ProtTrans and multi-window scanning convolutional neural networks for the prediction of protein-peptide interaction sites.

This study delves into the prediction of protein-peptide interactions using advanced machine learning techniques, comparing models such as sequence-based, standard CNNs, and traditional classifiers. Leveraging pre-trained language models and multi-view window scanning CNNs, our approach yields significant improvements, with ProtTrans standing out based on 2.1 billion protein sequences and 393 billion amino acids. The integrated model demonstrates remarkable performance, achieving an AUC of 0.856 and 0.823 on the PepBCL Set_1 and Set_2 datasets, respectively. Additionally, it attains a Precision of 0.564 in PepBCL Set 1 and 0.527 in PepBCL Set 2, surpassing the performance of previous methods. Beyond this, we explore the application of this model in cancer therapy, particularly in identifying peptide interactions for selective targeting of cancer cells, and other fields. The findings of this study contribute to bioinformatics, providing valuable insights for drug discovery and therapeutic development.

Metasurfaces for generating higher-order Poincaré beams by polarization-selective focusing and overall elimination of co-polarization components.

Focused higher-order Poincaré (HOP) beams are of particular interest because they facilitate understanding the exotic properties of structured light and their applications in classical physics and quantum information. However, generating focused HOP beams using metasurfaces is challenging. In this study, we proposed a metasurface design comprising two sets of metal nanoslits for generating coaxially focused HOP beams. The nanoslits were interleaved on equispaced alternating rings. The initial rings started at the two adjacent Fresnel zones to provide opposite propagation phases for overall elimination of the co-polarization components. With the designed hyperbolic and helical profiles of the geometric phases, the two vortices of the opposite cross-circular-polarizations were formed and selectively focused, realizing HOP beams of improved quality. Simulations and experimental results demonstrated the feasibility of the proposed metasurface design. This study is of significance in the integration of miniaturized optical devices and enriches the application areas of metasurfaces.

Ionic Solvent-Assisted MAPbBr3 Perovskite Film for Two-Photon Pumped Single-Mode Laser.

Miniaturized coherent light sources on the nanoscale are highly desired for on-chip photonics integration. However, when approaching the diffraction limit, the sub-wavelength-scale all-dielectric lasers are difficult to realize due to the trade-off between lasing performance and physical size. Especially for a thin-film laser, usually an externally complex cavity is required to provide the necessary optical feedback. Herein, we successfully shrink the MAPbBr3 perovskite thin-film laser to sub-wavelength scale (300 nm) with simplified cavity design using only an ultraviolet glue layer and a quartz glass. The morphology quality and the gain properties of the film are enhanced by introducing ionic liquid. Consequently, the stable and low-threshold single-mode laser with a highly linear polarization degree of 78.6% and a narrow line width of 0.35 nm is achieved under two-photon excitation. The excellent single-mode laser with sub-wavelength scale and ultrasimplified structure could provide a facile and versatile platform for future integrated optoelectronic devices.

Generation of spatiotemporal optical vortices in ultrashort laser pulses using rotationally interleaved multispirals.

Ultrashort optical vortex pulses carrying spatiotemporal orbital angular momentum (OAM) have inspired versatile applications such as the micromachining of integrated quantum chips and discoveries such as optical toroidal structures and OAM-carrying X-waves. Generating high-quality ultrashort vortices with controllable topological charges remains a crucial issue. Thus, we propose a rotationally interleaved multispiral to generate such vortices. A multispiral comprises multiple identical spirals rotated around the center in the equal-azimuthal interval and interleaved in equal-radius increments; this structure overcomes the previous structural asymmetry of the single spiral and improves the vortex quality. Accordingly, we conducted theoretical analyses, numerical simulations, and experimental investigations that demonstrated the feasibility of multispirals in generating the ultrashort vortices with symmetric distributions and flexibly controlling the topological charges. The proposed study is significant for broader applications involving ultrashort vortices and extensive investigations in related areas such as research on electron vortices, plasmonic vortices, and other matter vortices.

Enhanced Amplified Spontaneous Emission in Quasi-2D Perovskite by Facilitating Energy Transfer.

