Total Internal Reflection Mechanism Research Articles

Lattice Transformation-Induced Retroreflective Structural Colors.

Retroreflective structural colors can usually be achieved based on interference combined with a total internal reflection mechanism or diffraction of a monolayer hexagonal two-dimensional (2D) colloidal array. Here, a novel retroreflective structural color was generated based on a hexagonal-parallelogram lattice transformation by stretching 3D photonic crystals with nonclosely packed long-range order. Compared to previous retroreflective colors, this new retroreflective color exhibits two unique off/on color switches: (1) a strain-dependent off/on color switch along the stretching direction and (2) a sample horizontal rotation angle-dependent off/on color switch under the fixed strain. These strain-responsive retroreflective colors are ideal candidates for visually sensing kinesio tapes' strain in practical applications and anticounterfeiting. This work reveals a new structural color regulation mechanism and will advance potential applications in anticounterfeiting, sensing, displays, etc.

Highly Birefringent and Low-Loss Hollow-Core Anti-Resonant Fiber Based on a Hybrid Guidance Mechanism

A highly birefringent and low-loss hollow-core anti-resonant fiber (HC-ARF) based on a hybrid guidance mechanism is proposed and investigated by using a finite element method. The hybrid guidance mechanism is caused by the anti-resonance effect and the total internal reflection effect. The proposed HC-ARF is obtained by employing twin symmetrical and mutually tangential elliptical arc anti-resonance layers (EA-ARLs) in a conventional 8-tube HC-ARF. Because of the anti-resonance mechanism and the total internal reflection mechanism in the EA-ARL, mode coupling appears between the core mode and the cladding mode. Simulation results indicate that the proposed HC-ARF can achieve birefringence as high as 10−2 in a near-infrared range of 1400 nm to 1600 nm and a low confinement loss (CL) of 7.74 × 10−4 dB/m (9.26 × 10−4 dB/m) for x- and y-polarization components of the fundamental mode (FM) at 1550 nm. In addition, the existence of the 8-tube anti-resonance structure in the cladding significantly suppresses the CL of the x-polarization component of the FM significantly, but the impact on the CL of the y-polarization FM can be ignored, which is determined mainly by the twin EA-ARLs. Furthermore, the performance of the birefringence and CL are also investigated by changing the values of other fiber structure parameters. Our proposed structure successfully shows the ability of the hybrid guidance mechanism in the application of CL manipulation of orthogonal polarization components.

Gradients of Orientation, Composition, and Hydration of Proteins for Efficient Light Collection by the Cornea of the Horseshoe Crab.

The lateral eyes of the horseshoe crab, Limulus polyphemus, are the largest compound eyes within recent Arthropoda. The cornea of these eyes contains hundreds of inward projecting elongated cuticular cones and concentrate light onto proximal photoreceptor cells. Although this visual system has been extensively studied before, the precise mechanism allowing vision has remained controversial. Correlating high-resolution quantitative refractive index (RI) mapping and structural analysis, it is demonstrated how gradients of RI in the cornea stem from structural and compositional gradients in the cornea. In particular, these RI variations result from the chitin-protein fibers architecture, heterogeneity in protein composition, and bromine doping, as well as spatial variation in water content resulting from matrix cross-linking on the one hand and cuticle porosity on the other hand. Combining the realistic cornea structure and measured RI gradients with full-wave optical modeling and ray tracing, it is revealed that the light collection mechanism switches from refraction-based graded index (GRIN) optics at normal light incidence to combined GRIN and total internal reflection mechanism at high incident angles. The optical properties of the cornea are governed by different mechanisms at different hierarchical levels, demonstrating the remarkable versatility of arthropod cuticle.

Highly birefringent hollow-core anti-resonant terahertz fiber with a thin strut microstructure.

