Photon Branching Research Articles

Search for light long-lived neutral particles from Higgs boson decays via vector-boson-fusion production from pp collisions at s=13\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\sqrt{s}=13$$\\end{document} TeV with the ATLAS detector

A search is reported for long-lived dark photons with masses between 0.1 GeV and 15 GeV, from exotic decays of Higgs bosons produced via vector-boson-fusion. Events that contain displaced collimated Standard Model fermions reconstructed in the calorimeter or muon spectrometer are probed. This search uses the full LHC Run 2 (2015–2018) data sample collected in proton–proton collisions at s=13\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\sqrt{s}=13$$\\end{document} TeV, corresponding to an integrated luminosity of 139 fb-1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$fb^{-1}$$\\end{document}. Dominant backgrounds from Standard Model processes and non-collision sources are estimated using data-driven techniques. The observed event yields in the signal regions are consistent with the expected background. Upper limits on the Higgs boson to dark photon branching fraction are reported as a function of the dark photon mean proper decay length or of the dark photon mass and the coupling between the Standard Model and the potential dark sector. This search is combined with previous ATLAS searches obtained in the gluon–gluon fusion and WH production modes. A branching fraction above 10% is excluded at 95% CL for a 125 GeV Higgs boson decaying into two dark photons for dark photon mean proper decay lengths between 173 and 1296 mm and mass of 10 GeV.

Metal–organic frameworks for nonlinear optics and lasing

AbstractNonlinear optics (NLO) is a crucial branch of photonics that greatly facilitates the transmission, processing, and storage of photonic signals. It meets the needs of the rapidly growing information demands of modern society. Materials with NLO properties and laser capabilities have a wide range of applications in fields such as optical communication, optical information storage, biomedical imaging, laser technology, and quantum information technology. Metal–organic frameworks (MOFs) have emerged as particularly exciting hybrid inorganic–organic porous materials that can be easily self‐assembled from corresponding inorganic metal ions/clusters and organic linkers. The structural diversity and flexibility of MOFs offer ample opportunities for the orderly organization of highly hyperpolarizable chromophore molecules within confined spaces. This makes it ideal for NLO signal and laser emissions. In this review, we provide a comprehensive overview of strategies to construct MOFs with NLO and laser properties, as well as recent research developments for enhancing and adjusting these properties. Through analysis of chromophore arrangement and various interactions within the framework, we aim to gain insight into the correlation between MOF structures and optical properties. This will facilitate the design and synthesis of MOFs with excellent NLO and laser capabilities through the judicious selection of metal ions and organic linkers. Finally, we outline the future challenges and potential research directions for MOFs in NLO and laser fields.

Non-reciprocal topological photonics

The proposal and development of topological photonics have provided a new approach to fundamentally addressing the susceptibility of traditional photonic devices to defects or disorders, significantly enhancing the transmission efficiency and robustness of photonic devices. Among them, non-reciprocal topological photonics which break time-reversal symmetry and support chiral topological states are crucial branches of topological photonics. Their topological properties are characterized by non-zero Chern numbers in two dimensions or topological Chern vectors in three dimensions, exhibiting a rigorous and complete topological protection beyond that of reciprocal topological photonics. This review focuses on introducing the remarkable achievements of non-reciprocal topological photonics in exploring novel physical phenomena (chiral/antichiral edge/surface states, two-dimensional/three-dimensional photonic Chern insulators, magnetic Weyl photonics crystals, etc.) and constructing non-reciprocal robust topological photonic devices (unidirectional waveguides, broadband slow-light delay lines, arbitrarily shaped topological lasers, high-orbital-angular-momentum coherent light sources, etc.). Finally, the present status, potential challenges, and possible breakthroughs in the development of non-reciprocal topological photonics are discussed.

Microwave Photonic Filters and Applications

Microwave photonics is a promising and rapidly developing interdisciplinary field. It combines microwave and photonic techniques to generate, transmit, process, and manipulate microwave signals by using the advantages of broadband, high frequency, and low loss provided by photonics. As an important branch of microwave photonics, the microwave photonic filter (MPF) can overcome the limitations set by traditional electronic technology and can realize advanced signal processing in modern communication systems due to its higher performance, selectivity, and flexibility. This review provides a comprehensive overview of MPFs, including fundamental principles, typical structures, and key applications. Additionally, the microwave photonic integration is a very important tendence because of its advantages of small size, light weight, low power consumption, and low cost. The recent advances in integrated MPF are also reviewed.

