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Laser Diodes (laser + diode)
Selected AbstractsQuantum Well Intermixing Revolutionizes High Power Laser DiodesLASER TECHNIK JOURNAL, Issue 5 2007Monolithically integrated systems drive applications Quantum well intermixing (QWI), an innovative monolithic integration platform, is changing the way diode lasers solve evolving optoelectronic needs , from high density, individually addressable laser arrays to high power laser products. QWI-enabled lasers deliver superior performance in terms of power, brightness, reliability, and yield, and are driving a revolution across market sectors including digital printing, defense, industrial, and medical imaging. [source] Laser diodes with highly strained InGaAs MQWs and very narrow vertical far fieldsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 3 2006F. Bugge Abstract The effect of variation of the number of highly strained InGaAs quantum wells embedded in GaAs layers on the crystal quality of the epitaxial layers and AlGaAs/GaAs laser diodes was investigated. With four quantum wells and very thick waveguide layers, reasonable efficient laser diodes emitting above 1100 nm with a narrow vertical far field (FWHM = 15°) were obtained. Broad area laser diodes with 200 µm stripe width and an optimised doping profile emit nearly 20 W cw output power. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] X-ray structure study of the light-induced metastable states of the spin-crossover compound [Fe(mtz)6](BF4)2JOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 3 2001Joachim Kusz Iron(II) complexes exhibiting thermal spin-crossover may be converted from the 1A1 low-spin (LS) state to the 5T2 high-spin (HS) state by irradiation with green light (light-induced excited spin-state trapping, LIESST) and from the LS to the HS state by irradiation with red light (reverse LIESST). The lifetime of the metastable LIESST states may be sufficiently long to enable an X-ray diffraction study. The lattice parameters of a single crystal of [Fe(mtz)6](BF4)2 (mtz = methyltetrazole) (space group P21/n) were measured between 300 and 10,K. While one Fe lattice site (A) of the crystal changes from the HS to the LS state near 78,K, the other site (B) remains in the LS state. Using the green light (514,nm) of an argon ion laser the crystal was quantitatively converted to the HS state at 10,K. Irradiation of the crystal at 10,K by red light of a laser diode (820,nm) with site A in the LS and site B in the HS state converts site B almost completely to the LS state. The lattice parameters of both metastable states were measured up to 50,K, where they start to decay on a minute timescale. At 10,K, a full data set for evaluation of the crystal structure was recorded. The volume change of the crystal per complex molecule accompanying the spin transition is 31.5,Å3 at site A and close to zero [,0.21,(14),Å3] at site B. [source] Optimum acquisition of Raman spectra in pigment analysis with IR laser diode and pulsed UV irradiationJOURNAL OF RAMAN SPECTROSCOPY, Issue 10 2006Alejandro López-Gil Abstract Fluorescence, due to the binding media, is the main problem that one encounters in the molecular analysis of artistic pigments using Raman spectroscopy. With the object of minimizing this problem, we propose the use of a semiconductor IR laser in Raman spectral acquisition and the application of local irradiation with a pulsed UV laser on the analysis zone. The Raman analysis with an IR source shows advantages compared to that with visible lasers, such as the reduction of fluorescence and its shot noise, although a price has to be paid in the form of the small intensity of the obtained spectra with the same acquisition time. Also, in this paper we demonstrate that controlled levels of pulsed UV radiation over the analyzed painting (pigment + binding media) can improve even more the Raman spectral quality obtained with the IR laser, which leads us to conclude that the local use of a pulsed UV laser, prior to Raman analysis with the IR source, can bring optimum quality results in pigment identification. The spectral quality of these experimental results for different pigments has been measured by calculating in each case the signal-to-noise ratio (SNR) of the corresponding spectra. From a quantitative point of view, in some practical cases (chromium yellow and ultramarine blue) an SNR improvement of 16 dB is achieved when pulsed UV irradiation and IR laser Raman analysis are used instead of a simple Raman analysis with a visible laser. Copyright © 2006 John Wiley & Sons, Ltd. [source] 980-nm laser diode and treatment of subcutaneous mass in Proteus-like syndromeJOURNAL OF THE EUROPEAN ACADEMY OF DERMATOLOGY & VENEREOLOGY, Issue 1 2010J Buis No abstract is available for this article. [source] 1064 nm Nd:YAG laser intracavity pumped at 946 nm and sum-frequency mixing for an emission at 501 nmLASER PHYSICS LETTERS, Issue 5 2010Y.F. Lü Abstract We present for the first time a Nd:YAG laser emitting at 1064 nm intracavity pumped by a 946 nm diode-pumped Nd:YAG laser. A 809 nm laser diode is used to pump the first Nd:YAG crystal emitting at 946 nm, and the second Nd:YAG laser emitting at 1064 nm intracavity pumped at 946 nm. Intracavity sum-frequency mixing at 946 and 1064 nm was then realized in a LBO crystal to reach the cyan range. We obtained a continuous-wave output power of 485 mW at 501 nm with a pump laser diode emitting 25.4 W at 809 nm. (© 2010 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source] Repetition rate continuously controllable passively Q-switched Nd:YAG bonded microchip laserLASER PHYSICS LETTERS, Issue 8 2007H. Lei Abstract A stable repetition rate continuously controllable passively Q-switched Nd:YAG bonded microchip laser is presented. A 0.8 mm-thickness 7 mm-diameter Nd:YAG crystal at 1.6 at.