Yellow Light Generation Research Articles

Luminescence studies and Judd Ofelt parameterization of Dy3+ activated La2(WO4)3 yellow phosphor

The synthesis and detailed luminescence studies of a series of La2-xDyx(WO4)3 (x = 0.02, 0.1, 0.2, 0.4, 0.6, 0.8) phosphors synthesized via microwave-assisted co-precipitation technique is reported in this paper. The XRD analysis confirmed that the phosphors were crystalized in a monoclinic structure with space group C2/c and FTIR analysis identified the characteristic vibrational modes. Morphological studies were conducted using FESEM analysis, and the EDS technique substantiated the effective incorporation of Dy3+ ions in La2(WO4)3. The photoluminescence excitation and emission spectra of varying concentrations of Dy3+ ions were recorded and an optimum concentration of 10% exhibited the highest intensity. The emission spectra of all phosphors were dominated by peaks at 484 nm and 574 nm. The radiative properties were evaluated using Judd-Ofelt analysis and the JO intensity parameters followed the trend Ω2 > Ω6 > Ω4. The gradual decrease in the decay lifetime value of 4F9/2 excited level with an increase in doping concentration elucidates concentration quenching phenomena due to dipole – quadrupole interaction. The emission data were also analyzed by calculating CIE coordinates and concluded that Dy3+ doped La2(WO4)3 phosphors have potential applications in yellow light generation.

High-Power High-Repetition-Rate Tunable Yellow Light Generation by an Intracavity-Frequency-Doubled Singly Resonant Optical Parametric Oscillator

An efficient intracavity-frequency-doubled singly resonant optical parametric oscillator (SR-OPO), pumped by a high-maturity 532 nm laser, tunable in the yellow wavelength region is demonstrated. An elaborate V-shaped idler cavity design is employed for a potassium titanyl phosphate (KTP) OPO nonlinear crystal to achieve a 5.06 W idler output at 1151.2 nm at a 10 kHz pulse repetition frequency. Using a second KTP crystal to intracavity frequency double the circulating idler wave, a 2.37 W yellow output at 575.6 nm is generated. High optical conversion efficiency (25.4% and 11.2%), 0.5 nm spectral linewidth, and 32 ns pulse duration of the 575.6 nm yellow output are achieved.

Plasmon-enhanced up-conversion luminescence and oxygen vacancy defect-induced yellow light in annealed Cu8S5@SiO2@Er2O3 nanocomposites

Monodispersed Cu8S5 nanoparticles were successfully synthesized by modified hot-injection method, and Cu8S5@SiO2@Er2O3 core-shell particles were designed and prepared for up-conversion luminescence. Under the excitation of 980 nm laser, the local surface plasmon resonance of Cu8S5 nanoparticles coupled with annealed Er2O3 crystals to enhance the up-conversion luminescence of Cu8S5@SiO2@Er2O3 nanocomposites in the green and red emission bands, compared with that of SiO2@Er2O3 particles. After addition of Cu8S5 nanoparticles, the local near-field enhancement of Cu8S5@SiO2@Er2O3 nanocomposites was ~36-folds stronger than that of annealed Er2O3 crystals under 980 nm incident light, indicating that Cu8S5 nanoparticles have excellent potential for enhancing the up-conversion luminescence of rare earth elements. The generation of yellow light at ~610 nm was attributed to oxygen vacancy defects in annealed Er2O3. The formation mechanism of oxygen vacancy defects in annealed Er2O3 was proposed and investigated. Furthermore, the mechanism of up-conversion luminescence of Cu8S5@SiO2@Er2O3 composites and the electronic band structure of annealed Er2O3 crystals were also discussed.

Towards Multi-Functional SiO2@YAG:Ce Core-Shell Optical Nanoparticles for Solid State Lighting Applications.

This paper aims to investigate the synthesis, structure, and optical properties of SiO2@YAG:Ce core–shell optical nanoparticles for solid state lighting applications. YAG:Ce phosphor is a key part in white light emitting diodes (LEDs), with its main functionality being the generation of yellow light. Generated yellow light from phosphor will be combined with blue light, emitted from chip, resulting in the generation of white light. Generated light in LEDs will often be scattered by SiO2 nanoparticles. SiO2 nanoparticles are often distributed within the optical window, aiming for a more homogeneous light output. The main idea in this research is to combine these functionalities in one core–shell particle, with its core being SiO2 and its shell being phosphor. In this study core–shell nanoparticles with different Ce3+ concentrations were synthesized by a sol–gel method. Synthesized nanoparticles were characterized by X-ray diffraction (XRD), small angle X-ray scattering (SAXS) analysis, high resolution transmission electron macroscopy (HRTEM), Fourier transform infrared (FTIR), and photoluminescence spectroscopy. Luminescence characteristics of SiO2@YAG:Ce core–shell particles were compared with that of SiO2/YAG:Ce mixture composite, which is now used in commercial LEDs. Obtained results showed that core–shell nanoparticles have comparatively much better optical properties, compared to SiO2/YAG:Ce mixture composite and can therefore be potentially used in LEDs.

Compact non-cascaded all-fiber Raman laser operating at 1174 nm

We investigate a non-cascaded, all-fiber, single-mode Raman fiber laser (RFL) operating at 1174 nm with an optical slope efficiency of 68%. An ~1-km commercial single-mode fiber is used as the Raman gain medium. The RFL cavity is formed between a high reflectivity fiber Bragg grating (FBG) and a perpendicularly-cleaved fiber facet. The laser is pumped by using a homemade ytterbium-doped fiber laser (YDFL) and can be frequency doubled to generate yellow light. Under the optimum condition, A 6.9-W 1174-nm laser is obtained at maximum available power (24 W) of a laser diode pump. The optical conversion efficiency and the net slope efficiency of the RFL were respectively, 29% and 38%, with respect to launched diode laser power. We also demonstrate yellow-light generation by frequency doubling of the RFL.

