Shangzhong Jin

GaInN light-emitting diodes with omni-directional reflector using nanoporous SnO2 film

Enhancement of light extraction in a GaInN light-emitting diode (LED) employing an omni-directional reflector (ODR) consisting of GaN, SnO2 nanorod and an Ag layer was presented. The ODR comprises a transparent, quarterwave layer of SnO2 nanorod claded by silver and serves as an ohmic contact to p-type GaN. Transparent SnO2 sols were obtained by sol-gel method from SnCl 2H2O, and SnO2 thin films were prepared by dip-coating technique. The average size of the spherical SnO2 particles obtained is 200 nm. The refractive index of the nanorod SnO2 film layer is 2.01. The GaInN LEDs with GaN/SnO2/Ag ODR show a lower forward voltage. This was attributed to the enhanced reflectivity of the ODR that employs the nanorod SnO2 film layer. Experimental results show that ODR-LEDs have lower optical losses and higher extraction efficiency as compared to conventional LEDs with Ni/Au contacts and conventional LEDs employing a distributed Bragg reflector (DBR).

Synthesis and luminous characteristics of Ba2SiO3Cl2:Eu2+, Mn2+ phosphor for white LED

Ba2SiO3Cl2:Eu2+, Mn2+ phosphor was synthesized by high-temperature solid state reaction at 900~1200°C in a slightly reducing atmosphere for 2.0~8.0 hours. The raw materials were the mixture of BaCO3, SiO2, MnCO3, NH4Cl, and Eu2O3 in the mol ratio of 3, 2, 0.004, 2 and 0.02. Ba2SiO3Cl2:Eu2+, Mn2+ phosphors absorption and luminescence spectra were studied. The results indicated that the emission band consists of three peaks located at 425 nm, 492nm and 608nm, respectively. The emission peaks at 425 and 492nm originate from the transition 5d→4f of Eu2+ ions that occupy the two Ba2+ sites in the crystal of Ba2SiO3Cl2, while the 608nm emission is attributed to the energy transfer from Eu2+ ions to Mn2+ ions. The white light can be obtained by mixing the three emission colors of blue (425 nm), green (492 nm) and red-orange (608 nm) in the single host. When the concentrations of the Eu2+ ions and Mn2+ ions were 0.02mol and 0.004mol respectively, the sample presented intense white emitting. The excitation spectra of the three emissions extending from 300 nm to 460 nm indicated that Ba2SiO3Cl2:Eu2+ phosphor can be excitated by InGaN chip UV emission effectively, and it is a single-phase white phosphor with low-cost and high brightness for white LEDs.

The design of color spectrophotometer based on diffuse illumination and compatible SCE/SCI geometric condition

The geometric conditions of diffuse illumination, 8 degree observation, specular light include (SCI) and specular light exclude (SCE) often be employed to measure the surface color of material with different gloss value. The SCE condition is usually realized by setting light trap on the integrating sphere. However, the structure of light trap has its negative influence on the light intensity uniformity, and can led to the inaccuracy of the test results under SCE or SCI condition. Due to the different sizes of the light trap, structures of the measurement instrument will led to inter instrument agreement among the measurement of sample with different gloss. This paper designs a measuring structure to measure the SCE and SCI results simultaneously; proposes a method to calculate the 8 degree gloss value based on the SCE and SCI test result; proposes a computing modal to modify the SCI and SCE measure result based on the 8 degree gloss value, experimental verifying is also carried out. The experimental results demonstrate the structure and modified model effectively reduce the negative influence of light trap. The inter instrument disagreement caused by the geometric dimension of different light trap is significantly decreased.

Research on Measurement of Optical Fiber Raman Gain Coefficient

To design Fiber Raman Amplifier, Raman gain coefficient is important data. Stimulated Raman spectrum by backward pump measured at high pump is demodulated by spontaneous Raman spectrum measured at low pump which is a convenience method to measure Raman gain coefficient. Comparing to low-signal gain method, we can measure Raman gain coefficient stably and quickly. We measure two kinds of fibers, G652 and DCF. There are two gain peaks of G652 at 1523nm, 1533nm .The maximum gain peak is at 1523nm, and the gain coefficient is 3.7×10-14m/W. The maximum gain of DCF is at 1523nm, and the value is 15.7×10-14m/W. The measurement results are in good agreement with those by low-signal gain method.

Optical design in packaging and illuminating system for high power light-emitting diodes for projection system

High power Light-Emitting Diodes are used as the illuminating system of the portable projection system more recently. Through analysis the optical structure of high-power LEDs, the LEDs optical model and package were simulated and the luminous intensity distribution diagram was obtained. According to the rectangle illuminating requirement of the projection system (the ratio of illuminating length and width is 4:3), a pair of reflective fly eye lens illuminating system with the characteristic of high-bright and uniformity illuminating was designed. Experimental results showed that greater than 85% of the uniform degree of illumination, the output light energy utilization ratio of 80% and the angle of divergence of 38 degree on the object plane were obtained while using the white LED as the light source with illuminating model of Lambertian distribution, luminous flux of 120lm and angle of divergence of 150 degree. This system will be fit for the portable and mini-projection system and other small light-emitting area, uniformity illuminating projection system.