The exploration and application of Bragg Reflector band gaps

by Dorothy Pavlidis

Publisher: National Library of Canada in Ottawa

Written in English
Published: Downloads: 648
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Edition Notes

Thesis (M.Sc.) -- University of Toronto, 1996.

SeriesCanadian theses = -- Thèses canadiennes
The Physical Object
FormatMicroform
Pagination1 microfiche : negative. --
ID Numbers
Open LibraryOL16057845M
ISBN 100612126633
OCLC/WorldCa46530236

We report the fabrication of monolithic dielectric mirrors by stacking layers of metal–organic frameworks (MOFs) and indium tin oxide (ITO). Such Hybrid Photonic Band-Gap (PBG) Materials exhibit high optical quality (reflectivities of 80%) and are color tunable over the whole visible range. While the ITO deposition is accomplished by using a conventional sputter process, the highly porous. Schematic of a 1D Bragg reflector showing in-phase and phase-shifted reflection. structure has an electromagnetic band gap which overlaps the electronic band edge, then spontaneous emission. Efficient semitransparent polymer solar cells (ST-PSCs) have been fabricated with one-dimensional photonic crystals (1DPCs) as a high reflector. The 1DPCs are composed of several pairs of WO3 ( nm)/LiF ( nm). By optimizing the pairs of WO3/LiF, 1DPCs can reflect the light back into the ST-PSCs due to the photonic band gap, when the high reflectance range of 1DPCs is matched with. Vertically oriented GaN-based air-gap distributed Bragg reflector structure fabricated using band-gap-selective photoelectrochemical etching. Appl. Phys. Lett. 87, (). Chen D. et al.. High reflectance membrane-based distributed Bragg reflectors for GaN photonics. Appl. Phys. Lett. , (). Mitsunari T. et al.

Photonic crystal cavities. Not only band gap, photonic crystals may have another effect if we partially remove the symmetry through the creation a nanosize defect allows you to guide or to trap the light with the same function as nanophotonic resonator and it is characterized by the strong dielectric modulation in the photonic crystals. For the waveguide, the propagation of light. The mode gap works as a distributed Bragg grating reflector that propagates the light-wave through the line defect waveguide, and can be used as an optical filter. The Bragg reflector is a multi-layer structure, and the high-acoustic-impedance layers and low-acoustic-impedance layers are stacked alternatively. Currently, there are many combinations of Bragg reflector (BR) layers that have been prepared and explored for different piezoelectric films. Among them, SiO 2 and W have the highest reflective.   The dark grey (light grey) layers correspond to high (low) porosity. The PBG structure with certain optical parameters can be estimated by the Bragg condition. The band gap can be simulated according to the thickness of the layers (t 1, t 2) and the corresponding refractive indices (n 1, n 2). On the other hand, a band gap with a certain.

The U.S. Department of Energy's Office of Scientific and Technical Information.   Amorphous silicon Bragg reflectors fabricated by oblique angle deposition Manipulating 3C-SiC nanowire morphology through gas flow dynamics Investigation of band-gap states in AlGaN/GaN hetero-structures with different growth conditions of GaN buffer layers Epitaxial growth and characterization of cubic GaN on BP/Si(   ZrO 2 /zircone nanolaminate thin films fabricated by atomic layer deposition were used for a distributed Bragg reflector (DBR) in green organic light-emitting diodes (OLEDs). It is found that the novel ZrO 2 /zircone DBR structure significantly improves the light purity of green OLEDs without interfering with intrinsic electroluminescence properties. The full width at half maximum (FWHM) of. Figure 3 a shows the transmission spectra of the MIM-based Bragg grating with different grating groove depth, while w 1 = w 2 = nm, n = 8 are fixed. With the depth increasing, the central wavelength displays a red shift varying from 1 μm to μm, and the band-gap gets widened dramatically.

The exploration and application of Bragg Reflector band gaps by Dorothy Pavlidis Download PDF EPUB FB2

Porous silicon is used as chirped Bragg reflector to enhance optical confinement in thin solar cell. • New design named Fermi Bragg reflector is presented. • Bragg reflector with Fermi quasi-profile is easier for fabrication. • Width of the bandgap of the chirped reflector made at low temperature reaches ~ : N.

Guermit, L. Remache, Nathalie Lorrain, Mohammed Guendouz, Joël Charrier. Abstract: Based on the coupled mode theory of the 1D coaxial Bragg structure, numerical analysis is carried out to study the band-gap peculiarity of an overmoded coaxial Bragg reflector.

