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Third-order nonlinear optical properties of Ge10AsxTe90-x chalcogenide glasses were investigated utilizing the Z-scan method at the mid-infrared wavelengths of 2.5 and 3.0 µm. The compositional dependence of the third-order nonlinearity was analyzed, and their correlation with the refractive index and the optical bandgap was discussed. The results show that nonlinear refractive index n2 can be significantly enhanced by the addition of tellurium, and larger n2 values are observed at 3.0 µm rather than 2.5 µm due to the two-photon resonance effect, and the maximum of n2 is 4.96 × 10−13 cm2/W at the composition of Ge10As20Te70. In addition, the experimental results are in good agreement with the semi-empirical Miller’s rule whilst the variation of dispersive n2 values are in relatively good coincidence with the theoretical model by Sheik-Bahae et.al. for direct bandgap semiconductors.

Rechargeable Li-O

Li-CO

Lithium–oxygen batteries are regarded as the most promising candidate for future energy storage systems. However, their poor rechargeability and low efficiency remain critical barriers for practical applications. By using first-principles computations, we disclosed that NiFe2O4 has superior oxygen evolution reaction (OER) activity for the decomposition of Li2O2. Guided by computations, we prepared a composite of NiFe2O4 and carbon nanotubes (CNTs) through a hydrothermal route and applied it to Li–O2 batteries. The batteries with NiFe2O4–CNT air cathodes displayed lower charging overpotential and better cycling performance than those with CNT air cathodes. The improved electrochemical performance was attributed to the high OER activity of NiFe2O4 for the decomposition of Li2O2.

It has been a long-standing challenge to produce air-stable few- or monolayer samples of phosphorene because thin phosphorene films degrade rapidly in ambient conditions. Here we demonstrate a new highly controllable method for fabricating high quality, air-stable phosphorene films with a designated number of layers ranging from a few down to monolayer. Our approach involves the use of oxygen plasma dry etching to thin down thick-exfoliated phosphorene flakes, layer by layer with atomic precision. Moreover, in a stabilized phosphorene monolayer, we were able to precisely engineer defects for the first time, which led to efficient emission of photons at new frequencies in the near infrared at room temperature. In addition, we demonstrate the use of an electrostatic gate to tune the photon emission from the defects in a monolayer phosphorene. This could lead to new electronic and optoelectronic devices, such as electrically tunable, broadband near infrared lighting devices operating at room temperature., It has been a long-standing challenge to produce air-stable few- or monolayer phosphorene. Here, the authors demonstrate a new highly controllable method for fabricating high quality, air-stable mono- and few-layer phosphorene films, enabling precise defect engineering in monolayer phosphorene.

Mid-infrared spectroscopy attracts growing interests because of its coverage over the characteristic spectral absorption features for many molecules. This paper will review our study in mid-infrared photonics including material characterization, on-chip waveguide fabrication and supercontinuum generation for the spectroscopic applications.

Fusion-bonded suspended silicon waveguides with exemplary stability and geometrical design flexibility are fabricated at different sizes for nonlinear broadening in the mid-infrared. Pumping with a femtosecond laser source at ∼4 μm, broadband supercontinuum spectra are observed from λ = 2–5 and 3–6 μm.

Li‐CO2 batteries could skillfully combine the reduction of “greenhouse effect” with energy storage systems. However, Li‐CO2 batteries still suffer from unsatisfactory electrochemical performances and their rechargeability is challenged. Here, it is reported that a composite of Ni nanoparticles highly dispersed on N‐doped graphene (Ni‐NG) with 3D porous structure, exhibits a superior discharge capacity of 17 625 mA h g−1, as the air cathode for Li‐CO2 batteries. The batteries with these highly efficient cathodes could sustain 100 cycles at a cutoff capacity of 1000 mA h g−1 with low overpotentials at the current density of 100 mA g−1. Particularly, the Ni‐NG cathodes allow to observe the appearance/disappearance of agglomerated Li2CO3 particles and carbon thin films directly upon discharge/charge processes. In addition, the recycle of CO2 is detected through in situ differential electrochemical mass spectrometry. This is a critical step to verify the electrochemical rechargeability of Li‐CO2 batteries. Also, first‐principles computations further prove that Ni nanoparticles are active sites for the reaction of Li and CO2, which could guide to design more advantageous catalysts for rechargeable Li‐CO2 batteries.

