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High Reflectivity (high + reflectivity)
Selected AbstractsHigh Reflectivity AlGaN/AlN DBR Mirrors Grown by PA-MBEPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 1 2003F. Fedler Abstract High reflectivity (>90%) distributed Bragg reflectors (DBR) have been successfully produced utilizing the AlGaN/AlN material system. We present reflectivity and XRD data of Ga-polar AlxGa1,xN/AlN Bragg reflectors grown on sapphire. High peak reflectivities between 54% (5.5 period mirror) and 97% (25.5 period mirror) combined with large reflectivity FWHM of 30 nm have been found. All reflectors have been designed by ex-situ spectroscopic ellipsometry (SE) data of respective reference samples. [source] Formation of nitride laser cavities with cleaved facets on transferred laser diodes on GaAs substratesPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2008Wen-Chien Yu Abstract Smoothly cleaved facets with high reflectivities have been demonstrated on GaN laser diodes after the devices were transferred onto GaAs substrates. The GaN based laser diode structure was first fabricated by metal organic chemical vapor deposition (MOCVD) on c-plane sapphire substrates. The samples were then mounted onto thin GaAs substrates using wafer-bonding technology. Laser lift-off (LLO) technique was applied to remove the original sapphire substrate and transfer the GaN laser structure onto GaAs substrates. Since the cubic substrates have well-defined laser cavity cleavage facet, the GaN structures bonded onto the substrates also formed smooth facets after cleavage. The cleaved facets of GaN laser diodes have been characterized using atomic force microscopy (AFM) with less than 2 nm roughness. The present study demonstrated the feasibility of transferring GaN laser structures onto other more appealing substrates for formation of laser cavities. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Double-resonance grating mirror for polarization control in solid-state lasersLASER PHYSICS LETTERS, Issue 4 2006M. A. Ahmed Abstract The spectral width of the polarizing effect of a coupling grating on a standard quarter-wave multilayer laser mirror can be increased by applying dual-duty-cycle gratings. As an example this is discussed considering the requirements to polarize a Yb:YAG thin-disk laser. By applying dual-duty-cycle gratings the spectral tolerance can be widened by a factor of two as compared to single-duty-cycle designs and at the same time achieve a high reflectivity and low losses for the oscillating polarized laser mode. The calculations of the structures were carried out with the help of an exact modelling code based on the modal method. The code simulates the interaction of a plane electromagnetic wave with the corrugated multilayer structure to compute amplitude and power of all reflected and transmitted diffraction waves. (© 2006 by Astro, Ltd. Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source] Device characteristics and metal,dielectric high reflectivity coating analysis of ,,,,1.3,µm InGaAsP/InGaAsP MQW PBH lasersPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 1 2010J. W. Leem Abstract The cavity length-dependent characteristics of compressively strained InGaAsP/InGaAsP multiple quantum well planar buried heterostructure lasers operating at ,,,,1.3,µm were investigated under continuous-wave mode. The uncoated 600,µm long laser exhibits Pmax,=,33.6,mW and Ith,=,12.9,mA at 25,°C with d,/dT,=,0.35,nm/K and d,/dPe,=,0.044,nm/mW, leading to stable beam characteristics of 19.7° (parallel),×,24.1° (perpendicular). From the inverse slope efficiency versus cavity length plot, the loss parameters of internal differential efficiency (,i) and internal optical loss (,i) were extracted, i.e., ,i,=,78% and ,i,=,10.6,cm,1. The transparent current density of Jtr,=,0.12,kA/cm2 and modal gain of G,=,49.5,cm,1 were also estimated from cavity length-dependent threshold current density measurements. Metal,dielectric Au/Ti/SiO2 layers for high reflectivity (HR) coating were analyzed using theoretical calculations and experimental results. For the HR-coated 600,µm long laser with Au (150,nm)/Ti (5,nm)/SiO2 (250,nm), Pmax increased up to 61,mW at 25,°C with a reduced Ith of 10.6,mA compared to the uncoated laser, providing an HR of about 94%. [source] Vertical-type InGaN/GaN light emitting diodes with high efficiency reflector ITO/APC alloy on p-GaNPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7-8 2010Sung Min Hwang Abstract We demostrate the efficient p-type reflector for high performance vertical InGaN/GaN light emitting diodes (LEDs) with 1 × 1mm2 chip size. The reflector consists of Indium-Tin-Oxide (ITO) and Ag-Pd-Cu (APC) alloy. The ITO was inserted between p-GaN layer and APC alloy using RF magnetron sputtering to prevent inter-diffusion of APC into GaN layer. Transmission electron microscopy (TEM) result shows that ITO plays an impotant role as a diffusion barrier to APC alloy. In addition, the contact resistivity of ITO to p-GaN layer was measured to be 1.32 × 10 -3 ,cm2 at annealing temperature of 600 °C for 1 minute. APC alloy was adpoted to acheive a higher reflectance for improvement of a light extraction efficiency. The APC alloy reflector appeared to have a higher reflectivity compared to conventional Ni/Ag film reflector. The verical LEDs with ITO/APC alloy reflectors showed the light-output power of 295 mW at an injection current of 350 mA, which is 15% higher than that with Ni/Ag reflectors. The output power enhancement is attributed to the increase of light extraction efficiency due to high reflectivity of APC alloy (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] The fabrication of GaN-based optical cavity mirrors by focused ion beam millingPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2003Qian Ren Abstract The study of focused Ga ion beam milling for making GaN-based cavity mirrors is presented. The FIB etching rate of GaN was found to be in the rang of 0.6 ,m3/nC , 0.43 ,m3/nC. Three kinds of mirrors including polishing mirror, tilt mirror and nitride/air distributed Bragg reflection (DBR) mirror were fabricated. In particular, by using the transfer matrix method, the dependences of reflectivity and tolerance on the DBR Bragg order combination, number of DBR pair and nitride fill factor were calculated. To take trade-off between high reflectivity and enough tolerance, the combination of 3rd Bragg order of air gap and 5th Bragg order of semiconductor wall and three pairs were chosen. A deeply etched nitide/air DBR with vertical sidewall was obtained by focused Ga ion beam milling. Negative effects of the FIB on the etched GaN-based mirrors were also noticed. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | ||||||||||