Observation of the photonic Hall effect and photonic magnetoresistance in random lasers.

Modulation of scattering in random lasers (RLs) by magnetic fields has attracted much attention due to its rich physical insights. We fabricate magnetic gain polymer optical fiber to generate RLs. From macroscopic experimental phenomena, with the increase of the magnetic field strength, the magnetic transverse photocurrent exists in disordered multiple scattering of RLs and the emission intensity of RLs decreases, which is the experimental observation of photonic Hall effect (PHE) and photonic magnetoresistance (PMR) in RLs. At the microscopic level, based on the field dependence theory of magnetic disorder in scattered nanoparticles and the replica symmetry breaking theory, the magnetic-induced transverse diffusion of photons reduces the scattering disorder, and then decreases the intensity fluctuation disorder of RLs. Our work establishes a connection between the above two effects and RLs, visualizes the influence of magnetic field on RL scattering at the microscopic level, which is crucial for the design of RLs.

Research progress on diarrhoea and its mechanism in weaned piglets fed a high-protein diet.

In order to pursue faster growth and development of weaned piglets, increased dietary protein (CP) levels were favoured by the pig industry and the feed industry. The digestive organs of piglets were not fully developed at weaning, and the digestive absorption capacity of protein was limited. High-protein diets can cause allergic reactions in piglets, destroy intestinal structural integrity, reduce immunity, and cause intestinal flora imbalance. Undigested proteins were prone to produce toxic substances, such as ammonia and biogenic amines, after fermentation in the hindgut, which negatively affects the health of the intestine and eventually causes reduced growth performance and diarrhoea in piglets. This review revealed the mechanism of diarrhoea caused by high-protein diets in weaned piglets and provided ideas for preventing diarrhoea in weaned piglets.

Spray coated perylenebisimide/polymer film with controllable molecular aggregation state and emission properties.

Dye doped organic thin films with controllable molecular aggregation and emission properties are of broad interest to the scientific community owing to their large number of potential applications in physics, chemistry, and materials science. Here, a spray coating method was used to prepare perylenebisimides (PBI) doped polymer films. In this study, the effects of the dye concentration, polymer matrix, solvent, and casting process on the optical properties of the resulting films were studied. The aggregation of the PBI into monomer, dimer, and oligomer forms, was rapidly and simply controlled based on the concentration dependence of PBI. The molecular aggregation mechanism in the film forming process for PBI doped polystyrene (PS) was further analyzed by computer simulations. The blends rapidly reached their lowest Gibbs free energy owing to the "frozen" polymer chains and confinement of PBI, molecules with different aggregation states. Therefore, the PBIs/PS films prepared under different conditions had different fluorescent lifetimes and absolute quantum yields. Narrow emission, amplified spontaneous emission (ASE) and random lasing (RL) were observed in PBI doped PS films when photo-pumped at 532 nm in transmittance and waveguide modes, respectively. A lower ASE and RL threshold were obtained for PS films doped with monomeric PBI than those in other aggregation states. Moreover, the solvent use in film deposition greatly influenced the emission properties of the PS films by altering their microstructures. These results indicate potential applications for spray coated dye/polymer films in organic solid-state lasers.

Experimental observation of wave localization at the Dirac frequency in a two-dimensional photonic crystal microcavity.

Trapping light within cavities or waveguides in photonic crystals is an effective technology in modern integrated optics. Traditionally, cavities rely on total internal reflection or a photonic bandgap to achieve field confinement. Recent investigations have examined new localized modes that occur at a Dirac frequency that is beyond any complete photonic bandgap. We design Al2O3 dielectric cylinders placed on a triangular lattice in air, and change the central rod size to form a photonic crystal microcavity. It is predicted that waves can be localized at the Dirac frequency in this device without photonic bandgaps or total internal reflections. We perform a theoretical analysis of this new wave localization and verify it experimentally. This work paves the way for exploring localized defect modes at the Dirac point in the visible and infrared bands, with potential applicability to new optical devices.

Tunable random polymer fiber laser.

We have demonstrated the realization of on-line temperature-controlled random lasers (RLs) in the polyhedral oligomeric silsesquioxanes (POSS) nanoparticles (NPs) as well as Pyrromethene 597 (PM597) laser dye, Fe3O4/SiO2 NPs as well as PM597, and only PM597 doped polymer optical fibers (POFs), respectively. The RLs can be obtained from the gained POFs system caused by multiple scattering of emitted light. The refractive index of the fiber core materials can be easily tuned via temperature due to the polymer with large thermo-optic coefficient. Meanwhile, the scattering mean free path of core in the POFs, which is the key role for the emission wavelength of RLs, is strongly dependent on the matrix refractive index. Thus emission wavelength of RLs in the POF temperature can be controlled through changing the temperature. With the increasing the temperature, the RL emission wavelength has occurred red-shift effect for the POFs.