OBJECTIVE: To standardize the use of phototherapy consistent with the American Academy of Pediatrics clinical practice guideline for the management of hyperbilirubinemia in the newborn infant 35 or more weeks of gestation. METHODS: Relevant literature was reviewed. Phototherapy devices currently marketed in the United States that incorporate fluorescent, halogen, fiber-optic, or blue light-emitting diode light sources were assessed in the laboratory. RESULTS: The efficacy of phototherapy units varies widely because of differences in light source and configuration. The following characteristics of a device contribute to its effectiveness: (1) emission of light in the blue-to-green range that overlaps the in vivo plasma bilirubin absorption spectrum (∼460–490 nm); (2) irradiance of at least 30 μW·cm −2 ·nm −1 (confirmed with an appropriate irradiance meter calibrated over the appropriate wavelength range); (3) illumination of maximal body surface; and (4) demonstration of a decrease in total bilirubin concentrations during the first 4 to 6 hours of exposure. RECOMMENDATIONS (SEE APPENDIX FOR GRADING DEFINITION): The intensity and spectral output of phototherapy devices is useful in predicting potential effectiveness in treating hyperbilirubinemia (group B recommendation). Clinical effectiveness should be evaluated before and monitored during use (group B recommendation). Blocking the light source or reducing exposed body surface should be avoided (group B recommendation). Standardization of irradiance meters, improvements in device design, and lower-upper limits of light intensity for phototherapy units merit further study. Comparing the in vivo performance of devices is not practical, in general, and alternative procedures need to be explored.

https://pediatrics.aappublications.org/content/pediatrics/early/2011/09/21/peds.2011-1494.full.pdf

Phototherapy to prevent severe neonatal hyperbilirubinemia in the newborn infant 35 or more weeks of gestation.

AlN epilayers were grown by metal organic chemical vapor deposition on sapphire substrates. X-ray diffraction measurements revealed that the threading dislocation (TD) density, in particular, the edge TD density, decreases considerably with increasing the epilayer thickness. Photoluminescence results showed that the intensity ratio of the band edge emission to the defect related emission increases linearly with increasing the epilayer thickness. Moreover, the dark current of the fabricated AlN metal-semiconductor-metal deep ultraviolet (DUV) photodetectors decreases drastically with the AlN epilayer thickness. The results suggested that one effective way for attaining DUV optoelectronic devices with improved performance is to increase the thickness of the AlN epilayer template, which results in the reduction of the TD density.

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Correlation between optoelectronic and structural properties and epilayer thickness of AlN

Room temperature pulsed-operation lasing has been achieved for the first time in an InGaN laser grown on a 6H-SiC substrate. The laser structure is an 8-well InGaN/GaN MQW having Al0.06Ga0.94N waveguide and Al0.13Ga0.87N cladding layers. The index-guided laser having uncoated cleaved facets emits at 402 nm with a threshold current Ith of 1.2 A (42V), corresponding to a current density of 48 kA/cm2. A narrow line width of 0.8 A is observed at 1.09 Ith. Far field measurements indicate that the devices operate in the TEM01 mode with FWHP of 5.7 and 19° for the in-plane and perpendicular directions, respectively.

Pulsed operation lasing in a cleaved-facet InGaN/GaN MQW SCH laser grown on 6H-SiC

High intensity light-emitting diodes (LEDs) are being studied as possible light sources for the phototherapy of hyperbilirubinemic neonates. These power-efficient, low heat-producing light sources have the potential to deliver high intensity light of narrow wavelength band in the blue-green portion of the visible light spectrum, which overlaps the absorption spectrum of bilirubin (BR). We compared the efficacy between single LEDs of different color and then constructed a prototype phototherapy device using 300 blue LEDs. The efficacy of this device was compared with that of conventional phototherapy devices by measuring the in vitro photodegradation of BR in human serum albumin. When blue, blue-green, green, and white LEDs were compared, the blue light was the most effective in degrading BR by 28% of dark control, followed by blue-green (18% of control), and then white light (14% of control). Green light was the least effective (11% of control). The prototype device with three focused arrays, each with 100 blue LEDs, generated greater irradiance (> 200 microW.cm-2.nm-1) than any of the conventional devices tested. It also supported the greatest rate of BR photodegradation. We conclude that light from LEDs should be considered a more effective treatment for hyperbilirubinemia than light from presently used phototherapy devices. Furthermore, the unique characteristics of this light source may make it especially suitable for use in safe and lightweight home phototherapy devices.

/pdf/light-emitting-diodes-a-novel-light-source-for-phototherapy-149atky16p.pdf

Light-emitting diodes: a novel light source for phototherapy.

