Development of an aptamer capable of multidrug resistance reversal for tumor combination chemotherapy.

Multidrug resistance (MDR) is a major factor in the failure of many forms of tumor chemotherapy. Development of a specific ligand for MDR-reversal would enhance the intracellular accumulation of therapeutic agents and effectively improve the tumor treatments. Here, an aptamer was screened against a doxorubicin (DOX)-resistant human hepatocellular carcinoma cell line (HepG2/DOX) via cell-based systematic evolution of ligands by exponential enrichment. A 50 nt truncated sequence termed d3 was obtained with high affinity and specificity for HepG2/DOX cells. Multidrug resistance protein 1 (MDR1) is determined to be a possible recognition target of the selected aptamer. Aptamer d3 binding was revealed to block the MDR of the tumor cells and increase the accumulation of intracellular anticancer drugs, including DOX, vincristine, and paclitaxel, which led to a boost to the cell killing of the anticancer drugs and lowering their survival of the tumor cells. The aptamer d3-mediated MDR-reversal for effective chemotherapy was further verified in an in vivo animal model, and combination of aptamer d3 with DOX significantly improved the suppression of tumor growth by treating a xenograft HepG2/DOX tumor in vivo. This work demonstrates the feasibility of a therapeutic DNA aptamer as a tumor MDR-reversal agent, and combination of the selected aptamer with chemotherapeutic drugs shows great potential for liver cancer treatments.

Template-Assisted Synthesis of 2D Perovskite Grating Single Crystal Films at Low Temperatures for UV Polarization-Sensitive Photodetectors.

2D perovskites have attracted tremendous attention due to their superior optoelectronic properties and potential applications in optoelectronic devices. Especially, the larger bandgap of 2D perovskite means that they are suitable for UV photodetection. However, the layered structure of 2D perovskites hinders the interlayer carrier transport, which limits the improvement of device performance. Therefore, nanoscale structures are normally used to enhance the light absorption ability, which is an effective strategy to improve the photocurrent in 2D perovskite-based photodetectors. Herein, a template-assisted low-temperature method is proposed to fabricate 2D perovskite ((C6H5C2H4NH3)2PbBr4, (PEA)2PbBr4) grating single crystal films (GSCFs). The crystallinity of the (PEA)2PbBr4 GSCFs is significantly improved due to the slow evaporation of the precursor solution under low temperatures. Based on this high crystalline quality and extremely ordered microstructures, the metal-semiconductor-metal photodetectors are assembled. Finite-different time-domain (FDTD) simulation and experiment indicate that the GSCF-based photodetectors exhibit significantly improved performance in comparison with the plane devices. The optimized 2D perovskite photodetectors are sensitive to UV light and demonstrate a responsivity and detectivity of 28.6 mA W-1 and 2.4 × 1011 Jones, respectively. Interestingly, the photocurrent of this photodetector varies as the angle of the incident polarized light, resulting in a high polarization ratio of 1.12.

Fast simulation for interacting four-level Rydberg atoms: electromagnetically induced transparency and Autler-Townes splitting.

Quantum sensing using Rydberg atoms is an emerging technology for precise measurement of electric fields. However, most existing computational methods are all based on a single-particle model and neglect Rydberg-Rydberg interaction between atoms. In this study, we introduce the interaction term into the conventional four-level optical Bloch equations. By incorporating fast iterations and solving for the steady-state solution efficiently, we avoid the computation of a massive 4N × 4N dimensional matrix. Additionally, we apply the Doppler frequency shift to each atom used in the calculation, eliminating the requirement for an additional Doppler iteration. These schemes allow for the calculation of the interaction between 7000 atoms around one minute. Based on the many-body model, we investigate the Rydberg-Rydberg interaction of Rydberg atoms under different atomic densities. Furthermore, we compare our results with the literature data of a three-level system and the experimental results of our own four-level system. The results demonstrate the validity of our model, with an effective error of 4.59% compared to the experimental data. Finally, we discover that the many-body model better predicts the linear range for measuring electric fields than the single-particle model, making it highly applicable in precise electric field measurements.

