We report indium incorporation properties on various nonpolar and semipolar free-standing GaN substrates. Electroluminescence characterization and x-ray diffraction (XRD) analysis indicate that the semipolar (202¯1¯) and (112¯2) planes have the highest indium incorporation rate among the studied planes. We also show that both indium composition and polarization-related electric fields impact the emission wavelength of the quantum wells (QWs). The different magnitudes and directions of the polarization-related electric fields for each orientation result in different potential profiles for the various semipolar and nonpolar QWs, leading to different emission wavelengths at a given indium composition.

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A study of the influence of embedded circular hollow vascules on structural performance of a fibre-reinforced polymer (FRP) composite laminate is presented. Incorporating such vascules will lead to multi-functional composites by bestowing functions such as self-healing and active thermal management. However, the presence of off-axis vascules leads to localized disruption to the fibre architecture, i.e. resin-rich pockets, which are regarded as internal defects and may cause stress concentrations within the structure. Engineering approaches for creating these simple vascule geometries in conventional FRP laminates are proposed and demonstrated. This study includes development of a manufacturing method for forming vascules, microscopic characterization of their effect on the laminate, finite element (FE) analysis of crack initiation and failure under load, and validation of the FE results via mechanical testing observed using high-speed photography. The failure behaviour predicted by FE modelling is in good agreement with experimental results. The reduction in compressive strength owing to the embedding of circular vascules ranges from 13 to 70 per cent, which correlates with vascule dimension.

For poly (9,9-di(6-(2-(3-oxetanyl)butoxyl)hexyl)-2,7-fluorene) (POBOHF), measurements on field induction-thermally stimulated current (FI-TSC) and electroluminescence (EL) under a wide temperature range demonstrate that electric field induction (FI) accompanied by side chain motion can lead to a formation of excimers, which contribute to a growth of a green component in the EL spectrum. This phenomenon also happens to poly(9,9-di-n-octyl-2,7-fluorene) (PFO), especially under long-term operations with higher electric fields (1 × 10 6 V/cm), copolymers of OBOHF and FO (PF-1/1 and PF-1/3), and even cross-linked POBOHF. The higher polarity of the side chain in the polyfluorenes (PFs) can cause a more pronounced FI effect. For POBOHF, the green component can even dominate after a few cycles of device operation. Lowering the content of cross-linkable commoner in the copolymers from 50 to 25 mol % only moderately suppresses the formation of FI excimers.

We demonstrate electrically driven InGaN based laser diodes (LDs), with a simple AlGaN-cladding-free epitaxial structure, grown on semipolar (2021) GaN substrates. The devices employed In0.06Ga0.94N waveguiding layers to provide transverse optical mode confinement. A maximum lasing wavelength of 506.4 nm was observed under pulsed operation, which is the longest reported for AlGaN-cladding-free III-nitride LDs. The threshold current density (Jth) for index-guided LDs with uncoated etched facets was 23 kA/cm2, and 19 kA/cm2 after application of high-reflectivity (HR) coatings. A characteristic temperature (T0) value of ∼130 K and wavelength red-shift of ∼0.05 nm/K were confirmed.

An advanced light-fidelity (Li-Fi) system based on the blue Gallium nitride (GaN) laser diode (LD) with a compact white-light phosphorous diffuser is demonstrated for fusing the indoor white-lighting and visible light communication (VLC). The phosphorous diffuser adhered blue GaN LD broadens luminescent spectrum and diverges beam spot to provide ample functionality including the completeness of Li-Fi feature and the quality of white-lighting. The phosphorous diffuser diverged white-light spot covers a radiant angle up to 120o with CIE coordinates of (0.34, 0.37). On the other hand, the degradation on throughput frequency response of the blue LD is mainly attributed to the self-feedback caused by the reflection from the phosphor-air interface. It represents the current state-of-the-art performance on carrying 5.2-Gbit/s orthogonal frequency-division multiplexed 16-quadrature-amplitude modulation (16-QAM OFDM) data with a bit error rate (BER) of 3.1 × 10−3 over a 60-cm free-space link. This work aims to explore the plausibility of the phosphorous diffuser diverged blue GaN LD for future hybrid white-lighting and VLC systems.

Porphine bearing triphenylamine (TPA) pendant groups and their zinc complexes, zinc meso-tetra-p-(di-p-phenylamino)phenylporphyrin (ZnTDPAPP) and zinc meso-tetra-p-(di-p-tolylamino)phenylporphyrin (ZnTDTAPP) are synthesized and their spectral and electrochemical characteristics are studied. Zinc meso-tetraphenylporphyrin (ZnTPP) and zinc meso-tetra-p-aminophenylporphyrin (ZnTAPP) are also used as reference complexes. The B and Q bands of ZnTDPAPP and ZnTDTAPP are located at higher wavelengths and the bandwidths become broader compared with those of ZnTPP and ZnTAPP, indicating the peripheral TPA affects the electronic configuration of zinc porphyrins. Upon excitation in CH2Cl2 at room temperature, the compounds exhibit intramolecular singlet energy transfer from the TPA to the porphyrin core, and emission from the porphyrins are observed. Both ZnTDPAPP and ZnTDTAPP are easier to be oxidized and harder to be reduced than ZnTPP, in agreement with the strong electron-donating effect of the TPA groups. Extra waves corresponding to the oxidation of TPA substituents are also observed. The cation radical ZnTDTAPP+* exhibits an absorption spectrum very different from the typical spectra for porphyrin cation radicals. The NIR absorption band at 1296 nm indicates the electron transfer occurs intramolecularly. The above results evince the ability of TPA to modulate the electronic structure of zinc porphyrins.

The optical polarization ratio of spontaneous emission was investigated by electroluminescence measurements for semipolar (202¯1¯) InGaN/GaN light-emitting diodes, covering the blue to green spectral range. Devices fabricated on semipolar (202¯1¯) substrates exhibit polarization ratios ranging from 0.46 at 418 nm to 0.67 at 519 nm. These polarization ratios are significantly higher than those reported on semipolar (202¯1) devices. The valence band energy separation is extracted from spectral measurements and is consistent with the increased polarization ratio and theoretical predictions. Quantum well interdiffusion induced valence band mixing is suggested as a possible explanation for the low experimental value of polarization ratio observed for the (202¯1) devices.