Pore Etching in Compound Semiconductors for the Production of Photonic Crystals

2002 ◽  
Vol 722 ◽  
Author(s):  
Helmut Foell ◽  
Sergiu Langa ◽  
Juergen Carstensen ◽  
Marc Christophersen ◽  
Ivan Tiginyanu ◽  
...  
Keyword(s):  
Photonic Crystals ◽  
Current Flow ◽  
Three Dimensional ◽  
Perfect Crystal ◽  
Self Organization ◽  
Strong Tendency ◽  
Ordered Arrays ◽  
Self Organized ◽  
First Results ◽  
Made In

AbstractOrdered arrays of pores in Si provided the first (two dimensional) photonic crystals with bandgaps in the μm region. The paper explores the potential of pore etching for two- and threedimensional photonic crystals in GaAs, InP, and GaP. A striking feature of pore etching in III-V semiconductors is the strong tendency to self-organization and pattern formation. As an example, self-organized well-defined pore lattices (a = 100 nm – 1 μm) can be made in InP. All materials show self organized diameter oscillations, often synchronized over large distances between pores. Extremely strong diameter oscillations are observed in GaAs. Pores in all materials tend to grow in <111> directions, but can be induced to grow in the direction of current flow, too. These features can be used to produce two- and three dimensional photonic crystals. The latter goal might be achieved by switching periodically between different pore morphologies with depth, or by modulating the diameter with depth - always helped by the tendency to self organization. Self organization, however, will not lead to perfect crystal structures; lithographically defined nucleation is needed and has been tried. First results show that there are pronounced differences to what is known from Si. While the production of externally defined photonic crystals in the sub μm region appears to be feasible, the strong tendency to self organization must be taken into account by matching internal time and length scales to the desired external ones.

Two- and Three-Dimensional Photonic Crystals Built with VLSI Tools

MRS Bulletin ◽  
2001 ◽  
Vol 26 (8) ◽  
pp. 627-631 ◽  
Author(s):  
Shawn-Yu Lin ◽  
J.G. Fleming ◽  
E. Chow
Keyword(s):  
Photonic Crystal ◽  
Photonic Crystals ◽  
Integrated Circuit ◽  
Three Dimensional ◽  
Photonic Devices ◽  
Processing Technology ◽  
Photonic Crystal Slabs ◽  
The Creation ◽  
On Chip ◽  
Made In

The drive toward miniature photonic devices has been hindered by our inability to tightly control and manipulate light. Moreover, photonics technologies are typically not based on silicon and, until recently, only indirectly benefited from the rapid advances being made in silicon processing technology. In the first part of this article, the successful fabrication of three-dimensional (3D) photonic crystals using silicon processing will be discussed. This advance has been made possible through the use of integrated-circuit (IC) fabrication technologies (e.g., very largescale integration, VLSI) and may enable the penetration of Si processing into photonics. In the second part, we describe the creation of 2D photonic-crystal slabs operating at the λ = 1.55 μm communications wavelength. This class of 2D photonic crystals is particularly promising for planar on-chip guiding, trapping, and switching of light.

scholarly journals Three-Dimensional Reconstruction and Morphologic Measurements of Human Embryonic Hearts: A New Diagnostic and Quantitative Method Applicable to Fetuses Younger than 13 Weeks of Gestation

2005 ◽  
Vol 8 (4) ◽  
pp. 463-473 ◽  
Author(s):  
Jean-Marc Schleich ◽  
Jean-Louis Dillenseger ◽  
Laurence Loeuillet ◽  
Jacques-Philippe Moulinoux ◽  
Claude Almange
Keyword(s):  
Cardiac Development ◽  
Three Dimensional ◽  
Optical Microscope ◽  
Cardiac Volume ◽  
3 Dimensional ◽  
Dimensional Reconstruction ◽  
First Results ◽  
Made In