A novel highly birefringent and low transmission loss hollow-core anti-resonant (HC-AR) fiber with a central strut is proposed for terahertz waveguiding. To the best of our knowledge, it is the first time that a design of a highly birefringent terahertz fiber based on the hybrid guidance mechanism of the anti-resonant mechanism and the total internal reflection mechanism is provided. Several HC-AR fibers with both ultra-low transmission loss and ultra-low birefringence have been achieved in the near-infrared optical communication band. We propose a HC-AR fiber design in terahertz band by introducing a microstructure in the fiber core which leads to tremendous improvement in birefringence. Calculated results indicate that the proposed HC-AR fiber achieves a birefringence higher than 10-2 in a wide wavelength range. In addition, low relative absorption loss of 0.8% (8.6%) and negligible confinement loss of 1.69×10-4 dB/cm (9.14×10-3 dB/cm) for x-polarization (y-polarization) mode at 1THz are obtained. Furthermore, the main parameters of the fiber structure are evaluated and discussed, proving that the HC-AR fiber possesses great design and fabrication tolerance. Further investigation of the proposed HC-AR fiber also suggests a good balance between birefringence and transmission loss which can be achieved by changing strut thickness to cater numerous applications ideally.

Single mode dispersion shifted photonic crystal fiber with liquid core for optofluidic applications

Abstract An endlessly single mode defectless circular photonic crystal fiber (C-PCF) has been proposed and numerically analyzed using Full Vector Finite Element Method (FV-FEM). The central hole is infiltrated with low refractive index liquids to get zero dispersion at communication window. The fundamental mode is guided through the liquid core by total internal reflection mechanism over the desired wavelength range although the liquid has lower refractive index than silica. Dispersion has been studied thoroughly in this work for different infiltred liquids as well as for structural flexibility. The proposed structure has zero dispersion wavelength tunability over a large refractive index range from 1.34 to 1.40 of core liquid and zero dispersion wavelength has been found at 1.3 µm for liquid of refractive index 1.35. In this paper we also have reported detailed parametric studies in terms of confinement loss, effective index, and V-parameter of this proposed C-PCF.

Optical Attenuation of Linear Composites Containing SEPOF

Start Optical fibers are one category of specialty fibers originally developed for light transmission (fiber optic) and information (optical cables). The fiber consists of a core surrounded by a cladding. Standard polymer optical fiber (POF) is transferring light across its axis by the mechanism of total internal reflection. In the side emitting plastic optical fibers (SEPOF) the light leaks out from their surface. The conditions for obtaining side illumination can be derived from POF geometrical model composed of two materials with different refractive indexes. The main aim of this contribution is description of SEPOF optical properties and their efficient embedding into fibrous structures for creation of line illumination hybrid structure useful for design purposes and creation of safety textile structures with active visibility in shadows. The special device for measurement of light intensity on surface and cross section at various distances from light source is described. Light intensity of textile structures is compared with light intensity of fibers.

16.1: Invited Paper: Enhancement of optical efficiency in white OLED using a patterned quantum dot film with light recycling components

We applied the patterned QD film to white OLED displays to increase the optical efficiency by converting the unnecessary light from white OLED before being cut by color filter. The red and green patterned quantum dot (QD) film has been developed using general photolithography process. In addition, we have studied on further enhancement of optical efficiency by applying various light recycling components, such as long‐pass filter (LPF), air‐gapped bridges, and TiO2 nanoparticles. Compared with a white OLED display with only color filters (CFs), it was confirmed experimentally that the optical efficiencies of red and green light were increased up to 158% and 117% in our proposed white OLED display after applying patterned QD film with light recycling components which are based on the mechanism of total internal reflection (TIR) and scattering characteristics.

One-Way Electromagnetic Mode Guided by the Mechanism of Total Internal Reflection

One-way electromagnetic mode that is guided by the mechanism of total internal reflection (TIR) can be realized in terahertz regime. In the optical system consisting of a dielectric layer sandwiched between magnetized semiconductor and metal, the one-way TIR mode can be immune to backscattering at imperfections. This mode possesses a broad band when high-order TIR modes are suppressed in the relevant semiconductor bandgap. Furthermore, it is shown that compared with one-way surface magnetoplasmons, the one-way TIR mode can more effectively match with the fundamental mode of conventional optical waveguide.

One-way regular electromagnetic mode immune to backscattering.

In this paper, we present a basic model of robust one-way electromagnetic modes at microwave frequencies, which is formed by a semi-infinite gyromagnetic yttrium-iron-garnet with dielectric cladding terminated by a metal plate. It is shown that this system supports not only one-way surface magnetoplasmons (SMPs) but also a one-way regular mode, which is guided by the mechanism of total internal reflection. Like one-way SMPs, the one-way regular mode can be immune to backscattering, and two types of one-way modes together make up a complete dispersion band for the system.