Despite the superior optoelectronic properties of quasi-two-dimensional (quasi-2D) Ruddlesden-Popper halide perovskites, the inhomogeneous distribution of mixed phases result in inefficient energy transfer and multiple emission peaks. Herein, the insufficient energy funneling process at the high-energy phase is almost completely suppressed and the excitonic understanding of gain nature is studied in the energy funneling managed quasi-2D perovskite via introducing poly(vinyl pyrrolidone) (PVP) additive. The energy transfer process is facilitated from 0.37 to 0.26 ps after introducing the PVP additive, accelerating the exciton accumulation in the emissive state, and increasing the ratio of the high-dimensional phase for enhancing radiative emission. The gain lifetime is promoted to be as fast as 28 ps to outcompete nonradiative recombination during the build-up of population inversion. Simultaneously, the net gain coefficient is increased by more than twofold that of the pristine perovskite film. Owing to the remarkable gain properties, room-temperature amplified spontaneous emission is realized with a low threshold of 11.3 µJ/cm2, 4 times lower than 43 µJ/cm2 of the pristine film. Our findings suggest that the PVP-treated quasi-2D perovskite shows great promise for high-performance laser devices.

Design of Metasurface with Nanoslits on Elliptical Curves for Generation of Dual-Channel Vector Beams.

The manipulations of nanoscale multi-channel vector beams (VBs) by metasurfaces hold potential applications in various important fields. In this paper, the metasurface with two sets of nanoslits arranged on elliptic curves was proposed to generate the dual-channel focused vector beams (FVBs). Each set of nanoslits was composed of the in-phase and the out-of-phase groups of nanoslits to introduce the constructive interference and destructive interference of the output light field of the nanoslits, focusing the converted spin component and eliminating the incident spin component at the focal point. The two sets of nanoslits for the channels at the two focal points were interleaved on the same ellipses, and by setting their parameters independently, the FVBs in the two channels are generated under illumination of linearly polarized light, while their orders and polarization states of FVBs were controlled independently. The generation of the FVBs with the designed metasurfaces was demonstrated by the finite-difference time domain (FDTD) simulations and by the experimental verifications. The work in this paper is of great significance for the generation of miniaturized multi-channel VBs and for broadening the applications of metasurfaces.

High-Stability Hybrid Organic-Inorganic Perovskite (CH3NH3PbBr3) in SiO2 Mesopores: Nonlinear Optics and Applications for Q-Switching Laser Operation.

Hybrid organic-inorganic perovskite shows a great potential in the field of photoelectrics. Embedding methyl ammonium lead bromide (MAPbBr3) in a mesoporous silica (mSiO2) layer is an effective method for maintaining optical performance of MAPbBr3 at room temperature. In this work, we synthesized MAPbBr3 quantum dots, embedding them in the mSiO2 layer. The nonlinear optical responses of this composite thin film have been investigated by using the Z-scan technique at a wavelength of 800 nm. The results show plural nonlinear responses in different intensities, corresponding to one- and two-photon processing. Our results support that composites possess saturation intensity of ~27.29 GW/cm2 and varying nonlinear coefficients. The composite thin films show high stability under ultrafast laser irradiating. By employing the composite as a saturable absorber, a passively Q-switching laser has been achieved on a Nd:YVO4 all-solid-state laser platform to generate a laser at ~1 µm.

Subwavelength-Polarized Quasi-Two-Dimensional Perovskite Single-Mode Nanolaser.

When approaching the subwavelength or deep subwavelength scale, there is a fundamental trade-off between the ultimate shrinking size and the performance for miniaturized lasers. Herein, to overcome this trade-off, we investigated the excitonic gain nature of quasi-two-dimensional (quasi-2D) perovskites and revealed that both singlet excitons and polarons would make nearly the entire contribution within ∼50 ps to a high net gain of 558 cm-1. Inspired by the gain characteristic, we successfully shrank the quasi-2D perovskites laser to the subwavelength scale using only a layer of ultraviolet glue and a glass substrate in the vertical dimension. In spite of the compact and simple cavity structure, single-mode lasing with a highly linear polarization degree of 81% and a quality factor of 1635 was achieved. The extremely short cavity, excellent lasing performance, and simple structure of the quasi-2D perovskite laser are expected to provide insights into next-generation integrated laser sources.

Optical Spin Hall Effect in Closed Elliptical Plasmonic Nanoslit with Noncircular Symmetry.