Improvements in the diagnosis of congenital malformations explain the increasing early termination of pregnancies. Before 13 weeks of gestation, an accurate in vivo anatomic diagnosis cannot currently be made in all fetuses with current imaging instrumentation. Anatomopathologic examinations remain the gold standard to make accurate diagnoses, although they reach limits between 9 and 13 weeks of gestation. We present the first results of a methodology that can be applied routinely, using standard histologic section, thus enabling the reconstruction, visual estimate, and quantitative analysis of 13-week human embryonic cardiac structures. The cardiac blocks were fixed, embedded in paraffin, and entirely sliced by a microtome. One of 10 slices was topographically colored and digitized on an optical microscope. Cardiac volume was recovered by semiautomatic realignment of the sections. Another semiautomatic procedure allowed extracting and labeling of cardiac structures from the volume. Structures were studied with display tools, which disclosed the internal and external cardiac components and enabled determination of size, thickness, and precise positioning of ventricles, atria, and large vessels. This pilot study confirmed that a new 3-dimensional reconstruction and visualization method enables accurate diagnoses, including in embryos younger than 13 weeks. Its implementation at earlier stages of embryogenesis will provide a clearer view of cardiac development.

scholarly journals High-energy angle resolved reflection spectroscopy on three-dimensional photonic crystals of self-organized polymeric nanospheres

2008 ◽  
Vol 16 (2) ◽  
pp. 897 ◽  
Author(s):  
S. Schutzmann ◽  
I. Venditti ◽  
P. Prosposito ◽  
M. Casalboni ◽  
M. V. Russo
Keyword(s):  
Photonic Crystals ◽  
Three Dimensional ◽  
High Energy ◽  
Reflection Spectroscopy ◽  
Self Organized ◽  
Polymeric Nanospheres

Other topics

2018 ◽  
Author(s):  
Ted Janssen ◽  
Gervais Chapuis ◽  
Marc de Boissieu
Keyword(s):  
Photonic Crystals ◽  
Crystal Morphology ◽  
Three Dimensional ◽  
Icosahedral Quasicrystal ◽  
Crystal Surfaces ◽  
Decagonal Quasicrystal ◽  
System A ◽  
Fundamental Law ◽  
Quasiperiodic Systems ◽  
Aperiodic Crystals

The law of rational indices to describe crystal faces was one of the most fundamental law of crystallography and is strongly linked to the three-dimensional periodicity of solids. This chapter describes how this fundamental law has to be revised and generalized in order to include the structures of aperiodic crystals. The generalization consists in using for each face a number of integers, with the number corresponding to the rank of the structure, that is, the number of integer indices necessary to characterize each of the diffracted intensities generated by the aperiodic system. A series of examples including incommensurate multiferroics, icosahedral crystals, and decagonal quaiscrystals illustrates this topic. Aperiodicity is also encountered in surfaces where the same generalization can be applied. The chapter discusses aperiodic crystal morphology, including icosahedral quasicrystal morphology, decagonal quasicrystal morphology, and aperiodic crystal surfaces; magnetic quasiperiodic systems; aperiodic photonic crystals; mesoscopic quasicrystals, and the mineral calaverite.

scholarly journals Self-replication of a quantum artificial organism driven by single-photon pulses

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Daniel Valente
Keyword(s):  
Self Assembly ◽  
Artificial Life ◽  
Single Photon ◽  
Self Organization ◽  
Physical Systems ◽  
Self Organized ◽  
Living Organisms ◽  
A Chain ◽  
Thermodynamic Mechanism ◽  
Self Replication

