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Highly efficient frequency doubling of a continuous-wave Yb-doped fiber laser with a passively-locked enhancement cavity is achieved. The increase in efficiency is a result of improved transverse mode matching between the fiber and doubling cavities, which is enabled by an alignment method presented here. An optical conversion efficiency as high as 36.8% from a launched 976?nm diode pump to a 532?nm green laser is obtained. The maximum 532?nm output is 24.5 W, which is limited by the onset of parasitic oscillations in the fiber laser.

Miniature microbial fuel cell (MFC) technology has received growing interest due to its potential applications in high-throughput screening of bacteria and mutants to elucidate mechanisms of electricity generation. This paper reports a novel miniature MFC with an improved output power density and short startup time, utilizing electrospun conducting poly(3,4-ethylenedioxythiophene) (PEDOT) nanofibers as a 3D porous anode within a 12 μl anolyte chamber. This device results in 423 μW cm−3 power density based on the volume of the anolyte chamber, using Shewanella oneidensis MR-1 as a model biocatalyst without any optimization of bacterial culture. The device also excels in a startup time of only 1hr. The high conductivity of the electrospun nanofibers makes them suitable for efficient electron transfer. The mean pore size of the conducting nanofibers is several micrometers, which is favorable for bacterial penetration and colonization of surfaces of the nanofibers. We demonstrate that S. oneidensis can fully colonize the interior region of this nanofibers-based porous anode. This work represents a new attempt to explore the use of electrospun PEDOT nanofibers as a 3D anode material for MFCs. The presented miniature MFC potentially will provide a high-sensitivity, high-throughput tool to screen suitable bacterial species and mutant strains for use in large-size MFCs.