Photometric Monitoring of Blazar 3C 66A with the Yunnan University Astronomical Observatory 1 m Telescope

3C 66A is one of our first batches of photometric monitoring objects with the 1 m optical telescope at Yunnan University Astronomical Observatory.In the present work,the observational campaign was performed from 2021 November 1 to 2022 February 27 in the Johnson-Morgan system V and R bands.The average magnitudes in each band were■=15.52±0.18 mag and■=15.07±0.17 mag.The overall variability amplitudes wereΔV=■,Amp=70.27%andΔR=■,Amp=68.56%,respectively.Most of the intraday variabilities(IDVs)occurred in 2021 December and 2022 February.The minimal rise/decay timescale was about 6 minutes(5.82±2.74 minutes and 6.18±2.81 minutes on 2022 February 11,6.99±3.70 minutes and 6.17±2.91 minutes on 2022 February 12).Durations of these rapid variabilities were from 11.99 to 179.67 minutes.The discrete correlation function analyses between V and R bands showed significantly correlated variability.Color index analysis of ID Vs showed that the spectrums do not change with variabilities.

Improvement of tunnel compensated quantum well infrared detector

To reduce the difficulty of the epitaxy caused by multiple quantum well infrared photodetector(QWIP)with tunnel compensation structure,an improved structure is proposed.In the new structure,the superlattices are located between the tunnel junction and the barrier as the infrared absorption region,eliminating the effect of doping concentration on the well width in the original structure.Theoretical analysis and experimental verification of the new structure are carried out.The experimental sample is a two-cycle device,each cycle contains a tunnel junction,a superlattice infrared absorption region and a thick barrier.The photosurface of the detector is 200×200μm^2 and the light is optically coupled by 45°oblique incidence.The results show that the optimal operating voltage of the sample is-1.1 V,the dark current is 2.99×10^-8A,and the blackbody detectivity is1.352×10^8 cm·Hz^1/2·W^-1at 77 K.Our experiments show that the new structure can work normally.

On the encounter desorption of hydrogen atoms on an ice mantle

At low temperatures(10 K),hydrogen atoms can diffuse quickly on grain ice mantles and frequently encounter hydrogen molecules,which cover a notable fraction of grain surface.The desorption energy of H atoms on H2 substrates is much less than that on water ice.The H atom encounter desorption mechanism is adopted to study the enhanced desorption of H atoms on H_(2 )substrates.Using a small reaction network,we show that the steady-state surface H abundances predicted by the rate equation model that includes H atom encounter desorption agree reasonably well with the results from the more rigorous microscopic Monte Carlo method.For a full gas-grain model,H atom encounter desorption can reduce surface H abundances.Therefore,if a model adopts the encounter desorption of H atoms,it becomes more difficult for hydrogenation products such as methanol to form,but it is easier for C,O and N atoms to bond with each other on grain surfaces.

利用Java编程对窦房结体系搏动过程进行视图仿真

目的动态观察窦房结起搏活动随外界刺激的演变过程,揭示传导阻滞与心律失常之间的联系。方法以窦房结细胞模型为研究对象,利用Java语言编程,对窦房结起搏活动进行视图仿真研究。首先,利用其视图功能,将复杂体系各控制参量设置为面板上不同按钮,通过点击按钮观察膜电压随控制参数变化的情况;其次,添加恰当的鼠标响应效果,观察不同条件下的视图效果。结果加入外界刺激对神经系统的调控作用,调节细胞死亡比例或钠电导等控制参量,模拟窦房结体系在体的搏动过程,观察搏动电信号传导受阻现象,与临床观察到的心律失常症状相吻合;利用视图仿真,动态跟踪不同参数条件下,膜电压产生及传导的演变过程,直观形象地模拟了窦房结体系动力学过程。结论利用Java编程的视图仿真可直观了解传导阻滞与心律失常之间的内在联系,模拟过程直观形象,方便明了。

