TEM and STEM Observations of a Flat Continuous Silicon-Germanium Thin Film Epitaxially Grown on Porous Silicon

Strain-relaxed SiGe is an attractive material for use as a substrate of strained Si, in which carrier mobility is higher than that of bulk Si. The concept of this study is the use of porous Si as a sponge like substrate so that a SiGe lattice can relax without introducing dislocations. We produced porous Si specimens by electrochemical anodization and annealed them under a H2 atmosphere. Then, SiGe thin films were grown by gas-source molecular beam epitaxy. We observed the microstructure of the specimens using transmission electron microscopy. The result showed that we succeeded in producing a single-crys- tal continuous Si0.73Ge0.27 film with a 10% relaxation ratio and a low dislocation density on porous Si.

Optical mode study of III-V-nanowire-based nanophotonic crystals for an integrated infrared band microlaser

In this paper,we study an original strategy to generate an infrared waveband microlaser by an integrated III–V-nanowire(NW)-based photonic array for on-chip interconnects.The optical modes of the III–V-NW-based photonic array are investigated for utilization as an all-in-one gain medium,waveguide,and cavity.Adequate designs of periodic arrays of InP NWs with different polarization TM and TE modes are studied by 3D electromagnetic simulation finite difference time domain to optimize the resonant active photonic crystal(hybrid Bloch modes)in the infrared band at 1.3μm.According to our calculations,NWs larger than 0.2μm in diameter are needed to conceive optic modes inside NW photonics in TM polarization.However,smaller NW photonics,such as 0.1μm in diameter,can obtain only the TE mode inside the NWs.This phenomenon is theoretically illustrated by the dispersive curves of NW-based photonics.It aims at demonstrating that the slow velocity mode inside the NW photonics will cause amplification of lightwaves and generate microlasers in the infrared band at 1.3μm.These studies are of prime importance for further microlaser integration to silicon-on-insulator(SOI)waveguides for on-chip optical interconnects.

Engineering a light–matter strong coupling regime in perovskite-based plasmonic metasurface: quasi-bound state in the continuum and exceptional points

We present theoretically the formation of exciton–photon polaritons and exciton-surface plasmon polaritons in a perovskite-based subwavelength lattice on the metallic plane.It is shown that the later polaritons will be achieved as the perovskite layer is ultra-thin(<50 nm),while the co-existence of both polaritons will dominate,as the thickness of the perovskite metasurface approaches wavelength-scale.In the two cases,the lower polaritonic branches consist of dark and bright modes corresponding to infinite and finite radiative quality factors,respectively.Another salient property in this work is that it allows one to obtain exceptional points(EPs)in momentum space with a four-fold enhancement of local density of states through engineering the perovskite metasurface.Our findings show that the perovskite metasurface is an attractive and rich platform to make polaritonic devices,even with the presence of a lossy metallic layer.

Nonlinear integrated photonics

The field of nonlinear photonics is in full development. This special issue of Photonics Research takes you through the current issues of this fast-growing field of research, drawing on the current state of the art and seeking, through a selection of articles, to outline some trends for the future.