We investigated the optical spin Hall effect (OSHE) of the light field from a closed elliptical metallic curvilinear nanoslit instead of the usual truncated curvilinear nanoslit. By making use of the characteristic bright spots in the light field formed by the noncircular symmetry of the elliptical slit and by introducing a method to separate the incident spin component (ISC) and converted spin component (CSC) of the output field, the OSHE manifested in the spot shifts in the CSC was more clearly observable and easily measurable. The slope of the elliptical slit, which was inverse along the principal axes, provided a geometric phase gradient to yield the opposite shifts of the characteristic spots in centrosymmetry, with a double shift achieved between the spots. Regarding the mechanism of this phenomenon, the flip of the spin angular momentum (SAM) of CSC gave rise to an extrinsic orbital angular momentum corresponding to the shifts of the wavelet profiles of slit elements in the same rotational direction to satisfy the conservation law. The analytical calculation and simulation of finite-difference time domain were performed for both the slit element and the whole slit ellipse, and the evolutions of the spot shifts as well as the underlying OSHE with the parameters of the ellipse were achieved. Experimental demonstrations were conducted and had consistent results. This study could be of great significance for subjects related to the applications of the OSHE.

Generation of vector beams of Bell-like states by manipulating vector vortex modes with plasmonic metasurfaces.

Metasurfaces with orthogonal nano-slit pairs arranged on spirals are proposed to generate vector beams (VBs) of Bell-like states and slanted polarizations. The design of the metasurfaces is based on the theoretically derived parameter condition for manipulation of the two vector vortex modes, which is satisfied by matching the three parameters of rotation order m, the spiral order n, and incident polarization helicity σ. The linear polarization states of the VBs are controlled by the initial orientation angle φ0 of slit pairs. VBs of satisfying quality are experimentally obtained, with the analytical and simulated results validated.

The Interference Pattern of Plasmonic and Photonic Modes Manipulated by Slit Width.

We demonstrate that the interference pattern of the plasmonic and photonic modes can be controlled by changing the slit width of a square slit structure. Based on the analyses of the plasmonic and photonic modes of slits with different widths, we theoretically derived the expressions of wavefield generated by a square slit. A far-field scattered imaging system is utilized to collect the intensity distribution experimentally. Various interference patterns, including stripes, square-like lattice array, and diamond-like lattice array, have been observed by adjusting the slit widths. In addition, the results were validated by performing finite-difference time-domain simulations, which are consistent with the theoretical and experimental results.

Flexible generation of higher-order Poincaré beams with high efficiency by manipulating the two eigenstates of polarized optical vortices.

Vector beams contain complex polarization structures and they are inherently non-separable in the polarization and spatial degrees of freedom. The spatially variant polarizations of vector beams have enabled many important applications in a variety of fields ranging from classical to quantum physics. In this study, we designed and realized a setup based on Mach-Zehnder interferometer for achieving the vector beams at arbitrary points of higher-order Poincaré sphere, through manipulating two eigenstates in the Mach-Zehnder interferometer system with the combined spiral phase plate. We demonstrated the generation of different kinds of higher-order Poincaré beams, including the beams at points on a latitude or longitude of higher-order Poincaré sphere, Bell states for |l| = 1 and |l| = 2, radially polarized beams of very high order with l = 16, etc. Vector beams of high quality and good accuracy are experimentally achieved, and the flexibility, feasibility and high efficiency of the setup are demonstrated by the practical performance.

Nanoscale optical lattices of arbitrary orders manipulated by plasmonic metasurfaces combining geometrical and dynamic phases.

Metasurfaces can be used to manipulate light at the subwavelength scale, and miniaturized photonic devices can be designed to generate subwavelength lattices, which are important for exploring phenomena in novel fields of physics such as topology. Analogous to multi-beam interference, plasmonic metasurfaces composed of nano-slit pairs on truncated spiral segments were designed and fabricated to realize lattice wave fields at a subwavelength resolution. The interference of the analogous beams was controlled by combining the geometric and dynamic phases, and lattices of different morphologies were realized by adjusting the orientation and position of the nano-slits simultaneously. The numerical and measured results showed good agreement, demonstrating the feasibility of the method and its ability to miniaturize lattice patterns. Owing to the compactness and flexible tunability, the nanoscale optical lattices generated using the metasurfaces are expected to find wide applications in integrated and on-chip optical systems.

Generation of a plasmonic radially polarized vector beam with linearly polarized illumination.

Polarization state of a wave field can be manipulated through the plasmonic metasurface consisting of orthogonal nanoslit pairs; the output polarization angle is independent of the incident linearly polarized light and is highly dependent on the orientations of nanoslit pairs. We combine the Archimedes spiral with the nanoslit pairs to compensate for the Pancharatnam-Berry (PB) phase induced by the orientation of nanoslits, as well as achieve the radially polarized vector beam (RPVB) under the illuminations of different linearly polarized lights. Experiments are performed to successfully realize the RPVB, and the results are in excellent agreement with the numerical simulations.