Phenomenon Of Total Internal Reflection Research Articles

Enhanced Extraction of Silicon-Vacancy Centers Light Emission Using Bottom-Up Engineered Polycrystalline Diamond Photonic Crystal Slabs

Silicon vacancy (SiV) centers are optically active defects in diamond. The SiV centers, in contrast to nitrogen vacancy (NV) centers, possess narrow and efficient luminescence spectrum (centered at ≈738 nm) even at room temperature, which can be utilized for quantum photonics and sensing applications. However, most of light generated in diamond is trapped in the material due to the phenomenon of total internal reflection. In order to overcome this issue, we have prepared two-dimensional photonic crystal slabs from polycrystalline diamond thin layers with high density of SiV centers employing bottom-up growth on quartz templates. We have shown that the spectral overlap between the narrow light emission of the SiV centers and the leaky modes extracting the emission into almost vertical direction (where it can be easily detected) can be obtained by controlling the deposition time. More than 14-fold extraction enhancement of the SiV centers photoluminescence was achieved compared to an uncorrugated sample. Computer simulation confirmed that the extraction enhancement originates from the efficient light-matter interaction between light emitted from the SiV centers and the photonic crystal slab.

A novel recurrent neural network soft sensor via a differential evolution training algorithm for the tire contact patch

In this paper we propose a novel Recurrent Neural Network Soft Sensor designed to estimate and predict the contact area that tires of a car are making with the ground. This is one of the most critical issues regarding car modelling for improving its performance. The proposed sensor is particularly useful for an active suspension because it allows its suspension to be prepared instead of reacting to a disturbance. The recurrent neural network enables the Soft Sensor to have a correct prediction of the contact area of the tire. This sensor uses data from 11 sensors mounted on the car while the tire contact patch is obtained by means of frustrated total internal reflection phenomenon. The training process of the Recurrent Neuronal Network presents several difficulties caused by the existence of spurious valleys. For this reason, we address this problem as an optimization problem, solved by using a modified differential evolution algorithm. Our Soft Sensor performance is successfully validated by physical experiments under real operation.

Transmission and reflection of vector Bessel beams through an interface between dielectrics

Simple full vectorial analytical exact results are obtained for the propagation of Bessel beams through an interface separating different media characterized by material parameters (ϵ1,μ1) and (ϵ2,μ2). A real space description is used and all the results are written in terms of the transverse wavevector kt of the incident beam, taken as an input parameter. It is shown that perfect transmissions are obtained when the incident wave is either in a medium of larger or lower index of refraction, compared to the medium of the transmitted wave, and we provide the particular values, ktF, that the transverse wavevector must obey in order to observe such effects. The phenomenon of total internal reflection is also verified for normal incidence.

Design and implementation of uniform light guide based, force and de-flection measurement device

This paper presents the investigation prepared in order to verify light guide based optical sensor for force and deformation measurements. Based on the results ob-tained during the whole period of investigation, design of prototype sample for light guide based optical sensor has to be approved, improvements based on the received re-sults included. In order to define design (geometry) a theoretical design model has been created based on Snell’s Law and Total Internal Reflection phenomenon. Based on the out-put from the theoretical investigation, a CAD model has been created. This virtual model of the sensor has been used to perform optical simulations in wide range of light guide deflection angles, to record flux changes with de-creasing the deflection angle from critical (TIR) to 30˚ by 0.5° step. After simulation is completed by reviewing simu-lation results we can confirm that the light guide based optical sensor for force and deflection measurements has linear output flux correlation with changing incidence an-gle in the range of 1˚ - 2˚. For further investigation to confirm correlation between simulation and measurement results the light guide based force and deformation measurement func-tional prototype device has been assembled.DOI: http://dx.doi.org/10.5755/j01.mech.22.4.15414

Enhancement of Light Extraction Efficiency in Organic Light Emitting Diode with Nano-Scaled Random Patterns