Results indicate that, usually, the band-gap overlapping becomes very serious under the overmoded operation; however, it can be controlled by tuning the relative initial corrugation phase shift between Author: The exploration and application of Bragg Reflector band gaps book Lai, Shi-Chang Zhang.

We model the effects of a quasibound photonic state that can exist within a substrate/metal film/Bragg reflector/air structure. The photonic state is confined as a result of total internal reflection at the air interface coupled with the effect of the photonic band gap of the Bragg reflector.

The presence of the thin metallic film ensures that distinctive features are observable in the Cited by: The goal of this project is to grow and characterize distributed Bragg reflector (DBR) stacks with high reflectivity and conductivity, paving the way to high quality VCSELs.

These VCSELs will serve as a candidate as the light emitting elements in our Epitaxy-on. Refractive index profile (a) and photonic band structure (b) of 7DBR based Bragg reflector using plane wave method. The photonic band diagram shows the forbidden gap in the frequency range from to (in the units of ωa /2 πc) or wavelength from to nm which represents the maximum reflectance for the perpendicular polarization Cited by: 5.

Based on the coupled mode theory of the 1D coaxial Bragg structure, numerical analysis is carried out to study the band-gap peculiarity of an overmoded coaxial Bragg reflector. Results indicate that, usually, the band-gap overlapping becomes very serious under the overmoded operation; however, it can be controlled by tuning the relative initial corrugation phase shift between the outer wall.

An important potential application of integrated optic Bragg reflection is the fabrication of narrow band add-drop filters (Kashyp, Maxwell, and Ainslie ).The method is illustrated in Fig.

a (Erdogan et al. ).The waveguides form an MZ geometry with two 3-dB couplers separated by equal-length arms. V.M. Andreev, in Practical Handbook of Photovoltaics (Second Edition), Solar Cells with Internal Bragg Reflector.

The Bragg reflector (BR) made of semiconductor layers is widely used in lasers and other optical devices. By using a multiple layer composed of two materials with different refractive indices, nearly % reflectance can be achieved over a restricted wavelength range. My book has a discussion of how the Bragg model can explain the origin of energy band gaps in solid.

I have attached the relevant part of this discussion. I would very much like if someone could help me understand what it's basically trying to say. Facts: 1) In the free electron model, the eigenstates of the hamiltonian are plane waves. A thin film Bragg reflector consists of a multilayer-stack of alternate high- and low-index films, all one quarter wavelength thick (see figure right).

The geometrical thicknesses of the high- und low-index films are t H = λ/(4n H) and t L = λ/(4n L) respectively. A distributed Bragg reflector (DBR) is a reflector used in waveguides, such as optical is a structure formed from multiple layers of alternating materials with varying refractive index, or by periodic variation of some characteristic (such as height) of a dielectric waveguide, resulting in periodic variation in the effective refractive index in the guide.

Ursula Keller, in Semiconductors and Semimetals, d Saturable Bragg Reflector (SBR) An earlier version of a nonlinear or saturable Bragg reflector design was introduced by Kim et al.

().In this case the nonlinear Bragg reflector operates on saturable absorption owing to band filling in all low-index quarter-wave layers with the narrower bandgap inside the Bragg reflector.

For the first time, a mesoporous 1D photonic crystal biosensor based on periodically alternated stacks of TiO 2 and SiO 2 nanoparticles grown by wet methodologies and working as a Bragg reflector was demonstrated.

Bragg reflector photonic gap response can be tuned according to biosensing features, i.e. analytical platforms, light source wavelength or detector, by simple. A tapered-3D HWG-Bragg-reflector has been reviewed in which DGD can be tuned by varying the taper angle. The schematic side-view of tunable Bragg reflector based on a 3D HWG is shown in Fig.

5(a), in which a grove (step), of height h and width W, has been formed in a top DBR while the bottom DBR is loaded with a SiO 2 grating.

Based on the coupled mode theory of the 1D coaxial Bragg structure, numerical analysis is carried out to study the band-gap peculiarity of an overmoded coaxial Bragg reflector. (a) Projected band structure for a conventional quarter wave Bragg reflector with n l = and n h = Dotted (red) lines indicate the light line for air medium of incidence; solid (blue) lines indicate the light line for glass medium of incidence.

Brewster point can be. Although Bragg reflection exists at any number of Bragg periods, a reflector with more periods yields a lower and flatter transmission dip at the band gap.

