Topological metasurfaces [Invited

The most appealing technique for contactless testing of the integrated circuit die has been determined to be through the use of optical signals in the visible or infrared region to supply test signals to and from the integrated circuit chip. The generation of light in silicon for the purpose of producing the output optical signal is difficult. Silicon, being an indirect bandgap semiconductor, is a poor material for light emission. The light-emission properties of a reverse biased silicon diode under avalanche breakdown are being investigated. The intensity of this emission is low; however, for the purpose of this technique, the emission strength is only limited by the ability to detect the signal a short distance away, indicating its potential as a suitable light source for contactless testing. Many diode geometries of p-n junctions for light emission have been designed and fabricated on silicon substrates. The design criteria for these studies are to optimize photon emission from the smallest junction area. The processing parameter optimization is aimed at obtaining low breakdown voltages and minimum power dissipation. >

Light generation with Fenton's reagent its relationship to granulocyte chemiluminescence

Control of the cool/warm white light generation from lanthanide ions in monoclinic double tungstate crystals

There has been a recent demand for the development of luminescent materials for visualizations of latent fingerprints (LFPs) for achieving enhanced security. Also recently, there has been a new research trend in the development of 2D materials from non-layered semiconductors with strong luminescence properties in the visible region. The conventional growth process of luminescent materials limits their capacity of tuning the structure and light emission efficiency. However, multi-atom doping provides an additional degree of freedom to tune the basic morphologies and optical properties of luminescent semiconductors by controlling the defect levels. Here, by using a simple chemical technique, multi-atom (Cu and Mn) doped rarely reported 2D nanosheets of zinc sulphide (ZnS) have been grown. Thus, a stable high fluorescence efficiency of ∼62% in the visible region has been realized for the visualization of LFPs. Furthermore, near-white light emission has been demonstrated by coating the synthesized materials with a suitable doping concentration on a commercially available UV-LED chip. The proposed technique may be utilized further to build up other 2D nanostructured materials for multifunctional applications in solid state lighting, LFPs and forensic science.

Generation of visible and NIR frequency upconversion emission light within the first biological window spectral region using excitation at 1319 nm in the second biological window in Tm3+/Er3+-codoped TeO2-based glass, is demonstrated. Efficient energy upconversion of cw radiation at 1319 nm into near infrared 800 nm emission in Tm3+ single-doped 60TeO2-10GeO2-10K2O-10Li2O-10Nb2O5 glass is observed. The 800 nm signal is the sole light emission observed in the entire UV-VIS-NIR spectral region. Luminescence emission around 1480 nm, and 1800 nm was also observed. The proposed excitation mechanism for the 800 nm thulium emitting level is assigned to a multiphonon-assisted excitation from the ground-state 3H6 to the 3H5 excited-state level, a rapid relaxation to the 3H4 level and followed by an excited state absorption of the pump photons mediated by multiphonons connecting the 3H4 level to the 3F4 emitting level. For Tm3+/Er3+-codoped tellurite glass samples, radiations at 550 nm, 660 nm and 980 nm owing to erbium ions in addition to the main 800 nm signal originating form thulium ions is readily observed. Here, energy-transfer from Tm3+ (3H6 - 3F4) to Er3+(4I9/2) producing the NIR emission, followed by excited-state absorption of 1319 nm photons populating 2H11/2, 4S3/2, and 4F9/2 visible emitting levels. Erbium single-doped samples did not exhibited visible detectable emissions for excitation powers as high as 1.8 W of cw radiation at 1319 nm. This spectroscopic characteristics is highly requested for applications in biomedicine such as fluorescence based nano-thermometers and fluorescence-based bio-imaging, once the penetration depth is a major issue to be considered.

Topological defects and disorder counteract each other1-5. Intuitively, disorder is considered detrimental, requiring efforts to mitigate its effects in conventional topological photonics6-9. We propose a counter-intuitive approach that exploits a real-momentum topological photonic crystal that harnesses real-space disorder to generate a Pancharatnam-Berry phase10,11, without disrupting the momentum-space singularity originating from bound states in the continuum12. This methodology allows flat optical devices to encode spatial information or even extra topological charge in real space while preserving the topology of bound states in the continuum in momentum space with inherent alignment. Here, as a proof of concept, we demonstrate the simultaneous and independent generation of a real-space broadband vortex or a holographic image alongside resonant momentum-space vortex beams with a narrow bandwidth, which cannot be achieved with conventional methods. Such engineered disorder contributes to vast intrinsic freedoms without adding extra dimensions or compromising the optical flatness13,14. Our findings of real-momentum duality not only lay the foundation for disorder engineering in topological photonics but also open new avenues for optical wavefront shaping, encryption and communications.

