A porous InGaN/GaN blue light-emitting diode isdemonstrated using selective area sublimation. Transmissionelectron microscopy reveals that the structure is porous down tothe Si substrate; however, the porosity is higher in the GaN buffer,while smaller pores are observed in the active region. This changeof porosity between the active region and the buffer is explained bythe modification of the dislocation pattern in the heterostructure,which is evidenced by weak beam transmission electronmicroscopy on a nonporosified reference sample. Cathodolumi-nescence mapping and electron beam-induced current microscopy(EBIC) analyses are used to probe the impact of porosification onthe optical and electrical properties of the structure at nanoscaledimensions. It is observed that neither the quantum well emissionnor the p−n junction EBIC spatial profile was degraded after porosification with respect to the nonannealed reference sample. A light-emitting diode with a fully porous active region is fabricated using a parylene pore filling for electrical insulation, and its electroluminescence is analyzed.

Light-assisted micronanoscale temperature control in a complex nanoparticle network has attracted a lot of research interest. Many efforts have been put into the optical properties of nanoparticle networks, and only a few investigations have reported its light-induced thermal behavior. We consider a two-dimensional (2D) square-lattice nanoparticle ensemble made of typical metal Ag with a radius of 5 nm. The effect of complex multiple scattering and thermal accumulation on light-induced thermal behavior in plasmonic resonance frequency (around 383 nm) is analyzed through the Green's function approach. The regime borders of both multiple scattering and thermal accumulation effects on the photothermal behavior of the 2D square-lattice nanoparticle ensemble are figured out clearly and quantitatively. The dimensionless parameter φ is defined as the ratio of a full temperature increase to that without considering the multiple scattering or thermal accumulation to quantify the multiple scattering and thermal accumulation effects on photothermal behavior. The more compact the nanoparticle ensemble is, the stronger the multiple scattering effect on thermal behavior is. When the lattice spacing increases to dozens times of the radius, the multiple scattering becomes insignificant. When φ≈1 (lattice spacing increases to hundreds times of the radius), the thermal accumulation effects are weak and can be neglected safely. The polarization-dependent distribution of the temperature increase of nanoparticles is observed only in the compact nanoparticle ensemble, while for a dilute ensemble, such a polarization-dependent temperature increase distribution can no longer be observed. This work may help with the understanding of the light-induced thermal transport in the 2D particle ensemble.

We propose and numerically implement a local probe of the static self-induced heterogeneity characterizing glass-forming liquids. The method relies on the equilibrium statistics of the overlap between pairs of configurations measured in mesoscopic cavities with unconstrained boundaries. By systematically changing the location of the probed cavity, we directly detect spatial variations of the overlap fluctuations. We provide a detailed analysis of the statistics of a local estimate of the configurational entropy and we infer an estimate of the surface tension between amorphous states, ingredients that are both at the basis of the random first-order transition theory of glass formation. Our results represent the first direct attempt to visualize and quantify the self-induced heterogeneity underpinning the thermodynamics of glass formation. They pave the way for the development of coarse-grained effective theories and for a direct assessment of the role of thermodynamics in the activated dynamics of deeply supercooled liquids.

BiFeO3 is a rich room-temperature multiferroic material in which noncollinear antiferromagnetic spin cycloids can be deterministically controlled by an electric field through the magnetoelectric interaction, opening perspectives for low-power reconfigurable antiferromagnetic spintronics. Using a commercial scanning nitrogen-vacancy (N-V) magnetometer, we are able to image two different types of spin cycloids stabilized in strain-engineered BiFeO3 epitaxial thin films. We show that, in these samples harboring two ferroelectric variants, each ferroelectric domain is coupled to a single spin cycloid, giving rise to a zigzag magnetic pattern. These ferroelectric domains can be manipulated at the local scale by piezoresponse force microscopy, allowing the design of micron-sized single domains. Thanks to its coupled optical microscope and fast-imaging capabilities, the scanning N-V magnetometer enables a quick repositioning in such areas of interest. Finally, quantitative imaging on single ferroelectric domains provides insights into the physical parameters of each spin-cycloid type and their impact on the magnetic-stray-field measurements.

We will discuss recent results: (i) on the theory of the Casimir torque between two gratingsrotated by an angle θ with respect to each other [1]; and (ii) on the theory and experimenton the Casimir force between interpenetrating gratings [2]. These findings pave the way tothe design of contactless quantum vacuum torsional spring and sensors with possiblerelevance to micro and nanomechanical devices.References[1] Mauro Antezza, H. B. Chan, Brahim Guizal, V.N. Marachevsky, Riccardo Messina,Mingkang Wang, Phys. Rev. Lett. 124, 013903 (2020)[2] Mingkang Wang, L. Tang, C.Y. Ng, Riccardo Messina, Brahim Guizal, J. A. Crosse,Mauro Antezza, C.T. Chan, H.B. Chan, Nature Communication 12, 600 (2021)

The presence of interlayer interactions in twisted bilayer graphene(TBG) enhances several characteristics, including the optical and electronic properties. We theoretically investigate the magic angle of TBG according to the vanishing of Fermi velocity and find double magic angles in a series. Thermal radiation from TBG can be tuned to the far infrared range by changing twist angles. The peculiar radiation spectrum is out of atmospheric window, which can be of great use in invisibility and keeping warm. The total radiation of TBG is slightly more than twice of a single layer graphene.

We present an accurate and simple semi analytical model for investigating the magneto-plasmonic response of a 1D subwavelength graphene strip grating under an external static magnetic field when the graphene is considered as an anisotropic layer with atomic thickness. It is based on an effective medium approach (EMA) and a rigorous phase correction. The proposed model is numerically validated and evaluated by comparing the results with those obtained from the PMM method and from methods published in the litterature.