We show directional light routing and high–bit rate data transmission using a nanoantenna integrated on a low-loss waveguide., Optical nanoantennas provide a promising pathway toward advanced manipulation of light waves, such as directional scattering, polarization conversion, and fluorescence enhancement. Although these functionalities were mainly studied for nanoantennas in free space or on homogeneous substrates, their integration with optical waveguides offers an important “wired” connection to other functional optical components. Taking advantage of the nanoantenna’s versatility and unrivaled compactness, their imprinting onto optical waveguides would enable a marked enhancement of design freedom and integration density for optical on-chip devices. Several examples of this concept have been demonstrated recently. However, the important question of whether nanoantennas can fulfill functionalities for high-bit rate signal transmission without degradation, which is the core purpose of many integrated optical applications, has not yet been experimentally investigated. We introduce and investigate directional, polarization-selective, and mode-selective on-chip nanoantennas integrated with a silicon rib waveguide. We demonstrate that these nanoantennas can separate optical signals with different polarizations by coupling the different polarizations of light vertically to different waveguide modes propagating into opposite directions. As the central result of this work, we show the suitability of this concept for the control of optical signals with ASK (amplitude-shift keying) NRZ (nonreturn to zero) modulation [10 Gigabit/s (Gb/s)] without significant bit error rate impairments. Our results demonstrate that waveguide-integrated nanoantennas have the potential to be used as ultra-compact polarization-demultiplexing on-chip devices for high–bit rate telecommunication applications.

The main purpose of this study was to investigate the rheology evolution of sludge through high-solid anaerobic digestion (AD) and its dependency on sludge retention time (SRT) and temperature of AD reactor. The operation performance of high-solid AD reactors were also studied. The results showed that sludge became much more flowable after high-solid AD. It was found that the sludge from reactors with long SRT exhibited low levels of shear stress, viscosity, yield stress, consistency index, and high value of flow behaviour index. While the flowability of sludge from thermophilic AD reactors were better than that of sludge from mesophilic AD reactors though the solid content of the formers were higher than that of the latters, which could be attributed to the fact that the formers had more amount of free and interstitial moisture. It might be feasible to use sludge rheology as an AD process controlling parameter.

Cation exchange resin (CER) has been widely utilized as a method to extract extracellular polymeric substance. It was demonstrated in the author’s preliminary study that CER could also be used as a sludge pretreating method to enhance the efficiency of subsequent anaerobic digestion. In this study, the solubilization and disintegration of sludge during CER pretreatment were reported. Proteins, polysaccharides, fluorescent dissolved organic matter (DOM), and molecular weight distribution of DOM were measured to assess and explain the solubilization of sludge. Particle-size distribution and scanning electron microscope were determined to evaluate the disintegration of sludge. Besides, it also indicated that the dewatering and settling ability of sludge were deteriorated. Proteins, polysaccharides, particle size, and monovalent to divalent cation ratio were revealed to have significant correlations with the sludge dewaterability and settleability during the CER conditioning process.

The production of a broadband supercontinuum spanning from 1.8 μm to >7.5 μm is reported which was created by pumping a chalcogenide glass waveguide with ≈320 fs pulses at 4 μm. The total power was ≈20 mW and the source brightness was >×100 that of current synchrotrons. This source promises to be an excellent laboratory tool for infrared microspectroscopy.

Yi Yu acknowledges the financial support from the China Scholarship Council for her PhD Scholarship No. 201206110048. This research was conducted by the Australian Research Council Centre of Excellence for Ultrahigh Bandwidth Devices for Optical Systems (project number CE110001018). Support for this work was also provided by the FP7-ERC-MIRACLE project.

I will review our work on nonlinear waveguides for supercontinuum generation in the mid-infrared focusing on the nonlinear properties and waveguide performance of chalcogenide, silicon and silicon-germanium devices

This Letter reports the production of a supercontinuum extending from ≈2 μm to >10 μm generated using a chalcogenide buried rib waveguide pumped with 330 femtosecond pulses at 4.184 μm. This is, to the best of our knowledge, the broadest mid-infrared supercontinuum generated in any planar waveguide platform. Because the waveguide is birefringent, quasi-single-mode, and uses an optimized dispersion design, the supercontinuum is linearly polarized with an extinction ratio >100. Dual beam spectrophotometry is performed easily using this source.