Studying infall in infrared dark clouds with multiple HCO transitions

We investigate the infall properties in a sample of 11 infrared dark clouds(IRDCs) showing blue-asymmetry signatures in HCO^(+)J=1-0 line profiles.We used JCMT to conduct mapping observations in HCO^(+)J=4-3 as well as single-point observations in HCO+J=3-2,towards 23 clumps in these IRDCs.We applied the HILL model to fit these observations and derived infall velocities in the range of 0.5-2.7 km s^(-1),with a median value of 1.0 km s^(-1),and obtained mass accretion rates of 0.5-14 ×10^(-3) Mo yr^(-1).These values are comparable to those found in massive star forming clumps in later evolutionary stages.These IRDC clumps are more likely to form star clusters.HCO^(+)J=3-2 and HCO^(+)J=1-0 were shown to trace infall signatures well in these IRDCs with comparable inferred properties.HCO^(+)J=4-3,on the other hand,exhibits infall signatures only in a few very massive clumps,due to smaller opacities.No obvious correlation for these clumps was found between infall velocity and the NH3/CCS ratio.

Metal to insulator transition for conducting polymers in plasmonic nanogaps

Conjugated polymers are promising material candidates for many future applications in flexible displays, organic circuits, and sensors. Their performance is strongly affected by their structural conformation including both electrical and optical anisotropy. Particularly for thin layers or close to crucial interfaces, there are few methods to track their organization and functional behaviors. Here we present a platform based on plasmonic nanogaps that can assess the chemical structure and orientation of conjugated polymers down to sub-10 nm thickness using light. We focus on a representative conjugated polymer, poly(3,4-ethylenedioxythiophene) (PEDOT), of varying thickness (2-20 nm) while it undergoes redox in situ. This allows dynamic switching of the plasmonic gap spacer through a metal-insulator transition. Both dark-field (DF) and surface-enhanced Raman scattering (SERS) spectra track the optical anisotropy and orientation of polymer chains close to a metallic interface. Moreover, we demonstrate how this influences both optical and redox switching for nanothick PEDOT devices.

Helicity dependent directional surface plasmon polariton excitation using a metasurface with interfacial phase discontinuity

Surface plasmon polaritons(SPPs)have been widely exploited in various scientific communities,ranging from physics,chemistry to biology,due to the strong confinement of light to the metal surface.For many applications,it is important that the free space photon can be coupled to SPPs in a controllable manner.In this Letter,we apply the concept of interfacial phase discontinuity for circularly polarizations on a metasurface to the design of a novel type of polarization-dependent SPP unidirectional excitation at normal incidence.Selective unidirectional excitation of SPPs along opposite directions is experimentally demonstrated at optical frequencies by simply switching the helicity of the incident light.This approach,in conjunction with dynamic polarization modulation techniques,opens gateway towards integrated plasmonic circuits with electrically reconfigurable functionalities.

Malus-metasurface-assisted polarization multiplexing

Polarization optics plays a pivotal role in diffractive,refractive,and emerging flat optics,and has been widely employed in contemporary optical industries and daily life.Advanced polarization manipulation leads to robust control of the polarization direction of light.Nevertheless,polarization control has been studied largely independent of the phase or intensity of light.Here,we propose and experimentally validate a Malus-metasurface-assisted paradigm to enable simultaneous and independent control of the intensity and phase properties of light simply by polarization modulation.The orientation degeneracy of the classical Malus’s law implies a new degree of freedom and enables us to establish a one-to-many mapping strategy for designing anisotropic plasmonic nanostructures to engineer the Pancharatnam–Berry phase profile,while keeping the continuous intensity modulation unchanged.The proposed Malus metadevice can thus generate a near-field greyscale pattern,and project an independent far-field holographic image using an ultrathin and single-sized metasurface.This concept opens up distinct dimensions for conventional polarization optics,which allows one to merge the functionality of phase manipulation into an amplitudemanipulation-assisted optical component to form a multifunctional nano-optical device without increasing the complexity of the nanostructures.It can empower advanced applications in information multiplexing and encryption,anti-counterfeiting,dual-channel display for virtual/augmented reality,and many other related fields.