Electrodynamic modeling of threshold-free lasing in photonic time crystals.

An electrodynamic model is presented in this Letter to describe thresholdless lasers, utilizing the application of photonic time crystals (PTCs). By integrating the distinctive physical properties of PTCs and employing a comprehensive model based on a four-level system, the feasibility of achieving thresholdless laser operation is demonstrated. The proposed electrodynamic model comprehensively captures the intricate interplay between the electromagnetic field and the PTC medium. The model takes into account the ultrafast periodic variations in the refractive index of the PTCs, which arise from their time crystal-like behavior. Additionally, the dynamic response of the four-level system is considered, factoring in the processes of population inversion and relaxation. This Letter seeks to elucidate the underlying mechanisms that facilitate thresholdless laser operation in PTC-based systems. Through our electrodynamic modeling approach, we demonstrate that the ultrafast variations in the refractive index of PTCs give rise to a self-sustaining laser action, obviating the need for a lasing threshold. Moreover, we investigate the impact of various parameters, including pump power and modulation period, on the laser's performance and output characteristics. The developed electrodynamic model provides a comprehensive framework for comprehending and designing thresholdless lasers based on photonic time crystals. This research contributes to the advancement of thresholdless laser technology and opens up possibilities for applications in optical communications, sensing, and quantum photonics.

Low-frequency electric field sensing via superposition orbital angular momentum light.

The polarization and orbital angular momentum (OAM) degrees of freedom carried by light have important applications in precision optical measurement and optical sensing. Here we show that the electro-optic Pockels effect of a magnesium-doped lithium niobate (MgO:LiNbO3) crystal can be used to measure a low-frequency electric field. By exploiting the rotation property of superposition OAM light, we experimentally observe that the minimum measured precision of electric field intensity is about 0.18 V/m. This study offers a method to perform low-frequency electric field sensing.

ILK inhibition reduces osteophyte formation through suppression of osteogenesis in BMSCs via Akt/GSK-3ß/ß-catenin pathway.

BACKGROUND: Osteophyte development is a common characteristic of inflammatory skeletal diseases. Elevated osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) participates in pathological osteogenesis. Integrin-linked kinase (ILK) positively regulates the osteoblastic differentiation of osteoprogenitors, but whether the ILK blockage prevents osteophytes and its potential mechanism is still unknown. Furthermore, the low-dose tumor necrosis factor-α (TNF-α) promotes osteogenic differentiation, but a lack of study reports on the relationship between this cytokine and ILK. OSU-T315 is a small ILK inhibitor, which was used to determine the effect of ILK inhibition on osteogenesis and osteophyte formation. METHODS AND RESULTS: The osteogenesis of BMSCs was evaluated using Alizarin red S staining, alkaline phosphatase, collagen type I alpha 2 chain, and bone gamma-carboxyglutamate protein. The expression and phosphorylation of protein were assessed through western blot. Immunofluorescence was employed to display the distribution of ß-catenin. microCT, hematoxylin-eosin, and safranin O/fast green staining were utilized to observe the osteophyte formation in collagen antibody-induced arthritis mice. We found that ILK blockage significantly declined calcium deposition and osteoblastic markers in a dose- and time-dependent manner. Furthermore, it lowered osteogenesis in the TNF-α-induced inflammatory microenvironment by diminishing the effect of ILK and inactivating the Akt/ GSK-3ß/ ß-catenin pathway. Nuclear ß-catenin was descended by OSU-T315 as well. Finally, the ILK suppression restrained osteophyte formation but not inflammation in vivo. CONCLUSIONS: ILK inhibition lowered osteogenesis in TNF-α-related inflammatory conditions by deactivating the Akt/ GSK-3ß/ ß-catenin pathway. This may be a potential strategy to alleviate osteophyte development in addition to anti-inflammatory treatment.