Room-temperature (RT) pulsed operation of blue (420 nm) nitride-based multiquantum-well laser diodes grown on a-plane and c-plane sapphire substrates has been demonstrated. Structures investigated include etched and cleaved facets as well as doped and undoped quantum wells. A combination of atmospheric and low-pressure metal organic chemical vapor deposition using a modified two-flow horizontal reactor was employed. Threshold current densities as low as 12.6 kA/cm/sup 2/ were observed for 10/spl times/1200 /spl mu/m lasers with uncoated reactive ion etched facets on c-plane sapphire. Cleaved facet lasers were also demonstrated with similar performance on a-plane sapphire. Laser diodes tested under pulsed conditions operated up to 6 h at RT. Lasing was achieved up to 95/spl deg/C and up to a 150-ns pulselength (RT). Threshold current increased with temperature with a characteristic temperature T/sub 0/ of 114 K.

Cleaved and etched facet nitride laser diodes

As discussed in previous sections, recent research on III-V nitrides has paved the way for the realization of high-quality crystals of A1GaN and InGaN, and p-type conduction in AlGaN. The hole-compensation mechanism of p-type A1GaN has also been elucidated. High-brightness blue and blue-green light emitting diodes (LEDs) with a luminous intensity of 2 cd have been fabricated using these techniques and are now commercially available. In order to obtain blue and blue-green emission centers in these InGaN/A1GaN double-heterostructure (DH) LEDs, Zn doping of the InGaN active layer was performed. Although these InGaN/A1GaN DH LEDs produce a high-power light output in the blue and blue-green region with a broad emission spectrum (full width at half-maximum (FWHM = 70 nm), green or yellow LEDs with a peak wavelength longer than 500 nm have not been fabricated. The longest peak wavelength of the electroluminescence (EL) of InGaN/A1GaN DH LEDs achieved thus far is 500 nm (blue-green) because the crystal quality of the InGaN active layer of DH LEDs becomes poor when the indium mole fraction is increased to obtain a green band-edge emission. On the other hand, in conventional green GaP LEDs the external quantum efficiency is only 0.1% due to the indirect band-gap and the peak wavelength is 555 nm (yellowish green) [304]. As another material for green emission devices, AllnGaP has been used. The present performance of green AlInGaP LEDs is an emission wavelength of 570 nm (yellowish green) and maximum external quantum efficiency of 1% [304]. When the emission wavelength is reduced to the green region, the external quantum efficiency drops sharply because the band structure of AlInGaP approaches an indirect transition. Therefore, high-brightness pure green LEDs, which have a high efficiency of above 1% at the peak wavelength of 510–530 nm with a narrow FWHM, are not yet commercially available.

InGaN Single-Quantum-Well LEDs

The previous chapters of this book demonstrated the development of commercial Group-III-nitride based high-power blue (5 mW) and green (3 mW) LEDs [330, 331]. In order to obtain LEDs with such high-power emission in different spectal regions, an InGaN single-quantum-well (SQW) structure is used as the active layer. LEDs have a large range of applications including lighting and displays. Previous chapters showed, that LEDs have many advantages compared to traditional light bulbs and fluorescent tubes.

Room-Temperature Pulsed Operation of Laser Diodes

The present Chap. 9 shows, how Zn-, and Si-co-doping together with other improvements can dramatically improve the output power and quantum efficiency. While the previous Chap. 8 described the development of InGaN superlattice and double heterostructure based light emitting diodes in the 100 µW, 0.15% range, the present Chap. 9 will demonstrate the developments which have led to LED’s in the 3 mW output power — 5% efficiency class. Several research developments lead to this strong improvement. One is Zn-doping, another is the replacement of LEEBI by thermal annealing. Thus both Sects. 8.8 and 9.1 discuss InGaN double heterostructure blue diodes. However, in Sect. 9.1 Zn-doping and thermal annealing are used together with other advances discussed below.

Zn and Si Co-Doped InGaN/AlGaN Double-Heterostructure Blue and Blue-Green LEDs

In this chapter, the first successful CW operation of InGaN multi-quantumwell (MQW)-structure LDs at 233 K is described.

Room Temperature CW Operation of InGaN MQW LDs

Gallium nitride and related compounds have been propelled from obscurity into the mainstream of physics and electrical engineering research within the time-span of a few months through Nakamura’s development of commercially viable blue and green light emitters.

Shuji Nakamura

Papers

InGaN Single-Quantum-Well LEDs

Room-Temperature Pulsed Operation of Laser Diodes

Zn and Si Co-Doped InGaN/AlGaN Double-Heterostructure Blue and Blue-Green LEDs

Room Temperature CW Operation of InGaN MQW LDs

Physics of Gallium Nitride and Related Compounds