Large-scale optical-field measurements with geometric fibre constructs

Optical fields are measured using sequential arrangements of optical components such as lenses, filters, and beam splitters in conjunction with planar arrays of point detectors placed on a common axis. All such systems are constrained in terms of size, weight, durability and field of view. Here a new, geometric approach to optical-field measurements is presented that lifts some of the aforementioned limitations and, moreover, enables access to optical information on unprecedented length and volume scales. Tough polymeric photodetecting fibres drawn from a preform are woven into light-weight, low-optical-density, two- and three-dimensional constructs that measure the amplitude and phase of an electromagnetic field on very large areas. First, a three-dimensional spherical construct is used to measure the direction of illumination over 4pi steradians. Second, an intensity distribution is measured by a planar array using a tomographic algorithm. Finally, both the amplitude and phase of an optical wave front are acquired with a dual-plane construct. Hence, the problem of optical-field measurement is transformed from one involving the choice and placement of lenses and detector arrays to that of designing geometrical constructions of polymeric, light-sensitive fibres.     

Photo-Stability Measurement of Electro-Optic Polymer Waveguides With High Intensity at 1550-nm Wavelength

Photo-stability measurements of electro-optic polymer inverted ridge waveguides, fabricated from AJ-CKL1, AJ416 and LPD-80, are conducted up to 30, 100, and 100 mW of input power coupled into the waveguides respectively. These experiments are performed in a N₂ atmosphere to exclude absorbed O₂. AJ416 and LPD-80 are found to be stable up to at least 1 MW/cm² at 1550 nm. In contrast, photo-degradation was observed in an ambient atmosphere with 1 mW (LPD-80) and 10 mW (AJ-CKL1) coupled into the waveguides.     

Nanoscale Controlled Oxidation of Liquid Metals for Stretchable Electronics and Photonics

Liquid metals based on gallium have attracted considerable attention for soft and bioelectronics, thanks to their excellent combination of stretchability and conductivity. Nevertheless, owing to their large surface tension, these materials are notoriously difficult to pattern and shape into thin continuous films, or nanoscale 2D architectures, hindering practical use in systems with reduced dimensions. Herein, thanks to fine control in both substrate surface state and oxidation dynamics, a process for producing stretchable gallium-based conducting films with percolation down to 90 nm thickness is presented. By further combining this process with lithography, it is also demonstrated that the approach enables, for the first time, stable stretchable gallium-based optical metasurfaces with tunable resonance in the infrared. It is shown that oxygen partial pressure during evaporation determines the initial film percolation via an interplay between oxidation and dewetting. With this approach, conducting films with relative resistance change as low as 3% over 50% strain, with an excellent stability over 15k cycles are also demonstrated. Tunable soft optical metasurfaces with sub-micrometer feature sizes are also realized, paving the way toward a novel paradigm in soft electronics and photonics.     

Eco-efficient Separation of Mono- and Dichloroacetic Acid by Thermally Coupled Extractive Distillation

Due to its high reactivity, monochloroacetic acid (MCA) is an essential intermediate used in the manufacturing of a wide variety of chemicals. Its industrial production process is highly energy- and capital-intensive, requiring costly purification steps to remove dichloroacetic acid (DCA) impurities. Here, an innovative eco-efficient process for MCA-DCA separation is proposed based on extractive distillation in a fully thermally coupled system (a dividing-wall column (DWC) or an equivalent side-rectifier configuration) using a new effective solvent: diethylene glycol dipentylether. The design was optimized by performing sensitivity analyses and varying key operating and design parameters. The study proves that separating MCA-DCA by an extractive DWC (or thermally coupled) is feasible, efficient, controllable, economic, and sustainable.     

Synthesis and characterization of side-chain poly(methacrylate)s bearing new azo-moieties

New side-chain poly(methacrylate)s with azo moieties were prepared by free radical copolymerization, starting from methyl methacrylate (MMA) and some original azo-monomers. The chromophore content was evaluated from ¹H-NMR spectroscopy and elemental analyses; all structures exhibited a high content of azobenzene units. UV–Vis measurements have also supported this fact. Reactivity ratios for the methacrylate systems and their corresponding Q–e values were calculated based on several initial feed compositions (MMA and the newly synthesized azo-monomers) using an integral method with its appropriate software. The polymers were also characterized by FTIR, SEC and DSC-TGA techniques. The coloured poly(methacrylate)s exhibited glass transition temperatures between 141 and 168 °C and thermal stabilities up to 306 °C.     

Synthesis of a new oxazoline macromonomer for dispersion polymerization

We synthesized new macromonomers containing vinylsilane moiety by cationic ring-opening polymerization of 2-ethyl-2-oxazoline. Kinetic studies proved that initiation with vinylsilane derivative, bearing chloride counterion, is a fast process followed by a slow propagation and absence of termination. We used the dispersion polymerization of styrene as test for the stabilizing efficiency of the newly synthesized macromonomer. The dispersion polymerization tests allowed the investigation of the effect of the macromonomer concentration on the number average diameter of the prepared polystyrene microspheres and its polydispersity index. In addition, we compared the stabilizing efficiency of commercial poly(N-vinylpyrollidone) with that of our macromonomer. Copolymerization of styrene with 10 wt% oxazoline macromonomer yielded stable and monodisperse microspheres, having the number average diameter of 1.8 μm and a good size polydispersity index of 1.05.     

Dynamics and control of a biodiesel process by reactive absorption

Integrated biodiesel processes based on reactive separations powered by solid acid/base catalysts are available nowadays, offering significant advantages such as minimal capital investment and operating costs, as well as no catalyst-related waste streams and no soap formation. However, the controllability of the process is just as important as the capital and operating savings. In such processes the small number of degrees of freedom is a drawback which makes it difficult to correctly set the ratio of reactant feeds and consequently to avoid impurities in the products. This work considers the process control of biodiesel production by reactive absorption, the main result being an efficient control structure that ensures the excess of methanol that is necessary for the total conversion of the fatty acids and for prevention of the difficult separations, while maintaining high purity of the water by-product. Rigorous simulations were performed - using Aspen Plus and Aspen Plus Dynamics as efficient computer-aided process engineering tools - for a plant producing 10 ktpy biodiesel from waste vegetable oil with high free fatty acids content, using solid acids as green catalysts. This reactive absorption process eliminates all conventional catalyst-related operations, and efficiently uses the raw materials and the reactor volume in an integrated setup that is well controllable in spite of the reduced number of degrees of freedom.     

Hybrid Integrated Cascaded 2-bit Electrooptic Digital Optical Switches (DOSs)

Hybrid integrated cascaded 1 times 4 electrooptic (EO) polymeric digital optical switches (DOSs) are proposed and demonstrated. The hybrid integration of passive polymer on the same chip with EO polymer can lower the overall device loss without affecting the EO effects. The cascaded DOS can be controlled by only two voltage signal sources without bias stabling mechanism. The device can be operated as a 2-bit reconfigurable switch. The switching voltage is around 15 V for single arm driving with reasonable extinction ratio (9~12 dB) and the loss is improved by ~2.5 dB. This device is ideal for implementing variable optical delay network