A5111939438- Semiconductor Quantum Structures and Devices
- Photonic and Optical Devices
- Semiconductor Lasers and Optical Devices
- Advanced Semiconductor Detectors and Materials
- Optical Network Technologies
- Semiconductor materials and devices
- GaN-based semiconductor devices and materials
- Advanced Photonic Communication Systems
- Fiber-reinforced polymer composites
- Graphite, nuclear technology, radiation studies
- Graphene research and applications
- Photonic Crystals and Applications
- Surface Roughness and Optical Measurements
- Adaptive optics and wavefront sensing
- Chalcogenide Semiconductor Thin Films
- Crystallization and Solubility Studies
- Optical Polarization and Ellipsometry
- Advanced Fiber Laser Technologies
- Optical measurement and interference techniques
- Phase-change materials and chalcogenides
- Molecular Junctions and Nanostructures
- Advancements in Battery Materials
- Optical Wireless Communication Technologies
- Semiconductor materials and interfaces
- Advanced Fiber Optic Sensors
Forestry Commission England
2024
The Tavistock and Portman NHS Foundation Trust
2024
Temple Group (United Kingdom)
2023
Imperial College London
1979-2007
University College London
1988-2005
Imperial Valley College
2005
University of Bristol
2003
University of Oxford
1994-1999
Brooke
1995
University of London
1988-1992
Abstract Electron and X-ray diffraction studies have identified three metastable phases in 1T TaS2. Extra reflexions are interpreted as arising from charge density waves coupled to periodic distortions modulating a trigonal lattice. These incommensurate with the matrix 1T1 1T2, but form commensurate super-lattice 1T3. Within temperature dependence of wave vector is correlated change cross-section Fermi surface, while diffuse scattering which accompanies discrete discussed an image this...
The progressive intercalation of graphite by potassium has been studied x-ray diffraction methods. It established that graphites stages 4, 3, 2 and 1 (with intercalated layers separated respectively) can be formed successively within a single sample encapsulated with excess potassium. Each stage was prepared in turn adjusting the temperature difference between specially designed double furnace. layer stacking sequences repeat distances for 2, 3 4 are AB| BC| CA| A c =26·2 5 Å ABA| ACA| 24·2...
Abstract Diffraction studies have enabled the deformation structure of 1T TaS2to be interpreted in terms charge density waves arising from a Kohn anomaly. There is good agreement between observed periodicity lattice distortion and value predicted Fermi surface based on recent band calculations.
The c/a ratios of the hexagonal AlN and BeO structures show that they do not have a regularly tetrahedral distribution bonds. structural details been studied by x-ray analysis are discussed in relation to concepts electronegativity electroneutrality atoms. This gives basis for an understanding wurtzite zinc blende lattices binary compounds group III/V II/VI elements.
Studies of the x-ray diffraction pattern from different potassium graphites have shown that intercalation graphite by is accompanied an expansion carbon layers. This uniform within a single layer and constant for all n layers separating successive intercalate in stagen compound composition C12nK (n > 1). Preferred values C-C bond length stages 1 to 6, derived value a-axis parameter extrapolated θ = 90° are:
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTThe Crystal Structure of Sodium OxalateG. A. Jeffrey and G. S. ParryCite this: J. Am. Chem. Soc. 1954, 76, 21, 5283–5286Publication Date (Print):November 1, 1954Publication History Published online1 May 2002Published inissue 1 November 1954https://pubs.acs.org/doi/10.1021/ja01650a007https://doi.org/10.1021/ja01650a007research-articleACS PublicationsRequest reuse permissionsArticle Views560Altmetric-Citations81LEARN ABOUT THESE METRICSArticle Views...
We report the demonstration of a high-contrast (> 100:1), low-voltage multiple quantum well reflection modulator. The performance is achieved by using resonantly-enhanced electroabsorption in GaAs wells embedded spacer region an asymmetric Fabry-Pérot cavity, which at same time pin diode. Optimum contrast observed ≃860nm with only 9 V bias and ≈3.5dB insertion loss.
Experimental results are presented which suggest that the probability distribution of fluctuations in intensity laser light propagating through atmospheric turbulence reasonably well described by K distributions intermediate range propagation path lengths, L ≃ 600 m, β0≃1–2, where mean square fluctuation 〈I2〉 /〈I〉2 can be as high five.
The authors present a simple computer model for the electric field dependence of absorption semiconductor multiple-quantum-well (MQW) structure that will be used to optimize performance MQW modulators. This has been compared spectra derived from photocurrent measurements on GaAs/(GaAl)As p-i-n diode and it found well-established Stark shifts exciton subband continua energies are significantly overestimated. might linked uncertainty in knowing fields over wells; if drop 1.4 V somewhere device...
The first page of this article is displayed as the abstract.
Using synthetic near-ideal graphite obtained by hot-pressing and annealing pyrolytic material, we have prepared nitrates from the first to fourth sequence, under controlled conditions. For sequence compound, present determinations on form I (room temperature) agree with previous publications confirm stacking A | . Form sequences 2, 3 4 show well defined of networks, characterized X-ray methods as follows: network stacking* system unit cell (Å) space group 2 AB BC CA rhombohedral a H = 2⋅46 R...
Line-of-sight free-space optical links can provide extremely high bandwidth communications, but this usually requires that transmitter and receiver are precisely aligned. In order to allow terminals be mobile, must able track users within their field of view so the link is maintained. There various means do this, all require complex subsystems with a number different optical, optoelectronic, electrical components. A solid-state tracking architecture introduced seven-channel system...
Abstract We report measurements of the statistical properties intensity fluctuations in a He/Ne laser beam which had propagated 1·125 km through earth's atmosphere. The size was such that as spherical wave, and atmospheric conditions most were made 'saturation' region (β0 ∼ 1-4). found (1) variance considerably larger than previously reported for plane wave propagation, (2) probability distribution derived moments close to K-distribution its moments. origin significance propagation is...
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We have modelled the properties of a multiple quantum well pin diode optical modulator with natural semiconductor reflectivity (R ≈ 0.3) at its front surface and high reflector 0.95), such as an integrated quarterwave stack, back. By using resonant electroabsorption, rather than electrorefraction, our calculations show that it is possible to achieve contrast ratios over 200, less 3dB insertion loss.
Abstract Moments and the first order probability density function of intensity in a speckle pattern are considered as spectral bandwidth incident light. It is shown that standard deviation generally depends on surface roughness diffuser, position measurement far field. Numerical results given for diffuser with Gaussian distribution height limited by circular aperture. Exact approximate forms discussed. The analysis applies when fluctuations optical path greater than maximum wavelength incident.
Single crystals of pure potassium cyanide, and cyanide containing various amounts sodium in solid solution, have been subjected to cyclic temperature changes traversing the thermaltransformation at around — 110 °C. By means Laue Bragg photographs, persistence crystal axes has observed a ‘normal cycle’ high → low high, but metastable form was also produced by particular sequence changes. There considerable hysteresis transformation single crystals. Introducing lattice disturbances...
Intercalated layers of alkali metals in C24Rb and C24Cs are disordered (liquid-like) at room temperature but undergo a reversible transformation to an ordered state (freeze) −114 °c −110 respectively. The origin structural differences between the form II these compounds that corresponding potassium compound, C24K, is discussed.