Gigantic vortical differential scattering as a monochromatic probe for multiscale chiral structures.

Spin angular momentum of light is vital to investigate enantiomers characterized by circular dichroism (CD), widely adopted in biology, chemistry, and material science. However, to discriminate chiral materials with multiscale features, CD spectroscopy normally requires wavelength-swept laser sources as well as wavelength-specific optical accessories. Here, we experimentally demonstrate an orbital-angular-momentum-assisted approach to yield chiroptical signals with monochromatic light. The gigantic vortical differential scattering (VDS) of ∼120% is achieved on intrinsically chiral microstructures fabricated by femtosecond laser. The VDS measurements can robustly generate chiroptical properties on microstructures with varying geometric features (e.g., diameters and helical pitches) and detect chiral molecules with high sensitivity. This VDS scheme lays a paradigm-shift pavement toward efficiently chiroptical discrimination of multiscale chiral structures with photonic orbital angular momentum. It simplifies and complements the conventional CD spectroscopy, opening possibilities for measuring weak optical chirality, especially on mesoscale chiral architectures and macromolecules.

Diagnostic values and relevant factors of lumbar posterior lesions in axial spondyloarthritis.

OBJECTIVES: To compare the lumbar posterior lesions between axial spondyloarthritis (axSpA) and lumbar disc herniation (LDH) patients, then their diagnostic value and related factors were evaluated. METHODS: This cross-sectional study included axSpA patients from January 2020 to September 2023. They were classified as ankylosing spondylitis (AS) and non-radiographic axSpA (nr-axSpA) individuals. Canada-Denmark (CANDEN) magnetic resonance imaging (MRI) scoring system was used to assess the defects of the lumbar spine. Receiver operating characteristic curve analysis was utilized to determine the value of distinguishing nr-axSpA. Linear regression analyses were adopted to find the relevant factors for lumbar posterior lesions. RESULTS: Ninety-six AS, 98 nr-axSpA, and 108 LDH patients were included. The CANDEN scores were greater in axSpA patients, AS in particular. Furthermore, lumbar posterior lesions can distinguish AS, nr-axSpA, and LDH. Besides, lumbar posterior lesions were positively related to the similar MRI changes in their adjacent structures, but were inversely associated with the other abnormalities. CONCLUSIONS: Lumbar posterior lesions were more serious in axSpA patients. These alterations had value in distinguishing axSpA. Lumbar posterior defects were related to their adjacent components, and they may not fully follow the MRI changing pattern of vertebral bodies and sacroiliac joints.

Auxiliary differential equation (ADE) method based complying-divergence implicit FDTD method for simulating the general dispersive anisotropic material.

The preceding works introduced the leapfrog complying divergence implicit finite-difference time-domain (CDI-FDTD) method, which exhibits high accuracy and unconditional stability. In this study, the method is reformulated to simulate general electrically anisotropic and dispersive media. The auxiliary differential equation (ADE) method is employed to solve the equivalent polarization currents, which are then integrated into the CDI-FDTD method. The iterative formulae are presented, and the calculation method is similar to that of the traditional CDI-FDTD method. Additionally, the Von Neumann method is utilized to analyze the unconditional stability of the proposed method. To evaluate the performance of the proposed method, three numerical cases are conducted. These include calculating the transmission and reflection coefficients of a monolayer graphene sheet and a monolayer magnetized plasma, as well as the scattering properties of a cubic block plasma. The numerical results obtained by the proposed method demonstrate its accuracy and efficiency in simulating general anisotropic dispersive media, compared to both the analytical method and the traditional FDTD method.

Physical Mechanism of Nonlinear Spectra in Triangene.

