Characterization Of Photonic Crystals Research Articles

An Exhaustive Analysis of the Characterization of Photopolymer Material (SZ2080) by Two-Photon Polymerization, Waves Moving in a Periodic Potential, and Two-Photon Absorption

This paper presents an Exhaustive Analysis of the Characterization of Photopolymer Material (SZ2080) by Two-Photon Polymerization, and some of the modern concepts like Characterization of Photonic Crystals in Photopolymer SZ2080 by Two-Photon Polymerization, Waves Moving in a Periodic Potential, and Optical Quantum metamaterials. Two-photon polymerization for fabricating three-dimensional subdiffraction-limited structures has been discussed. Experimental and Computed Curves of line thickness (nm) vs feed rate (μm/s) have been technically analyzed. Waves moving in a Periodic Potential and Photonic Crystals have been technically discussed. In addition, Optical Quantum metamaterials have been discussed in terms of quantum coherence, and quantum dots with emphasis on cavity array metamaterial.

Photonic Crystal Characterization of the Cuticles of Chrysina chrysargyrea and Chrysina optima Jewel Scarab Beetles.

A unified description involving structural morphology and composition, dispersion of optical constants, modeled and measured reflection spectra and photonic crystal characterization is devised. Light reflection spectra by the cuticles of scarab beetles (Chrysina chrysargyrea and Chrysina optima), measured in the wavelength range 300–1000 nm, show spectrally structured broad bands. Scanning electron microscopy analysis shows that the pitches of the twisted structures responsible for the left-handed circularly polarized reflected light change monotonically with depth through the cuticles, making it possible to obtain the explicit depth-dependence for each cuticle arrangement considered. This variation is a key aspect, and it will be introduced in the context of Berreman’s formalism, which allows us to evaluate reflection spectra whose main features coincide in those displayed in measurements. Through the dispersion relation obtained from the Helmholtz’s equation satisfied by the circular components of the propagating fields, the presence of a photonic band gap is established for each case considered. These band gaps depend on depth through the cuticle, and their spectral positions change with depth. This explains the presence of broad bands in the reflection spectra, and their spectral features correlate with details in the variation of the pitch with depth. The twisted structures consist of chitin nanofibrils whose optical anisotropy is not large enough so as to be approached from modeling the measured reflection spectra. The presence of a high birefringence substance embedded in the chitin matrix is required. In this sense, the presence of uric acid crystallites through the cuticle is strongly suggested by frustrated attenuated total reflection and Raman spectroscopy analysis. The complete optical modeling is performed incorporating the wavelength-dependent optical constants of chitin and uric acid.

Fabrication and Characterization of Photonic Crystals in Photopolymer SZ2080 by Two-Photon Polymerization Using a Femtosecond Laser

Two-photon polymerization (2PP) is a powerful technique in fabricating three-dimensional subdiffraction-limited structures. In this paper, 2PP was applied to generate woodpile structures, one kind of photonic crystal, using SZ2080, which is widely used in 2PP due to its negligible shrinkage. First, the relationship between scanning speed, laser power, and resolution was determined through fabricating free-hanging lines by theoretical and experimental study. Based on this relationship, woodpile structures with different period distances were fabricated with high uniformity as shown by scanning electron microscopy (SEM) images. Then optical properties of woodpile structures were investigated using Fourier transform infrared spectroscopy (FTIR) and a quantitative empirical relationship between period distance and band gaps was established. The empirical relationship can be applied to design woodpile photonic crystals for the optical sensors and filters.