AbstractImitating the transition from inanimate to living matter is a longstanding challenge. Artificial life has achieved computer programs that self-replicate, mutate, compete and evolve, but lacks self-organized hardwares akin to the self-assembly of the first living cells. Nonequilibrium thermodynamics has achieved lifelike self-organization in diverse physical systems, but has not yet met the open-ended evolution of living organisms. Here, I look for the emergence of an artificial-life code in a nonequilibrium physical system undergoing self-organization. I devise a toy model where the onset of self-replication of a quantum artificial organism (a chain of lambda systems) is owing to single-photon pulses added to a zero-temperature environment. I find that spontaneous mutations during self-replication are unavoidable in this model, due to rare but finite absorption of off-resonant photons. I also show that the replication probability is proportional to the absorbed work from the photon, thereby fulfilling a dissipative adaptation (a thermodynamic mechanism underlying lifelike self-organization). These results hint at self-replication as the scenario where dissipative adaptation (pointing towards convergence) coexists with open-ended evolution (pointing towards divergence).

scholarly journals Magnetotelluric study in the Los Lagos Region (Chile) to investigate volcano-tectonic processes in the Southern Andes

2021 ◽  
Vol 73 (1) ◽  
Author(s):  
Maria Jose Segovia ◽  
Daniel Diaz ◽  
Katarzyna Slezak ◽  
Felipe Zuñiga
Keyword(s):  
Electrical Resistivity ◽  
Three Dimensional ◽  
Phase Changes ◽  
Fault System ◽  
Electrical Anisotropy ◽  
Mountain Range ◽  
Southern Andes ◽  
Nazca Plate ◽  
First Results ◽  
Dimensional Parameters

AbstractTo analyze the process of subduction of the Nazca and South American plates in the area of the Southern Andes, and its relationship with the tectonic and volcanic regime of the place, magnetotelluric measurements were made through a transversal profile of the Chilean continental margin. The data-processing stage included the analysis of dimensional parameters, which as first results showed a three-dimensional environment for periods less than 1 s and two-dimensional for periods greater than 10 s. In addition, through the geomagnetic transfer function (tipper), the presence of structural electrical anisotropy was identified in the data. After the dimensional analysis, a deep electrical resistivity image was obtained by inverting a 2D and a 3D model. Surface conductive anomalies were obtained beneath the central depression related to the early dehydration of the slab and the serpentinization process of the mantle that coincides in location with a discontinuity in the electrical resistivity of a regional body that we identified as the Nazca plate. A shallow conductive body was located around the Calbuco volcano and was correlated with a magmatic chamber or reservoir which in turn appears to be connected to the Liquiñe Ofqui fault system and the Andean Transverse Fault system. In addition to the serpentinization process, when the oceanic crust reaches a depth of 80–100 km, the ascending fluids produced by the dehydration and phase changes of the minerals present in the oceanic plate produce basaltic melts in the wedge of the subcontinental mantle that give rise to an eclogitization process and this explains a large conductivity anomaly present beneath the main mountain range.

scholarly journals Travelling colourful patterns in self-organized cellulose-based liquid crystalline structures

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Pedro E. S. Silva ◽  
Ricardo Chagas ◽  
Susete N. Fernandes ◽  
Pawel Pieranski ◽  
Robin L. B. Selinger ◽  
...  
Keyword(s):  
Simple Model ◽  
Temporal Variation ◽  
Liquid Crystalline ◽  
Diffusion Mechanism ◽  
Reaction Diffusion ◽  
Self Organization ◽  
Spatial And Temporal Variation ◽  
Living Matter ◽  
Equilibrium Conditions ◽  
Self Organized

AbstractCellulose-based systems are useful for many applications. However, the issue of self-organization under non-equilibrium conditions, which is ubiquitous in living matter, has scarcely been addressed in cellulose-based materials. Here, we show that quasi-2D preparations of a lyotropic cellulose-based cholesteric mesophase display travelling colourful patterns, which are generated by a chemical reaction-diffusion mechanism being simultaneous with the evaporation of solvents at the boundaries. These patterns involve spatial and temporal variation in the amplitude and sign of the helix´s pitch. We propose a simple model, based on a reaction-diffusion mechanism, which simulates the observed spatiotemporal colour behaviour.

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