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• The GaSb-microfiber saturable absorber is prepared using the magnetron sputtering deposition technique. • The maximum single pulse energy is 233.67 nJ. • The highest average output power is 21.8 mW. In this study, we report the use of GaSb as a saturable absorber (SA) material in an Er-doped fiber (EDF) laser. The GaSb-based SA is prepared through the magnetron sputtering deposition technology, wherein a thin GaSb film is deposited on a microfiber. The modulation depth, saturable intensity, and non-saturable loss of the SA are determined to be 5.45 %, 37.3 MW/cm2, and 29.12 %, respectively. Under the Q-switching working state, the repetition frequeny is tuned from 73.15 to 93.7 kHz, and the pulse duration is changed from 5.17 to 2.33 μs at a pumping power of 310 to 500 mW. The highest average output power is 21.8 mW, which corresponds to a single pulse energy of 233.67 nJ. The generated laser pulses are in a stable state with a signal to noise ratio (SNR) of 65 dB. These results confirm the potential of GaSb as a successful saturable absorber candiatiate for building pulsed fiber lasers and in ultrafast optics applications. [ABSTRACT FROM AUTHOR]

• Bioelectro-barriers based on electroactive bacteria were first constructed. • Bioelectro-barriers achieved nearly 100 % nitrate interception through DNRA. • Periodic application of weak electricity can consistently prevent nitrate leaching. • Bioelectro-barriers were universal for nitrate interception in more diverse areas. • G. sulfurreducens was found to efficiently secrete nitrite reductase for rapid DNRA. Groundwater, the main freshwater resource for humans, has been widely contaminated with nitrate from fertilizers. Here, we report a new and chemical-free strategy to prevent nitrate leaching from soil based on the enrichment of electroactive bacteria, mainly of the genus Geobacter , with bioelectro-barriers, which leads to a nearly 100 % interception of nitrate and partly conserves reactive nitrogen in the form of weakly mobile ammonium by dissimilatory nitrate reduction to ammonium (DNRA). G. sulfurreducens was recognized to efficiently secrete nitrite reductase (NrfA) for rapid DNRA because it lacks nitrate reductase, which inhibits DNRA by competing with nitrite and producing toxic intracellular nitric oxide. With an increase in G. sulfurreducens abundance, near-zero nitrate leaching and 3-fold greater N retention was achieved. Periodic application of weak electricity to the bioelectro-barrier ensured the dominance of G. sulfurreducens in the microbial community and therefore its ability to consistently prevent nitrate leaching. The ability of G. sulfurreducens to intercept nitrate was further demonstrated in more diverse agricultural soils, providing a novel way to prevent nitrate leaching and conserve bioavailable nitrogen in the soil, which has broader implications for both sustainable agriculture and groundwater protection. [Display omitted] [ABSTRACT FROM AUTHOR]