Characterization of Photonic Colloidal Single Crystals by Microradian X‐ray Diffraction

Photonic crystals (PCs) can provide unprecedented control over both the emission and the propagation of light, allowing important applications in, for example, infrared telecommunications. [1–3] However, fabrication and characterization of PCs is challenging owing to the large refractive-index contrast that is needed to open up a photonic bandgap. [4] Here we demonstrate that microradian X-ray diffraction can be used to characterize various (inverse) PCs with lattice spacings as large as 1.3 lm at different stages of their fabrication. We have even fabricated non-close-packed (non-cp) PC structures by selfassembly of colloidal microspheres in an external electric field. Inverse PCs have been obtained by infiltration of the colloidal-crystal templates with amorphous silicon. The size of the colloidal particles allows us to characterize the internal 3D structure of these crystal templates in both real and reciprocal space. PCs are structures in which the refractive index varies periodically in space on a length scale comparable to the wavelength of light. [3] If the refractive-index contrast is large enough,PCs can have a photonic bandgap, which is the photonic analogue of the electronic bandgap in semiconductors. [5–7] A

Characterization of Photonic Crystals Based on Opal–Semiconductor Composites by Bragg Reflection Spectroscopy

The Bragg reflection spectra of photonic crystals based on the opal-semiconductor (GaP, GaN) composites are studied. An approach is developed which provides a means for characterizing the opal-like structures. The approach is based on examination of the Bragg reflection spectral features and of the conditions for multiwave Bragg diffraction. The shape of the Bragg spectra is analyzed in the context of the approximation of a periodic planar-layered medium taking into account sintering and axial compression of the a-SiO2 spheres that constitute the three-dimensional opal lattice. The diameters and the coefficient of compression of the spheres are determined with regard to the spectroscopic structural invariant suggested in the study for defining the conditions for observation of multiwave Bragg diffraction at the system of the {111} planes.

Fabrication and characterization of photonic crystals from colloidal processes

The self-assembly of monodispersed colloids into an ordered three-dimensional structure, i.e., the opal structure, is routinely employed to fabricate the photonic crystal. Moreover, with the aim of obtaining complete photonic band gap, inverse opal structure with better optical properties can also be formed by infiltrating nanochannels with materials of appropriate refractive index. This paper describes the preparation and characterization of opals and their consequent infiltration for forming inverse opals. First, monodisperse P(St-co-MAA) microspheres are prepared and used as building units for opal structures. The random particles self-assembled into a well-ordered structure in three dimensions for 24 h due to an enhanced-capillary-induced gathering force among the particles in system with controlled humidity. The inverse opal can then be formed by electrophoresis of silica nanoparticles 12 nm in diameter into the nanochannels, followed by subsequent calcination in air. Finally, well-formed three-dimensional porous structures consisting of interconnected close packed arrays of spherical voids are obtained. Therefore, we succeed to fabricate both the opal and inverse opal structures by the proposed capillary-enhanced method and the electrophoresis method, respectively.

Photonic crystal characterization by FDTD and principal component analysis

We demonstrate the capabilities of principal component analysis (PCA) for studying the results of finite-difference time-domain (FDTD) algorithms in simulating photonic crystal microcavities. The spatial-temporal structures provided by PCA are related to the actual electric field vibrating inside the photonic microcavity. A detailed analysis of the results has made it possible to compute the phase maps for each mode of the arrangement at their respective resonant frequencies. The existence of standing wave behavior is revealed by this analysis. In spite of this, some numerical artifacts induced by FDTD algorithms have been clearly detailed through PCA analysis. The data we have analyzed are a given set of maps of the electric field recorded during the simulation.