Fast response, true color representation, and applicability to flexible display, organic light emiting diodes (OLED) become prominent next generation display devices. However, light extraction efficiency of OLED is still limited to below 30% due to surface plasmon polaritons (SPP) and total internal reflection phenomena at each layer. In order to improve the lower value of light extraction efficiency, various works are investigated. The main reasons of trapped light inside OLED device are total internal reflection and waveguide and SPP mode. Total internal reflection effect can be decreased by application of micro-lenz array and surface scattering structures. However, the clarity of image can also be damaged as an unwanted side effect. Captured light inside the device, due to waveguide and SPP mode can be decreased by photonic crystal pattern or moth-eye pattern. In both cases, device fabrication process is the key issue.In order to fabricate highly efficient OLED display without blurring of image, nano-scaled random pattern was formed on glass substrate using direct ptinting method[1]. Nano-scaled random pattern has low haziness and smoothed curvatures on the surface. It was formed by direct printing of spin on glass (SOG)materials such as hydrogen silsesquioxane (HSQ). After proper heat treatment, HSQ becomes SiO2. Current efficiency and power efficiency of OLED, formed on glass substrate with nano-scaled random pattern, exhibit 25% and 35% increase, compared to OLED device on flat glass substrate, respectively. External quantum efficiency of OLED device on nano-patterned substrate also shows 28% of increase[1]. Keywords: optical scattering pattern, nanoimprint, OLED, light extraction efficiency

Ground-penetrating radar for observing tree trunks and other cylindrical objects

To improve forest management and to prevent collapses of trees, it is necessary to investigate the internal part of tree trunks. In order to do it non-invasively, ground-penetrating radar (GPR) appears as a promising inspection device. The objective of this paper is to investigate particularities of tree trunks radar images, considering the circumferential data acquisition geometry, as a function of the radar configuration and trunk section structures. In order to better understand this kind of data, a target reflection curve was analytically described, then, the total internal reflection (TIR) phenomenon was explained and illustrated. Subsequently, classical radar measurements were compared with an application of differently shaped (planar and circular) metal shields acting as perfect electrical conductors (PEC). For comparing the methods, three experiments were performed: (1) numerical simulations using the software gprMax2D, based on Finite-Difference Time-Domain method, (2) GPR investigation of a laboratory model of a tree trunk, (3) real tree trunk measurements. The use of a planar or circular PEC increased the visibility of the medium edges, so, these GPR images were considered of a better quality. Internal object reflection curve and TIR detection were essential for general description of a GPR image. All experiments showed satisfactorily the internal inhomogeneity and the information will be useful for future tomographic reconstruction.

A Novel Technique to Design Flat Fresnel Lens with Uniform Irradiance Distribution

In this paper, we propose a novel technique to design flat Fresnel lens to achieve big concentration ratio, high uniform irradiance distribution while keeping F-number small using both refraction and total internal reflection (TIR) phenomena. Also, this method can be used to design concentrated photovoltaic (CPV) system without secondary optics lens (SOE). In this technique, Fresnel lens is constructed by many prisms, which are built by ideal Cartesian oval. The design process of Fresnel lens was performed using Matlab program. Ray tracing technique has been used to optimize the structure of lens using LightToolsTM software. The simulation results have been shown that Fresnel lens has a good optical property such asconcentration ratio is 2500x, F-number =0.4, and high uniform irradiance distribution.

The Phenomenon of Total Internal Reflection and Acceleration of Light in Fiber Optics

Generally the light transmitted as a radiation in a certain velocity whose value depends on the type of the medium in which the transmission occurs, in fiber optics light transmits in the form of rays, and in order that the light be totally reflected, the incident angle should be greater than the critical angle so that continuous reflections would happen on the wall of the cladding inside the fiber optics. This depends on a physical phenomenon called the phenomenon of total internal reflection; the ray that enters the fiber with an angle less than the acceptance angle is reflected in an angle so that when the incident angle is change the exit angle will also be changed. When the incident angle is changed, a displacement will take place; this displacement affects the value of the exit angle, in such a case there will be a difference between the point of the incidence and the point of refraction, this difference will lead to a variance in the distance and the arrival time at the end point which is an indication of acceleration in the speed of light which will be discussed in this paper. General Terms Communication media, network signally, physics.

