We present a method of creation of photonic structures whose optical spectrum of the reflection coefficient has an arbitrary shape and has predetermined features. We develop an algorithm for the construction of a photonic crystal structure, perform numerical simulation of its reflection spectra, and create an experimental sample of a photonic crystal that has a spectral response corresponding to a given shape.
Abstract In photonic crystals, the propagation of light is governed by their photonic band structure, an ensemble of propagating states grouped into bands, separated by photonic band gaps. Due to discrete symmetries in spatially strictly periodic dielectric structures their photonic band structure is intrinsically anisotropic. However, for many applications, such as manufacturing artificial structural color materials or developing photonic computing devices, but also for the fundamental understanding of light-matter interactions, it is of major interest to seek materials with long range nonperiodic dielectric structures which allow the formation of isotropic photonic band gaps. Here, we report the first ever 3D isotropic photonic band gap for an optimized disordered stealthy hyperuniform structure for microwaves. The transmission spectra are directly compared to a diamond pattern and an amorphous structure with similar node density. The band structure is measured experimentally for all three microwave structures, manufactured by 3D laser printing for metamaterials with refractive index up to n=2.1. Results agree well with finite-difference-time-domain numerical investigations and a priori calculations of the band gap for the hyperuniform structure: the diamond structure shows gaps but being anisotropic as expected, the stealthy hyperuniform pattern shows an isotropic gap of very similar magnitude, while the amorphous structure does not show a gap at all. Since they are more easily manufactured, prototyping centimeter scaled microwave structures may help optimizing structures in the technologically very interesting region of infrared.
We study theoretically the band-gap structures of several types of three-dimensional photonic crystals with the fee lattice symmetry: synthetic opals, inverted yablonovite and woodpile. The samples of inverted yablonovite, inverted yablonovite with a glassy superstructure and woodpile are fabricated by two-photon polymerization through a direct laser writing technique, which allows the creation of complex three-dimensional photonic crystals with a resolution better than 100 nm. A material is polymerized along the trace of a moving laser focus, thus enabling the fabrication of any desirable three-dimensional structure by direct ''recording" into the volume of a photosensitive material. The correspondence of the structures of the fabricated samples to the expected fee lattices is confirmed by scanning electron microscopy. We discuss theoretically how the complete photonic band-gap is modified by structural and dielectric parameters. We demonstrate that the photonic properties of opal and yablonovite are opposite: the complete photonic band gap appears in the inverted opal, and direct yablonovite is absent in direct opal and inverted yablonovite. ; This work was supported by the Government of the Russian Federation (grant 074-UOl) and Russian Foundation for Basic Research (grant 14-29-10172).
Helicoidal structures of lamellae of nanofibrils constitute the cuticle of some scarab beetle; with iridescent metallic-like shine reflecting left-handed polarized light. The spectral and polarization properties of the reflected light depend on the pitch of the helicoidal structures, dispersion of effective refractive indices and thicknesses of layers in the cuticle. By modelling the outer exocuticle of the scarab beetle Cotinis mutabilis as a stack of continuously twisted biaxial slices of transparent materials, we extract optical and structural parameters by nonlinear regression analysis of variable-angle Mueller-matrix spectroscopic data. Inhomogeneities in the beetle cuticle produce depolarization with non-uniformity in cuticle thickness as the dominant effect. The pitch across the cuticle of C. mutabilis decreased with depth in a two-level profile from 380 to 335 nm and from 390 to 361 nm in greenish and reddish specimens, respectively, whereas in a yellowish specimen, the pitch decreased with depth in a three-level profile from 388 to 326 nm. ; Funding Agencies|Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University (Faculty Grant SFO-Mat-LiU) [2009-00971]
1: Modularity in Underlying Structure -- 1.1 Introduction -- 1.2 On Defining Grammatical Relations in a Modular Theory -- 1.3 What is a Lexical Entry? -- 1.4 The Organization of Argument Structure: the Thematic Hierarchy -- 1.5 Case Theory and the Lexicon -- 1.6 S and S?: Extended X-bar Theory and the Lexical Clause Hypothesis -- 1.7 Dominance, Precedence and Phrase Markers -- Notes -- 2: Syntactic Projection and Licensing -- 2.1 Preliminaries: Licensing, the UTAH, the Projection Principle and the Theta Criterion -- 2.2 X-bar Theory and the Projection of Heads -- 2.3 Licensing Non-head Daughters: Thematic Grids and Thematic Relations -- 2.4 Functional Categories and Licensing -- 2.5 Summary -- Notes -- 3: On Configurationality Parameters -- 3.1 Introduction -- 3.2 Parametric Variation in D-Structure Principles -- 3.3 What is a Nonconfigurational Language? -- 3.4 The Empirical Evidence for D-Structure Variation -- 3.5 Summary and Conclusions -- Notes -- 4: Projection, Pronouns, and Parsing in Navajo Syntax -- 4.1 Introduction -- 4.2 An Overview of Navajo Syntax and Morphology -- 4.3 Parsing, Null Arguments, and Grammatical Relations in Navajo -- 4.4 On Navajo Nominals as Adjuncts -- 4.5 Navajo Agreement and Incorporated Pronouns -- 4.6 Conclusion: Projection from the Lexicon in Navajo -- Notes -- 5: Concluding Remarks -- References -- Index of Names -- Index of Subjects.