In this work, we theoretically investigate the linear and nonlinear optical absorption properties of open triangulene spin chains and cyclic triangulene spin chains in relation to their lengths and shapes. The physical mechanism of local excitation within the triangular alkene unit and the weak charge transfer between the units are discussed. The uniformly distributed electrostatic potential allows the system to have a small permanent dipole moment that blocks the electronic transition in the light excitation such that the electronic transition can only be carried out between adjacent carbon atoms. The one-photon absorption (OPA) spectra and two-photon absorption (TPA) spectra are red-shifted with the addition of triangulene units compared to N = 3TSCs (triangulene spin chains, TSCs). Here, TPA is mainly caused by the first step of the transition. The length of the spin chain has a significant adjustment effect on the photon cross-section. TSCs of different lengths and shapes can control chirality by adjusting the distribution of the electric dipole moment and transition magnetic dipole moment. These analyses reveal the photophysical properties of triangulene and provide a theoretical basis for studying the photophysical properties of triangulene and its derivatives.

Co-Fe-P Nanosheet Arrays as a Highly Synergistic and Efficient Electrocatalyst for Oxygen Evolution Reaction.

The rational design and synthesis of highly efficient electrocatalysts for oxygen evolution reaction (OER) is of critical importance to the large-scale production of hydrogen by water electrolysis. Here, we develop a bimetallic, synergistic, and highly efficient Co-Fe-P electrocatalyst for OER, by selecting a two-dimensional metal-organic framework (MOF) of Co-ZIF-L as the precursor. The Co-Fe-P electrocatalyst features pronounced synergistic effects induced by notable electron transfer from Co to Fe, and a large electrochemical active surface area achieved by organizing the synergistic Co-Fe-P into hierarchical nanosheet arrays with disordered grain boundaries. Such features facilitate the generation of abundant and efficiently exposed Co3+ sites for electrocatalytic OER and thus enable Co-Fe-P to deliver excellent activity (overpotential and Tafel slope as low as 240 mV and 36 mV dec-1, respectively, at a current density of 10 mA cm-2 in 1.0 M KOH solution). The Co-Fe-P electrocatalyst also shows great durability by steadily working for up to 24 h. Our work thus provides new insight into the development of highly efficient electrocatalysts based on nanoscale and/or electronic structure engineering.

Design of compact dual-mode photoelectric modulator with high process tolerance based on vanadium dioxide.

Opto-electro modulators with nanometer-scale footprint are indispensable in integrated photonic electronic circuits. Due to weak light-matter interactions and limits of micro-nano fabrication technology, it is challenging to shrink a modulator to subwavelength size. In recent years, hybrid modulators based on surface plasmons have been proposed to solve this problem. Although the introduced high lossy surface plasmons provide large modulation depth, the polarization selectivity limits its application. Toward this end, in this paper, we present a design of an ultra-compact vanadium oxide (VO2)-based plasmonic waveguide modulator for both transverse electric (TE) and transverse magnetic (TM) modes. The device consists of two silicon tapers and a silicon waveguide embedded with a VO2 wedge. When electrical signals put on the device change the phase of VO2 from a metal to an insulator, the output optical signals along the waveguide are significantly modulated. For a 1.5 µm length modulator operating at 1.55 µm wavelength, the extinction ratio is 11.62 dB for the TE mode and 8.86 dB for the TM mode, while the insertion loss is 4.31 dB for the TE mode and 4.12 dB for the TM mode. Furthermore, the proposed design has excellent tolerance for fabrication process error, which greatly increases the yield rate of products and indicates a promotable application prospect.

Comparison of open, laparoscopic, and robotic left colectomy for radical treatment of colon cancer: a retrospective analysis in a consecutive series of 211 patients.