% is adapted as active medium and the saturable absorber for passively Q-switched pulse generating, a 0.2 mm-thickness 6.8-mm diameter Cr4+:YAG piece was thermal bonded into the Nd:YAG after primary optical contact. By using pulse pump and controlling the duty cycle of electric pulse and temperature of laser diode, a 1 W C-mount packaged fast-collimated laser diode, we can continuously achieve repetition rate from 1 kHz to 10 kHz as active Q-switched laser. The delay time at 10 kHz is 90 ,s, while the single pulse energy is 2.8 ,J with pulse width of 2 ns. (© 2007 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source] Simplified heat exchange model for semiconductor laser diodes thermal parameters extractionLASER PHYSICS LETTERS, Issue 11 2005P. S. André Abstract By investigating the heat flow mechanism in a semiconductor laser diode, we demonstrate a comprehensive technique for optical device thermal parameters extraction to be used in the prediction of the laser performance This accurate and precise heat exchange model takes into account the relevant heat exchange mechanism and mechanical considerations of the laser diode mounting. We measured the thermal response of a semiconductor laser diode attach to a substrate, deriving from those the device thermal parameters such as heat capacity and thermal conductance for the device and subtract. From the estimated values a prediction of the real laser temperature response is obtained directly from the measurements realized in the substrate. (© 2005 by Astro, Ltd. Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source] Subtraction of scattering parameters for small-signal modulation characteristics of laser diodeLASER PHYSICS LETTERS, Issue 4 2005S. J. Zhang Abstract An extended subtraction method of scattering parameters for characterizing laser diode is proposed in this paper. The intrinsic response is extracted from the measured transmission coefficients of laser diode, and the parasitics of packaging network and laser chip are determined from the measured reflection coefficient of laser diode simultaneously. It is shown that the theories agree well with the experimental results. (© 2005 by Astro, Ltd. Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source] Rubidium spectroscopy at 778,780 nm with a distributed feedback laser diodeLASER PHYSICS LETTERS, Issue 2 2005S. Kraft Abstract We have performed high resolution spectroscopy of rubidium with a single mode continuous wave distributed feedback (DFB) laser diode. The saturation spectrum of the D2 -line of 85Rb and 87Rb was recorded with a resolution close to the natural line width. The emission frequency was actively stabilized to Doppler-free transitions with a relative accuracy of better than 7 parts in 109 using commercially available servo devices only. An output power of 80 mW was sufficient to allow for two-photon spectroscopy of the 5S-5D-transition of 87Rb. Further, we report on the spectral properties of the DFB diode, its tuning range and its frequency modulation properties. The line width of the diode laser, determined with high resolution Doppler free two photon spectroscopy, was 4 MHz without applying any active stabilization techniques. For time scales below 5 ,s the line width drops below 2 MHz. (© 2005 by Astro, Ltd. Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source] Continuous changes in the optical properties of liver tissue during laser-induced interstitial thermotherapyLASERS IN SURGERY AND MEDICINE, Issue 4 2001Joerg P. Ritz MD Abstract Background and Objective Laser-induced thermotherapy (LITT) is a promising treatment for irresectable liver tumors. To predict the effects of laser applications and to optimize treatment planning in LITT, it is essential to gain knowledge about light distribution in tissue, tissue optical properties (absorption, scattering, anisotropy, penetration depth), and their continuous changes during therapy. Study Design/Materials and Methods Measurements of optical properties were performed with a double integrating-sphere system and a laser diode (830 nm). Porcine liver tissue samples were examined in a native state (35°C) and after exposure to different temperatures (45°C to 80°C). Results Rising temperature was accompanied by a decrease in the absorption coefficient and anisotropy factor and an increase in the scattering coefficient. These changes were only significant in the temperature range of 50° to 65°C (P,<,0.01). The optical penetration depth decreased from 3.1mm in the native state to 1.7mm at 65°C (P,<,0.01). Above 