Lock-in phenomena in non-Hermitian coupled systems

Coupled-mode theory has been widely employed in various branches of photonics, such as nano-photonics and non-Hermitian optics. Here we show that it can also be used as an effective physical model for clarifying various optical mode lock-in phenomena, which have been revealed to essentially originate from non-Hermitian degeneracies. We discuss the lock-in effects in physical systems through prototypical examples of optical feedback self-injection frequency lock-in technology and lock-in phenomena of ring laser gyroscopes (RLGs). Seemingly unrelated effects have been unified through one general non-Hermitian mode coupling model. Furthermore, based on our theoretical framework, we have uncovered the underlying mechanism of lock-in in RLGs and analyzed how this effect can be systematically suppressed or even eliminated

Bio-photonics in dentistry: A review

Biophotonics is the new extended branch of photonics, which is the combination of photonics and biology. It is also known as biomedical optics as it has become an important tool for biomedical diagnosis, therapy, monitoring, imaging, and surgery. This branch deals with action of light on biological mattermainly tissue. Three types of laser-tissue interactions are known based on interaction time and active power density. Photochemical, photothermal, photomechanical and photoionization effects.

Various topological phases and their abnormal effects of topological acoustic metamaterials

AbstractThe last 20 years have witnessed growing impacts of the topological concept on the branches of physics, including materials, electronics, photonics, and acoustics. Topology describes objects with some global invariant property under continuous deformation, which in mathematics could date back to the 17th century and mature in the 20th century. In physics, it successfully underpinned the physics of the Quantum Hall effect in 1984. To date, topology has been extensively applied to describe topological phases in acoustic metamaterials. As artificial structures, acoustic metamaterials could be well theoretically analyzed, on‐demand designed, and easily fabricated by modern techniques, such as three‐dimensional printing. Some new theoretical topological models were first discovered in acoustic metamaterials analogous to electronic counterparts, associated with novel effects for acoustics closer to applications. In this review, we focused on the concept of topology and its realization in airborne acoustic crystals, solid elastic phononic crystals, and surface acoustic wave systems. We also introduced emerging concepts of non‐Hermitian, higher‐order, and Floquet topological insulators in acoustics. It has been shown that the topology theory has such a powerful generality that among the disciplines from electron to photon and phonon, from electronic to photonics and acoustics, from acoustic topological theory to acoustic devices, could interact and be analogous to fertilize fantastic new ideas and prototype devices, which might find applications in acoustic engineering and noise‐vibration control engineering in the near future.

Nuclear Structure and Decay Data for A=231 Isobars

The present evaluation of currently known nine nuclides of A=231: (231Rn, 233Fr, 231Ra, 231Ac, 231Th, 231Pa, 231U, 231Np and 231Pu) represents an update and revision of previous A=231 evaluation by 2013Br04. All the known decay and reaction data are evaluated, with recommended properties given in the Adopted Levels, Gammas datasets, for gamma-ray energies, photon branching ratios, level half-lives, spins, parities, transition probabilities, and configuration assignments. For 231Rn, only an identification of the nuclide has been made without an experimental determination of its half-life. For 231Fr, no excited states are known. About 30 levels in 231Ra up to 1774 keV excitation are known only from β− decay of 231Fr with level half-lives determined for five excited states. For 231Ac, excited states up to 3122 keV are known from β− decay, (t,α), and fragmentary information for high-spin levels from two heavy-ion reaction studies, with lifetimes of excited states measured for five levels. Extensive structure and rotational band information for 231Th is available for a large number of levels up to 1714 keV from β− and α decays, (n,γ) thermal and resonance, single-particle transfer reactions (d,p), (d,t) and (3He,α), with limited data for high-spin levels from one secondary reference, and half-lives available for five excited states. Very detailed structure data are available for 231Pa up to 2139 keV from β−, ε and α decays, (α,t), (d,d′) and high-spin data from heavy-ion Coulomb excitation and (p,2nγ) reaction, with level half-lives known for 34 excited states, mostly deduced by evaluators from transition probabilities determined in Coulomb excitation. Only eight excited states are known in 231U up to 1268 keV from ε and α decays, with no data for half-lives of excited states. For 231Np and 231Pu, only the ground-state is known from α decays, with a tentative level at 324 keV in 231Pu. Measurements of nuclear rms charge radius and isotope shifts for 231Ra have been made by 2018Ly01, and that for rms charge radius for 231Fr by 2014Bu06.235U is a well known nuclide for nuclear structure and reactor applications. There have been a large number of studies of its alpha decay to levels in 231Th, including some recent ones such as 2018Ma03 and 2017Le03, yet evaluators' analysis of the decay scheme suggests that, while α-particle transitions are well established, but several issues still remain about intricacies of gamma-ray and conversion electron spectroscopy which need to be resolved through dedicated experiments for a complete understanding of the decay scheme characteristics, although, this sort of research project would seem a challenging spectroscopic problem. As commented in individual datasets for other decays, important spectral information is lacking for most of the decay schemes, with almost no information available for some of these, resulting in many incomplete decay schemes in A=231 mass chain.