Method for determining the reflection-induced retardance of the Fresnel rhomb

A method used for measurement of the reflection-induced retardance of the Fresnel employing two polaroids is reported. The concept we propose is based on optimized Fresnel rhombs, using the total internal reflection phenomenon. The total internal reflection induces phase retardance between the polarization components of the incident light. The theoretical analysis of the principle is given taking Stokes–Mueller formalism as a mathematical tool. An application example of the method is shown; this method has advantages such as easy procurement of the optical devices needed and simplicity of operation.

High-efficiency fused-silica reflection grism

A fused-silica reflection grism (combination of grating and prism) based on the phenomenon of total internal reflection (TIR), and used in the -1st order, is designed and fabricated. The grism is etched directly into the fused-silica prism, which greatly facilitates the use of the TIR grating as no other angle coupling devices are involved. The grating profile is optimized by the use of the rigorous coupled-wave analysis method. Diffraction efficiency of larger than 99% at a wavelength of 980 nm for TM-polarized waves can be theoretically obtained. Two-beam interference lithography and inductively coupled plasma etching techniques are used to manufacture such grism. Diffraction efficiencies of larger than 95% are experimentally demonstrated.

Full-field refractive index measurement with simultaneous phase-shift interferometry

Using the phenomenon of total internal reflection and a beam splitting device, a technique of simultaneous phase-shift interferometry is proposed for measuring the full-field refractive index. Because this method applies a beam splitting device that mimics the characteristics of beam splitting and phase modulation, four interferemetric images of various phase distributions can be simultaneously captured. Therefore, this setup can avoid errors caused by non-simultaneous capturing of images and offers the benefits of high stability, ease of operation, and real-time measurement. Furthermore, using the phenomenon of total internal reflection, the phase difference between p- and s-polarized light varies considerably with the refractive index of a tested specimen. This can substantially increase the measurement resolution. The feasibility of this method is verified using an experiment, and the measurement resolution can be higher than 3.65×10−4RIU.

In-line characterization and identification of micro-droplets on-chip

AbstractWe present an integrated optofluidic sensor system for in-line characterization of micro-droplets. The device provides information about the droplet generation frequency, the droplet volume, and the content of the droplet. Due to its simplicity this principle can easily be implemented with other microfluidic components on one and the same device. The sensor is based on total internal reflection phenomena. Droplets are pushed through a microfluidic channel which is hit by slightly diverging monochromatic light. At the solid-liquid interface parts of the rays experience total internal reflection while another part is transmitted. The ratio of reflected to transmitted light depends on the refractive index of the solution. Both signals are recorded simultaneously and provide a very stable output signal for the droplet characterization. With the proposed system passing droplets were counted up to 320 droplets per second and droplets with different volumes could be discriminated. In a final experiment droplets with different amounts of dissolved CaCl

A proposal for digital electro-optic switches with free-carrier dispersion effect and Goos-Hanchen shift in silicon-on-insulator waveguide corner mirror

In a silicon-on-insulator (SOI) waveguide corner mirror (WCM) structure, with the quantum process of a frustrated total internal reflection (FTIR) phenomenon and the time delay principle in the two-dimensional potential barrier tunneling process of a mass of particles, we derive an accurate physical model for the Goos-Hanchen (GH) shift of optical guided-mode in the FTIR process, and in principle match the GH shift jumping states with the independent guided-modes. Then, we propose and demonstrate a new regime of 1 × N digital optical switches with a matching state between the free-carrier dispersion (FCD) based refractive index modulation (RIM) of silicon to create a GH shift jumping function of a photonic signal at the reflecting interface and the independent guided-modes in the FTIR process, where a MOS-capacitor type electro-optic modulation regime is proposed and discussed to realize an effective FCD-based RIM. At the critical matching state, i.e., the incident of an optical beam is at the vicinity of Brewster angle in the WCM, a mini-change of refractive index of waveguide material can cause a great jump of GH shift along the FTIR reflecting interface, and further a 1 × N digital optical switching process could be realized. For a 350–500 nm single-mode rib waveguide made on the 220 nm CMOS-compatible SOI substrate and with the FCD effect based RIM of silicon crystal, a concentration variation of 1018–1019 cm−3 has caused a 0.5–2.5 μm GH shift of reflected beam, which is at 2–5 times of a mode-size and hence radically convinces an optical switching function with a 1 × 3-1 × 10 scale.