BACKGROUND: Robotic surgery has been widely used in the radical treatment of colonic cancer. However, it is unclear what advantages the robotic approach offers over other approaches in left colectomy. This study aims to explore the advantage of robotic surgery in left colectomy by comparing open, laparoscopic, and robotic surgery. METHODS: A retrospective analysis was performed on the clinical data of patients with radical left colectomy for colon cancer who were admitted to the Department of General Surgery, The First Affiliated Hospital of Nanchang University, from November 2012 to November 2017. Two hundred eleven patients included were divided into the open surgery group (OS, n=49), laparoscopic surgery group (LS, n=92), and robotic surgery group (RS, n=70) according to surgical techniques. The clinicopathologic data were collected for clinical outcome assessment. Finally, the clinical value of RS in radical left colectomy was further evaluated by propensity score matching (PSM) analysis. RESULTS: Three groups were similar in demographics and clinical characteristics. Compared with OS, LS and RS groups had better intraoperative and perioperative clinical outcomes. Moreover, the RS group exhibited the minimum operative times, length of stay (LOS), and evaluated blood loss. LS and RS also exhibited less perioperative and postoperative long-term complications. Three groups showed similar postoperative pathological outcomes. The overall survival and disease-free survival were also similar among the three groups (all P > 0.05). Cox regression analysis showed surgical approach was not a prognostic factor for overall survival (P = 0.671) and disease-free survival (P = 0.776). PSM analysis of RS and LS by clinical characteristics showed RS showed shorter operation time (P < 0.001) and LOS for patients without complications (P = 0.005). However, no significant differences were found in perioperative and long-term postoperative complications, pathological outcomes, overall survival, and disease-free survival. CONCLUSIONS: Among three techniques for radical left colectomy, LS and RS had significant advantages over OS in short-term clinical outcomes, and no significant differences were found in overall, disease-free survival, local recurrence, and distant metastasis incidence. Moreover, RS shows better perioperative clinical outcomes but without compromising survival compared with LS.

A Sensor for Characterisation of Liquid Materials with High Permittivity and High Dielectric Loss.

This paper reports on a sensor based on multi-element complementary split-ring resonator for the measurement of liquid materials. The resonator consists of three split rings for improved measurement sensitivity. A hole is fabricated at the centre of the rings to accommodate a hollow glass tube, through which the liquid sample can be injected. Electromagnetic simulations demonstrate that both the resonant frequency and quality factor of the sensor vary considerably with the dielectric constant and loss tangent of the liquid sample. The volume ratio between the liquid sample and glass tube is 0.36, yielding great sensitivity in the measured results for high loss liquids. Compared to the design based on rectangular split rings, the proposed ring structure offers 37% larger frequency shifts and 9.1% greater resonant dips. The relationship between dielectric constant, loss tangent, measured quality factor and resonant frequency is derived. Experimental verification is conducted using ethanol solution with different concentrations. The measurement accuracy is calculated to be within 2.8%, and this validates the proposed approach.

Adaptive CFAR Method for SAR Ship Detection Using Intensity and Texture Feature Fusion Attention Contrast Mechanism.

Due to the complexity of sea surface environments, such as speckles and side lobes of ships, ship wake, etc., the detection of ship targets in synthetic aperture radar (SAR) images is still confronted with enormous challenges, especially for small ship targets. Aiming at the key problem of ship target detection in the complex environments, the article proposes a constant false alarm rate (CFAR) algorithm for SAR ship target detection based on the attention contrast mechanism of intensity and texture feature fusion. First of all, the local feature attention contrast enhancement is performed based on the intensity dissimilarity and the texture feature difference described by local binary pattern (LBP) between ship targets and sea clutter, so as to realize the target enhancement and background suppression. Furthermore, the adaptive CFAR ship target detection method based on generalized Gamma distribution (GΓD) which can fit the clutter well by the goodness-of-fit analyses is carried out. Finally, the public datasets HRSID and LS-SSDD-v1.0 are used to verify the effectiveness of the proposed detection method. A large number of experimental results show that the proposed method can suppress clutter background and speckle noise and improve the target-to-clutter rate (TCR) significantly, and has the relative high detection rate and low false alarm rate in the complex background and multi-target marine environments.

Integrated Terahertz Generator-Manipulators Using Epsilon-near-Zero-Hybrid Nonlinear Metasurfaces.