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A compact dispersive element based on a photonic crystal with a modulated period has been experimentally demonstrated. The position of the photonic band gap of this crystal gradually shifts with depth towards long waves, so different spectral components are reflected from different depths of the structure. At inclined incidence, this provides a significant Goos-H¨anchen shift and its strong spectral dependence and contributes to the spatial separation of the spectral components.
In this article the Raman and Raman Optical Activity (ROA) spectra of a series of enantiomeric twisted anthracenes are presented. The evolution of their vibrational spectra is understood in the context of the variation of p-electron delocalization as a result of the twisting imparted by the belt structure and in terms of the modulation of the resonance Raman/ROA effects which are photonic properties also tuned by anthracene twisting. The Raman/ROA vibrational spectra are simulated by several theoretical approaches to account for their vibrational and electronic properties including the theoretical evaluation of resonance effects. We furthermore incorporate a vibrational and ROA activity dissection analysis as provided in the Pyvib2 program valid to establish correlations among vibrational modes of different molecules with different electronic structures and equivalent vibrational dynamics. This paper is one of the very first attempts to use ROA spectroscopy in p-conjugated molecules with twisted and helical morphologies that contrast with the well-known cases of ROA studies of chiral helicenes in which the impact of p-electron delocalization in the electronic/photonic/vibrational (Raman/ROA) spectra is negligible. ; Funding for open access charge: Universidad de Málaga. We thank MINECO/FEDER of the Spanish Government (project reference PGC2018-098533-B-100) and the Junta de Andalucía, Spain (UMA18FEDERJA057). We also thank the vibrational spectroscopy unit of the Research Central Services (SCAI) of the University of Ma´laga. O. G. acknowledges support from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program (grant agreement no. 850836, ERC Starting Grant ''PolyHelix'')
A review on all-fiber lasers based on photonic crystal fibers is presented. Photonic crystal fibers present improved features beyond what conventional optical fibers can offer. Due to their geometric versatility, photonic crystal fibers can present special properties and abilities which can lead to enhanced lasing structures. A brief description of photonic crystal fibers and fiber laser's properties is presented. All-fiber laser structures developed using photonic crystal fibers are described and divided in two groups, depending on the cavity topology: ring cavity fiber lasers and linear cavity fiber lasers. All-fiber lasers applications in the photonic crystal fiber related sensing field are described. ; The authors are grateful to the Spanish government project TEC2010-20224-C02-01 and the European project ECOAL-MGT – SUDOE Program.
[EN] Periodic photonic configurations as photonic crystals (PhCs) and subwavelength grating (SWG) waveguides are gaining a renewed interest for the development of biosensing structures. By performing a proper design, these periodic configurations allow a significant sensitivity increase while keeping a compact footprint, what is achieved by exploiting concepts such as the slow-wave effect, the increase of the light-matter overlap or the interference of dispersion engineered modes. ; These results were achieved thanks to the funding received from the European Union (ICT-644242-SAPHELY, PHC634013-PHOCNOSIS and the operational program of the European Regional Development Fund (FEDER) of the Valencia Regional Government 2014¿2020), the Spanish Government (TEC2015-63838-C3-1-R-OPTONANOSENS and PID2019-106965RB-C21-PHOLOW), the Generalitat Valenciana (AVANTI/2019/123, ACIF/2019/009 and PPC/2020/037), the Universitat Politècnica de València (PAID-01-17, PAID-01-18 and OCUSENSOR). ; García-Rupérez, J.; Torrijos-Morán, L.; Gómez-Gómez, MI.; Martinez-Perez, P.; Ponce-Alcántara, S. (2021). High performance photonic biosensors based on periodic configurations. SPIE. 1-6. https://doi.org/10.1117/12.2576401 ; S ; 1 ; 6
Certain bird species have evolved spectacular colors that arise from organized nanostructures of melanin. Its high refractive index (similar to 1.8) and broadband absorptive properties enable vivid structural colors that are nonsusceptible to photo-bleaching. Mimicking natural melanin structural coloration could enable several important applications, in particular, for non-iridescent systems with colors that are independent of incidence angle. Here, we address this by forming melanin photonic crystal microdomes by inkjet printing. Owing to their curved nature, the microdomes exhibit noniridescent vivid structural coloration, tunable throughout the visible range via the size of the nanoparticles. Large-area arrays (>1 cm(2)) of high-quality photonic microdomes could be printed on both rigid and flexible substrates. Combined with scalable fabrication and the nontoxicity of melanin, the presented photonic microdomes with noniridescent structural coloration may find use in a variety of applications, including sensing, displays, and anticounterfeit holograms. ; Funding Agencies|Wenner-Gren Foundation; Swedish Research CouncilSwedish Research Council; Knut and Alice Wallenberg foundationKnut & Alice Wallenberg Foundation; Swedish Foundation for Strategic researchSwedish Foundation for Strategic Research; Linkoping University; Wallenberg Wood Science Center the Wallenberg Wood Science Centre; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University (Faculty Grant SFO-Mat-LiU) [2009 00971]