III-Nitride Quantum Devices—Microphotonics

Photonic devices based on III-nitrides offer benefits such as UV/blue emission, large band offsets of InN/GaN/AlN heterostructures allowing novel quantum well (QW) device design, and inherently high-emission efficiencies. Furthermore, due to their mechanical hardness and larger band gaps (when compared with conventional semiconductor devices), III-nitride-based devices may operate at much higher temperatures and voltages/power levels for any dimensional configuration and in harsher environments than other semiconductor devices and are expected to provide much lower temperature sensitivities. These are crucial advantages for many applications.Over the last decade, the physics of microsize photonic devices has been investigated. New physical phenomena and properties are expected to dominate as the device size scales down. The microsize light emitters offer benefits over edge emitters such as the ability to create arrays of individually controllable pixels on a single chip, enhanced quantum efficiency, and greatly reduced lasing threshold. Rapid progress in the area of III-nitride microphotonics has been made. The growth and fabrication of micron and submicron size photonic structures based on III-nitride wide bandgap semiconductors has been achieved, and the technology has made it possible to integrate arrays of optical elements to form active photonic-integrated devices.One example is an interconnected µ-LED with enhanced emission efficiency over the conventional LEDs for the same device area. Another example is a µ-LED array with independently addressed pixels or III-nitride microdisplay. III-nitride microdisplay may offer performance that is superior to microdisplays fabricated from liquid crystals and organic LEDs. The third example presented is III-nitride UV Focal Plane Arrays (UV-FPA) of detectors. So far, the operation of AlGaN UV-FPA with size up to 256×256 pixels with 30×30 μm2 unit cells has been demonstrated. Together with the nature of their two-dimensional array, these active micro-photonic devices show promise in many important applications, such as optical communications, signal and image processing, optical interconnects, computing, enhanced energy conversion and storage, chemical, biohazard substances, and disease detection, missile and shellfire, atmospheric ozone-level, and flame sensing.III-nitride microlens arrays have been fabricated successfully for blue and UV wavelength applications on GaN and AlN. The successful fabrication of microlens arrays based on III-nitride materials opens the possibility for monolithically integrating nitride-based micro-size photonic devices, as well as coupling light into, out of, and between arrays of III-nitride emitters and detectors, especially for short wavelengths covering the green-blue to deep UV (200 nm) region.Nanofabrication and characterization of photonic crystals with diameter/periodicity as small as 100/180 nm on InGaN/GaN MQW has been achieved. An unprecedented maximum enhancement factor of 20 was obtained under optical pumping.Single-mode ridged optical waveguide devices using GaN/AlGaN heterostructures have been designed, fabricated, and characterized for operation in 1550 nm wavelength window. The feasibility of developing novel photonic integrated circuits based on III-nitride wide bandgap semiconductors for fiber-optical communications has been investigated.

Fabrication and characterization of photonic crystals with well-controlled thickness and stop-band attenuation

Photonic crystals with stop bands located in the visible region have been fabricated by crystallizing monodispersed spherical colloids (made of polystyrene or silica) into cubic-close-packed lattices within specially designed packing cells. These crystals were oriented with their (111) planes parallel to their solid supports, and the number of these planes could be conveniently controlled from 13 to 127 layers by varying the thickness of packing cells. In accordance, the stop-band attenuation of these crystals monotonically increased from 1 to 21 dB. Our transmission spectral measurements indicated that there exists a non-linear dependence between the stop-band attenuation and the total number of (111) planes, and this dependence could be quantitatively simulated using the dynamic light scattering model or the photonic analogy to KKR method. The colloidal crystals presented here should find use as components in fabricating optical devices that include sensors, mirrors, filters, switches and waveguides.

Characterization of internal order of colloidal crystals by optical diffraction

We report the results of the optical characterization of photonic crystals consisting of close-packed arrays of polymeric monodispersed microspheres. The excellent agreement of the diffraction peak wavelengths with Bragg's law enables a precise determination of the sphere diameter. Optical diffraction is used to assess the quality of the internal order of colloidal crystals and to identify optimum growth conditions. This work leads to an estimate of the average free propagation distance of light, which is limited by incoherent scattering due to lattice imperfections, of up to 30 lattice constants.

Synthesis and characterisation of photonic crystals

The formation of two types of photonic crystal is described. Normal opal is formed by close packing of silica spheres. The synthesis of the silica spheres is described and some of the factors that influence the size of the spheres in the product are discussed. Three different methods for the preparation of close packed arrangements of the spheres are described and the photonic properties of the crystals produced are demonstrated. Inverse opal is based on a close packed array of “air” spheres in a dielectric matrix. Different methods for the formation of this ordered microporous solid based on titanium dioxide are described and the photonic properties of this material are discussed.