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A high power Nd:YAG end-pumped slab amplifier chain with a Nd:YVO4 innoslab laser as the master oscillator is demonstrated. A chain output power of 5210 W with beam quality of 4 times the diffraction limit is achieved by double-passing the first amplifier stage and single-passing the second stage with an optical efficiency of 29% while working at a frequency of 1 kHz and pulse width of 200 μs.

We present a design of a low frequency ultra-thin compact and polarization-insensitive metamaterial absorber (MA). The designed MA is a two-layer structure, a periodic array of novel split-ring resonators (SRRs), which are constructed in an FR4 dielectric layer, and another ultra-thin grounded sheet is attached to the bottom. Numerical simulated results show that the proposed MA can realize effective absorption at the frequency 281.9 MHz, and its overall thickness is just only 0.29% of the resonant wavelength, the unit space is only 2.57%, and the absorbance is kept well for a wide range of incident angles for different polarizations. In addition, the proposed MA is changed into a more compact one when the inter-digital structures are introduced in the SRRs. One convenient experiment is carried out in a rectangular waveguide simulator.

We report on the photoluminescent characteristics of InGaN/GaN multiple quantum well (MQW) nanorod arrays with high internal quantum efficiency. The InGaN/GaN MQWs are grown by metalorganic chemical vapor deposition on c-plane sapphire substrates, and then the MQW nanorod arrays are fabricated by using inductively coupled plasma etching with self-assembled Ni nanoparticle mask with low-damage etching technique. The typical diameter of the nanorods is from 200 nm to 300 nm and the length is around 800 nm, which almost is dislocation free. At room temperature, an enhancement of 3.1 times in total integrated photoluminescence intensity is achieved from the MQW nanorod arrays, in comparison to that of the as-grown MQW structure. Based on the temperature-dependent photoluminescence measurements, the internal quantum efficiency of the nanorod structure is 59.2%, i.e., 1.75 times of as-grown MQW structure (33.8%). Therefore, the nanorod structure with a significant reduction of defects can be a very promising candidate for highly efficient light emitting devices.

The in-plane optical anisotropic properties of the non-polar a-plane GaN films grown by metal organic chemical vapour deposition are investigated by using polarised photoluminescence (PL), optical transmission and Raman scattering measurements. Through polarised PL and transmission spectra, the in-plane optical anisotropic properties of a-plane GaN film are found, which are attributed to the topmost valance band (at Γ point) split into three sub-bands under anisotropic strain. The PL spectra also exhibit that the light hole band moves up more rapidly than the spin-orbit crystal-field spilt-off hole band with the increasing in-plane anisotropic compressive strain. Raman scattering spectra under different configurations further indicate the in-plane anisotropy and the hexagonal crystalline structure of these a-plane GaN films.

Blue-red complex light emitting InGaN/GaN multi-quantum well (MQW) structures are fabricated by metal organic chemical vapor deposition (MOCVD). The structures are grown on a 2-inch diameter (0001) oriented (c-face) sapphire substrate, which consists of an approximately 2-μm-thick GaN template and a five-period layer consisting of a 4.9-nm-thick In0.18Ga0.82N well layer and a GaN barrier layer. The surface morphology of the MQW structures is observed by an atomic force microscope (AFM), which indicates the presence of islands of several tens of nanometers in height on the surface. The high resolution x-ray diffraction (XRD) θ/2θ scan is carried out on the symmetric (0002) of the InGaN/GaN MQW structures. At least four order satellite peaks presented in the XRD spectrum indicate that the thickness and alloy compositions of the individual quantum wells are repeatable throughout the active region. Besides the 364 nm GaN band edge emission, two main emissions of blue and amber light from these MQWs are found, which possibly originate from the carrier recombinations in the InGaN/GaN QWs and InGaN quasi-quantum dots embedded in the QWs.