Semiconductor-doped liquid-core optical fiber

A semiconductor liquid-core optical fiber has been made by simply filling the hollow core of a capillary waveguide with nanoparticles suspended in toluene media. Under a low continuous optical power excitation at 532 nm, the emission of PbSe particles was clearly demonstrated in the infrared region and then partially maintained in the core of the fiber by the total internal reflection mechanism. Finally, due to the guided propagation, which results in multiple absorption effects, a linear shift of the emission peak toward longer wavelengths was observed (~0.32 nm/cm). As a proof of concept, this original demonstration of visible-to-infrared conversion could lead to the development of active fibered devices at wavelengths not covered by the conventional rare-earth ion doping.

The high-transmission photonic crystal heterostructure Y-branch waveguide operating at photonic band region

We design a high-efficiency two-dimensional photonic crystal (PhC) Y-branch waveguide formed as a heterostructure with two different triangular PhCs composed of air holes. At photonic-band frequency regions corresponding to circular equifrequency surfaces, the two PhCs could be taken as effective homogeneous media with effective refractive indices. A triangular coupler composed of the PhC is designed at the input port in order to divide the incident beam into two parts. The two parts finally propagate into different channels. A case demonstrated here shows that the total transmission of light passing through the Y-branch waveguide is about 91.2%. The propagation phenomena can be explained by the mechanism of total internal reflection very well.

Dual-Channel Single-Molecule Imaging of pRNA on phi29 DNA-Packaging Motor

Bacteriophage phi29 DNA-packaging motor is geared by six packaging RNAs (pRNA). The pRNA molecules have been reported to serve as building blocks in RNA nanotechnology, and as vehicles for specific delivery of therapeutics to treat cancers and viral infections. The understanding of the 3D structure of pRNA and its location and positioning on the motor are both fundamentally and practically important. A customized single-molecule dual-color imaging system has been constructed to study the structures of pRNA molecules. The system is the combination of a low-temperature (−80 °C) sensitive electron multiplied CCD camera and the prism-type total internal reflection mechanism. A laser combiner was introduced to facilitate simultaneous dual-channel imaging. It has been applied to study the structure, stoichiometry, distance and function of the phi29 DNA packaging motor. Single molecule photobleaching analysis clarified the stoichiometry of pRNA on the motor and elucidated the mechanism of pRNA hexamer assembly. The feasibility of the single-molecule imaging system was demonstrated in single-molecule FRET studies. Distance rulers made of dual-labeled dsDNA and RNA/DNA hybrids were used to evaluate the system. The single-molecule FRET was also applied to the reconstructed the 3D structure of phi29 motor pRNA monomers and pRNA dimers. Ten pRNA monomers labeled with single donor or acceptor fluorophore at various locations were constructed, and eight partner pairs were assembled into dimers. FRET signals were detected and utilized to assess the distance between each donor/acceptor pair. The results provide the distance constraints for computer modeling of the motor. We have also re-engineered the energy conversion protein, gp16, of phi29 motor for single fluorophore labeling to facilitate the single molecule studies of motor mechanism. The potential applications of nanometer localization approaches (SHRImP and SHREC) to the study of the phi29 nanomotor were also investigated.

Overview on Solid Core Photonic BandGap Fibers

General properties of solid core photonic bandgap fibers are presented as well as general guidelines, found thanks to numerical investigations, helpful for designing this kind of fibers. We give two examples of applications and a new fiber design with interstitial air holes that lead to a significant reduction of both confinement and bend losses. This design allows the light to be guided in the fiber core thanks to a modified total internal reflection mechanism at long wavelengths and by photonic bandgap at short wavelengths. Furthermore, this new design satisfies the phase index matching condition for either second- or third-harmonic generation between two fundamental modes.