65°, there was no significant change in the tissue optical properties. Conclusions The optical properties of liver tissue change significantly under the influence of tissue heating, resulting in a decreased optical penetration depth. These changes occur mainly in the temperature range of 50°C to 65°C, corresponding to protein denaturation. To ensure a safe and effective procedure, an adjustment of the laser power to the actual penetration depth is recommended during therapy. Lasers Surg. Lasers Surg. Med. 28:307,312, 2001. © 2001 Wiley-Liss, Inc. [source] Micro-fabrication and monitoring of three-dimensional microstructures based on laser-induced thermoplastic formationMICROSCOPY RESEARCH AND TECHNIQUE, Issue 10 2009Leyan Wang Abstract This article reports a novel laser-induced micro-fabrication method and its monitoring system for three-dimensional (3D) microstructures. The mechanism of the method is that a small zone of thermoplastic material melted by laser heating grows in liquid surrounding environment, solidifying into a convex microstructure, such as micro-dot or micro-pillar. A laser diode (808 nm) with maximum power output of 130 mW is used as power source, and a kind of paraffin mixed with stearic acid and paint serves as the thermoplastic material for 3D microstructure formation experiments. A light microscope system consisting of a charge-coupled device (CCD) and a computer is utilized to realize real-time observation of the micro-fabricating process. The distribution of local temperature rise on material surface created by laser irradiation is simulated. The effects of liquid environment on microstructure formation have been theoretically analyzed and experimentally studied. Experiments are further carried out to investigate the relationship between laser spot and fabricated microstructures. The results indicate that the widths of micro-dots or micro-pillars are mostly determined by the size of focal spot, and their heights increase with the enlargement of laser power density. With this method, a micro-dot array of Chinese characters meaning "China" has been successfully fabricated through computer programming. This method has the advantages of implementing direct, mask-less, real-time and inexpensive 3D microstructure fabrication. Therefore, it would be widely applied in the fields of micro/nano-technology for practical fabrication of different kinds of 3D microstructures. Microsc. Res. Tech., 2009. © 2009 Wiley-Liss, Inc. [source] All-optical clock division with simultaneous wavelength conversion using an optically injected Fabry-Perot laser diodeMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 10 2009Yu-Xiang Lv Abstract The authors propose and experimentally demonstrate a novel technique that uses a single Fabry-Perot laser diode (FP-LD) to perform simultaneous all-optical clock division and wavelength conversion. By utilizing the nonlinear dynamical period-one oscillation and the cross-gain modulation effect of the light injection semiconductor laser, we achieve the all optical clock frequency division of 12.36 GHz to 6.18 GHz with simultaneous wavelength conversion from 1550.24 nm to 1545.91 nm. The phase noise of the extracted optical clock is less than ,105 dBc/Hz. It was empirically found that the best clock division and wavelength conversion occurred when the injected signal power was approximately 2,2.5 times as the injected probe light power, and the range of optimum wavelength detuning was about from ,0.01 nm to 0.06 nm. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2428,2431, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24626 [source] Subtraction of scattering parameters for adiabatic intrinsic responses of semiconductor lasersMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 4 2008S. J. Zhang Abstract Thermal effects will make chip temperature change with bias current of semiconductor lasers, which results in inaccurate intrinsic response by the conventional subtraction method. In this article, an extended subtraction method of scattering parameters for characterizing adiabatic responses of laser diode is proposed. The pulsed injection operation is used to determine the chip temperature of packaged semiconductor laser, and an optimal injection condition is obtained by investigating the dependence of the lasing wavelength on the width and period of the injection pulse in a relatively wide temperature range. In this case, the scattering parameters of laser diode are measured on adiabatic condition and the adiabatic intrinsic responses of packaged laser diode are first extracted. It is found that the adiabatic intrinsic responses are evidently superior to those without thermal consideration. The analysis results indicate that inclusion of thermal effects is necessary to acquire accurate intrinsic responses of semiconductor lasers. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 992,995, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23278 [source] Double-cladding Yb3+ fiber for free-space optical communicationMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 4 2007Yong Kong Abstract The experiment result of Nd:YVO4 laser pumped by laser diode that was amplified by double-cladding Yb3+ fiber is reported. Stable mode-locking pulses are obtained at repetition rate of 320 MHz and the output power is 15 mW. When laser power is amplified by Yb3+ -doped double-cladding fiber amplifier, its power can get to 600 mW. Based on these, experiment of double-frequency is carried out, and green laser with power of 4 mW is obtained. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 889,892, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22264 [source] All-optical frequency up-conversion for WLAN over fiber applicationsMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 3 2006Y. Le Guennec Abstract This paper investigates up-conversion of a 54-Mb/s 802.11a WLAN signal in a radio-over-fiber (RoF) link. The frequency conversion is realized using either a DFB laser diode or an electro-optical modulator (EOM) (both biased in nonlinear regimes). Very low error-vector magnitude (EVM) measurements are reported at minimum of transmission of electro-optical modulator for a large 802.11a input power range, and an acceptable EVM degradation is obtained using the cost-effective LD mixing technique, but with a limited input power range. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 421,424, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21369 [source] Tunable dual-wavelength linear-cavity fiber laser by using an external injection-seeding schemeMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 5 2004Peng-Chun Peng Abstract In this paper, we propose and demonstrate a tunable dual-wavelength fiber laser by using an external injection-seeding scheme with a Fabry,Perot laser diode. The wavelength tuning range of this tunable dual-wavelength fiber laser is 12.6 nm, and the optical side-mode suppression ratio (SMSR) is more than 27 dB. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 40: 406,408, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11394 [source] Analysis and determination of coupling efficiency and misalignment tolerances between a laser diode and a conically lensed fiberMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 3 2004A. R. Faidz Abstract In this paper, we present a simple analysis, utilising the ABCD transformation matrix method, to analyze and determine the coupling efficiency and misalignment tolerances between a laser diode and a conically lensed fibre. The calculated and measured results, that is, the coupling efficiencies and transverse misalignments, were compared for microlenses etched at 20, 30, and 40 min. The calculated results agree well with the measured values. The angular misalignments are also calculated to determine their tolerances. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 40: 191,195, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11325 [source] Electrically wavelength-tunable optical short-pulse generation in a self-seeding scheme with intensity controllable feedbackMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 2 2003D. N. Wang Abstract A simple and robust system is presented to generate electrically wavelength-tunable optical short pulses from a gain-switched Fabry,Perot laser diode. The laser external cavity consists of a tunable filter and an erbium-doped fiber amplifier, which provides wavelength selectivity and intensity controllable feedback. As a result, a side mode suppression ratio SMSR of better than 30 dB over the wavelength tuning range of 17.5 nm can be obtained. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 38: 98,99, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10982 [source] High-performance UV emitter grown on high-crystalline-quality AlGaN underlying layerPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 6 2009Hirotoshi Tsuzuki Abstract Al0.25Ga0.75N films were grown on a grooved-Al0.25Ga0.75N/ AlN/sapphire template by MOVPE. The dislocation density on the grooved areas was as low as 1 × 108 cm,2. We fabricated a UVA light-emitting diode grown on such an AlGaN underlying layer exhibiting an output power of 12 mW at a DC current of 50 mA with a peak emission wavelength of 345 nm, which corresponds to an external quantum efficiency of 6.7%. This efficiency is the highest reported to date in this wavelength region. We also fabricated a 358 nm UVA laser diode (LD) using a GaN/AlGaN MQW active layer grown on an AlGaN underlying layer. This UV LD exhibits a threshold current of 73 mA and a corresponding current density of 3.8 kA/cm2 at 7 °C. The characteristic temperature T0 was 174 K in the temperature range of 7,27 °C. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Highly reliable blue-violet inner stripe laser diodes using planar regrowth of AlGaN/GaN superlattice cladding layerPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 6 2007K. Fukuda Abstract We describe highly reliable operation of a novel planar inner stripe blue-violet laser diode (BV-LD). A planar regrowth technique makes it possible to simultaneously fabricate a low-resistive superlattice (SL) structure both on the current-injecting narrow stripe area and on the AlN current-blocking layer. This allows for low operating voltage and over 1000 h stable operation at a single-mode output power of 200 mW at 80 °C. The results obtained here clearly indicate that this inner stripe laser structure is a desirable candidate for a reliable high-power light source for the next generation of optical disc systems. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Lu2O3:Yb3+ ceramics , a novel gain material for high-power solid-state lasersPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 1 2005K. Takaichi Abstract We have developed Yb3+:Lu2O3 ceramics with nanocrystalline technology and a vacuum sintering method. A laser diode end-pumped efficient Yb3+:Lu2O3 ceramic laser was demonstrated. A 0.7 W cw output power was obtained with the slope efficiency of ,36% at 1035 nm wavelength, and 0.95 W with the slope efficiency of ,53% at 1079 nm. We classify the Lu2O3:Yb3+ ceramics as gain medium for high-power solid-state lasers (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Large enhancement of GaN-UV light emission using silver mirror resonatorPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2006N. M. Ahmed Abstract In this paper we used new microcavity resonator design of extracting light with high efficiency from a high index material (GaN), n > 2 for use in light emitting diode (LED) and laser diode (LD). A GaN/sapphire structure as an active layer was sandwiched between two silver mirrors. For the study two types of microcavity were fabricated: (air/GaN/sapphire/silver) and (silver/GaN/sapphire/silver). Via photo-luminescence measurements we observed 2-fold intensity enhancement in the UV region (364 nm) at room temperature by using 400 nm silver back mirror compared with uncoated sample. The amplitude of the photoluminescence is enhanced 10-times when we used 400 nm back coated together with 50 nm silver as front mirror. Further, a tremendous enhancement was obtained when a small hole was made in the front mirror with 50 nm thickness. The large increment of GaN/sapphire light emission in this microcavity could be caused by few important factors: increasing absorption in the cavity, optical field enhancement due to the resonator and coupling of plasmon in the metallic layer with the UV light. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Thermal analysis of GaN-based laser diode packagePHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2006W. J. Hwang Abstract This paper reports on the thermal behavior of GaN-based laser diode (LD) package as functions of cool-ing systems, die attaching materials, and chip loading conditions. Thermal resistance and junction tem-perature was determined by electrical-thermal transient method. Significant change of thermal resistance with input current was observed under natural cooling condition due to the sensitive change of heat trans-fer coefficient (h ) with temperature. Employment of PbSn as a die attachment was more advantageous over Ag-paste in thermal behavior of LD package. Compare the thermal resistance of LD packages epi-down and epi-up structures. The partial thermal resistance from junction to submount is 4.68 K/W for epi-down structure, and 9.65 K/W to epi-up structure. The results demonstrate that the total thermal resistance of LD package be controlled mainly by the packaging design rather than the chip structure itself. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Analysis of self-pulsation characteristics of InGaN laser diodePHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2003V. Z. Tronciu Abstract Self-pulsation characteristics of InGaN laser diode emitting at 395 nm wavelength are investigated theoretically and experimentally. The laser structure consists of a multi-quantum well InGaN active layer and an InGaN single quantum well saturable absorber. Self-pulsations with the frequency range from 1.6 to 2.9 GHz have been obtained. The results show a good agreement between measured and calculated characteristics of self-pulsation. We also discuss the impact of the saturable absorber on the laser dynamics. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Spatially resolved X-ray diffraction as a tool for strain analysis in laterally modulated epitaxial structuresCRYSTAL RESEARCH AND TECHNOLOGY, Issue 10 2009A. Wierzbicka Abstract Spatially resolved X-ray diffraction (SRXRD) is applied for micro-imaging of strain in laterally modulated epitaxial structures. In GaAs layers grown by liquid phase epitaxial lateral overgrowth (ELO) on SiO2 -masked GaAs substrates a downward tilt of ELO wings caused by their interaction with the mask is observed. The distribution of the tilt magnitude across the wings width is determined with ,m-scale spatial resolution. This allows measuring of the shape of the lattice planes in individual ELO stripes. If a large area of the sample is studied the X-ray imaging provides precise information on the tilt of an individual wing and its distribution. In heteroepitaxial GaSb/GaAs ELO layers local mosaicity in the wing area is found. By the SRXRD the size of microblocks and their relative misorientation were analyzed. Finally, the SRXRD technique was applied to study distribution of localized strain in AlGaN epilayers grown by MOVPE on bulk GaN substrates with AlN mask. X-ray mapping proves that by mask patterning strain in AlGaN layer can be easily engineered, which opens a way to produce thicker, crack-free AlGaN layers with a higher Al content needed in GaN-based laser diodes. All these examples show that high spatial and angular resolutions offered by SRXRD makes the technique a powerful tool to study local lattice distortions in semiconductor microstructures. