Erbium-Doped Zirconia-Alumina Silica Glass-Based Fiber as a Saturable Absorber for High Repetition Rate Q-Switched All-Fiber Laser Generation

We propose and demonstrate a Q-switched erbium-doped fiber laser （EDFL） using an erbium-doped zirconia-alumina silica glass-based fiber （Zr-EDF） as a saturable absorber. As a 16-cm-long Zr-EDF is incorporated into a ring EDFL cavity, a stable Q-switching pulse train operating at 1565？nm wavelength is successfully obtained. The repetition rate is tunable from 33.97？kHz to 71.23？kHz by increasing the pump power from the threshold of 26？mW to the maximum of 74？mW. The highest pulse energy of 26.67？nJ is obtained at the maximum pump power.

Activity and characteristics of ＂Oxygen-enriched＂ highly reactive absorbent for simultaneous flue gas desulfurization and denitrification

An ＂Oxygen-enriched＂ highly reactive absor- bent was prepared by mixing fly ash, lime and a small quantity of KMnO4 for simultaneous desulfiarization and denitrification. Removal of SO2 and NO simultaneously was carried out using this absorbent in a flue gas circulating fluidized bed （CFB）. The highest simultaneous removal efficiency, 94.5% of SO2 and 64.2% of NO, was achieved under the optimal experiment conditions. Scanning Electron Microscope （SEM） and Accessory X-ray Energy Spectrometer （EDX） were used to observe the surface characteristics of fly ash, lime, ＂Oxygen-enriched＂ highly reactive absorbent and the spent absorbent. An ion chromatograph （IC） and chemical analysis methods were used to determine the contents of sulfate, sulfite, nitrate and nitrite in the spent absorbents, the results showed that sulfate and nitrite were the main products for desulfurization and denitrification respectively. The mechanism of removing SO2 and NO simultaneously was proposed based on the analysis results of SEM, EDX, IC and the chemical analysis methods.

High energy soliton pulse generation by a magnetron-sputtering-deposition-grown MoTe_2 saturable absorber

The pulse energy in the ultrafast soliton fiber laser oscillators is usually limited by the well-known wave-breaking phenomenon owing to the absence of a desirable real saturable absorber(SA) with high power tolerance and large modulation depth. Here, we report a type of microfiber-based MoTe_2 SA fabricated by the magnetron-sputtering deposition(MSD) method. High-energy wave-breaking free soliton pulses were generated with pulse duration/pulse energy/average output power of 229 fs/2.14 nJ/57 mW in the 1.5 μm regime and 1.3 ps/13.8 nJ/212 mW in the 2 μm regime, respectively. To our knowledge, the generated soliton pulses at 1.5 μm had the shortest pulse duration and the highest output power among the reported erbium-doped fiber lasers mode locked by transition metal dichalcogenides. Moreover, this was the first demonstration of a MoTe_2-based SA in fiber lasers in the 2 μm regime, and the pulse energy/output power are the highest in the reported thulium-doped fiber lasers mode locked by two-dimensional materials. Our results suggest that a microfiber-based MoTe_2 SA could be used as an excellent photonic device for ultrafast pulse generation, and the MSD technique opens a promising route to produce a high-performance SA with high power tolerance and large modulation depth, which are beneficial for high-energy wave-breaking free pulse generation.

Effect of rare earths on microwave absorbing properties of RE-Co alloys

The powders of RE2Co17（RE=Y, Ce, Nd, Ho, Er） and Ho x Co100–x（x=6, 8, 10, 12） alloys were prepared by the arc melting method and high-energy ball mill process. The compositions and morphologies of the alloys were characterized by X-ray diffraction（XRD） and scanning electron microscopy（SEM）, and the microwave absorbing properties were studied by a vector network analyzer. The results showed that the alloy of Y2Co17 had better absorbing properties at low frequencies and its lowest reflectivity value was –9.5 d B at 3.8 GHz. The lowest reflectivity value of Ho2Co17 alloy was –13.7 d B at 7.02 GHz and it obtained large absorbing bandwidth. Reflectivity value less than –5 d B was from 5.1 to 10.2 GHz. When x=6 and x=8, the alloys of Ho x Co100–x consisted of Ho2Co17 phase and Co phase. They had good radar absorbing properties. With increase in Ho content, the minimum reflectivity value worsened and the absorbing peak frequency shifted toward higher frequencies. But when x=12, the absorbing peak frequency shifted toward lower frequencies but the minimum reflectivity value worsened.