Extra-narrowband metallic filters with an ultrathin single-layer metallic grating

Narrowband and high-transmission optical filters are extensively used in color display technology, optical information processing, and high-sensitive sensing. Because of large ohmic losses in metallic nanostructures, metallic filters usually exhibit low transmittances and broad bandwidths. By employing both strong field enhancements in metallic nano-slits and the Wood’s anomaly in a periodic metallic grating, an extra-narrowband and high-transmission metallic filter is numerically predicted in an ultrathin single-layer metallic grating. Simulation results show that the Wood’s anomaly in the ultrathin(thickness H = 60 nm) single-layer metallic grating results in large field enhancements in the substrate and low losses in the metallic grating. As a result, the transmission bandwidth(transmittance T > 60%) at λ = 1200 nm is as small as △λFWHM=1.6 nm, which is smaller than 4% of that in the previous thin dielectric and metallic filters. The corresponding quality factor is as high as Q = λ/△λFWHM= 750, which is 40 times greater than that in the previous reports. Moreover, the thickness of our metallic filter(H = 60 nm) is smaller than 40% of that in the previous reports, and its maximum transmittance can reach up to 80%. In experiments, a narrowband metallic filter with a bandwidth of about △λFWHM = 10 nm, which is smaller than 25% of that in the previous metallic filters, is demonstrated.

Laser-induced Alignment and Coulomb Explosion of CO2

Dynamic processes of CO2 are experimentally studied in intense femtosecond laser fields with laser intensity varying from 1×10^13 W/cm^2 to 6×10^14 W/cm^2. When the laser intensity is below the ionization threshold, a coherent rotational wave-packet is formed for CO2 at room temperature through nonadiabatic rotational excitation. The evolution of the wave-packet leads to transient alignment. The field-free alignment revives periodically after the laser pulse is over. The revival structure can be modified by a second laser pulse for the rotational wave-packet through precisely adjusting the time delays between the two laser pulses. When the laser intensity excesses the ionization threshold, ionization and Coulomb explosion occur. The atomic ions C^m＋ （re=1-3） and On＋ （n=1-3） observed in the experiment exhibit highly anisotropic angular distributions relative to the laser polarization. Using two linearly polarized laser pulses with crossed polarization, we conclude that the anisotropic angular distribution results from dynamic alignment, in which the rising edge of the laser pulse aligns the neutral CO2 along the laser polarization direction prior to ionization.

Spectrally multiplexed and bright entangled photon pairs in a lithium niobate microresonator

On-chip bright quantum sources with multiplexing ability are extremely high in demand for integrated quantum networks with unprecedented scalability and complexity.Here,we demonstrate a bright and broadband biphoton quantum source with spectral multiplexing generated in a lithium niobate microresonator system.Without introducing the conventional domain poling,the on-chip microdisk produces photon pairs covering a broad bandwidth promised by natural phase matching in spontaneous parametric down conversion.Experimentally,the multiplexed photon pairs are characterized by 30 nm bandwidth limited by the filtering system,providing over 40 multiplexing channels with a 0.8 nm channel spacing.Meanwhile,the generation rate reaches 5.13 MHz/μW with a coincidence-to-accidental ratio up to 804,and the quantum source manifests a high purity with a heralded single photon correlation g^((2))_(H)(0)=0.0098±0.0021.Furthermore,the energy-time entanglement is demonstrated with an excellent interference visibility of 96.5%±2%.Such a quantum source at the telecommunication band paves the way for high-dimensional entanglement and future integrated quantum information systems.

Fast-growing procedure for perovskite films in planar heterojunction perovskite solar cells

A fast-growing procedure（FGP） to fabricate perovskite films with large grain sizes is described in this article. In the FGP method, the perovskite precursor solution is coated onto the substrates at a temperature of 240 8C. The solvent in the precursor solution evaporates quickly in about 2 s, resulting in the rapid formation of a perovskite film without further annealing process. Millimeter-scale perovskite grain clusters are obtained in the film. Based on such perovskite films, fabricated planar heterojunction perovskite solar cells give a power conversion efficiency（PCE） above 8%.

Enhanced entanglement and asymmetric EPR steering between magnons

The generation and manipulation of strong entanglement and Einstein-Podolsky-Rosen(EPR)steering in macroscopic systems are outstanding challenges in modern physics.Especially,the observation of asymmetric EPR steering is important for both its fundamental role in interpreting the nature of quantum mechanics and its application as resource for the tasks where the levels of trust at different parties are highly asymmetric.Here,we study the entanglement and EPR steering between two macroscopic magnons in a hybrid ferrimagnet—light system.In the absence of light,the two types of magnons on the two sublattices can be entangled,but no quantum steering occurs when they are damped with the same rates.In the presence of the cavity field,the entanglement can be significantly enhanced,and strong two-way asymmetric quantum steering appears between two magnons with equal dissipation.This is very different from the conventional protocols to produce asymmetric steering by imposing additional unbalanced losses or noises on the two parties at the cost of reducing steerability.The essential physics is well understood by the unbalanced population of acoustic and optical magnons under the cooling effect of cavity photons.Our finding may provide a novel platform to manipulate the quantum steering and the detection of bi-party steering provides a knob to probe the magnetic damping on each sublattice of a magnet.

One-year-old Fundamental Research,full steam ahead

Featuring a rapid development of science and technology in the new era,Fundamental Research(FR),a comprehensive academic journal supervised and sponsored by the National Natural Science Foundation of China(NSFC),was launched in January 2021.It aims to provide a platform for academic communication between Chinese and foreign scientists,facilitate the inter-disciplinary integration,and strengthen the worldwide academic connection.

Fundamental Research-Reporting cutting-edge basic research to the world

The open access English-language international journal Fundamental Research(FR),sponsored by the National Natural Science Foundation of China(NSFC),has now been officially inaugurated.The motivation to initiate a new journal was to report on the cutting-edge fundamen-tal research being carried out in the world.NSFC is one of the world’s largest funding agencies for fundamental research,and undoubtedly,the largest funding body for basic research in China.