Chiral surface waves supported by biaxial hyperbolic metamaterials

We discover a new kind of surface wave on biaxial hyperbolic metamaterial,which,in the k-space,connects the two diabolical points(or conical singularities)of the equifrequency surface.Interestingly,the propagation of such surface wave is found to be sensitive to the refractive index of the surrounding dielectric medium,showing a convex,concave or flat phase front when the refractive index is varied.Furthermore,the surface wave shows an elliptically polarized state,in which helicity is dependent on the propagation direction.This feature can be utilized for the spin-controllable excitation of surface waves,opening a gateway towards integrated photonic circuits with reconfigurable functionalities.

Photonic Hall effect and helical Zitterbewegung in a synthetic Weyl system

Systems supporting Weyl points have gained increasing attention in condensed physics,photonics and acoustics due to their rich physics,such as Fermi arcs and chiral anomalies.Acting as sources or drains of Berry curvature,Weyl points exhibit a singularity of the Berry curvature at their core.It is,therefore,expected that the induced effect of the Berry curvature can be dramatically enhanced in systems supporting Weyl points.In this work,we construct synthetic Weyl points in a photonic crystal that consists of a honeycomb array of coupled rods with slowly varying radii along the direction of propagation.The system possesses photonic Weyl points in the synthetic space of two momenta plus an additional physical parameter with an enhanced Hall effect resulting from the large Berry curvature in the vicinity of the Weyl point.Interestingly,a helical Zitterbewegung(ZB)is observed when the wave packet traverses very close to a Weyl point,which is attributed to the contribution of the non-Abelian Berry connection arising from the near degenerate eigenstates.

Wavelength stability in a hybrid photonic crystal laser through controlled nonlinear absorptive heating in the reflector

The need for miniaturized,fully integrated semiconductor lasers has stimulated significant research efforts into realizing unconventional configurations that can meet the performance requirements of a large spectrum of applications,ranging from communication systems to sensing.We demonstrate a hybrid,silicon photonicscompatible photonic crystal(PhC)laser architecture that can be used to implement cost-effective,high-capacity light sources,with high side-mode suppression ratio and milliwatt output output powers.The emitted wavelength is set and controlled by a silicon PhC cavity-based reflective filter with the gain provided by a Ⅲ–Ⅴ-based reflective semiconductor optical amplifier(RSOA).The high power density in the laser cavity results in a significant enhancement of the nonlinear absorption in silicon in the high Q-factor PhC resonator.The heat generated in this manner creates a tuning effect in the wavelength-selective element,which can be used to offset external temperature fluctuations without the use of active cooling.Our approach is fully compatible with existing fabrication and integration technologies,providing a practical route to integrated lasing in wavelength-sensitive schemes.

Chirality Enhancement Using Fabry-Pérot-Like Cavity

Chiral molecules that do not superimpose on their mirror images are the foundation of all life forms on earth.Chiral molecules exhibit chiroptical responses,i.e.,they have different electromagnetic responses to light of different circular polarizations.However,chiroptical responses in natural materials,such as circular dichroism and optical rotation dispersion,are intrinsically small because the size of a chiral molecule is significantly shorter than the wavelength of electromagnetic wave.Conventional technology for enhancing chiroptical signal entails demanding requirements on precise alignment of the chiral molecules to certain nanostructures,which however only leads to a limited performance.Herein,we show a new approach towards enhancement of chiroptical effects through a Fabry-Pérot(FP)cavity formed by two handedness-preserving metamirrors operating in the GHz region.We experimentally show that the FP cavity resonator can enhance the optical activity of the chiral molecule by an order of magnitude.Our approach may pave the way towards state-of-the-art chiral sensing applications.

