Bidirectional mode-locked erbium-doped fiber laser based on an all-fiber gold nanofilm saturable absorber.

We demonstrate a bidirectional mode-locked erbium-doped fiber laser by incorporating gold nanofilm as a saturable absorber (SA). The gold nanofilm SA has the advantages of high stability and high optical damage threshold. Besides, the SA exhibits a large modulation depth of 26% and a low saturation intensity of 1.22 MW/cm2 at 1.56 µm wavelength band, facilitating the mode-locking of bidirectional propagating solitons within a single laser cavity. Bidirectional mode-locked solitons are achieved, with the clockwise pulse centered at 1568.35 nm and the counter-clockwise one at 1568.6 nm, resulting in a slight repetition rate difference of 19 Hz. Moreover, numerical simulations are performed to reveal the counter-propagating dynamics of the two solitons, showing good agreement with the experimental results. The asymmetric cavity configuration gives rise to distinct buildup and evolution dynamics of the two counter-propagating pulses. These findings highlight the advantage of the gold nanofilm SA in constructing bidirectional mode-locked fiber lasers and provide insights for understanding the bidirectional pulse propagation dynamics.

Diphenyl-1-pyrenylphosphine: photo-triggered AIE/ACQ transition with remarkable third-order nonlinear optical signal change.

A propeller-like pyrene derivative of diphenyl-1-pyrenylphosphine (DPPP) is designed and synthesized. DPPP exhibits a unique photo-triggered AIE/ACQ transition with a remarkable third-order nonlinear optical signal change, which is proved to originate from the photo-induced oxidation of a phosphorus atom.

Luminescent CePO4:Tb colloids for H2O2 and glucose sensing.

Hydrogen peroxide (H2O2) is an essential molecule in intracellular signaling transduction and normal cell functions. It is critical to be able to detect H2O2 quantitatively in cellular processes for getting useful physiological information. Herein, we developed a novel fluorescent probe for H2O2 sensing, CePO4:Tb colloidal solution. Upon addition of H2O2, the luminescence of the colloidal CePO4:Tb solution responds linearly in a wide H2O2 concentration range of 0-200 µM, allowing for quantitative detection of H2O2. The H2O2 sensing by this method exhibits a rapid response within several minutes, a detection limit of 1.03 µM H2O2, and a relative standard deviation lower than 3.1%. This sensing material for H2O2 is also suitable for the detection of glucose since H2O2 is generated via the catalytic oxidation of glucose by oxidase enzymes. In addition to a wide linear response, a low detection limit and a high reproducibility, our present method for glucose sensing shows a highly specific response to glucose in a mixed carbohydrate solution due to the specificity of glucose oxidase to glucose. This lanthanide-based fluorescent sensing material might have potential for detecting H2O2 and glucose in biological applications.

Synthesis of porous upconverting luminescence α-NaYF4:Ln(3+) microspheres and their potential applications as carriers.

The present work reports a self-sacrificing template strategy to synthesize porous α-NaYF4 microspheres via the reaction of as-prepared Y(OH)CO3·H2O@SiO2 with NH4F and NaNO3 solutions. XRD, SEM, TEM and N2 adsorption-desorption measurements were used to characterize the resulting product. The surface SiO2 shell was shown to play a vital role in size and shape control and porosity formation. A possible reaction mechanism was explored in terms of a surface-protected etching and ion-exchange reaction process. To explore their application potential, the storage and release behavior of Rhodamine 640 dye in the porous α-NaYF4 microspheres was investigated, showing a relatively high loading efficiency and a sustained release ratio. Under near-infrared (NIR) irradiation, porous α-NaYF4 microspheres doped with lanthanide ions showed typical upconverting luminescence characteristics that can convert NIR photons to ultraviolet/visible photons. The above features and properties indicate that our present porous upconverting luminescence particles are promising in biological applications as luminescence imaging agents and drug carriers.