Reduction of guided waves in ITO/glass interface of white organic light emitting diodes (WOLEDs): Layer optimization

In this paper, our main purpose is to reduce Total Internal Reflection (TIR) phenomenon that is happening at Indium Tin Oxide (ITO, nito=1.8+0.01i) and Glass (nglass=1.51) interface in WOLED to achieve higher output power. In normal WOLED because of higher refractive index contrast between ITO and Glass, guided waves usually limited into ITO layer and approximately 50% of generated light is trapped into ITO layer. Here, we tried to reduce this portion of trapped light by using 12-fold quasi-photonic crystal in mentioned interface. With some gentle changes in 12-folds structure, we could reduce TIR in this interface to less than 9%. Also, far field results before and after adding the structure were studied, which represents success of this idea and will open a new insight to lightning applications.

SU-E-CAMPUS-I-05: Optical Based Elastography Method for Breast Tumor Detection

Purpose: In this research, we present an optical based elastography device which can be used for practical medical diagnostic experiments for measuring stiffness and geometry of lesion. Methods: The optical elastography incorporates an optical waveguide sensing probe unit, a light source unit, a camera unit, and a computer unit. The optical method of total internal reflection phenomenon in an optical waveguide is adapted for the tissue elasticity measurement principle. The light sources are attached along the edges of the waveguide and illuminates at a critical angle to totally reflect the light within the waveguide. Once the waveguide is deformed due to the stiff inclusion, it causes the trapped light to change the critical angle and diffuse outside the waveguide. The scattered light is captured by a camera. From elastography images, we developed a novel method to estimate that size, depth, and elasticity of the embedded lesion using 3-D finite element-model-based forward algorithm, and neural-network based inversion algorithm. Results: The proposed elasticity characterization device and method were validated by the realistic tissue phantom with inclusions to emulate the tumors. The phantom was made of a silicone composite having a Youngs modulus of approximately 5kPa. The inclusion was made using another silicone composite; the stiffness of which was higher than the surrounding tissue phantom. The Youngs modulus of each inclusion was 120kPa, which is for fibrous tissue at 5% pre-compression with loading frequency of 4.0Hz. The experimental results showed that, the proposed characterization method estimated the size, depth, and Youngs modulus of a tissue inclusion within 0.16mm, 0.18mm, and 0.66kPa relative errors, respectively. Conclusion: An elastography device using the total internal reflection principle and its algorithms were designed and experimentally evaluated. The work presented in this research is the initial step towards early detection of malignant breast tumors.

An electromagnetic world without polarization

The majority of natural sources (black-bodies, fluorescent bulbs, etc) generate completely un-polarized light; the majority of detectors (eyes, photo-cameras, photomultipliers, etc) are polarization-insensitive. To reflect this, we attempt to describe approximately electromagnetic waves without polarization. Corresponding scalar equations are non-trivial modifications of standard d’Alembert and Helmholtz equations to the case of spatially inhomogeneous propagation speed . A description of Fresnel reflection (FR) and Goos–Hänchen shift for total internal reflection phenomena is given on the basis of these modified equations.

