Bragg Reflectors (bragg + reflector)

Distribution by Scientific Domains

Kinds of Bragg Reflectors

  • distributed bragg reflector


  • Selected Abstracts


    The experimental study of a polarization orthogonal single-longitudinal-mode distributed Bragg reflector fiber laser

    MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 6 2008
    Luo Jian-Hua
    Abstract In this article, we reported a polarization orthogonal single-longitudinal-mode distributed Bragg reflector (DBR) fiber laser. The laser operated robustly in single longitudinal mode and dual polarizations with frequency difference of 976.93 MHz. This laser has simple structure as well as frequency adjustable. It can be used in a wide range of communication, sensor, and spectroscopic applications. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1658,1660, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23454 [source]


    Low thermal resistance, high-speed 980 nm asymmetric intracavity-contacted oxide-aperture VCSELs

    PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 7 2009
    Y. M. Song
    Abstract We demonstrated high-speed characteristics of an oxide-aperture vertical-cavity surface-emitting laser (VCSEL) with intracavity structures for both p- and n-contacts, based on InGaAs/GaAs multiple quantum wells operating at , , 980 nm, indicating a low thermal resistance (Rth). The asymmetric current injection scheme is employed for reducing current crowding around the rim of the oxide aperture. A high aluminium content undoped Al0.88Ga0.12As and GaAs distributed Bragg reflector (DBR) mirror is used for efficient heat dissipation. The VCSEL with a 7 ,m oxide aperture exhibited an output power of 2.5 mW and a threshold current of 0.8 mA with a slope efficiency of 0.39 mW/mA at 20 °C under continuous-wave operation and it still worked with 1.3 mW at 90 °C. The temperature tuning coefficient of 0.081 nm/°C and dissipated electrical power tuning coefficient of 0.104 nm/mW were observed, leading to a low Rth of 1.28 °C/mW. A high modulation bandwidth up to 13 GHz with a modulation current efficiency factor of 6.1 GHz/mA1/2 was achieved. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Reflectance and photoluminescence studies of InGaN/GaN multiple-quantum-well structures embedded in an asymmetric microcavity

    PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 7 2006
    D. Y. Lin
    Abstract Using reflectance (R) and photoluminescence (PL) measurements InGaN/GaN multiple-quantum-well (MQW) structures embedded in an asymmetric microcavity with different thickness of stacking pairs have been studied. The asymmetric microcavity structures are composed of a cavity sandwitched between the air/semiconductor interface and a mirror using distributed Bragg reflector (DBR). For the DBR with thinner AlN layers the high-reflectivity stop band locates at higher photon energy. The luminescence efficiency and the spectrum of InGaN/GaN multiple-quantum-well structures will be modified by the microcavity. A comparison of PL with R spectra shows that the emission efficiency can be enhanced by matching up the luminescence spectrum coming from the MQW and the high-reflectivity stop band. From the blue shift of the cavity modes as a function of incident angles the refractive index and cavity length can be determined. By measuring the PL spectra as a function of emission angle, it is found that the PL spectra were predominatly determined by microcavity resonances. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    The influence of aluminum composition of AlxGa1,xAs in distributed Bragg reflector on surface morphology

    PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 12 2004
    B. Kim
    Abstract Surface morphology of the AlGaAs/GaAs Vertical Cavity Surface Emitting Laser (VCSEL) grown by metalorganic vapor phase epitaxy (MOVPE) was investigated using atomic force microscopy. It is shown that the morphology of the structure strongly depends on the aluminum composition of the low Al content layer of distributed Bragg reflector (DBR) pairs and epi thickness. Whereas a high Al content layer in DBRs had little effect on the surface morphology, it was attributed that the influence of Al composition on the morphology of AlxGa1,xAs on GaAs was stronger in the range of 0 < x < 0.5 than 0.5 < x < 1. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Effects of the artificial Ga-nitride/air periodic nanostructures on current injected GaN-based light emitters

    PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2005
    Bei Zhang
    Abstract In this report, III-nitride/air deeply etched one-dimensional (1D) distributed Bragg reflector (DBR) stacks and two-dimensional (2D) photonic octagonal quasi-crystals (8PQCs) were formed on the GaN-based light emitters by focused Ga ion beam (FIB) milling. The effects of these 1D and 2D GaN/air periodic nanostructures on the properties of the GaN-based light emitters were studied by the measurements of microscopic optical reflection, flourescence, electrical luminescence and current-voltage characteristics. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Selectively Transparent and Conducting Photonic Crystals

    ADVANCED MATERIALS, Issue 5 2010
    Paul G. O'Brien
    Selectively transmissive and conductive 1D photonic crystals (PCs) are fabricated by alternately depositing sputtered ITO and spin-coated ATO nanoparticle films. These Bragg reflectors exhibit broad and intense Bragg peaks (tunable via the thickness of their ITO layers) over their stop gap but are highly transmissive over remaining spectral regions of the visible and infrared spectrum. [source]


    Stacking the Nanochemistry Deck: Structural and Compositional Diversity in One-Dimensional Photonic Crystals

    ADVANCED MATERIALS, Issue 16 2009
    Leonardo D. Bonifacio
    Abstract One-dimensional photonic structures, known as Bragg stacks or Bragg reflectors or Bragg mirrors, represent a well-developed subject in the field of optical science. However, because of a lack of dynamic tunability and their dependence on complex top-down techniques for their fabrication, they have received little attention from the materials science community. Herein, we present recent and ongoing developments on the way to functional one-dimensional photonic structures obtained from simple bottom-up techniques. We focus on the versatility of this new approach, which allows the incorporation of a wide range of materials into photonic structures. [source]


    Structural and Electric Properties of Sol,Gel-Derived Ba0.9Sr0.1TiO3 Multilayers

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 4 2007
    X. K. Hong
    Crack-free Ba0.9Sr0.1TiO3 (BST) and Mn-doped Ba0.9Sr0.1TiO3 (BSTM) multilayers with thickness over 2 ,m have been prepared by chemical solution deposition based on one single precursor. Both multilayers exhibit good performance as Bragg reflectors. Mn doping tends to suppress the leakage current in BST multilayers effectively by smoothing the layers and the reduction of the charge carries. The Mn-doped BST multilayer displays an excellent ferroelectric property, with an average remnant polarization (Pr+,Pr,)/2 of 12.69 ,C/cm2 and an average coercive field (E+,E,)/2 of about 72.95 kV/cm under an applied field of 440 kV/cm. [source]


    Optimization of Bragg reflectors in AlGaAs/GaAs VCSELs

    LASER PHYSICS LETTERS, Issue 5 2005
    V. M. N. Passaro
    Abstract In this paper a detailed investigation of the distributed Bragg reflectors in GaAs-based vertical cavity surface emitting lasers is presented. The influence of layer doping concentration, number of periods, oxide aperture and AlxGa1,xAs alloy composition on output emission power and threshold current has been found. Both oxidized and non oxidized structures have been considered. A number of interpolation curves are extracted and presented for design and fabrication purposes. Although the results are presented for GaAs-based structures, the theoretical approach is very general. (© 2005 by Astro, Ltd. Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source]


    A novel fabrication technique of FBAR devices for mobile broadband WiMAX applications

    MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 2 2008
    Linh Mai
    Abstract In this study, we present a novel fabrication technique of FBAR devices as a feasibility study for mobile broadband WiMAX applications. This novel technique features the formation of very thin-film Cr adhesion layers between W and SiO2 film layers in the Bragg reflectors, particularly to enhance the adhesion in-between. As a result, the resonances were found to occur at 2.7,3.0 GHz. In addition, excellent resonance characteristics were achieved in terms of return loss and Q-factor. This finding indicates that the proposed fabrication technique can be useful for the future mobile WiMAX applications. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 375,378, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23088 [source]


    Crack free monolithic nitride vertical-cavity surface-emitting laser structures and pillar microcavities

    PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 7 2006
    Henning Lohmeyer
    Abstract We report on the successful fabrication and optical investigation of monolithicly grown GaN based vertical-cavity surface-emitting laser structures featuring quality factors of 250. Short-period AlN/InGaN superlattices are used for the low-index layers of the distributed Bragg reflectors. Pillar microcavities are realized by focused-ion-beam etching. Micro-photoluminescence measurements reveal the longitudinal and transversal mode spectra of the cavities in good agreement with theoretical calculations based on a vectorial transfer matrix method. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    GaN/air gap based micro-opto-electro-mechanical (MOEM) Fabry-Pérot filters

    PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2007
    E. Cho
    Abstract Structural and optical properties of Fabry-Pérot filters (FPFs) with GaN/air gap based distributed Bragg reflectors (DBRs) were studied. Reflectance of GaN/air gap DBRs on sapphire substrate was calculated from the standard transmission matrix method and results showed that 98% reflectance is achievable with only 3.5 pairs at a center wavelength of 450 nm. The thickness of the GaN layer and the first AlN layer was determined according to the deformation induced by the residual stress. In-plane strain corresponding to growth conditions and the thickness of the GaN epilayer was considered for this analysis. Optical tuning efficiency and spectral range were found to be 0.27 and 25 nm respectively for FPFs with GaN/air gap (322 nm/113 nm) based DBRs and a ,0/2 air resonant cavity. The calculated pull-in voltage was 1.5 V. Crack free AlN grown on GaN by in-house MOCVD showed an etching rate of 0.2 nm/min. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    (ZnSe/MgS)/ZnCdSe DBRs grown by molecular beam epitaxy using ZnS as a sulphur source

    PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 4 2006
    S. V. Sorokin
    Abstract MBE growth and study of optical and structural properties of (ZnSe/MgS)/ZnCdSe distributed Bragg reflectors with , = 520 nm and Rmax = 97% are presented. The samples were grown pseudomorphically on GaAs (001) substrate using ZnS as a sulphur source. The details of MBE growth of such structures are discussed. Scanning electron microscopy, X-ray diffraction and optical measurements demonstrate good optical and structural characteristics of the Bragg reflectors. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    High Reflectivity AlGaN/AlN DBR Mirrors Grown by PA-MBE

    PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 1 2003
    F. 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]


    Large-area epitaxial silicon solar cells based on industrial screen-printing processes

    PROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 8 2005
    Filip Duerinckx
    Abstract Thin-film epitaxial silicon solar cells are an attractive future alternative for bulk silicon solar cells incorporating many of the process advantages of the latter, but on a potentially cheap substrate. Several challenges have to be tackled before this potential can be successfully exploited on a large scale. This paper describes the points of interest and how IMEC aims to solve them. It presents a new step forward towards our final objective: the development of an industrial cell process based on screen-printing for >,15% efficient epitaxial silicon solar cells on a low-cost substrate. Included in the discussion are the substrates onto which the epitaxial deposition is done and how work is progressing in several research institutes and universities on the topic of a high-throughput epitaxial reactor. The industrial screen-printing process sequence developed at IMEC for these epitaxial silicon solar cells is presented, with emphasis on plasma texturing and improvement of the quality of the epitaxial layer. Efficiencies between 12 and 13% are presented for large-area (98,cm2) epitaxial layers on highly doped UMG-Si, off-spec and reclaim material. Finally, the need for an internal reflection scheme is explained. A realistically achievable internal reflection at the epi/substrate interface of 70% will result in a calculated increase of 3,mA/cm2 in short-circuit current. An interfacial stack of porous silicon layers (Bragg reflectors) is chosen as a promising candidate and the challenges facing its incorporation between the epitaxial layer and the substrate are presented. Experimental work on this topic is reported and concentrates on the extraction of the internal reflection at the epi/substrate interface from reflectance measurements. Initial results show an internal reflectance between 30 and 60% with a four-layer porous silicon stack. Resistance measurements for majority carrier flow through these porous silicon stacks are also included and show that no resistance increase is measurable for stacks up to four layers. Copyright © 2005 John Wiley & Sons, Ltd. [source]