Optical cavity resonance with magnetized plasma

Indefinite media with mixed signs of dielectric tensor elements possess unbounded equifrequency surfaces that have been utilized for diverse applications such as superimaging, enhanced spontaneous emission, and thermal radiation. One particularly interesting application of indefinite media is an optical cavity supporting anomalous scaling laws. In this Letter, we show that by replacing an indefinite medium with magnetized plasma one can construct a tunable indefinite cavity. The magnetized plasma model is based on realistic semiconductor material properties at terahertz frequencies that show hyperbolic dispersion in a certain frequency regime. The hyperbolic dispersion features are utilized for the design of optical cavities. Dramatically different sizes of cavities can support the same resonance mode at the same frequency. For a cavity of fixed size, the anomalous scaling law between the resonance frequency and mode number is confirmed. The resonance frequency can be strongly modulated by changing the strength of the applied magnetic field. The proposed model provides active controllability of terahertz resonances on the deep subwavelength scale with realistic semiconductor materials.

Probing tq Z anomalous couplings in the trilepton signal at the HL-LHC,HE-LHC,and FCC-hh

We investigate the prospect of discovering the Flavour Changing Neutral Current(FCNC)tqZ couplings via two production processes yielding trilepton signals:top quark pair production pp→tt with one top quark decaying to the Z boson and one light jet and the anomalous single top quark plus Z boson production process pp→tZ.We study these channels at various successors of the Large Hadron Collider(LHC),i.e,the approved High-Luminosity LHC(HL-LHC)as well as the proposed High-Energy LHC(HE-LHC)and Future Circular Collider in hadron-hadron mode(FCC-hh).We perform a full simulation for the signals and the relevant Standard Model(SM)backgrounds and obtain limits on the Branching Ratios(BRs)of t→qZ(q=u,c),eventually yielding a trilepton final state through the decay modes t→bW+→bl^(+)V_(l)and Z→l^(+)l^(-).The upper limits on these FCNC BRs at 95%Confidence Level(CL)are obtained at the HL-LHC with√s=14 TeV and 3 ab^(-1),at the HE-LHC with√s=27TeV and 15 ab^(-1),and at the FCC-hh with√s=100 TeV and 30ab^(-1).

All-angle reflectionless negative refraction with ideal photonic Weyl metamaterials

Negative refraction,an unnatural optical phenomenon in which the incident and the refracted waves reside on the same side of the surface normal,has been demonstrated with the invention of negative index media based on artificially engineered photonic structures called metamaterials.It has received wide attention due to its potential applications in imaging,nonlinear optics,and electromagnetic cloaking.However,it is highly challenging to realize negative refraction operating at all angles and with the perfect transmission.In this work,leveraging the recent development in topological photonics,we propose to realize reflection less negative refraction for all incident angles with a topological metamaterial.The proposed metamaterial possesses two Weyl points of opposite topological charges.By interfacing the metamaterial with a perfect electric conductor(PEC)or a perfect magnetic conductor(PMC),the Fermi arc connecting the two Weyl points can take the form of a half-circle possessing a positive or a negative refractive index.Importantly,due to the topological protection,there is no reflection at the interface between the PEC and PMC covered areas,leading to the observation of all-angle negative refraction without reflection at the boundary.Our work provides a new platform for manipulating the propagation of surface waves,which may find applications in the construction of integrated photonic devices.