By numerical calculation, the transmission dip at the discrete number N = 8 is %, compared with % at. The Bragg regime shifts when conventional materials in a multilayer distributed Bragg reflector (DBR) are replaced by artificial materials with the so‐called negative index of refraction.

Kuan-Chung Ting, Tzong-Jer Yang and Chien-Jang Wu, Investigation of photonic band gap in a one-dimensional lossy DNG/DPS photonic crystal, Solid State. An SiGe/Si-distributed Bragg reflector (DBR) is a key structure to realize new devices such as resonant microcavity light emitters and detectors and Fabry–Perot modulators.

To fabricate an SiGe/Si DBR with high reflectivity, however, many repetitions of thick layers are needed, since the difference in refractive indices between SiGe and Si is. In this paper, we present a new plasmonic Bragg reflector with high reflectance efficiency in the optical frequency range.

This structure is based on dielectric thickness modulation in the metal-insulator-metal (MIM) geometry which provides sub-wavelength light confinement and is suitable for high integration. We investigate and compare the performance of the presented structure with a.

A low-threshold miniaturized single-mode nanowire laser operating at telecommunication wavelengths was proposed and simulated. The device was constructed by combining a single InGaAs nanowire with a photonic crystal microcavity and asymmetric distributed-Bragg-reflector mirrors.

The mode characteristics and threshold properties were calculated using the three-dimensional finite-different. A Bragg mirror (also called distributed Bragg reflector) is a mirror structure which consists of an alternating sequence of layers of two different optical materials.

The most frequently used design is that of a quarter-wave mirror, where each optical layer thickness corresponding to one quarter of the wavelength for which the mirror is designed.

The phonon band gap for an infinitely long Bragg reflector with this parameter is shown by the horizontal line of width f gap in Fig. 1(c). A single resonant mode appears as a sharp dip at f = f C for, where the resonator mode is concentrated inside the resonator with a small penetration length as shown by trace (i) in Fig.

1(d). A distributed Bragg reflector (DBR) is a periodic structure formed from alternating dielectric layers that can be used to achieve nearly total reflection within a range of frequencies, with minimal losses. In this tutorial a Bragg reflector is modeled with a central wavelength of [nm] and stopband of [nm].

UNDERSTANDING THE COLORS OF PBG FIBERS:‐Colorful PBG Bragg fibers. a)When launching white light into the Braggfibers, after a few cm from the coupling end the fibers appear intenselycolored.

Color of an individual fiber is defined by the spectral position of thefiber reflector band gap. Periodic structures with dimensions on the order of the wavelength of light can tailor and improve the performance of optical components, and they can enable the creation of devices with new functionalities.

For example, distributed Bragg reflectors (DBRs), which are created by periodic modulations in a structure’s dielectric medium, are essential in dielectric mirrors, vertical cavity. Bragg reflector (DBR), is composed of a multilayer stack of materials with alternating high and low refractive indexes.

Applications for these structures have included lasers, [38] waveguides. Design and optimization of distributed Bragg reflector for nm vertical cavity surface emitting lasers The use of high-energy band gap materials, such as GaP, allows for applications in the. Self-organized TiO2 nanomaterials grown by anodic oxidation of Ti foils have attracted broad scientific interest due to their wide potential applications.

The majority of anodic TiO2 nanostructures studied to date are in the form of self-ordered nanotube arrays. Here we report an exotic type of multilayered nanoporous TiO2 films that are conveniently fabricated by anodizing Ti foils of high. A distributed Bragg reflector (DBR) is a high quality reflector used in waveguides, such as optical fibers.

It is a structure formed from multiple layers of alternating materials with varying refractive index, or by periodic variation of some characteristic (such as height) of a dielectric waveguide, resulting in periodic variation in the effective refractive index in the guide.

The Bragg reflector plays an important role in modern photonics because of its wide use in controllable switching, tunable polarizer, narrow-band filters, solid-state lasers, etc.

[]. The width of the omnidirectional band gaps (OBGs) plays an important role in the applications of 1D PhCs omnidirectional reflectors.A Bragg reflector composed of periodic cylindrically symmetric corrugations can provide a reflection of nearly unity through the principles of constructive interference, allowing the formation of a frequency selective resonator.

Mode conversion will occur, but can be. Silicon based devices are inexpensive due to compatible existing fabrication technology and availability of silicon in earth crust. Thin film based solar cells have disadvantage of weak absorption of long wavelength spectrum due to indirect band gap of silicon which limits their overall efficiency.

Hence, light trapping mechanism is essential for the enhancement of incident light absorption.