Light-Emitting Diodes. (Monographs in Electrical and Electronic Engineering.) By A. A. Bergh and P. J. Dean. Pp. viii+591. (Clarendon: Oxford; Oxford University: London, 1976.) £22.

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Light-emitting diodes

Light emitting diodes reliability review

Rare-earth ion doped TeO2 and GeO2 glasses as laser materials

Er3+-doped tellurite singlemode fibre is fabricated and signal amplification and laser oscillation are demonstrated for the first time. A small-signal gain of 16 dB at 1560 nm is obtained for a pump power of 130 mW at 978 nm. A laser oscillation is observed with a threshold pump power of 120 mW at 978 nm and a slope efficiency of 0.65% using this fibre.

Erbium-doped tellurite glass fibre laser and amplifier

The signal-gain characteristics of tellurite-based erbium-doped fiber amplifiers are clarified based on spectroscopic properties and signal-gain measurements. The potential of tellurite-based erbium-doped fiber for use as a broadband light source is also described.

Gain characteristics of tellurite-based erbium-doped fiber amplifiers for 1.5-µm broadband amplification

Tellurite glass: a new candidate for fiber devices

Tellurite glasses are examples of non-silica oxide glass hosts which are the subject of intensive materials research. Because their characteristic phonon energies are lower than those of silica glasses, praseodymium- and neodymium-doped tellurite glasses are considered for 1.3 μm fiber amplifiers. The glass formation, waveguide fabrication, optical properties and suitability for fiber drawing of sodium, zinc, tellurium oxide glasses doped with rare earth ions are described.

1.3 μm emission of neodymium and praseodymium in tellurite-based glasses

A single-mode Nd(3+)-doped tellurite glass fiber laser operating at 1.061 microm is described. We believe this is the first demonstration of a single-mode fiber laser in tellurite glass. A lasing threshold of 27 mW of 818-nm absorbed pump power and a slope efficiency output power versus pump power of 23% emitted from one end were observed in the fiber cavity with 11.9% Fresnel reflection at both ends.

Neodymium-doped tellurite single-mode fiber laser.

In this paper, high-power phosphor-converted white-light-emitting diodes (PC-LEDs) with selected concentration and thickness of cerium-doped yttrium aluminum garnet (Ce:YAG) phosphor-doped silicones are investigated to study the thermal-degradation effect of the Ce:YAG phosphor-silicone layer. The experimental results showed that the lumen loss, chromaticity (CIE shift), and spectrum intensity reduction increase as the concentration of Ce:YAG phosphor-doped silicone increases. Although silicone degradation attributed to the final thermal degradation, it is not a dominant factor until a much thicker silicone is employed in PC-LEDs. The major degradation mechanism of the PC-LEDs results from the higher doping concentration of Ce:YAG in silicone. We found that 94% lumen loss was attributed to 5.5 wt% Ce:YAG doping and only 6% of the lumen loss was due to a 1-mm thickness of silicone degradation. However, the negligible differences of measured fluorescent lifetimes among the test samples before and after thermal aging (at 150 degC for 500 h) eliminated any significant nonradioactive quenching processes that existed in the aged samples. The emission spectra indicate that a higher doping concentration in silicone causes a higher degree of loss at the emission wavelength of Ce:YAG. Therefore, minimizing any unwanted interactions, such as refractive index and thermal-expansion mismatches, between the phosphor and the silicone during thermal aging is a new direction of addressing thermal reliability for high-power PC-LEDs. From practical points of view, we found that a lower doping concentration of the Ce:YAG phosphor in thin silicone is a better choice in terms of having less thermal degradation for use in packaging of the high-power PC-LEDs modules and is essential to extend the operating lifetime of the phosphor-based white LED modules.

Jau-Sheng Wang

Papers

Tellurite glass: a new candidate for fiber devices

1.3 μm emission of neodymium and praseodymium in tellurite-based glasses

Neodymium-doped tellurite single-mode fiber laser.

Investigation of Ce:YAG Doping Effect on Thermal Aging for High-Power Phosphor-Converted White-Light-Emitting Diodes

1.47, 1.88 and 2.8 μm emissions of Tm3+ and Tm3+-Ho3+-codoped tellurite glasses