Athermal silicon ring resonators are experimentally demonstrated by overlaying a polymer cladding on narrowed silicon wires. The ideal width to achieve athermal condition for the TE mode of 220 nm-height SOI waveguides is found to be around 350 nm. After overlaying a polymer layer, the wavelength temperature dependence of the silicon ring resonator is reduced to less than 5 pm/degrees C, almost eleven times less than that of normal silicon waveguides. The optical loss of a 350-nm bent waveguide (with a radius of 15 microm) is extracted from the ring transmission spectrum. The scattering loss is reduced to an acceptable level of about 50 dB/cm after overlaying a polymer cladding.

In diverse fields, much attention has been concentrated on the preparation of lignin nanospheres with various structures. Here we report a facile self-assembly strategy for preparing super long-term stable hollow and solid nanospheres based on lignin fractionation. We found that different lignins obtained at different pHs during fractionation can form nanospheres with different particle sizes and structures. The self-assembled and formation mechanisms of the nanospheres were surveyed by dynamic light scattering (DLS), elemental analysis, transmission electron microscopy (TEM), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR). The analysis results showed that the phenolic hydroxyl groups and the intermolecular π−π interaction play a decisive effect in the formation of nanospheres. This study can not only facilitate the advance of lignin-based nanotechnologies but also provide a broad prospect for the use of black liquor.

Lignocellulosic biomass has been widely considered as a renewable source for bioproducts and bioenergy production via various biorefinery techniques. Much effort has been taken for the valorization of carbohydrate compositions (cellulose and hemicellulose). Until recently, lignin has started to gain increasing attention as a renewable source that can be valorized to high-value products. It has unique advantages including low-cost, flexible modifiability, and wide compatibility that can be used for diverse purposes. The valorization of lignin into novel nanomaterials is a recent research endeavor that promises opportunities to increase the overall economy of conventional biorefineries, thus promoting the development of a circular bioeconomy, while its suitability for nanomaterial preparation and application is significantly related to its sources. To support the successful integration of conventional biorefineries and lignin nanomaterial preparation and utilization, this review first identify major biorefineries which produce lignin as byproducts, summarizes major preparation and applications of lignin, and then raises considerations and suggestions on the suitability of different lignin sources for nanomaterial preparation and application. Finally, some key challenges and perspectives are proposed for advancing the integration of lignin nanomaterials production and conventional biorefineries toward near-complete valorization of lignocellulosic biomass.

Abstract-Theoretical and experimental results on the reduction of the intensity noise in spectrum-sliced wavelength-divisionmultiplexing systems using a saturated semiconductor optical amplifier (SOA) are presented. The influence of the injected current and the input power to the saturated SOA on the noise reduction and its bandwidth are studied. The optimum condition for a high noise suppression ratio and a large bandwidth is derived. For the optimum operation of the SOA, an increase of 13.5 dB in the intensity-noise-limited signal-to-noise ratio for a bitrate of 2.488 Gb/s and of 17.5 dB for a bitrate of 622 Mb/s are obtained experimentally in a single-stage SOA.Index Terms-Optical fiber communication, optical noise, semiconductor optical amplifier, wavelength-division multiplexing.

Polymer materials exhibit unique properties in the fabrication of optical waveguide devices, electromagnetic devices, and bio-devices. Direct laser writing (DLW) technology is widely used for micro-structure fabrication due to its high processing precision, low cost, and no need for mask exposure. This paper reviews the latest research progresses of polymer-based micro/nano-devices fabricated using the DLW technique as well as their applications. In order to realize various device structures and functions, different manufacture parameters of DLW systems are adopted, which are also investigated in this work. The flexible use of the DLW process in various polymer-based microstructures, including optical, electronic, magnetic, and biomedical devices are reviewed together with their applications. In addition, polymer materials which are developed with unique properties for the use of DLW technology are also discussed.

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