The authors demonstrate a compact and efficient fiber coupling scheme for a surface-emitting photonic crystal laser by using a cleaved fiber tip connected to a wavelength-division-multiplexing 1×2 fiber coupler. Simultaneous optical excitation and laser light collection are achieved for a 1.55μm InGaAsP graphite-lattice Γ-point band edge laser. On comparing with the conventional microphotoluminescence setup based on an objective lens, their direct butt coupling setup is much simpler and yet offers the fiber-coupled output approximately ten times higher. Finite-difference time-domain simulations confirm that the Γ-point band edge laser exhibits the desired vertical emission property and that the fiber coupling efficiency can be as high as 30%.

In this paper, we used a simple and fast hydrothermal approach to create copper oxide (CuO) nanostructured thin film electrodes for supercapacitor applications. Nanostructures and material conductivity are critical in ion transport, and short ion and electron diffusion paths give more active sites for electrochemical processes. Activated carbon enhanced the conductivity of the CuO sample (AC). The specific capacitance obtained from CV curve is 333.3 F g ⁻¹ at 20 mV s ⁻¹ while from GCD curve is 277 F g ⁻¹ at 1 mA cm ⁻² . The CuOAC1 electrode preserves more than 66% of capacitance when operated at a high scan rate of 100 mV s ⁻¹ . Furthermore, the sample performs well, with an energy density of 9.63 Wh kg ⁻¹ and a power density of 509.8 W kg ⁻¹ at 1 mA cm ⁻² current density in 1 M acq. KOH electrolyte. The CuOAC1 sample had the lowest series (∼R _s = 0.9 Ω) and charge transfer resistance (∼R _s = 4.0 Ω). Also, the symmetric coin cell was assembled which exhibited areal capacitance of 16.7 mF cm ⁻² with 2.3 μ Wh cm ⁻² energy density at 500 μ W cm ⁻² power density measured at 2 mA cm ⁻² current density. This paper describes a new platform for increasing the conductivity of pseudocapacitive electrode materials, resulting in a high-performance supercapacitor for future portable electronic devices.

In order to improve efficiency of flexible III-V semiconductor multi-junction solar cells, it is important to enhance the current density for efficiency improvement and to attain an even efficiency of solar cells on a curved surface. In this study, the nanotextured InAlP window layer of a GaAs single-junction solar cell was employed to suppress reflectance in broad range. The nanotextured surface affects the reflectance suppression with the broad spectrum of wavelength, which causes it to increase the current density and efficiency of the GaAs single-junction solar cell and alleviate the efficiency drop at the high incident angle of the light source. Those results show the potential of the effectively suppressed reflectance of multi-junction solar cells and even performance of solar cells attached on a curved surface.

This work presents a synthesis of hierarchical manganese–iron-layered double hydroxide (MnFe-LDH) nanostructured electrodes using the hydrothermal synthesis route by varying the reaction time for electrochemical energy storage applications. The electrochemical behavior of the MnFe-LDH electrodes synthesized at different reaction times was analyzed in a three-electrode cell configuration using 2 M KOH electrolyte. The uniform and well-organized MnFe-LDH nanosheet electrode (MnFe-12h) showed the maximum areal capacitance of 2013 mFcm⁻² at a 5 mVs⁻¹ scan rate, and 1886 mFcm⁻² at a 25 mA applied current. Furthermore, the electrochemical behavior of MnFe-12h was examined by assembling an asymmetric cell device using activated carbon (AC) as a negative electrode and MnFe-12h as a positive electrode and it was tested in a wide voltage window range of 0.0 to 1.6 V. This asymmetric cell device achieved an appropriate energy density of 44.9 µW h cm⁻² (55.01 W h kg⁻¹), with a power density of 16 mW cm⁻² (5000 W kg⁻¹) at an applied current of 10 mA, and had a long-term cycling stability (93% capacitance retention after 5000 cycles) within the 1.6 V operating voltage window.

We have investigated the improvement of GaAs substrate reusing and the regrowth possibility of the epi-layer for the flexible InGaP/GaAs double junction solar cell. The presence of residues on the GaAs substrate surface separated by the epitaxial lift-off process is closely related to the regrowth of the epitaxial layer. A pre-patterning process was introduced to investigate the correlation between the lateral etch rate of the sacrificial layer and the generation of residues on the substrate. And the lateral etch rate was adjusted according to the changes in the pre-patterning area. The residues on surface of the GaAs substrate according to the lateral etch rate were observed by SEM/EDX. The structure of the InGaP/GaAs double junction solar cell re-grown on the GaAs substrate was measured by X-ray diffraction. The performance of the re-grown solar cell was measured by the current density-voltage curve at AM1.5G, 1sun with a solar simulator. The GaAs substrate was separated in the cleanest state by the pre-patterning area of 2 x 2mm ² , and the conversion efficiency of the re-grown solar cell by reusing this for three times was maintained similar to its conversion efficiency when a solar cell of initial growth.

The highly desirable properties of lithium ferrite and various metal ion substituted lithium ferrite make it a useful material for many electronic and magnetic applications. This research used a simple sol-gel auto-combustion method for the synthesis of Cr substituted Li _0.5 Fe _2.5 O ₄ ferrite. Here, in the B-site, Fe ³⁺ ions were swapped by non-magnetic Cr ³⁺ ions at different concentrations. All the samples of Cr substituted Li _0.5 Fe _2.5 O ₄ were confirmed through X-ray diffraction patterns to have a single-phase spinel-type structure with cubic symmetry, which was thereafter confirmed by its refinement through Rietveld. An increase in the substitution of Cr ³⁺ instead of Fe ³⁺ ions in the spinel ferrite system results in an increased nanocrystalline size. The average crystallite size decreased from 30 nm to 10 nm with an increase in Cr ³⁺ content. Analogous particle size was evaluated through transmission electron microscopy (TEM) analysis. Fourier transform infrared spectroscopy (FTIR) provides an overview of the structural distortion of the lithium ferrite lattice with the substitution of Cr ³⁺ ions. The Semiconducting (NTCR) nature of the Cr substituted Li _0.5 Fe _2.5 O ₄ nanoparticles was confirmed through the temperature-dependent DC resistivity. The evaluated trend of the dielectric properties ( ε ′, ε ″, and tan δ ) strengthens the facts observed in the electrical conduction mechanism.