Total Internal Reflection Fluorescence (TIRF) Microscopy Illuminator for Improved Imaging of Cell Surface Events

Total internal reflection fluorescence (TIRF) microscopy is a high-contrast imaging technique suitable for observing biological events that occur on or near the cell membrane. The improved contrast is accomplished by restricting the thickness of the excitation field to over an order of a magnitude narrower than the z-resolution of an epi-fluorescence microscope. This technique also increases signal-to-noise, making it a valuable tool for imaging cellular events such as vesicles undergoing exocytosis or endocytosis, viral particle formation, cell signaling, and dynamics of membrane proteins. This protocol describes the basic procedures for setting up a through-the-objective TIRF illuminator and a prism-based TIRF illuminator. In addition, an alternate protocol for incorporating an automated deflection system into through-the-objective TIRF is given. This system can be used to decrease aberrations in the illumination field, to quickly switch between epi- and TIRF illumination, and to adjust the penetration depth during multicolor TIRF applications. In the commentary, a description of the total internal reflection phenomenon is given, critical parameters of a TIRF microscope are discussed, and technical challenges and considerations are reviewed.

Visualization of Cortex Organization and Dynamics in Microorganisms, using Total Internal Reflection Fluorescence Microscopy

TIRF microscopy has emerged as a powerful imaging technology to study spatio-temporal dynamics of fluorescent molecules in vitro and in living cells. The optical phenomenon of total internal reflection occurs when light passes from a medium with high refractive index into a medium with low refractive index at an angle larger than a characteristic critical angle (i.e. closer to being parallel with the boundary). Although all light is reflected back under such conditions, an evanescent wave is created that propagates across and along the boundary, which decays exponentially with distance, and only penetrates sample areas that are 100-200 nm near the interface. In addition to providing superior axial resolution, the reduced excitation of out of focus fluorophores creates a very high signal to noise ratios and minimizes damaging effects of photobleaching. Being a widefield technique, TIRF also allows faster image acquisition than most scanning based confocal setups. At first glance, the low penetration depth of TIRF seems to be incompatible with imaging of bacterial and fungal cells, which are often surrounded by thick cell walls. On the contrary, we have found that the cell walls of yeast and bacterial cells actually improve the usability of TIRF and increase the range of observable structures. Many cellular processes can therefore be directly accessed by TIRF in small, single-cell microorganisms, which often offer powerful genetic manipulation techniques. This allows us to perform in vivo biochemistry experiments, where kinetics of protein interactions and activities can be directly assessed in living cells. We describe here the individual steps required to obtain high quality TIRF images for Saccharomyces cerevisiae or Bacillus subtilis cells. We point out various problems that can affect TIRF visualization of fluorescent probes in cells and illustrate the procedure with several application examples. Finally, we demonstrate how TIRF images can be further improved using established image restoration techniques.

1.55 μm silicon-based reflection-type waveguide-integrated thermo-optic 2 × 2 switch

In this work a waveguide-integrated 2×2 switch operating at the infrared communication wavelength of 1550nm is proposed and theoretically discussed. The device is based on the total internal reflection (TIR) phenomenon and the thermo-optic effect (TOE) in hydrogenated amorphous silicon (a-Si:H) and crystalline silicon (c-Si). It takes advantage of a bandgap-engineered a-Si:H layer to explore the properties of an optical interface between materials showing similar refractive indexes but different thermo-optic coefficients. In particular, thanks to modern plasma-enhanced chemical vapour deposition (PECVD) techniques, the refractive index of the amorphous film can be properly tailored to match that of c-Si at a given temperature. TIR may be therefore achieved at the interface by acting on the temperature. The device is integrated in a 4μm-wide and 3μm-thick single-mode rib waveguide. The substrate is a silicon-on-insulator (SOI) wafer with an oxide thickness of 500nm. We calculated an output crosstalk always better than 24dB and insertion losses as low as 3.5dB.

Symmetry breaking of optical vortices: birth and annihilation of singularities in the evanescent field

The interaction of optical vortices (or phase singularities, or screw dislocations) with ordinary matter is treated with a simple approach. Using the total internal reflection phenomenon and the superposition of four plane waves incident on a material with a refractive index lower than the original propagating medium, we are able to show the birth and annihilation of optical vortices in an evanescent field with curved topological features. Until now, this phenomenon has been explored only in free space propagation. By a suitable tuning process involving the incident angles and the amplitudes of the incident plane waves, it is possible to create unusual topological features of optical vortices in the vicinity of the material. We believe that this work can open new aspects of curved optical vortex manipulation in near-field optics.