Thermal Analysis of Blue Laser Diode for Solid State Lighting Application

Solid-state light sources based on laser diode are becoming great alternative for LEDs. Improvement of the thermal characteristics of InGaN LD is very important for realizing reliable devices. In this investigation the influence of the temperature of diode on light parameters was studied. White light was obtained by coupling blue light of diode with yellow phosphors: YAG:Ce3+ and GYAG:Ce3+ with nitride. For three values of the temperature of LD’s stem, regulated by Peltier module, CCT, CRI and chromaticity coordinates were measured by spectroradiometer. The importance of emission characteristics of materials was shown. Subsequently, the influence of temperature on laser diode intensity was investigated for 120 hours. This experiment was repeated for different levels of current and temperature. Finally, the steady state of thermal finite element analysis was performed to reveal the distribution of the temperature. The analysis showed the importance of heat sink and also temperature control.

Precise assembly and joining of silver nanowires in three dimensions for highly conductive composite structures

Three-dimensional(3D)electrically conductive micro/nanostructures are now a key component in a broad range of research and industry fields.In this work,a novel method is developed to realize metallic 3D micro/nanostructures with silver-thiol-acrylate composites via two-photon polymerization followed by femtosecond laser nanojoining.Complex 3D micro/nanoscale conductive structures have been successfully fabricated with∼200 nm resolution.The loading of silver nanowires(AgNWs)and joining of junctions successfully enhance the electrical conductivity of the composites from insulating to 92.9 Sm^−1 at room temperature.Moreover,for the first time,a reversible switching to a higher conductivity is observed,up to∼10^5Sm^−1 at 523 K.The temperature-dependent conductivity of the composite is analyzed following the variable range hopping and thermal activation models.The nanomaterial assembly and joining method demonstrated in this study pave a way towards a wide range of device applications,including 3D electronics,sensors,memristors,micro/nanoelectromechanical systems,and biomedical devices,etc.

Spectroscopic studies and Rietveld refinement of strontium-britholites

Strontium-britholites whose chemical formula was Sr10-xLax（PO4）6-x（SiO4）xF2, where x=0, 1, 2, and 4 were prepared by solid state reaction. The structural refinement carried out using the Rietveld method indicated that La^3＋ ions were located into the two sites with a strong preference for metal （2） sites especially for low contents. A progressive shift of the F position along the c-axis outside the centre of the triangle formed by metal （2）-atoms was observed with the increase of x. The infrared and Raman spectra exhibited the characteristic vibration modes of PO4 and SiO4groups confirming the incorporation of this last group into the apatite structure. The 295i MAS-NMR spectra exhibited one resonance peak confirming the data obtained by X-ray diffraction, indicating that P and Si were located in the same crystallographic site.

Ultraviolet laser photolysis of hydrocarbons for nondiamond carbon suppression in chemical vapor deposition of diamond films

In this work,we demonstrate that ultraviolet(UV)laser photolysis of hydrocarbon species alters the flame chemistry such that it promotes the diamond growth rate and film quality.Optical emission spectroscopy and laser-induced fluorescence demonstrate that direct UV laser irradiation of a diamond-forming combustion flame produces a large amount of reactive species that play critical roles in diamond growth,thereby leading to enhanced diamond growth.The diamond growth rate is more than doubled,and diamond quality is improved by 4.2%.Investigation of the diamond nucleation process suggests that the diamond nucleation time is significantly shortened and nondiamond carbon accumulation is greatly suppressed with UV laser irradiation of the combustion flame in a laser-parallel-to-substrate geometry.A narrow amorphous carbon transition zone,averaging 4 nm in thickness,is identified at the film–substrate interface area using transmission electron microscopy,confirming the suppression effect of UV laser irradiation on nondiamond carbon formation.The discovery of the advantages of UV photochemistry in diamond growth is of great significance for vastly improving the synthesis of a broad range of technically important materials.