Luminescence Properties and Morphology of ZnSe:Te Films

High-speed imaging applications, such as time-resolved X-ray diffraction, require detectors with high frame rates ranging from hundreds to thousands of frames per second. New high-resolution CCD imagers capable of operating at the required frame rates have been developed; however, the current X-ray to light converters are the performance limiting factor in such applications. Here we report on the development of a structured ZnSe:Te scintillator that promises to provide extraordinarily high scintillation efficiency, emission at 640 nm (ideally suited for CCD sensors), high density of 5.4 g/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> , and a fast decay time of ~3 mus to ~50 mus with no afterglow, which permits high speed imaging without the problem of ghosting due to persistence. Furthermore, the non-hygroscopic and non-toxic nature of the ZnSe:Te scintillator, along with its stability of response over a wide range of temperatures and extremely high levels of radiation, makes it an ideal material for radiation detection in general and for synchrotron applications in particular. At RMD, we have fabricated microcolumnar ZnSe:Te films measuring ~25 mum to 85 mum in thickness using co-evaporation of ZnSe and ZnTe on suitable substrates. These films show columnar structure with columns ranging from 0.2 mum to 5 mum in diameter. The scintillation light produced by the radiation interaction is channeled within the microcolumns by the mechanism of total internal reflection, thereby providing very high spatial resolution, even when films are made thick to achieve high X-ray absorption.

Wide-band optical field concentrator for low-index core propagation

We propose a novel chirped structure consisting of a low index polymer core bounded by modulated multilayer claddings, to realize an optical field concentrator with virtually zero propagation losses in a wide spectral range, independent of wave polarization. In spite of the absence of the total internal reflection mechanism, properly designed multilayer claddings ensure the achievement of unitary transmittance in a wide spectral range, including the widely used wavelengths for optical communications. Several cladding geometries obtained by varying the thicknesses of the cladding layers are reported and discussed.

Thermal Radiative Transport Enhancement via Electromagnetic Surface Modes in Microscale Spherical Regions Bounded by Silicon Carbide

A Green function approach is used with the fluctuation-dissipation theorem to develop a qualitative theoretical model of radiation heat transfer across an evacuated microscale spherical geometry bounded by silicon carbide. The appropriate scalar Green function is presented by employing an impedance boundary condition to describe the electromagnetic spherical interface condition and thus capture the surface modes. This work shows that the spherical boundary can result in spectral conditions for surface mode excitation that depend not only on the dielectric function, but on the sphere radius as well. The surface modes are shown to enhance the radiation significantly and are attributed to surface phonon polariton modes excited at the interface, and surface modes excited by the mechanism of total internal reflection.

Photonic Crystal Fibers

Photonic crystal fibers are a new class of optical fibers. Their artificial crystal-like microstructure results in a number of unusual properties. They can guide light not only through a well-known total internal reflection mechanism but using also photonic bandgap effect. In this paper different properties possible to obtain in photonic crystal fibers are reviewed. Fabrication and modeling methods are also discussed.

Photonic Crystal Fibers: A New Class of Optical Waveguides

Remarkable properties of optical fibers with a high-index core region and a surrounding silica/air photonic crystal cladding have recently been reported. Here we discuss the physics, the special guiding properties, and the theoretical tools developed for the modeling of these photonic crystal fibers. With an emphasis on the applicational aspects of the fibers, we study their single-mode operation, bending losses, and dispersion properties. While exhibiting certain unique properties, the high-index core photonic crystal fibers share many common features with conventional optical fibers, attributed to an operation based on the well-known mechanism of total internal reflection. Fundamentally different from all high-index core fibers, in this work we demonstrate a novel type of optical waveguide, operating truly by the photonic bandgap effect. The novel fiber has an improved photonic crystal cladding and a central low-index structural defect along which the light is guided. The novel fiber has several unique features due to its different waveguidance mechanism, including remarkable dispersion properties and the potential to localize part of the guided mode in air regions. The results presented are fundamental in the field of photonic bandgap guidance, and this new class of optical waveguide is, therefore, expected to be of future interest to a large variety of research areas.

A glass spherical Cherenkov counter based on total internal reflection

We built and tested a Cherenkov counter for particle identification, with spherical shape ( R = 600 mm), made of glass. The threshold at β = 0.92 is set by the mechanism of total internal reflection of the Cherenkov light.

The role of curvature of a smooth tropospheric boundary in beyond-the-horizon radio paths

This communication deals with the reflecting behavior of one spherical concave smooth atmospheric boundary in over-the-horizon radio propagation. First, the author examines how the convergence coefficient varies as a function of the ratio of the path length to the radius of curvature of the layer under different grazing angles. Next, the influence of the curvature on the mechanism of total internal reflection, regarding a subrefractive layer, is considered. Comparison of the obtained results with those corresponding to the case of a plane interface is also discussed.