Light-emitting Components Research Articles

A Novel 3-D Microcavity Based on Bragg Fiber Dual-Tapers

In this paper, a novel 3-D microcavity based on Bragg fiber dual-tapers is proposed. The principle and characteristics of the Bragg fiber dual-taper are analyzed firstly, showing that the dual-taper can function as a fiber mirror. Its reflection and transmission can be adjusted by the design of taper structure parameters. Then, the structure of a 3-D microcavity composed by two Bragg fiber dual-tapers is investigated by the finite-difference time domain method. The relation between the cavity-mode wavelengths and the cavity lengths shows that it can be looked as a Fabry-PEacuterot cavity, using the Bragg fiber dual-tapers as the mirrors. By proper design, a cavity-mode Q factor up to 4.0093times106 can be realized in this cavity. Its characteristics as narrowband filters are investigated, showing that its transmission spectrum has the shape of Lorenz curve and a finesse up to 105 can be realized if cavity mode with a high Q factor is used. The analysis shows that high-quality 3-D light confinement can be realized in the proposed Bragg fiber dual-taper microcavity, which has great potential in high-efficiency light-emitting devices and small fiber components.

Microbeam high-resolution x-ray diffraction in strained InGaAlAs-based multiple quantum well laser structures grown selectively on masked InP substrates

Structural and optical properties of the InGaAlAs-based multiple quantum well (MQW) 1.3μm laser structures produced on InP (001) substrates by metal organic vapor phase epitaxy (MOVPE) technique in the regime of selective area growth (SAG) have been studied. An x-ray beam of 10μm diameter generated by a microbeam high-resolution x-ray diffraction (μ-HRXRD) setup based on an imaging one-bounce capillary optic and a three-bounce channel cut Si(004) analyzer crystal has been utilized to measure the diffraction curves from MQW structures grown between oxide mask stripes. The high angular resolution achieved in our experiments allowed accurate measurements of θ–2θ scans over a broad range of angles that was necessary for utilization of fitting algorithms for quantitative analysis of the strain and thickness of individual layers in the MQW structures. The thickness and strain variations in the quantum well and the barrier layers of the MQW SAG structure have been analyzed as a function of the oxide mask width in the range of 15–140μm with the gap between the oxide masks in the range of 15–80μm. Dramatic structural changes from the perfect quality MQW’s in the SAG structures with the narrow oxide masks (less than 45μm) to the strain relaxed MQW’s in the SAG regime with the wide oxide masks (more than 50μm) have been experimentally detected. The spontaneous photoluminescence emission between 1.3 and 1.51μm from the simultaneously grown InGaAlAs-based MQW SAG laser structures have been measured. Using a combination of μ-HRXRD results with the microphotoluminescence data, the optimal SAG mask parameters for the growth of integrated InGaAlAs-based optoelectronic light-emitting components and devices have been determined.

High-efficiency visible photoluminescence from amorphous silicon nanoparticles embedded in silicon nitride

Confinement of silicon nanoparticles in silicon nitride instead of an oxide matrix might materially facilitate its potential applications as a light-emitting component in optoelectronics. We report in this letter the production of high-density (up to 4.0×1012/cm2 from micrographs) silicon nanoparticles in SiNx thin films by chemical vapor deposition on cold substrates. Strong room-temperature photoluminescence was observed in the whole visible light range from the deposits that were postannealed at 500 °C for 2 min. The Si-in-SiNx films provide a significantly more effective photoluminescence than Si-in-SiOx fabricated with similar processing parameters: for blue light, the external quantum efficiency is over three times as large. The present results demonstrate that the nanostructured Si-in-SiNx system can be a very competitive candidate for the development of tunable high-efficiency light-emitting devices.

PERFORMANCE DEGRADATION ANALYSIS FOR IRLEDs

Click to increase image sizeClick to decrease image sizeKey Words: Infrared light-emitting diodePrincipal component analysisPerformance characteristicDegradation modeDegradation mechanismReliability.

Ultrafast Förster transfer dynamics in tetraphenylporphyrin doped poly(9,9-dioctylfluorene)

Femtosecond pump-probe spectroscopy was used to directly monitor, in the time domain, energy transfer from the blue-emitting poly(9,9-dioctylfluorene) conjugated polymer to the red-emitting tetraphenylporphyrin molecule. This system is under investigation for use as saturated red light-emitting component in an organic full-color display. The differential transmission spectrum of the system evolves, within a few picoseconds after photoexcitation, from that of the host polymer to that of the guest molecule. Experiments performed at different acceptor concentrations provide clear evidence for a Förster energy transfer mechanism and allow a determination of the interaction radius. A value of 4.2±0.2 nm was found.

Luminescence from Porous Silicon

Recent observations of photoluminescene (PL) and electroluminescence (EL) from poroussilicon (PS) have prompted many theoretical and experimental studies. Bulk crystalline Si is anindirect band gap material in which .recombination is dominated by non-radiative processes.Therefore, it cannot be used as light-emitting component in Si circuits. PS is a new material formed byanodisation ofsingle crystal Si wafers in hydro fluoric (liF) solution. Luminescence from this materialis being explored for technological applications all over the world. The mechanism of luminescence isstill not well-understood. Several models have been proposed but still the facts about the strong lightemission at room temperature are unknown. This paper presents a review of the fabrication process andstudies on luminescent properties of PS. A hybrid model based on quantum confinement of carriers inthe nanometer size Si crystallites having a large number of surface states is suggested to explain theobserved properties.

First Blush for Integrated Light Emitter

Researchers at the University of Rochester in New York have just consummated an improbable marriage long sought by the microelectronics industry: They have combined light-emitting components with conventional microcircuitry on a single chip. The technology is far from being turned into a workable device, because it puts out too little light and too much heat, but it is being hailed as a research advance.

Light diode sound pressure transducer

The development of optoelectronics and the perfection of light guide, semiconductor laser and light-emitting diodes, and photodetector and other component characteristics are due to the creation of fiber optic transducers (FT) of sound [1-3]. Compared with traditional piezoelectric and electric acoustic transducers, the FT have high interference-immunity, sufficient sensitivity, small dimensions, are explosion-proof, reliable, and can be connected directly to fiber-optic information transmission lines.

K + /Na + -triggered bioluminescence in the oceanic squid Symplectoteuthis oualaniensis

A distinctive type of luminescent system present in the large dorsal luminous organ of the oceanic squid Symplectoteuthis oualaniensis is described. The organ produces an intense blue flash of light followed by a rapid decay in light intensity. Luminescence originates from numerous oval granules present in the luminous organ. The essential light-emitting components are membrane bound. Intact granules or washed homogenates of the granules are triggered to emit light by monovalent cations such as, in decreasing order of effectiveness, potassium, rubidium, sodium, cesium, ammonium, and lithium. Calcium, magnesium, and strontium ions do not trigger light emission. Analysis of the kinetics of the decay of light intensity suggests that two light-emitting components are involved, one decaying faster than the other. The light-emitting reaction has an absolute requirement for molecular oxygen. The optimum KCl or NaCl concentration is approximately 0.6 M and the optimum pH is approximately 7.8. A free sulfhydryl group is essential for activity.