for engineering the IDM interaction.

Cross section measurement for the (95)Mo(n, alpha)(92)Zr reaction at 4.0, 5.0 and 6.0MeV.

Measurements of cross sections of the (95)Mo(n, alpha)(92)Zr reaction at E(n)=4.0, 5.0 and 6.0MeV were carried out at the 4.5MV Van de Graaff of Peking University, China. A twin gridded ionization chamber and two large-area (95)Mo samples were adopted. Fast neutrons were produced through the D(d, n)(3)He reaction by using a deuterium gas target. A small (238)U fission chamber was employed for absolute neutron flux determination. Present data are compared with existing evaluations and measurement.