Efficient near UV-vacuum UV sources based on second-harmonic generation enhanced by high-Q quasi-BICs in all-dielectric metasurfaces of low-index materials

Ultraviolet (UV) nanophotonics is an increasingly important branch of modern photonics due to the fundamental importance and practical applications. This work presents the efficient generation of near UV-vacuum UV radiations based on the second-harmonic generation in all-dielectric metasurfaces exhibiting high-Q quasi-bound states in the continuum (quasi-BICs). For this purpose, lithium niobate (LN) is taken as the nonlinear material comprising the metasurface, which is transparent in the ultraviolet range. Since LN has much lower index compared with the dielectrics commonly used as nanophotonic materials, a specific measure should be taken for supporting high-Q quasi-BICs: the metasurface is constructed with periodic LN nanodisk array on the ultrathin film of the same material deposited on silica, such that the guiding wave couples to the far-field with high Q-factor, resulting in second-harmonic generation with significantly high efficiency up to 0.14 % in the range from near UV to vacuum UV for both transmitted and reflected radiations. The metasurface of similar structure, but with mirror symmetry-broken unit cells, exhibits nearly perfect second-harmonic generation circular dichroism with high efficiency. The presented results can find important applications for ultraviolet nanophotonics due to the significantly high efficiency and strong nonlinear circular dichroism.

Quantum microwave photonics in radio-over-fiber systems

As the main branch of microwave photonics, radio-over-fiber technology provides high bandwidth, low-loss, and long-distance propagation capability, facilitating wide applications ranging from telecommunication to wireless networks. With ultrashort pulses as the optical carrier, a large capacity is further endowed. However, the wide bandwidth of ultrashort pulses results in the severe vulnerability of high-frequency radio frequency (RF) signals to fiber dispersion. With a time-energy entangled biphoton source as the optical carrier combined with the single-photon detection technique, a quantum microwave photonics method in radio-over-fiber systems is proposed and demonstrated experimentally. The results show that it not only realizes unprecedented nonlocal RF signal modulation with strong resistance to the dispersion but also provides an alternative mechanism to distill the RF signal out from the dispersion effectively. Furthermore, the spurious-free dynamic ranges of the nonlocally modulated and distilled RF signals have been significantly improved. With the ultra-weak detection and the high-speed processing advantages endowed by the low-timing-jitter single-photon detection, the quantum microwave photonics method opens new possibilities in modern communication and networks.

Multimode parity-time symmetry and loss compensation in coupled waveguides with loss and gain

Loss compensation via inserting gain is of fundamental importance in different branches of photonics, nanoplasmonics, and metamaterial science. This effect has found an impressive implementation in the parity-time symmetric (PT-symmetric) structures possessing balanced distribution of loss and gain. In this work, we generalize this phenomenon to the asymmetric systems demonstrating loss compensation in the coupled multi-mode loss-gain dielectric waveguides of different radii. We show that similar to the PT-symmetric coupled single-mode waveguides of identical radii, the asymmetric systems support the exceptional points called here the loss compensation (LC) thresholds where the frequency spectrum undergoes a transition from complex to real values. Moreover, the LC-symmetry thresholds can be obtained for dissimilar modes excited in the waveguides providing an additional degree of freedom to control the system response. In particular, changing loss and gain of asymmetric coupled waveguides, we observe loss compensation for TM and TE modes as well as for the hybrid HE and EH modes.