Second-harmonic generation of surface-emitted blue light has been achieved in (In,Ga)As/GaAs quantum well edge-emitting lasers. The blue light is generated by the nonlinear interaction of the internal fundamental fields of a continuously pumped laser. These lasers exhibit room temperature threshold current densities as low as 200 A/cm2 and produce about 2.6 nW of blue light for 9.8 mW of fundamental power. The peak emission of the blue light is at 487 nm and the spectral spread is about 1.7 nm.

In this work, we investigate the generation of second-harmonic light by gold nanorods and demonstrate that the collected nonlinear intensity depends upon a phase interplay between different modes available in the nanostructure. By recording the backward and forward emitted second-harmonic signals from nanorods with various lengths, we find that the maximum nonlinear signal emitted in the forward and backward directions is not obtained for the same nanorod length. We confirm the experimental results with the help of full-wave computations done with a surface integral equation method. These observations are explained by the multipolar nature of the second-harmonic emission, which emphasizes the role played by the relative phase between the second-harmonic modes. Our findings are of particular importance for the design of plasmonic nanostructures with controllable nonlinear emission and nonlinear plasmonic sensors as well as for the coherent control of harmonic generations in plasmonic nanostructures.

The scattering properties of structures with periodicities in the optical wavelength scale have been widely employed to control the light propagation and generation of thin luminescent films. An example of the control on radiative properties of thin films through periodic modulations is the well known DFB (Distributed FeedBack) laser. Such devices consist of layers exhibiting a periodical modulation of their optical constants (refractive index and/or gain) which enable controlled modification of light emission and propagation resulting in lasing without mirrors. Light propagation and generation is then modified following interaction with the resulting waveguide grating.

A 2 × 2 thermo‐optic (TO) switch using dual topological photonic crystal nanobeam (PCN) cavities on the silicon‐on‐insulator (SOI) platform is proposed and experimentally demonstrated. A Fano resonance is observed due to the interference between the topological interface state of the 1D topological PCN cavity and the Fabry‐Perot (F‐P) cavity mode formed between the two facets of the finitely long nanobeam waveguide. Thanks to the sharp rising edge of the spectral response of the Fano resonance and the high confinement of light in the topological PCN cavities, a 2 × 2 TO switch is realized with short switching time and low power consumption. The measured switching power is only 1.55 mW, and the rising time and the falling time are 3 and 5.6 µs, respectively in the on‐off switching experiments. To the best of the knowledge, this is the first time that a dual topological PCN structure is utilized to realize a high‐speed and low‐power TO switch, revealing the possibility of designing high‐performance reconfigurable optical devices and networks using topological photonics.

Developing novel one‐dimensional (1D) luminescent nanostructures (e.g., nanowires and nanoribbons) is highly desired for enabling progress in nanophotonics and other emerging optical technologies. Previous studies on 1D luminescent nanostructures were mostly focused on elemental and binary semiconductor materials, the light emission of which originates from the radiative recombination of electrons and holes via either intrinsic states or extrinsic defect states. Herein, three kinds of ternary europium aluminate nanoribbons are reported that have localized Eu2+ luminescent centers and exhibit new compositions, new crystal lattice structures, and new luminescence properties and mechanisms. These three europium aluminate nanoribbons are: blue luminescent EuAl6O10 with a new composition and a new tetragonal lattice structure, green luminescent EuAl2O4 with a monoclinic lattice structure, and orange luminescent EuAl2O4 with a new hexagonal lattice structure and extremely large band width and Stokes shift of emission. These materials have promising applications as nanometer‐scale light generators and waveguides in nanophotonics and as light converting phosphors in warm white light‐emitting diodes.

Nonlinear interactions between optical modes in semiconductor lasers and optical amplifiers perturb optical parameters in the vicinity of a strong mode frequency. This effect is considered in terms of slow and fast light propagation.

We complete a classification of topological phases and their topological defects in crystalline insulators and superconductors. We consider topological phases and defects described by non-interacting Bloch and Bogoliubov de Gennes Hamiltonians that support additional order-two spatial symmetry, besides any of ten classes of symmetries defined by time-reversal symmetry and particle-hole symmetry. The additional order-two spatial symmetry we consider is general and it includes $Z_2$ global symmetry, mirror reflection, two-fold rotation, inversion, and their magnetic point group symmetries. We find that the topological periodic table shows a novel periodicity in the number of flipped coordinates under the order-two spatial symmetry, in addition to the Bott-periodicity in the space dimensions. Various symmetry protected topological phases and gapless modes will be identified and discussed in a unified framework. We also present topological classification of symmetry protected Fermi points. The bulk classification and the surface Fermi point classification provide a novel realization of the bulk-boundary correspondence in terms of the K-theory.

Bacterial expression and re-engineering of Gaussia princeps luciferase and its use as a reporter protein

Dy3+-doped nano-glass ceramics comprising NaAlSiO4 and NaY9Si6O26 nanocrystals for white light generation