Monolayer transition metal dichalcogenides favor the formation of a variety of excitonic quasiparticles,and can serve as an ideal material for exploring room-temperature many-body effects in two-dimensional systems.He...Monolayer transition metal dichalcogenides favor the formation of a variety of excitonic quasiparticles,and can serve as an ideal material for exploring room-temperature many-body effects in two-dimensional systems.Here,using mechanically exfoliated monolayer WS;and photoluminescence(PL)spectroscopy,exciton emission peaks are confirmed through temperature-dependent and electric-field-tuned PL spectroscopy.The dependence of exciton concentration on the excitation power density at room temperature is quantitatively analyzed.Exciton concentrations covering four orders of magnitude are divided into three stages.Within the low carrier concentration stage,the system is dominated by excitons,with a small fraction of trions and localized excitons.At the high carrier concentration stage,the localized exciton emission from defects coincides with the emission peak position of trions,resulting in broad spectral characteristics at room temperature.展开更多
Single-crystal erbium silicate nanowires have attracted considerable attention because of their high optical gain. In this work, we report the controlled synthesis of silicon-erbium ytterbium silicate core- shell nano...Single-crystal erbium silicate nanowires have attracted considerable attention because of their high optical gain. In this work, we report the controlled synthesis of silicon-erbium ytterbium silicate core- shell nanowires and fine-tuning the erbium mole fraction in the shell from x = 0.3 to x = 1.0, which corresponds to changing the erbium concentration from 4.8 ×10^21 to 1.6 ×10^22 cm^-3. By controlling and properly optimizing the composition of erbium and ytterbium in the nanowires, we can effectively suppress upeonversion photoluminescence while simultaneously enhancing near-infrared emission. The composition-optimized nanowires have very long photoluminescence lifetimes and large emission cross- sections, which contribute to the high optical gain that we observed. We suspended these concentration- optimized nanowires in the air to measure and analyze their propagation loss and optical gain in the near-infrared communication band. Through systematic measurements using wires with different core sizes, we obtained a maximum net gain of 20 ± 8 dB·mm^-1, which occurs at a wavelength of 1534 nm, for a nanowire with a diameter of 600 nm and a silicon core diameter of 300 nm.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61635001,52072117,and 51972105)。
文摘Monolayer transition metal dichalcogenides favor the formation of a variety of excitonic quasiparticles,and can serve as an ideal material for exploring room-temperature many-body effects in two-dimensional systems.Here,using mechanically exfoliated monolayer WS;and photoluminescence(PL)spectroscopy,exciton emission peaks are confirmed through temperature-dependent and electric-field-tuned PL spectroscopy.The dependence of exciton concentration on the excitation power density at room temperature is quantitatively analyzed.Exciton concentrations covering four orders of magnitude are divided into three stages.Within the low carrier concentration stage,the system is dominated by excitons,with a small fraction of trions and localized excitons.At the high carrier concentration stage,the localized exciton emission from defects coincides with the emission peak position of trions,resulting in broad spectral characteristics at room temperature.
基金Acknowledgements The authors are grateful to the National Natural Science Foundation of China （Grant Nos. 11374092, 61474040, 61574054, 61635001, and 61505051）, the National Basic Research Program of China （Grant No. 2012CB933703）, and the Aid Program for Science and Technology Innovative Research Team in Higher Educational Institutions of Hunan Province, the Hunan Provincial Science and Technology Department （Grant Nos. 2014FJ2001 and 2014GK3015）.
文摘Single-crystal erbium silicate nanowires have attracted considerable attention because of their high optical gain. In this work, we report the controlled synthesis of silicon-erbium ytterbium silicate core- shell nanowires and fine-tuning the erbium mole fraction in the shell from x = 0.3 to x = 1.0, which corresponds to changing the erbium concentration from 4.8 ×10^21 to 1.6 ×10^22 cm^-3. By controlling and properly optimizing the composition of erbium and ytterbium in the nanowires, we can effectively suppress upeonversion photoluminescence while simultaneously enhancing near-infrared emission. The composition-optimized nanowires have very long photoluminescence lifetimes and large emission cross- sections, which contribute to the high optical gain that we observed. We suspended these concentration- optimized nanowires in the air to measure and analyze their propagation loss and optical gain in the near-infrared communication band. Through systematic measurements using wires with different core sizes, we obtained a maximum net gain of 20 ± 8 dB·mm^-1, which occurs at a wavelength of 1534 nm, for a nanowire with a diameter of 600 nm and a silicon core diameter of 300 nm.