Improving the efficiency of perovskite solar cells via embedding random plasmonic nanoparticles: Optical–electrical study on device architectures

Perovskite solar cells (PSCs) based on lead halide and solution process face issues such as low efficiency and high manufacturing costs. Recently, the emerging field of plasmonics as a branch of photonics has been utilized in electronic, optic and electro-optic devices, which deals with optical phenomena in metallic nanostructures like Au, Ag and Cu. One way to enhance the efficiency is the increase of absorbent layer thickness, while increasing the manufacturing cost. Here, we intend to examine the size, number, and composition of random plasmonic nanoparticles (RPNPs) in the active layer (AL) so that we can increase the power conversion efficiency (PCE) without changing the absorbent layer thickness. The simulation results demonstrate an improve in photocurrent of the device as much as 11.12% (18.24–20.27 mA/cm2) using the near-field plasmon-enhanced properties of RPNPs, while the number and radius of PNPs embedded in the AL are 50 and 10 nm, respectively. With Ag RPNPs, the photocurrent increases up to 16.5% (18.24–21.25 mA/cm2). Utilizing RNPNs is an efficient method for improving PCE in PSCs with thin absorption layer (up to 200 nm). Given the optimal parameters obtained for RPNPs, our study is very useful for the development of PSCs.

Nonlinear Optical Investigation of Microbial Chromoproteins.

Membrane-bound or cytosolic light-sensitive proteins, playing a crucial role in energy- and signal-transduction processes of various photosynthetic microorganisms, have been optimized for sensing or harvesting light by myriads of years of evolution. Upon absorption of a photon, they undergo a usually cyclic reaction series of conformations, and the accompanying spectro-kinetic events assign robust nonlinear optical (NLO) properties for these chromoproteins. During recent years, they have attracted a considerable interest among researchers of the applied optics community as well, where finding the appropriate NLO material for a particular application is a pivotal task. Potential applications have emerged in various branches of photonics, including optical information storage and processing, higher-harmonic and white-light continuum generation, or biosensorics. In our earlier work, we also raised the possibility of using chromoproteins, such as bacteriorhodopsin (bR), as building blocks for the active elements of integrated optical (IO) circuits, where several organic and inorganic photonic materials have been considered as active components, but so far none of them has been deemed ideal for the purpose. In the current study, we investigate the linear and NLO properties of biofilms made of photoactive yellow protein (PYP) and bR. The kinetics of the photoreactions are monitored by time-resolved absorption experiments, while the refractive index of the films and its light-induced changes are measured using the Optical Waveguide Lightmode Spectroscopy (OWLS) and Z-scan techniques, respectively. The nonlinear refractive index and the refractive index change of both protein films were determined in the green spectral range in a wide range of intensities and at various laser repetition rates. The nonlinear refractive index and refractive index change of PYP were compared to those of bR, with respect to photonics applications. Our results imply that the NLO properties of these proteins make them promising candidates for utilization in applied photonics, and they should be considered as valid alternatives for active components of IO circuits.

Improved plutonium and americium photon branching ratios from microcalorimeter gamma spectroscopy

Photon branching ratios are critical input data for activities such as nuclear materials protection and accounting because they allow material compositions to be extracted from measurements of gamma-ray intensities. Uncertainties in these branching ratios are often a limiting source of uncertainty in composition determination. Here, we use high statistics, high resolution (̃60–70 eV full-width-at-half-maximum at 100 keV) gamma-ray spectra acquired using microcalorimeter sensors to substantially reduce the uncertainties for 11 plutonium (238Pu, 239Pu, 241Pu) and 241Am branching ratios important for material control and accountability and nuclear forensics in the energy range of 125 keV to 208 keV. We show a reduction in uncertainty of over a factor of three for one branching ratio and a factor of 2–3 for four branching ratios.

Scattering activities bounded by reciprocity and parity conservation

Scattering activities are generally manifest through different optical responses of scattering bodies to circularly polarized light of opposite handedness. Similar to the ubiquitous roles played by scattering theory across different branches of photonics, scattering activities can serve as a fundamental concept to clarify underlying mechanisms of various chiroptical effects, both within and beyond scattering systems. In this work we investigate scattering activities for reciprocal systems that exhibit various geometric symmetries but are intrinsically achiral. We reveal how scattering activities are generally bounded by reciprocity and parity conservation, demonstrating that though extinction activity is usually eliminated by symmetry, scattering activities in forms of distinct absorptions, scatterings or angular scattering patterns can more widely emerge. Since our analyses are solely based on fundamental laws of reciprocity and parity conservation, regardless of geometric and optical parameters of the scattering systems studied, the principles revealed are generically applicable. The intuitive and pictorial framework we have established is beyond any specific coupling models, able to reveal hidden connections between seemingly unrelated chiral manifestations, and thus more accessible for a unified understanding of various chiroptical effects.

