Decaying evolution dynamics of double-pulse mode-locking

Taking advantage of the dispersive Fourier transformation technique, the decaying evolution processes of doublepulse mode-locking in a single-walled carbon-nanotube-based Er-doped fiber laser are observed in detail for the first time to our knowledge. The decaying dynamics of the double-pulse mode-locking state is analyzed in the spectral and temporal domains. We reveal that the two pulses in one cluster disappear either simultaneously or one by one during the decaying processes of double-pulse mode-locking states. In addition, the spectral evolution patterns of the special double-pulse states(i.e., bound states) are extremely distinct at different decline rates of the pump power.

Generation of coexisting high-energy pulses in a mode-locked all-fiber laser with a nonlinear multimodal interference technique

We demonstrate a passively mode-locked all-fiber laser incorporating a piece of graded-index multimode fiber as a mode-locking modulator based on a nonlinear multimodal interference technique, which generates two types of coexisting high-energy ultrashort pulses [i.e., the conventional soliton(CS) and the stretched pulse(SP)]. The CS with pulse energy as high as 0.38 n J is obtained at the pump level of 130 mW. When the pump increases to175 mW, the high-energy SP occurs at a suitable nonlinear phase bias and its pulse energy can reach 4 n J at a 610 mW pump. The pulse durations of the generated CS and SP are 2.3 ps and 387 fs, respectively. The theory of nonlinear fiber optics, single-shot spectral measurement by the dispersive Fourier-transform technique, and simulation methods based on the Ginzburg–Landau equation are provided to characterize the laser physics and reveal the underlying principles of the generated CS and SP. A rogue wave, observed between the CS and SP regions, mirrors the laser physics behind the dynamics of generating a high-energy SP from a CS. The proposed all-fiber laser is versatile, cost-effective and easy to integrate, which provides a promising solution for high-energy pulse generation.

Spatiotemporal Mapping of Salt Marshes in the Intertidal Zone of China during 1985-2019

This study mapped the areal extent,identified the species composition,and analyzed the changes of salt marshes in the intertidal zone of China during the period 1985–2019.With the aid of the cloud platform of the Google Earth Engine,we selected Landsat 5/8 and Sentinel-2 images and used the support vector machine classification method to extract salt marsh information for the years of 1985,1990,1995,2000,2005,2010,2015,and 2019.Seven major species of salt marshes:Phragmites australis,Suaeda spp.,Spartina alterniflora,Scirpus mariqueter,Tamarix chinensis,Cyperus malaccensis,and Sesuvium portulacastrum were identified.Our results showed that salt marshes are mainly distributed in Liaoning,Shandong,Jiangsu,Shanghai,and Zhejiang,with varying patterns of shrinking,expansion,or wavering in different places.The distribution of salt marshes has declined considerably from 151,324 ha in 1985 to 115,397 ha in 2019,a drop of 23.7%.During the same period,the area of native species has dropped 95.4%from 77,741 ha to 3,563 ha for Suaeda spp.and 45.1%from 60,511 ha to 33,193 ha for P.australis;on the contrary,the area of exotic species,S.alterniflora,has exhibited a sharp rise from just 99 ha to 67,527 ha.For the past 35 years,the driving factors causing salt marsh changes are mainly land reclamation,variations in water and sand fluxes,and interspecific competition and succession of salt marsh vegetation.These results provide fundamental reference information and could form the scientific basis for formulating policies for the conservation and utilization of salt marsh resources in China.

Palladacycle-Catalyzed Carbonylation of Aryl Iodides or Bromides with Aryl Formates

有芳基碘化物或溴化物的芳基甲酸盐的有效催化 palladacycle 的芳香的 carbonylation 反应被开发了。没有外部碳一氧化物的使用，商业地可得到、容易准备的芳基甲酸盐作为羰基来源被采用。现在的催化系统显示出宽广的功能的组忍耐并且负担得起芳基安息香酸盐衍生物在对优秀收益好。

Dual-comb soliton rains based on polarization multiplexing in a single-walled carbon nanotube mode-locked Er-doped fiber laser

We experimentally demonstrate tunable dual-comb soliton rains in a polarization multiplexing fiber laser based on a singlewalled carbon nanotube.The repetition frequency difference of dual-comb pulses is about 39 Hz,with a maximum extinction ratio of 29 dB.With suitable polarization states,one of the dual-comb pulses switches into soliton rain sequence with chirped isolating soliton trains.The signal-to-noise ratio reaches 61 dB,which is 11 dB higher than that of the normal dual-comb pulses.The intervals between chirped isolating solitons are distributed progressively,and the number of isolating solitons can be flexibly tuned from 2 to 11 by adjusting polarization state or pump power.Our work will provide support for further understanding of interaction dynamics of solitons and give a new route to the application of precision measurement.