Magnetic abrasive grain is a kind of tool for magnetic abrasive finishing (MAF). The lifetime of the grains is the choke point which restricts its finishing efficiency and the surface quality processed by MAF .Therefore, a kind of magnetic abrasive grains based on Cr and Ni elements is investigated. The interrelated experimental results show: the new magnetic abrasive grains is a practical finishing tool with longer lifetime, higher finishing efficiency, better abrasive resistance compared with traditional magnetic abrasive grains. It supplies a power for promoting the development of MAF.

Li-CO2 batteries are promising energy storage systems by utilizing CO2 at the same time, though there are still some critical barriers before its practical applications such as high charging overpotential and poor cycling stability. In this work, iridium/carbon nanofibers (Ir/CNFs) are prepared via electrospinning and subsequent heat treatment, and are used as cathode catalysts for rechargeable Li-CO2 batteries. Benefitting from the unique porous network structure and the high activity of ultrasmall Ir nanoparticles, Ir/CNFs exhibit excellent CO2 reduction and evolution activities. The Li-CO2 batteries present extremely large discharge capacity, high coulombic efficiency, and long cycling life. Moreover, free-standing Ir/CNF films are used directly as air cathodes to assemble Li-CO2 batteries, which show high energy density and ultralong operation time, demonstrating great potential for practical applications.

Magnetic finishing is a new machining technology. It was widely developed for its high productivity and quality, especially its better flexibility and self-sharpness finishing tools. As a new material, Nd-Fe-B with high magnetic energy makes the internal finishing easier. Being used as permanent magnetic pole to finishing the surface of workpieces instead of solenoid, it makes the structure of magnetic pole more compact and the techniques adaptability better. Internal finishing using permanent magnetic pole is mainly discussed in this paper: a new technology to finishing the middle/small or deep hole using permanent magnetic pole is provided; a new kind of pole is developed, lots of experiments have been completed ,the roughness of internal surface is decreased from Ra0.8μm to about Ra0.3~0.1μm. The data prove that internal finishing using permanent magnetic pole is ideal technology.

In the paper, a new method of using rotating magnetic field generated by a stator of alternative electromotor to finish the inner surface of tube-type workpiece is proposed. Force and movements of magnetic abrasive are analyzed. The finishing mechanism is analyzed and the sliding, friction and scratching between magnetic abrasives and the workpiece inner surface may be main factors of material removal as the non-mechanical relative motion is produced.

We demonstrated vertically coupled, hydrogenated amorphous silicon ring resonators by leveraging low temperature deposition of the material where SU-8 polymer was employed as planarization layer and resonator gap material.

Magnetic abrasive finishing (MAF) is a kind of method for polishing the surfaces and the edges. The investigation for the technique of MAF and the development of the ferromagnetic poles lay a theoretical foundation for developing a new method for finishing the curved surfaces automatically under the numerical control. In the paper, the performance parameters of the developed magneto poles, which are used for finishing the plane surfaces and the curved ones, have been tested. The curvature of the finished surface, the sloping angle of the machined surface and the rotation speed of the poles, which affect the surface roughness, are studied theoretically. What mentioned above supply references to the practical uses of the MAF, especially in the mould manufacturing.

In the paper, a new method of using rotating magnetic field generated by a stator of alternative electromotor to polish the inner surface of tube-type workpieces is proposed; a finishing device using the stator construction and inverter is designed; the finishing mechanism is analyzed and experiments are carried out. Experimental investigations show that filling amount of magnetic abrasive influences the surface roughness of workpiece directly and have an optimal value. The higher magnetic conductivity is, and the finer finishing effect is. The attraction force of magnetic particles depends on intensity of magnetic induction directly and has the optimal value. The higher the rotation speed is, and the lower the value of surface roughness. Under the optimal experimental condition, the new method can reduce the value of surface roughness more than 2 grades. Therefore, this technique has prospective application future.

A low-loss suspended core As38Se62 fiber with core diameter of 4.5 μm and a zero-dispersion wavelength of 3.5 μm was used for mid-infrared supercontinuum generation. The dispersion of the fiber was measured from 2.9 to 4.2 μm and was in good correspondence with the calculated dispersion. An optical parametric amplifier delivering 320 fs pulses with a peak power of 14.8 kW at a repetition rate of 21 MHz was used to pump 18 cm of suspended core fiber at different wavelengths from 3.3 to 4.7 μm. By pumping at 4.4 μm with a peak power of 5.2 kW coupled to the fiber a supercontinuum spanning from 1.7 to 7.5 μm with an average output power of 15.6 mW and an average power >5.0 μm of 4.7 mW was obtained.

