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We present the design and fabrication of a 4 × 1 fiber combiner with low brightness loss. The effective area ratio (AR) of light transmission was first introduced to estimate the brightness loss. A square core fiber was used as the output fiber of the fiber combiner to achieve a high AR. The adiabatic criterion for tapering multimode fibers was investigated to obtain the structure parameters required for the fabrication. We used an auxiliary fiber of appropriate size to achieve a regular squared fiber bundle and improve bundle cutting and splicing quality. The fiber combiner yielded a high average power transmission efficiency of 97.8% when the brightness ratio was 1.05. In addition, the output power of 1030 W was obtained by combining two LDs. This type of fiber combiner can produce multi-kilowatts laser by combining high power LDs or fiber lasers. And it can be flexibly applied in laser welding, laser cladding, and laser cleaning.

We presented the chemical mask etching method to fabricate an all-fiber cladding light stripper (CLS). The morphology and density of the micron-sized microstructures generated on the fiber surface could be flexibly controlled in fabrication process, which was beneficial to the temperature performance and high-power operation capacity of the device. Based on the method, a theoretical model was developed to optimize the structure of the CLS. Initial experimental processing parameters were also obtained to realize uniform scattering and high attenuation coefficient. An all-fiber cladding light stripper with a high attenuation coefficient of 42 dB was achieved when the stripped cladding light was 1.117 kW. The temperature rising rate was only 0.011 °C/ input-Watt under the condition of air cooling, thanks to all-fiber structure and the uniform scattering design. The average stripped power density reached 9.19 × 106 W/m2 within a 135 mm long CLS. The CLS fabricated by this technique has great application in the high power fiber laser system.

A watt-level directly diode-pumped continuous-wave (CW) Ti:Sapphire oscillator was demonstrated for the first breakthrough by a high-power green laser-diode-pumped module employing the technologies of beam shaping, beam collimation, polarization beam combining, and fiber coupling. A 1.36-W output power and 10.6% of slope efficiency were obtained based on the double-concave (DC) cavity configuration. This is the highest CW output power from Ti:Sapphire (Ti:S) oscillator directly pumped by green laser diodes (LDs) reported so far.

For fiber-coupled green laser-diode pump beam, a simple model was proposed to calculate the average outputs. Then we presented a direct-pumping continuous-wave Ti:Sapphire laser producing an optimized output of 3.8-W with green diodes. It was the highest output of this kind reported so far corresponding to an optical/optical conversion efficiency of 11.5% and a high slope efficiency of 15.7% at 810 nm. A highest power of 1.41-W was also obtained with the single-sided pumping corresponding to a good slope efficiency of 14.3%. High-power green diodes realized the lowest threshold pumping intensity of ~ 16.7 × 103 W/cm2 under hundred-μm-level beam diameter size. This work would benefit the design for the direct-pumping Ti:Sapphire laser as a guide.

We present the second harmonic generation (SHG) of a low power and of both Q-switched mode-locked (QML) and CW (CWML) mode-locked picosecond (ps) laser at 1064 nm based on a single-pass frequency-doubling configuration of an end-pumped passively mode-locked Nd:YVO4 laser in a 3-mm periodically poled MgO-doped lithium-niobate (MgO:PPLN). The maximum SHG conversion efficiency is 27.4% when the laser is operated in the QML mode at an averaged pumping power of 895 mW and the conversion efficiency is reduced to 24.1% in the CWML mode with a maximum averaged pumping power of 1.37 W. The corresponding pulse width of the SHG output is estimated to be 15.5 ps. The repetition rates of the laser are 137 kHz for QML and 78.7 MHz for CWML. The theoretical efficiencies of SHG are calculated in both QML and CWML and the results agree very well with the experiments especially in the QML. This work provides a useful method for efficient frequency conversion for low power mode-locked lasers.

We report a 166 W burst mode pulse fiber amplifier seeded by a Q-switched mode-locked all-fiber laser at 1064 nm based on a fiber-coupled semiconductor saturable absorber mirror. With a pump power of 230 W at 976 nm, the output corresponds to a power conversion efficiency of 74%. The repetition rate of the burst pulse is 20 kHz, the burst energy is 8.3 mJ, and the burst duration is ∼ 20 μ s, which including about 800 mode-locked pulses at a repetition rate of 40 MHz and the width of the individual mode-locked pulse is measured to be 112 ps at the maximum output power. To avoid optical damage to the fiber, the initial mode-locked pulses were stretched to 72 ps by a bandwidth-limited fiber bragg grating. After a two-stage preamplifier, the pulse width was further stretched to 112 ps, which is a result of self-phase modulation of the pulse burst during the amplification.

We demonstrate a 150-mm long cladding light stripper for kW-level operation with high attenuation and low temperature rising. The first 100 mm of the device was designed based on theoretical simulation to achieve uniform extraction of the high-power scattered cladding light and it was constructed by self-developed experimental device for continuous gradient chemical etching. While in the last 50 mm, we reduced the cladding diameter from 400 to 65 μm and then roughed the surface to extract the residual low NA cladding light more efficiently. The power handling capability of this design was tested up to 1.01 kW for an hour stably without causing any damage. The cladding light stripper achieved a high attenuation of 39 dB and a low temperature elevation of 0.05 °C/ input-Watt under the condition of air cooling. The maximum temperature on the surface of the device was only 78.5 °C with an average stripped power density of 7.156 × 106 W/m2. To the best of our knowledge, the cladding light stripper reported here has the highest average stripped power density and attenuation coefficient without compromising temperature performance. This cladding light stripper is well suitable for application in multikilowatts class fiber lasers.

A novel and highly sensitive immunochromatographic strip based on a monoclonal antibody (3A9) was developed for the detection of cadmium in tap water. The 50% inhibition concentration of the antibody, which showed no cross-reactivity with other heavy metal ions, was 0.45 ng/mL and it recognized Cd(II)–1-(4-isothiocyanobenzyl) ethylenediamine-N,N,N′,N′-tetraacetic acid (EDTA) (Cd(II)–ITCBE) and not metal-free ITCBE and EDTA. The cutoff value for semi-quantitative detection of the strip was 5 ng/mL and the lower limit of detection for quantitative detection was 0.2 ng/mL using a scanning reader. The percent recovery ranged from 107.6% to 132% in tap water samples.

In this study, we developed an indirect competitive enzyme-linked immunosorbent assay (ic-ELISA) and an immunochromatographic strip assay based on a monoclonal antibody (mAb) against methylmercury (MeHg) to detect the presence of MeHg in tap water. Under optimum conditions (pH 8.0, 0.8% NaCl, and 0.1% Tween 20), the 50% half maximal inhibitory concentration (IC50) and limit of detection (LOD) were 16.64 and 2.03 ng/mL, respectively. The anti-MeHg mAb was specific to mercury with no cross-reactivity with other metal ions. The cut-off value of the immunochromatographic strip assay was 500 ng/mL for semi-quantitative detection, and the LOD was 11.3 ng/mL for quantitative detection. The average recovery rates of the ic-ELISA and immunochromatographic strip assay were 98.13% and 107.87%, respectively, in tap water. Therefore, ic-ELISA and the immunochromatographic strip assay can be used to detect MeHg in tap water.