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It is well known that the most important task of photocatalytic technology is to synthesize photocatalysts with compact heterojunction structure and high redox ability. To achieve the goal, a novel Z-scheme BiO2-x/BiOBr heterojunction containing oxygen vacancy was synthesized by an in-situ generation process. Several techniques, X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) have verified the BiO2-x/BiOBr heterojunction. XPS and electron spin resonance (ESR) reveals the presence of oxygen vacancy in the BiO2-x/BiOBr composite. As expected, the BiO2-x/BiOBr composite showed good performance in removing Escherichia coli (E. coli), Staphylococcus aureus (S. aureus), Rhodamine B (RhB) and tetracycline (TC). The effects of inorganic ions, pH value and water matrix were investigated with many details. The active species and proposed mechanism were revealed by trapping experiment and related characterizations. The synergistic effect of oxygen vacancy and Z-scheme heterojunction makes the BiO2-x/BiOBr composite possess excellent photocatalytic activity.

A novel dual-mode large-mode-area multicore fiber with air-hole structure, which is a quasi-37 core structured fiber with 20 air holes and 17 cores, is proposed in this paper. This fiber can realize strict dual-mode operation, that is, the fundamental mode HE11 and the second-order mode HE21 operation. The air-hole structure makes the second-order modes TE01 and TM01 cut off. Effects of structural parameters on effective refractive index and effective area of fundamental mode are investigated systematically. By optimizing the structural parameters of the fiber, effective area of fundamental mode is up to 1557.91 μm2 and maintaining a low bending loss (less than 10-4 dB/m at R > 0.47 m) while keeping dual-mode operation. The fiber can be used for large-mode-area high-power optical fiber laser, amplifier, FTTH and so on.

A multiwavelength fiber laser based on erbium-doped twin-core fiber (ED-TCF) and nonlinear optical loop mirror (NOLM) is proposed and demonstrated in this paper. The ED-TCF is employed as comb filter and gain medium simultaneously. The NOLM serves as an intensity equalizer. A fiber laser with 8 wavelength outputs is achieved at room temperature. The optical signal to noise ratio (OSNR) is larger than 40 dB. The fluctuation of peak power and wavelength is less than 1 dB and within 0.015 nm, respectively. This fiber laser has the advantages of simple structure and stable operation.

In this paper, a trench-assisted large-mode-field-area multi-core fiber with an air-hole structure composed of 21 conventional fiber cores and 16 air holes is proposed, and it can realize dual-mode transmission. By adjusting the structural parameters, the effective mode field area of fundamental mode can be up to 1916.042 µm2 at 1550 nm. In addition, the fiber has good bending characteristics by adding a trench with a lower refractive index than the cladding. When the bending radius is 1.4 cm, the bending loss is low to 2.96 × 10–3 dB/m. This fiber is of great significance for the design of bending insensitive fiber.

The density-functional theory is used to search for the candidate structures of Li-Ga-Te system below 100 GPa. Several new stable structures are uncovered, namely, P-3m1 LiGaTe2, P4/mmm Li9GaTe2, Immm Li9GaTe2. The band-gap of the I-42d LiGaTe2 and P4/mmm Li9GaTe2 corresponds to the peak position of the imaginary part of the dielectric function. Meanwhile, a new chemical valence of Ga atom under high pressure with [Ga]−5 ionic charge state is found. The dense accumulation of Li atoms and high pressure caused the change of valence state of Ga.

In this paper, a multi-core fiber with 22 air holes and 15 conventional cores is proposed. The fiber can realize dual-mode operation of fundamental mode HE11 and second-order mode HE21 under certain conditions. The relationship between performance of the fiber and the structural parameters that include core pitch, refractive index difference between core and cladding, and fiber core radius is investigated systematically. By adjusting the above parameters, the effective area of fundamental mode can be up to 1423.972 µm2 and keep a low bending loss at 1550 nm. Due to its flexibility of the structure, the proposed fiber is significant for theoretical research and practical manufacturing.

A novel trench-assisted dual-mode multi-core fiber with large-mode-field-area is proposed. The structure consists of 17 conventional cores and two air holes according to a regular hexagon, which can realize strict dual-mode transmission. The structural parameters’ effect on mode transmission characteristics, mode-field-area, and bending loss are analyzed systematically. By optimizing the structural parameters, the mode-field-area of the fundamental mode can reach 2100.619 µ m 2 . The introduction of the trench with a lower refractive index than cladding can reduce the bending loss to 9.88 × 10 − 4 d B / m when the bending radius is 2.3 cm. Besides, the structural design is flexible, and the manufacturing process is simple, which has broad application prospects.