Monolithic on-chip nonreciprocal photonics based on magneto-optical thin films

Monolithic integration of nonreciprocal optical devices on semiconductor substrates has been a long-sought goal of the photonics community. One promising route to achieve this goal is to deposit high quality magneto-optical (MO) oxide thin films directly on a semiconductor substrate. In this article, we will review our ongoing progress in material development and device engineering towards enabling a monolithically integrated, high-performance magneto-optical nonreciprocal photonics platform. In particular, we will discuss our recent work which has led to a new pulsed laser deposition (PLD) technique of Ce or Bi substituted yttrium iron garnet (YIG) thin films with reduced thermal budget, simplified growth protocols and improved magneto-optical characteristics. These materials were incorporated in monolithic resonator and interferometer based isolator devices to demonstrate on-chip optical isolation with improved device figure of merit. Challenges and opportunities for monolithic magneto-optical devices will be discussed in the context of our latest material and device performance metrics

Magnetism and Faraday Rotation in Oxygen-Deficient Polycrystalline and Single-Crystal Iron-Substituted Strontium Titanate

Both polycrystalline and single-crystal films of iron-substituted strontium titanate, Sr(Ti[subscript 0.65]Fe[subscript 0.35])O[subscript 3−δ], prepared by pulsed laser deposition, show room-temperature magnetism and Faraday rotation, with the polycrystalline films exhibiting higher saturation magnetization and Faraday rotation. The magnetic properties vary with the oxygen pressure at which the films are grown, showing a maximum at pressures of approximately 4  μ Torr at which the unit-cell volume is largest. The results are discussed in terms of the oxygen stoichiometry and corresponding Fe valence states, the structure and strain state, and the presence of small-volume fractions of metallic Fe in single-crystal films grown at the optimum deposition pressure. Integration of magneto-optical polycrystalline films on an optical-waveguide device demonstrates a nonreciprocal phase shift.National Science Foundation (U.S.) (Grants DMR1419807 and ECCS1607865)Semiconductor Research Corporation. Function Accelerated nanoMaterial Engineerin

Editor\u27s Notes, Chiba Medical Journal 90-1

Multiple sequence alignment of deduced amino acid sequences of 25 wheat annexin genes with rice annexin OsAnn2 (Os05g31760) obtained by ClustalW. (PDF 212 kb

Dual-gated mono-bilayer graphene junctions

| openaire: EC/H2020/820423/EU//S2QUIP | openaire: EC/H2020/834742/EU//ATOPA lateral junction with an atomically sharp interface is extensively studied in fundamental research and plays a key role in the development of electronics, photonics and optoelectronics. Here, we demonstrate an electrically tunable lateral junction at atomically sharp interfaces between dual-gated mono- and bilayer graphene. The transport properties of the mono–bilayer graphene interface are systematically investigated with Ids–Vds curves and transfer curves, which are measured with bias voltage Vds applied in opposite directions across the asymmetric mono–bilayer interface. Nearly 30% difference between the output Ids–Vds curves of graphene channels measured at opposite Vds directions is observed. Furthermore, the measured transfer curves confirm that the conductance difference of graphene channels greatly depends on the doping level, which is determined by dual-gating. The Vds direction dependent conductance difference indicates the existence of a gate tunable junction in the mono–bilayer graphene channel,due to different band structures of monolayer graphene with zero bandgap and bilayer graphene with a bandgap opened by dual-gating. Simulation of the Ids–Vds curves based on a new numerical model validates the gate tunable junction at the mono–bilayer graphene interface from another point of view. The dual-gated mono–bilayer graphene junction and new protocol for Ids–Vds curve simulation pave a possible way for functional applications of graphene in next-generation electronics.Peer reviewe

Coherent modulation of chiral nonlinear optics with crystal symmetry

| openaire: EC/H2020/820423/EU//S2QUIP | openaire: EC/H2020/834742/EU//ATOP | openaire: EC/H2020/965124/EU//FEMTOCHIPLight modulation is of paramount importance for photonics and optoelectronics. Here we report all-optical coherent modulation of third-harmonic generation (THG) with chiral light via the symmetry enabled polarization selectivity. The concept is experimentally validated in monolayer materials (MoS2) with modulation depth approaching ~100%, ultra-fast modulation speed (<~130 fs), and wavelength-independence features. Moreover, the power and polarization of the incident optical beams can be used to tune the output chirality and modulation performance. Major performance of our demonstration reaches the fundamental limits of optical modulation: near-unity modulation depth, instantaneous speed (ultra-fast coherent interaction), compact footprint (atomic thickness), and unlimited operation bandwidth, which hold an ideal optical modulation solution for emerging and future nonlinear optical applications (e.g., interconnection, imaging, computing, and quantum technologies).Peer reviewe

Quenching induced residue stress in M50 steel ring: a FEM simulation

A finite element method (FEM) combined with subroutines was established and used for tracing the evolution of stresses in M50 steel in quenching. The constitutive relation and thermal physical properties of M50 steel were tested and integrated into the modeling. The finite element analysis, taking into account of thermal stresses and martensitic phase transformation, predicts accurately the high-velocity nitrogen (HNQ) induced residual stresses in the M50 steel bulk. The simulation results suggested that the residual stresses in M50 steel is compressive at the surface while tensive at the center, along with very strong residual stresses at edges. The residual stress reaches to the high level of −810.3 MPa and −1436 MPa in the case of HNQ and water quenching, respectively. The evolution of stress is found to be jointly driven by the thermal stress and phase transformation stress. The thermal stress dominates the evolution at the initial stage while the phase transformation stress becomes dominating once the martensite transformation begins

Multiferroic Behavior of Templated BiFeO₃–CoFe₂O₄ Self-Assembled Nanocomposites

Self-assembled BiFeO₃–CoFe₂O₄ nanocomposites were templated into ordered structures in which the ferrimagnetic CoFe₂O₄ pillars form square arrays of periods 60–100 nm in a ferroelectric BiFeO₃ matrix. The ferroelectricity, magnetism, conductivity, and magnetoelectric coupling of the ordered nanocomposites were characterized by scanning probe microscopy. The insulating BiFeO₃ matrix exhibited ferroelectric domains, whereas the resistive CoFe₂O₄ pillars exhibited single-domain magnetic contrast with high anisotropy due to the magnetoelasticity of the spinel phase. Magnetoelectric coupling was observed in which an applied voltage led to reversal of the magnetic pillars

Thickness-Dependent Double-Epitaxial Growth in Strained SrTi_0.7Co_0.3O_3−δ Films

Perovskite-structured SrTi_0.7Co_0.3O_3−δ (STCo) films of varying thicknesses were grown on SrTiO₃(001) substrates using pulsed laser deposition. Thin films grow with a cube-on-cube epitaxy, but for films exceeding a critical thickness of about 120 nm, a double-epitaxial microstructure was observed, in which (110)-oriented crystals nucleated within the (001)-oriented STCo matrix, both orientations being epitaxial with the substrate. The crystal structure, strain state, and magnetic properties are described as a function of film thickness. Both the magnetic moment and the coercivity show maxima at the critical thickness. The formation of a double-epitaxial microstructure provides a mechanism for strain relief in epitaxially mismatched films