Photonic topological fermi nodal disk in non-Hermitian magnetic plasma

Topological physics mainly arises as a necessary link between properties of the bulk and the appearance of surface states,and has led to successful discoveries of novel topological surface states in Chern insulators,topological insulators,and topological Fermi arcs in Weyl,Dirac,and Nodal line semimetals owing to their nontrivial bulk topology.In particular,topological phases in non-Hermitian systems have attracted growing interests in recent years.In this work,we predict the emergence of the topologically stable nodal disks where the real part of the eigen frequency is degenerate between two bands in non-ideal magnetohydrodynamics plasma with collision and viscosity dissipations.Each nodal disk possesses continuously distributed topological surface charge density that integrates to unity.It is found that the lossy Fermi arcs at the interface connect to the middle of the projection of the nodal disks.We further show that the emergence,coalescence,and annihilation of the nodal disks can be controlled by plasma parameters and dissipation terms.Our findings contribute to understanding of the linear theory of bulk and surface wave dispersions of non-ideal warm magnetic plasmas from the perspective of topological physics.

The TMRT K band observations towards 26 infrared dark clouds:NH_3, CCS, and HC_3N

We present one of the first Shanghai Tian Ma Radio Telescope (TMRT) K Band observations towards a sample of 26 infrared dark clouds (IRDCs).We observed the (1,1),(2,2),(3,3),and (4,4) transitions of NH_(3) together with CCS (2_(1)–>1_(0)) and HC_(3)NJ=2-1,simultaneously.The survey dramatically increases the existing CCS-detected IRDC sample from 8 to 23,enabling a better statistical study of the ratios of carbon-chain molecules (CCM) to N-bearing molecules in IRDCs.With the newly developed hyperfine group ratio (HFGR) method of fitting NH_(3) inversion lines,we found the gas temperature to be between 10 and18 K.The column density ratios of CCS to NH_(3) for most of the IRDCs are less than 10^(-2),distinguishing IRDCs from low-mass star-forming regions.We carried out chemical evolution simulations based on a three-phase chemical model NAUTILUS.Our measurements of the column density ratios between CCM and NH_(3) are consistent with chemical evolutionary ages of 10^(5) yr in the models.Comparisons of the data and chemical models suggest that CCS,HC_(3)N,and NH_(3) are sensitive to the chemical evolutionary stages of the sources.

Intrinsic in-plane nodal chain and generalized quaternion charge protected nodal link in photonics

Nodal lines are degeneracies formed by crossing bands in three-dimensional momentum space.Interestingly,these degenerate lines can chain together via touching points and manifest as nodal chains.These nodal chains are usually embedded in two orthogonal planes and protected by the corresponding mirror symmetries.Here,we propose and demonstrate an in-plane nodal chain in photonics,where all chained nodal lines coexist in a single mirror plane instead of two orthogonal ones.Nodal lines are degeneracies formed by crossing bands in three-dimensional momentum space.Interestingly,these degenerate lines can chain together via touching points and manifest as nodal chains.These nodal chains are usually embedded in two orthogonal planes and protected by the corresponding mirror symmetries.Here,we propose and demonstrate an in-plane nodal chain in photonics,where all chained nodal lines coexist in a single mirror plane instead of two orthogonal ones.The chain point is stabilized by the intrinsic symmetry that is specific to electromagnetic waves at theГpoint of zero frequency.By adding another mirror plane,we find a nodal ring that is constructed by two higher bands and links with the in-plane nodal chain.The nodal link in momentum space exhibits non-Abelian characteristics on a C_(2)T-invariant plane,where admissible transitions of the nodal link structure are determined by generalized quaternion charges.Through near-field scanning measurements of bi-anisotropic metamaterials,we experimentally mapped out the in-plane nodal chain and nodal link in such systems.The chain point is stabilized by the intrinsic symmetry that is specific to electromagnetic waves at the r point of zero frequency.By adding another mirror plane,we find a nodal ring that is constructed by two higher bands and links with the in-plane nodal chain.The nodal link in momentum space exhibits non-Abelian characteristics on a C2T-invariant plane,where admissible transitions of the nodal link structure are determined by generalized quaternion charges.Through near-field scanning measurements of bi-anisotropic metamaterials,we experimentally mapped out the in-plane nodal chain and nodal link in such systems.