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In this study, the effects of different fine aggregates on the properties of polyethylene fiber engineered cementitious composite (PE-ECC) were systematically investigated. The PE-ECCs were prepared with four fine aggregates, respectively. Furthermore, their flowability, compressive strength, and uniaxial tensile properties were studied experimentally and comparatively analyzed by microscopic techniques including X-ray diffraction (XRD), scanning electron microscope (SEM), energy-dispersive spectroscopy (EDS), and mercury intrusion porosimetry (MIP). The results showed that all the different types of fine aggregates exhibited little effect on the flowability of PE-ECC, but a greater effect on the compressive strength, uniaxial tensile strength, and ultimate tensile strain. PE-ECC prepared from untreated desert sand showed the best comprehensive performance, with compressive strength, uniaxial tensile strength, and ultimate tensile strain of 47.92 MPa, 6.26 MPa, and 3.638%, respectively. Moreover, it was found that the ultra-fine particles in the desert sand promoted the hydration reaction of cement and produced more C–S–H gels. The pore structures of ECC prepared with different aggregates exhibited obvious fractal characteristics, and the fractal dimension ranged from 2.8 to 2.9. The fractal dimension showed a strong correlation with parameters including ultimate tensile strain and pore structure, and the larger the fractal dimension, the smaller the ultimate tensile strain, porosity, and average pore size of ECC.

An equivalently discrete coupling coefficient (EDCC) distributed feedback (DFB) semiconductor laser with EDCC grating is numerically investigated and experimentally demonstrated; the EDCC grating structure is designed by discretizing the duty cycle of sampled Bragg grating along the laser cavity, i.e., the cavity is divided into some subsections, and the duty cycle is constant in each subsection while it is different between two adjacent subsections, instead of the truly discrete coupling coefficient grating profile realized by discontinuously varying the duty cycle and/or etching depth of the uniform gating pitch. Moreover, the EDCC grating is fabricated by combining the conventional holographic exposure with a micrometer-level photolithography, which will simplify the fabrication process and reduce the fabrication cost. Based on experimental data, the analysis of spectral behavior as a function of injection current shows that the stable single-longitudinal-mode operation has been realized, even at large injection current and high temperature.