In terahertz (THz) technologies, generation and manipulation of THz waves are two key processes usually implemented by different device modules. Integrating THz generation and manipulation into a single compact device will advance the applications of THz technologies in various fields. Here, we demonstrate a hybrid nonlinear plasmonic metasurface incorporating an epsilon-near-zero (ENZ) indium tin oxide (ITO) layer to seamlessly combine efficient generation and manipulation of THz waves across a wide frequency band. The coupling between the plasmonic resonance of the metasurface and the ENZ mode of the ITO thin film enhances the THz conversion efficiency by more than 4 orders of magnitude. Meanwhile, such a hybrid device is capable of shaping the polarization and wavefront of the emitted THz beam via the engineered nonlinear Pancharatnam-Berry (PB) phases of the plasmonic meta-atoms. The presented hybrid nonlinear metasurface opens a new avenue toward miniaturized integrated THz devices and systems with advanced functionalities.

Comparison of robotic and laparoscopic rectal cancer surgery: a meta-analysis of randomized controlled trials.

OBJECTIVE: Robotic and laparoscopic surgery for rectal cancer has been applied in the clinic for decades; nevertheless, which surgical approach has a lower rate of postoperative complications is still inconclusive. Therefore, the aim of this meta-analysis was to compare the postoperative complications within 30 days between robotic and laparoscopic rectal cancer surgery based on randomized controlled trials. METHODS: Randomized controlled trials (until May 2020) that compared robotic and laparoscopic rectal cancer surgery were searched through PubMed, EMBASE, the Cochrane Library, China National Knowledge Infrastructure (CNKI), Wanfang Data Knowledge Service Platform, and China Biology Medicine disc (CBMdisc). Data regarding sample size, clinical and demographic characteristics, and postoperative complications within 30 days, including overall postoperative complications, severe postoperative complications (Clavien-Dindo score ≥ III), anastomotic leakage, surgical site infection, bleeding, ileus, urinary complications, respiratory complications, conversion to open surgery, unscheduled reoperation, perioperative mortality, and pathological outcomes, were extracted. The results were analyzed using RevMan v5.3. RESULTS: Seven randomized controlled trials that included 507 robotic and 516 laparoscopic rectal cancer surgery cases were included. Meta-analysis showed that the overall postoperative complications within 30 days [Z = 1.1, OR = 1.18, 95% CI (0.88-1.57), P = 0.27], severe postoperative complications [Z = 0.22, OR = 1.12, 95% CI (0.41-3.07), P = 0.83], anastomotic leakage [Z = 0.96, OR = 1.27, 95% CI (0.78-2.08), P = 0.34], surgical site infection [Z = 0.18, OR = 1.05, 95% CI (0.61-1.79), P = 0.86], bleeding [Z = 0.19, OR = 0.89, 95% CI (0.27-2.97), P = 0.85], ileus [Z = 1.47, OR = 0.66, 95% CI (0.38-1.15), P = 0.14], urinary complications [Z = 0.66, OR = 1.22, 95% CI (0.67-2.22), P = 0.51], respiratory complications [Z = 0.84, OR = 0.64, 95% CI (0.22-1.82), P = 0.40], conversion to open surgery [Z = 1.73, OR = 0.61, 95% CI (0.35-1.07), P = 0.08], unscheduled reoperation [Z = 0.14, OR = 0.91, 95% CI (0.26-3.20), P = 0.89], perioperative mortality [Z = 0.28, OR = 0.79, 95% CI (0.15-4.12), P = 0.78], and pathological outcomes were similar between robotic and laparoscopic rectal surgery. CONCLUSION: Robotic surgery for rectal cancer was comparable to laparoscopic surgery with respect to postoperative complications within 30 days.

No beneficial effect on survival but a decrease in postoperative complications in patients with rectal cancer undergoing robotic surgery: a retrospective cohort study.