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Hydrogen- and carbon-related defects in heavily carbon-doped GaAs induced degradation under minority-carrier injectionELECTRONICS & COMMUNICATIONS IN JAPAN, Issue 5 2010Hiroshi Fushimi Abstract GaAs/AlGaAs heterojunction bipolar transistors (HBTs) have attracted much attention because of their high-speed performance. However, long-term operation seriously degrades the device characteristics: the current gain decreases and the low-bias-leakage current increases. This degradation has long been an issue in GaAs-based devices operated under minority-carrier injection, such as laser diodes. The cause of degradation is thought to lie in the carbon-doped base, but this is not yet certain. In this paper the degradation of HBTs is described, especially that of GaAs/AlGaAs HBTs with a heavily carbon-doped base layer. Two types of device degradation are found, namely, hydrogen-related degradation and carbon-related degradation. The mechanisms governing the degradation are discussed in the framework of the recombination-enhanced defect reaction (REDR) and charge state effect (CSE). © 2010 Wiley Periodicals, Inc. Electron Comm Jpn, 93(5): 33,41, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecj.10208 [source] Analysis of GaInAsP laser diodes degraded by light absorption at an active layer of the facetELECTRONICS & COMMUNICATIONS IN JAPAN, Issue 2 2010Hiroyuki Ichikawa Abstract Electrostatic discharge-induced degradation is one of the serious reliability problems of GaInAsP/InP laser diodes. The authors have conducted an analysis of electrostatic discharge-induced degradation, and have elucidated the principal degradation mechanism. The main cause of degradation is heating by light absorption at the active layer of the facet. This phenomenon is similar to the catastrophic optical damage that occurs in GaAs-based high-power laser diodes. The problem has become more serious with the recent tendency to high power demand. Therefore, technology to suppress against degradation is extremely important. Focusing on facet coating, which is one of the key processes to suppress facet degradation, we demonstrated that facet degradation can be successfully suppressed by inserting an ultrathin aluminum layer between the semiconductor and the dielectric coaling films. This effect is caused by a reduction of surface recombination. This degradation suppression technology has the potential to be applied not only to GaInAsP/InP laser diodes, but to any InP-based laser diodes. © 2010 Wiley Periodicals, Inc. Electron Comm Jpn, 93(2): 32,38, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecj.10196 [source] Process Chain for Tailoring the Refractive Index of Thermoplastic Optical Materials using Ceramic NanoparticlesADVANCED ENGINEERING MATERIALS, Issue 6 2005E. Ritzhaupt-Kleissl Interconnections between active optical devices like laser diodes and polymer optical fibres are a crucial factor of optical damping due to coupling losses at the interfaces. Tailoring the refractive index of thermoplastic polymers can diminish these damping losses. The use of modified thermoplastics in an injection moulding process allows a high throughput and therefore a cost effective method for manufacturing passive optical parts with improved properties. [source] Combined Optical and MR Bioimaging Using Rare Earth Ion Doped NaYF4 NanocrystalsADVANCED FUNCTIONAL MATERIALS, Issue 6 2009Rajiv Kumar Abstract Here, novel nanoprobes for combined optical and magnetic resonance (MR) bioimaging are reported. Fluoride (NaYF4) nanocrystals (20,30,nm size) co-doped with the rare earth ions Gd3+ and Er3+/Yb3+/Eu3+ are synthesized and dispersed in water. An efficient up- and downconverted photoluminescence from the rare-earth ions (Er3+ and Yb3+ or Eu3+) doped into fluoride nanomatrix allows optical imaging modality for the nanoprobes. Upconversion nanophosphors (UCNPs) show nearly quadratic dependence of the photoluminescence intensity on the excitation light power, confirming a two-photon induced process and allowing two-photon imaging with UCNPs with low power continuous wave laser diodes due to the sequential nature of the two-photon process. Furthermore, both UCNPs and downconversion nanophosphors (DCNPs) are modified with biorecognition biomolecules such as anti-claudin-4 and anti-mesothelin, and show in vitro targeted delivery to cancer cells using confocal microscopy. The possibility of using nanoprobes for optical imaging in vivo is also demonstrated. It is also shown that Gd3+ co-doped within the nanophosphors imparts strong T1 (Spin-lattice relaxation time) and T2 (spin-spin relaxation time) for high contrast MR imaging. Thus, nanoprobes based on fluoride nanophosphors doped with rare earth ions are shown to provide the dual modality of optical and magnetic resonance imaging. 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