We prepared numbers of GeAsSe glasses and investigated their thermal stability and optical properties in order to search the best glasses with relatively high glass transition temperature Tg, strong structural stability, low optical loss and high optical nonlinearity. Through our systematical measurements, we concluded that the glasses with a mean coordination number around 2.45-2.5 are the best for the applications in photonics with Tg of 450K, low optical loss of 0.2dB/cm, high optical nonlinearity 7.5×10-14cm2/W and less photosensitivity.

In this chapter we summarize progress in materials and structures for all-optical signal processing that employ either the second or third order optical nonlinearity. Three-wave mixing and cascading in periodically-poled lithium niobate waveguides dominates signal processing in second order materials. In the case of third-order nonlinearities, four wave mixing is the dominant physical process but here the range of materials that have been employed is wider and ranges from glasses to both active and passive semiconductor devices. This chapter provides a brief summary of the advantages and disadvantages of each class of materials and device structure as well as the state-of-the-art for each case.

International audience; A more than two-octave mid-infrared supercontinuum with an average output power of 15.6 mW covering 1.7-7.5 mu m (1,333-5,900 cm(-1)) is generated in a low-loss As38Se62 suspended core fiber with core diameter of 4.5 mu m. (C) 2014 Optical Society of America

I report work on mid-infrared super-continuum generation in chalcogenide fibers and waveguides pumped by 320fsec pulses at 21MHz in the 3-4.6µm range. Average powers of ≈20mW were produced with spectral coverage from 11µm.

Li-CO2 batteries could skillfully combine the reduction of "greenhouse effect" with energy storage systems. However, Li-CO2 batteries still suffer from unsatisfactory electrochemical performances and their rechargeability is challenged. Here, it is reported that a composite of Ni nanoparticles highly dispersed on N-doped graphene (Ni-NG) with 3D porous structure, exhibits a superior discharge capacity of 17 625 mA h g-1, as the air cathode for Li-CO2 batteries. The batteries with these highly efficient cathodes could sustain 100 cycles at a cutoff capacity of 1000 mA h g-1 with low overpotentials at the current density of 100 mA g-1. Particularly, the Ni-NG cathodes allow to observe the appearance/disappearance of agglomerated Li2CO3 particles and carbon thin films directly upon discharge/charge processes. In addition, the recycle of CO2 is detected through in situ differential electrochemical mass spectrometry. This is a critical step to verify the electrochemical rechargeability of Li-CO2 batteries. Also, first-principles computations further prove that Ni nanoparticles are active sites for the reaction of Li and CO2, which could guide to design more advantageous catalysts for rechargeable Li-CO2 batteries.

Metasurfaces-based flat optics, which can make use of existing foundry planar technology for high-throughput production, allows the arbitrary control of the wavefront and polarization of light within subwavelength thick structures. So far, however, flat optics for the mid-infrared (MIR) has received far less attention than devices operating at visible or near-infrared wavelengths. Here, polarization-insensitive, highly efficient, all-dielectric metalenses operating in the MIR around 4 µm are demonstrated. The metalens is designed using rigorous coupled-wave analysis and is based on hydrogenated amorphous silicon (α-Si:H) nanopillars supported by an MgF2 substrate. The metalenses produce close to a diffraction-limited focal spot and can resolve structures on the wavelength scale where the focusing efficiency reaches 78% at a magnification of 120×. The imaging qualities are comparable with commercial bulk-molded chalcogenide aspheric lenses. These results provide novel solutions for existing MIR technology and nurture new functionalities with the population of miniaturized and planarized optoelectrical devices.

We present a novel CMOS-compatible fabrication technique for convex micro-nano lens arrays (MNLAs) with high packing density on the wafer scale. By means of conformal chemical vapor deposition (CVD) of hydrogenated amorphous silicon (a-Si:H) following patterning of silicon pillars via electron beam lithography (EBL) and plasma etching, large areas of a close packed silicon lens array with the diameter from a few micrometers down to a few hundred nanometers was fabricated. The resulting structure shows excellent surface roughness and high uniformity. The optical focusing properties of the lenses at infrared wavelengths were verified by experimental measurements and numerical simulation. This approach provides a feasible solution for fabricating silicon MNLAs compatible for next generation large scale, miniaturized optical imaging detectors and related optical devices.