Simulation of Intermediate State Absorption Enhancement in Rare-Earth Ions by Polarization Modulated Femtosecond Laser Field

We extend the third perturbation theory to study the polarization control behavior of the intermediate state absorption in Nd^（3＋）ions. The results show that coherent interference can occur between the single-photon and three-photon excitation pathways, and depends on the central frequency of the femtosecond laser field. Moreover,single-photon and three-photon absorptions have different polarization control efficiencies, and the relative weight of three-photon absorption in the whole excitation processes can increase with increasing the laser intensity.Therefore, the enhancement or suppression of the intermediate state absorption can be realized and manipulated by properly designing the intensity and central frequency of the polarization modulated femtosecond laser field.This research can not only enrich theoretical research methods for the up-conversion luminescence manipulation of rare-earth ions, but also can provide a clear physical picture for understanding and controlling multi-photon absorption in a multiple energy level system.

Atomic-level unveiling secondary recrystallization enabled microand macroscopic polarization enhancement for piezophotocatalytic oxygen activation

Piezoelectric semiconductors bear the bifunctional photocatalysis and piezocatalysis,while the absent or weak internal charge driving force severely restricts its catalytic activity.Developing polarization strategy is desirable,and particularly understanding its mechanism from a microscopic perspective remains scanty.Herein,we report a secondary recrystallization approach to achieving the simultaneous micro-and macroscopic polarization enhancement on Bi2WO6 nanosheets for boosting piezo-photocatalytic oxygen activation,and unravel the mechanism at an atom-level.The secondary recrystallization process not only results in a strengthened distortion of[WO6]octahedra with distortion index enhancement by~20%for a single octahedron,but also enables lateral crystal growth of nanosheets along the ab plane(av.50 to 180 nm),which separately allows the rise in dipole moment of unit cell(e.g.,1.63 D increase along a axis)and the stacking of the distorted[WO6]octahedron to accumulate the unit cell dipole,collectively contributing to the considerably strengthened spontaneous polarization and piezoelectricity.Besides,exposure of large-area{001}front facet enables more efficient capture and conversion of stress into piezo-potential.Therefore,the well-recrystallized Bi2WO6 nanosheets exhibit considerably promoted piezo-photocatalytic reactive oxygen species generation,given the decreased specific surface area.This work presents a feasible methodology to regulate inside-out polarization for guiding carriers transfer behavior,and may advance the solid understanding on the intrinsic mechanism.

High energy density and superior charge/discharge efficiency polymer dielectrics enabled by rationally designed dipolar polarization

Although many dielectric polymers exhibit high energy storage density(Ue)with enhanced dipolar polarization at room temperature,the substantially increased electric conduction loss at high applied electric fields and high temperatures remains a great challenge.Here,we report a strategy that high contents of medium-polar ester group and end-group(St)modification are introduced into a biode-gradable polymer polylactic acid(PLA)to synergistically reduce the loss and enhance Ue and charge-discharge efficiency(h).The resultant St-modified PLA polymer(PLA-St)exhibits an Ue of 6.5 J/cm^(3)with an ultra-high h(95.4%),far outperforming the best reported dielectric polymers.It is worth noting that the modified molecular structures can generate deep trap centers and restrict the local dipole motions in the polymer,which are responsible for the reduction of conduction loss and improvements in high-temperature capacitive performance.In addition,the PLA-St polymer shows intrinsically excellent self-healing ability and cyclic stability surviving over 500000 charge-discharge cycles.This work offers an efficient route to next-generation eco-friendly dielectric polymers with high energy density,low loss,and long-term stability.

A new strategy to achieve enhanced upconverted circularly polarized luminescence in chiral perovskite nanocrystals

Achieving large luminescence dissymmetry factors(pium)is challenging in the research field of circularly polarized luminescence(CPL).While various approaches have been developed to construct organic systems with CPL activity,there is still a lack of effective methods for fabricating CPL active inorganic materials.Herein,we propose an approach for endowing upconversion nanoparticles(UCNPs)and perovskite nanocrystal(PKNC)hybrid nanomaterials with upconverted circularly polarized luminescence(UC-CPL)activity.Chiral cesium lead bromides(CsPbBr_(3))PKNCs were synthesized by a chiral-ligand-assistant method.Meanwhile,UCNP could be embedded into the chiral PKNC,enabling a photon upconvesion feature to the PKNC.The embedded UCNPs in PKNCs were confirmed by electron tomography.Consequently,various CPL activities,including prompt CPL,UC-CPL,and energy transfer enhanced circularly polarized luminescence(ET-CPL),were realized.The chiral perovskite nanocrystals could reabsorb the chiral energy generated from UCNPs,showing energy transfer enhanced CPL activity with four times magnification of the circular polarization.These findings provide a meaningful strategy for designing chiral photon upconversion inorganic nanomaterials with highly efficient UC-CPL activity.

Enhancement of second-order harmonic generation in polarized BaTiO_3 thin films embedded with Ag nanoparticles

RECENTLY, much attention has been paid to optical properties of ferroelectric thin films. Be-

Algorithmic cooling based on cross-relaxation and decoherence-free subspace

Heat-bath algorithmic cooling(HBAC)has been proven to be a powerful and effective method for obtaining high polarization of the target system.Its cooling upper bound has been recently found using a specific algorithm,the partner pairing algorithm(PPAHBAC).It has been shown that by including cross-relaxation,it is possible to surpass the cooling bounds.Herein,by combining cross-relaxation and decoherence-free subspace,we present a two-qubit reset sequence and then generate a new algorithmic cooling(AC)technique using irreversible polarization compression to further surpass the bound.The proposed two-qubit reset sequence can prepare one of the two qubits to four times the polarization of a single-qubit reset operation in PPA-HBAC for low polarization.When the qubit number is large,the cooling limit of the proposed AC is approximately five times as high as the PPA-HBAC.The results reveal that cross-relaxation and decoherence-free subspace are promising resources to create new AC for higher polarization.