Yellow-light generation and engineering in zinc-doped cadmium sulfide nanobelts with low-threshold two-photon excitation

Through a simple doping route with zinc ion as a dopant in cadmium sulfide nanobelts, a bright yellow-colored light was obtained. The detailed chromaticity and brightness of the light can be engineered by the dopant concentration and the pumping power, which are used to control the dominant wavelength to any fine yellow color, and even cover the sodium-yellow-line of 589 nm. The nanobelts were synthesized through a chemical vapor deposition method. The peak shift of the XRD result proves that the zinc ions as a dopant exist in the nanobelts rather than in the ZnCdS alloy formation. Time-resolved photoluminescence of the nanobelt reveals the existence of the defect-related state, which induces a red band to further mix with green band-edge emission to form the yellow light. Moreover, low-threshold two-photon excitation was observed in the proper Zn-doped cadmium sulfide nanobelts. The dopant and pumping power-tuned generation and engineering of the yellow light makes it possible to use this kind of material as yellow light-emitting source.

Narrow linewidth 578 nm light generation using frequency-doubling with a waveguide PPLN pumped by an optical injection-locked diode laser

This study demonstrates 578 nm yellow light generation with a narrow linewidth using a waveguide periodically poled lithium niboate (PPLN) and an optical injection-locked diode laser. The frequency of an external cavity diode laser used as a master laser operating at 1156 nm in optical injection-locking mode was locked into a high-finesse cavity with the Pound-Drever-Hall technique, which results in a linewidth reduction of the master laser. The linewidth of the master laser was estimated to be approximately 1.6 kHz. In an effort to amplify the optical power, a distributed feed-back laser was phase-locked to the master laser by an optical injection-locking technique. A waveguide PPLN was used for second harmonic generation. Frequency-doubled yellow light of approximately 2.4 mW was obtained with a conversion efficiency of 6.5%.

Yellow-light generation of 57 W by intracavity doubling self-Raman laser of YVO_4/Nd:YVO_4 composite

A high-power 588 nm light produced by an intracavity frequency-doubling acousto-optic Q-switched self-frequency Raman laser is reported. A 20-mm-long YVO(4)/Nd:YVO(4) composite crystal and a 15-mm-long LiB(3)O(5) (LBO) with noncritical phase-matching (theta=90 degrees , phi=0 degrees ) cut were adopted for efficient self-Raman laser operation and second-harmonic generation, respectively. By the optimizing the focus position of incident pump light and Q-switch repetition rate, yellow light with 5.7 W average power was generated under the pump power of 23.5 W, corresponding to the overall diode-yellow conversion efficiency of 24.2% and slope efficiency of 32%. The pulse width is about 16 ns, and the pulse energy is up to 95 microJ.

Efficient yellow-light generation by frequency doubling a narrow-linewidth 1150 nm ytterbium fiber oscillator

A linearly polarized, narrow-linewidth, diode-pumped, Yb-doped silica-fiber oscillator operating at 1150 nm was frequency doubled to produce 40 mW of 575 nm radiation. The oscillator generated 89 mW of cw linearly polarized output power and was tunable over 0.80 nm. The laser output was coupled to a periodically poled LiNbO3 waveguide that converted 67% of the coupled power to the yellow. The system was fully integrated, with no free-space optics, and had an overall optical-to-optical efficiency of 7.0% with respect to the incident diode-laser pump power.

Yellow light generation by frequency doubling of a diode-pumped Nd:YAG laser

We demonstrate the generation of TEM00 mode yellow light in critically type II phase-matched KTiOPO4 (KTP) with intracavity frequency doubling of a diode-pumped Nd:YAG laser at room temperature. After a 150μm thick etalon have been inserted into the cavity, the stability and beam quality of the second harmonic generation (SHG) is enhanced. A continuous wave (CW) TEM00 mode output power of 1.67W at 556nm is obtained at a pump level of 16W. The total optical to optical conversion efficiency is about 10.44%. To the best of our knowledge, this is the first Watt-level yellow light generation by frequency doubling of Nd:YAG laser.

Light emission from electroluminescent Langmuir–Blodgett films of a polyester derived from oligothiophene

Electroluminescent devices using Z-type Langmuir–Blodgett multilayer films of poly(hexaethyleneglycol-3″,4″-dihexyl-2,2′;5′,2″;5″,2″′;5″′,2″″-pentathiophene-5,5″″-dicarboxylate) (PPOE6) as the active region have been fabricated. The organic material was incorporated in a sandwich structure between indium tin oxide (ITO) and aluminium electrodes. Diode-like characteristics were observed, with a power law relationship between current and voltage indicative of charge injection at the contacts. It is thought that the recombination of electrons and holes (injected at the aluminium and ITO contacts, respectively) was responsible for the electroluminescent effect. The threshold voltage for the generation of yellow light (visible in a darkened room) was ca. 4 V. Using a calibrated photodiode to measure the optical output power, a quantum efficiency of the order of 1×10 −2% was calculated.

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We demonstrate the generation of TEM00 mode yellow light in critically type II phase-matched KTiOPO4 (KTP) with intracavity frequency doubling of a diode-pumped Nd:YAG laser at room temperature. After a 150 μm thick etalon have been inserted into the cavity, the stability and beam quality of the second harmonic generation (SHG) is enhanced. A continuous wave (CW) TEM00 mode output power of 1.67 W at 556 nm is obtained at a pump level of 16 W. The total optical to optical conversion efficiency is about 10.44%. To the best of our knowledge, this is the first Watt-level yellow light generation by frequency doubling of Nd:YAG laser.