BACKGROUND: Robotic surgery has been taken as a new modality to surpass the technical limitations of conventional surgery. Here we aim to compare the oncologic outcomes of patients with rectal cancer receiving robotic vs. laparoscopic surgery. METHODS: Data from patients diagnosed with rectal cancer between March 2011 and December 2018 were obtained for outcome assessment at the First Affiliated Hospital of Nanchang University. All patients were separated into two groups: a robot group (patients receiving robotic surgery, n = 314) and a laparoscopy group (patients receiving laparoscopic surgery, n = 220). The primary endpoint was survival outcomes. The secondary endpoints were the general conditions of the operation, postoperative complications and pathological characteristics. RESULTS: The 5-year overall survival (OS) and disease-free survival (DFS) at years 1, 3 and 5 were 96.6%, 88.7%, and 87.7% vs. 96.7%, 88.1%, and 78.4%, and 98.6%, 80.2-, and 73.5% vs. 96.2-, 87.2-, and 81.1% in the robot and laparoscopy groups, respectively (P > 0.05). In the multivariable-adjusted analysis, robotic surgery was not an independent prognostic factor for OS and DFS (P = 0.925 and 0.451, respectively). With respect to the general conditions of the operation, patients in the robot group had significantly shorter operation times (163.5 ± 40.9 vs. 190.5 ± 51.9 min), shorter times to 1st gas passing [2(1) vs. 3(1)d] and shorter hospital stay days [7(2) vs. 8(3)d] compared to those in the laparoscopy group (P < 0.01, respectively). After the operation, the incidence of short- and long-term complications in the robot group was significantly lower than that in the laparoscopy group (15.9% vs. 32.3%; P < 0.001), especially for urinary retention (1.9% vs. 7.3%; 0.6% vs. 4.1%, P < 0.05, respectively). With regard to pathological characteristics, TNM stages II and III were more frequently observed in the robot group than in the laparoscopy group (94.3% vs. 83.2%, P < 0.001). No significant difference were observed in lymph nodes retrieved, lymphovascular invasion and circumferential resection margin involvement between the two groups (P > 0.05, respectively). CONCLUSIONS: This monocentre retrospective comparative cohort study revealed short-term advantages of robot-assisted rectal cancer resection but similar survival compared to conventional laparoscopy.

Linear and nonlinear spin-orbital coupling in golden-angle spiral quasicrystals.

The appealing characteristics of quasi-crystalline nanostructure offer tremendous possibilities to tailor the transmission of the angular momenta. Moreover, the second harmonic generation existing in nonlinear nanostructures also exhibits remarkable potential in the fundamental and applied research areas of the angular momenta conversion. By systematically studying the general angular momenta conservation law, we show that the high-dimensional angular momenta transformation and spin-orbital coupling are realized by the nonlinear sunflower-type quasicrystals, which feature the high-fold rotational symmetry and possess an increasing degree of rotational symmetry in Fourier space. Interestingly, since the sequential Fibonacci numbers are essentially encoded in the distinctive nonlinear sunflower-type patterns, the high-fold angular momenta transformation regularly occurs at both linear and nonlinear wavelengths. The investigations of fundamental physics for the unique quasi-crystals reveal scientific importance for manipulating the angular momenta of nonlinear optical signals, which plays a key role in the promotion and development of modern physics.

First-principle calculation of Chern number in gyrotropic photonic crystals.

As an important figure of merit for characterizing the quantized collective behaviors of the wavefunction, Chern number is the topological invariant of quantum Hall insulators. Chern number also identifies the topological properties of the photonic topological insulators (PTIs), thus it is of crucial importance in PTI design. In this paper, we develop a first principle computatioal method for the Chern number of 2D gyrotropic photonic crystals (PCs), starting from the Maxwell's equations. Firstly, we solve the Hermitian generalized eigenvalue equation reformulated from the Maxwell's equations by using the full-wave finite-difference frequency-domain (FDFD) method. Then the Chern number is obtained by calculating the integral of Berry curvature over the first Brillouin zone. Numerical examples of both transverse-electric (TE) and transverse-magnetic (TM) modes are demonstrated, where convergent Chern numbers can be obtained using rather coarse grids, thus validating the efficiency and accuracy of the proposed method.