Search

Cooperative upconversion luminescence (CUCL) occurs in spectral regions in which single ions do not have energy levels. However, all results reported so far are concentrated on luminescence properties from Yb3+ ions-doped various hosts. Here, we report the observation of nonlinear negative transmittance (NNT) at continuous-wavelength (CW) 980-nm laser diodes (LDs) pumping in silicate oxyfluoride glass ceramics (GCs)-containing CaF2:Yb3+ nanocrystals. The unique optical nonlinearity is analyzed based on energy-level transitions, dynamic evolution, rate equation, and power transmission equation, which can be explained as the cooperative optical absorption for the intense CUCL of Yb3+ ions. The NNT in the CaF2:Yb3+ nanocrystals-embedded GCs can be tailored with the power of a CW 980-nm LDs, which possesses potential for the development of future optical limiters and switches. [ABSTRACT FROM AUTHOR]

Optical modulation is a crucial operation in photonics for network data processing with the aim to overcome information bottleneck in terms of speed, energy consumption, dispersion and cross-talking from conventional electronic interconnection approach. However, due to the weak interactions between photons, a facile physical approach is required to efficiently manipulate photon-photon interactions. Herein, we demonstrate that transparent glass ceramics containing LaF3: Tm3+ (Er3+) nanocrystals can enable fast-slow optical modulation of blue/green up-conversion fluorescence upon two-step excitation of two-wavelengths at telecom windows (0.8-1.8 μm). We show an optical modulation of more than 1500% (800%) of the green (blue) up-conversion fluorescence intensity, and fast response of 280 μs (367 μs) as well as slow response of 5.82 ms (618 μs) in the green (blue) up-conversion fluorescence signal, respectively. The success of manipulating laser at telecom windows for fast-slow optical modulation from rear-earth single-doped glass ceramics may find application in all-optical fiber telecommunication areas. [ABSTRACT FROM AUTHOR]

An enhanced nonlinear optical (NLO) performance was observed in Se-doped MoS 2 nanosheets synthesized through a facile annealing process. Se-doped MoS 2 nanosheets with a large saturable intensity and high modulation depth generated stable passively Q-switched fiber laser pulses at 1559 nm. In comparison with the Q-switched fiber laser utilizing the pristine MoS 2 nanosheets as a saturable absorber, the passive Q-switching operation based on Se-doped MoS 2 nanosheets could be conducted at a lower threshold power of 50 mW, a wider range of repetition rates from 28.97 to 130 kHz, and a higher SNR of 56 dB. More importantly, the shortest pulse duration of 1.502 μs was realized and the output power and pulse energy reached 17.2 mW and 133.07 nJ, respectively. These results indicate that tailoring the chemical composition of optical nanomaterials by introducing a dopant is a feasible method of improving the NLO response of the MoS 2 nanosheets and realizing excellent ultrafast pulse generation.

Vertical layered MoS 2 nanosheets rooting into TiO 2 nanofibers were successfully prepared by a facile two-step method: prefabrication of porous TiO 2 nanofibers based on an electrospinning technique, and assembly of MoS 2 ultrathin nanosheets through a simple hydrothermal reaction. Significant enhancement of nonlinear optical response of the MoS 2 /TiO 2 nanocomposite was confirmed by an open-aperture z-scan measurement. The nanocomposite displayed strong optical limiting (OL) effects to ultrafast laser pulses with a low OL threshold of ~22.3 mJ/cm 2 , which is lower than that of pristine TiO 2 nanofibers and MoS 2 nanosheets. In addition to the contribution of the strong nonlinear absorption of MoS 2 nanosheets and TiO 2 nanofibers, such phenomenon is also attributed to the unique structure of vertically standing layered MoS 2 nanosheets on TiO 2 nanofibers with a large amount of exposed edge states, large surface areas and fast electron transfer between TiO 2 and MoS 2 . This work broadens our vision to engineering novel hierarchical MoS 2 -based nanocomposite for efficiently enhanced nonlinear light-matter interaction.

Six new terpenoids, including three diterpenoids (1-3), one norditerpenoid (4) and two sesquiterpenoids (11 and 12), were isolated from the roots of Chloranthus henryi. The structures were elucidated mainly by 1D, and 2D NMR and MS experiments, and their relative configurations were determined by NOE techniques., (Georg Thieme Verlag KG Stuttgart, New York.)