A Layered‐Composite Nanometric Sb2Te3 Material for Chiral Photonic Bandgap Engineering

Biological systems have been using nanometre‐scale architectures to produce striking optical effects and the way these natural photonic structures manipulate the flow of light has inspired many technological applications. Nevertheless, the applications of these natural structures in photonic devices require appropriate fabrication techniques able to tailor and enhance the natural features of the biological systems. In this communication the authors report on the development of a layered‐composite nanometric Sb2Te3 material for the realization of bio‐inspired three‐dimensional chiral photonic crystals exceeding their natural optical properties. The authors demonstrate that the deposition of Sb2Te3 on laser written polymer templates can fabricate biomimetic photonic structures with superior control over size, periodicity, filling fraction, and refractive index, compared with the natural counterparts. In this way the refractive index of the photonic crystals can be increased by 100% and the photonic bandgap for use in practical devices can be precisely engineered. These bio‐inspired structures can be useful in the investigation of new branches of photonics and in the development of novel chiral optical devices capable of manipulating photons in three dimensions.

Astrophysical relevance of the low-energy dipole strength of 206Pb

The dipole strength of 206Pb was studied below the neutron separation energy using photon scattering experiments at the HIGS facility. Utilizing the technique of nuclear resonance fluorescence with 100% linearly-polarized photon beams, the spins, parities, branching ratios and decay widths of excited states in 206Pb from 4.9 - 8.1 MeV have been measured. The new experimental information is used to reliably predict the neutron capture cross section of 205Pb, an important branch point nucleus along the s-process path of nucleosynthesis.

Beam Steering with Dielectric Metalattices

We study optical wave manipulations through high-index dielectric metalattices in both diffractionless metasurface and diffractive metagrating regimes. It is shown that the collective lattice couplings can be employed to tune the excitation efficiencies of all electric and magnetic multipoles of various orders supported by each particle within the metalattice. The interferences of those adjusted multipoles lead to highly asymmetric angular scattering patterns that are totally different from those of isolated particles, which subsequently enables flexible beam manipulations, including perfect reflection, perfect transmission and efficient large-angle beam steering. The revealed functioning mechanism of manipulated interplays between lattice couplings and multipolar interferences can shed a new light on both photonic branches of metasurfaces and metagratings, which can potentially inspire many advanced applications related to optical beam controls.

Diamond-Based Magnetic Imaging with Fourier Optical Processing

Diamond-based magnetic field sensors have attracted great interest in recent years. In particular, wide-field magnetic imaging using nitrogen-vacancy (NV) centers in diamond has been previously demonstrated in condensed matter, biological, and paleomagnetic applications. Vector magnetic imaging with NV ensembles typically requires an applied field (>10 G) to separate the contributions from four crystallographic orientations, hindering studies of magnetic samples that require measurement in low or independently specified bias fields. Here we decompose the NV ensemble magnetic resonance spectrum without such a bias field by modulating the collected light at the microscope's Fourier plane. In addition to enabling vector magnetic imaging at arbitrarily low fields, our method can be used to extend the dynamic range at a given bias field. As demonstrated here, optically-detected diamond magnetometry stands to benefit from Fourier optical approaches, which have already found widespread utility in other branches of photonics.

Optical Magnetism and Fundamental Modes of Nanodiamonds

The optical properties of color centers in nanodiamonds are widely used in various branches of photonics and interdisciplinary studies. Here, we report on an experimental study of the fundamental eigenmodes of subwavelength diamond nanoparticles. The eigenmodes reveal themselves as scattering resonances, which were measured by single-particle dark-field spectroscopy and calculated both numerically and analytically. The resonances experience a red-shift with increasing particle size, and in the case of an anisotropic particle, they change depending on the polarization of the input light. As an example of an application, the Purcell enhancement of the dipole emission from such nanodiamonds is numerically demonstrated. This study demonstrates a simple way to improve the efficiency of diamond-based sensors and single-photon sources by choosing nanoparticles of optimal size and shape.