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Pattern assisted ZnO nanorods (NRs) growth are performed using electron beam lithography (EBL) and hydrothermal method. The patterns of lines, circles and squares are prepared on polycrystalline ZnO seed layer using PMMA as photoresist. It is found that the ZnO NRs can only grow on the area with ZnO seed layer, not on the PMMA surface. The TEM results show that the ZnO NRs have single crystal structures with good orientation along the c-axis. The excitation power dependence of photoluminescence (PL) spectra of ZnO NRs shows that with excitation power increasing, the near band edge emission increases rapidly than the defects related visible emissions. The temperature dependence of PL spectra was measured in the temperature range of 13–300 K. The dependence of peak position and peak energy of exciton bound (D0X) emission of ZnO NRs on temperature were analyzed. Two non-radiative recombination channels for the D0X emission are discussed in detail.

Polycrystalline Cr,Nd:GSAG powders were synthesized by co-precipitation method using NH4OH as the precipitant. XRD, TG/DTA, FT-IR and Raman spectroscopy were used to characterize the structural properties of the precursor and the powders sintered at different temperatures. It was found that pure GSAG polycrystalline phase was obtained by sintering the precursor at 900 °C. The structure of the Cr,Nd:GSAG powder sintered at 1000 °C was refined using the Rietveld method. The lattice parameters are a = b = c = 12.4370(4) A, with α = β = γ = 90°. The highest photoluminescence intensity was achieved for the powder sintered at 1100 °C and optical properties of powders of different Cr3+ ions concentration were characterized by using photoluminescence spectroscopy.

In this work, ZnO thin films were prepared by sol–gel method on Ag substrates. The structural and optical properties of the films annealed at different temperatures were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and photoluminescence, respectively. The results of XRD showed that all the ZnO thin films had a wurtzite phase and were preferentially oriented along the c -axis direction. The sample annealed at 400 °C exhibited better crystalline quality than the ZnO thin film directly deposited on a Si substrate annealed at the same temperature. The photoluminescence spectra showed that ZnO thin films had an ultraviolet emission band and three visible emission bands including green, yellow and red band. The sample annealed at 400 °C exhibited a stronger green emission and a weaker ultraviolet emission compared with the ZnO thin film deposited on a Si substrate annealed at the same temperature. The difference of the luminescence properties was thought to be originated from different substrates. As for the ZnO films on Ag substrates, the increase of annealing temperature led to different changes of visible emissions; namely, the green emission was enhanced rapidly, the yellow emission was increased slowly and the red emission was slowly increased first and then decreased. These changes of visible emissions under different annealing temperatures were attributed to the variations of defects density in ZnO.

In this study, pure ZnO thin film, Mg-doped ZnO (ZnMgO) thin film, ZnO/ZnMgO and ZnMgO/ZnO composite thin films were prepared by sol–gel technique. The structural and optical properties of the samples were analyzed by X-ray diffraction, scanning electron microscopy, UV–visible spectrophotometer, ellipsometer and photoluminescence spectra, respectively. The results showed that the incorporation of Mg increased the strain, broadened the optical bandgap, and improved the intensity of ultraviolet emission of ZnO thin film. The full width at half maximum (FWHM) of the ultraviolet emission peak was also increased due to Mg-doping at the same time. Compared with pure ZnO and ZnMgO thin films, the ZnO/ZnMgO thin film showed better crystalline quality and ultraviolet emission performance, smaller strains and higher transmittance in the visible range.

GSAG and Nd:GSAG crystals were grown by standard Czochralski technique. The refractive index of GSAG in the wavelength range 500–3000 nm, effective segregation coefficient and absorption cross sections of Nd3+ in GSAG were determined by optical absorption method. The effective segregation coefficient was calculated to be 0.525. The spectroscopic and laser properties of Nd:GSAG crystal were studied by Judd–Ofelt analysis. The Judd–Ofelt parameters were calculated to be Ω2 = 1.32 × 10−21 cm2, Ω4 = 2.93 × 10−20 cm2 and Ω6 = 3.91 × 10−20 cm2. With these intensity parameters, the values of absorption and emission oscillator strengths, transition probabilities, fluorescence ratios and radiative lifetimes were obtained. The large fluorescence ratio of |[4F]3/2〉 is very favorable for laser operation at 942 nm. These results confirm that Nd:GSAG is a suitable laser material for water vapor detection by DIAL.

In this work, 1 at.% K-doped ZnO thin films were prepared by sol–gel method on Si substrates. The evolution behavior of the structures and photoluminescence of these films under different annealing temperatures was deeply studied. The crystal structures and surface morphology of the samples were analyzed by an X-ray diffractometer and an atomic force microscope, respectively. The photoluminescence spectra were used to study the luminescent behavior of the samples. The results showed that the films had a hexagonal wurtzite structure and were preferentially oriented along the c-axis perpendicular to the substrate surface. All the samples showed a strong ultraviolet emission and a weak blue emission. With the increase of annealing temperature, the ZnO grains gradually grew up; at the same time, the blue emission gradually decreased. The sample annealed at 500 ◦ C showed the best crystalline quality and strongest ultraviolet emission. The authors think that the blue emission in these samples is mainly connected with K interstitial defects. When the 1 at.% K-doped ZnO thin film is annealed at high temperatures (≥600 ◦ C), most of K interstitials move into ZnO lattice sites replacing Zn. As a result, the blue emission resulting from K interstitial defects also decreased.

Nd 3+ -doped gadolinium scandium aluminum garnet (Nd:GSAG) precursors were obtained from a mixed nitrate solution with precipitant of ammonium hydrogen carbonate. The precursors were sintered at different temperatures and the phase developments in heat treatments were investigated through methods of XRD and IR, showing the precursors transformed to pure-GSAG phase with no intermediate phases appeared at 900 °C. The TEM observation revealed that the powders sintered at 900–1000 °C were well-dispersed with average crystalline sizes of 30–80 nm. Photoluminescence analysis of the Nd:GSAG nano-powders showed that the PL intensities changing significantly with the Nd 3+ doping concentration, and the concentration quenching was observed as the Nd 3+ concentration reached to 1.5 at.%.