Frustrated Total Internal Reflection Research Articles

Three-dimensional polarization effects in optical tunneling.

We consider the three-dimensional (3D) polarimetric properties of an evanescent optical field excited in the gap of a double-prism system by a random plane wave. The analysis covers the case of frustrated total internal reflection (FTIR), i.e.,optical tunneling, and relies on the characteristic decomposition of the 3×3 polarization matrix. We find in particular that, for any incident partially polarized plane wave, the evanescent field inside the gap is necessarily in a nonregular, genuine 3D polarization state. We also show that the 3D polarimetric properties of the field at the second boundary are sensitive to the changes of the gap width and that the relevant effects occur for the smaller widths when the angle of incidence of the plane wave becomes larger. The results of this work uncover new aspects of the polarimetric structure of genuine 3D evanescent fields and may find applications in near-field optics and surface nanophotonics.

Validation of a portable shoe tread scanner to predict slip risk

Problem: Worn shoes are an important contributor to occupational slip and fall injuries. Tools to assess worn tread are emerging; imaging tools offer the potential to assist. The aim of this study was to develop a shoe tread scanner and evaluate its effectiveness to predict slip risk. Methods: This study analyzed data from two previous studies in which worn or new slip-resistant shoes were donned during an unexpected slip condition. The shoe tread for each shoe was scanned using a portable scanner that utilized frustrated total internal reflection (FTIR) technology. The shoe tread parameters of the worn region size (WRS) for worn shoes and total contact area for new shoes were measured. These parameters were then used to predict slip risk from the unexpected slip conditions. Results: The WRS was able to accurately predict slip risk, but the contact area was not. Discussion: These findings support that increased WRS on the shoe outsole is associated with worse slip outcomes. Furthermore, the tool was able to offer robust feedback across a wide range of tread designs, but the results of this study show that the tool may be more applicable for slip-resistant shoes that are worn compared to their new counterparts. Summary: This study shows that FTIR technology utilized in this tool may be a useful and portable method for determining slip risk for worn shoes. Practical Applications: This tool has the potential to be an efficient, objective, end-user tool that improves timely replacement of shoes and prevention of injuries.

A novel cantenna based demonstration of frustrated total internal reflection as an analog for quantum tunnelling

We use a ‘Cantenna’ (portmanteau of ‘Can’ and ‘Antenna’), which is a unidirectional homemade waveguide, coupled to a standard readily available, 2.4 GHz Wi-Fi router as a source of microwaves to demonstrate Frustrated Total Internal reflection (FTIR) using paraffin-wax prisms. This largely inexpensive experiment provides an opportunity to demonstrate a process closely analogous to quantum tunnelling in an undergraduate physics lab. FTIR is often demonstrated with glass prisms and lasers, which may not allow for an intuitive understanding of evanescent waves and tunnelling. Wi-Fi signals with a wavelength of 12.5 cm, and large maneuverable prisms, allow the length of the ‘barrier’ to be changed in a tactile way where measurements could be taken with tools available in a standard physics lab.

Coherent control of evanescent waves via beam shaping

Evanescent waves are central to many technologies such as near-field imaging that beats the diffraction limit and plasmonic devices. Frustrated total internal reflection (FTIR) is an experimental method commonly used to study evanescent waves. In this paper, we shape the incident beam of the FTIR process with a Mach–Zehnder interferometer and measure light transmittance while varying the path length difference and interferometric visibility. Our results show that the transmittance varies with the path length difference and, thus, the intensity distribution of the shaped beam. Experiment and finite element method simulation produce results that agree. We also show, through simulations, that the transmittance can be controlled via other methods of beam shaping. Our work provides a proof-of-concept demonstration of the coherent control of the FTIR process, which could lead to advancements in numerous applications of evanescent waves and FTIR.

High Resolution Interferometric Imaging of Liquid-Solid Interfaces with HOTNNET

BackgroundA variety of imaging methods are available to obtain kinematic data at an interface, with a widely varying range of spatial and temporal resolution. These methods require a trade-off between imaging rate and resolution.ObjectiveA deep learning framework trained on synchronous profilometry data acquired using two imaging modalities at two different spatial resolutions to enhance spatial resolution while maintaining temporal resolution is desired.MethodsFizeau interferometry (FIF) and frustrated total internal reflection (FTIR) are used to overcome the resolution-rate trade-off via a deep learning framework. The FTIR imaging data are recorded at high resolution, while the FIF imaging data are recorded with a lesser resolved, larger field of view. We apply a deep learning framework using a multi-layer convolutional neural network to enhance the FIF image resolution.ResultsWith the deep learning framework, we achieve the high spatial resolution of measurements obtained by FTIR imaging in all three dimensions from the lower resolution FIF data. A high-order overset technique ultimately yields full up-scaled images from the network outputs without losing precision. The accuracy of the super-resolved image is evaluated using test data.ConclusionsThis hybrid framework, called HOTNNET, is implemented in its entirety on high-speed imaging profilometry data acquired in the study of droplet impacts on a smooth, solid surface, and is used to recover full, high-resolution images at high rates by unwrapping the phase of the interferometry. This framework can be readily adapted to other paired datasets by retraining the network on the novel data.

“Tap, Tap Water”. Quantum Tunneling Demonstration

Quantum tunneling is a phenomenon in which an atom or a subatomic particle appears on the other side of a potential barrier that should be impenetrable to the particle, given the difference between the kinetic energy of the particle and the potential energy of the barrier, the former being significantly lesser. However, if the barrier shrinks enough the particle will be able to tunnel right through it. This is among the most well-known quantum physics phenomena. Historically, physicists struggled to grasp the wavelike and particle-like duality of light and subatomic particles. The aforementioned phenomenon occurs due to the wavelike behavior of photons. Quantum phenomena, such as quantum tunneling, might appear quite convoluted, therefore a simple experimental demonstration was performed to highlight the basic mechanisms of the phenomenon in a manner comprehensible to the wide masses. The demonstration, however, is just what we are in fact observing instead of quantum tunneling – “optical tunneling”, perhaps more commonly known as Frustrated Total Internal Reflection (FTIR). This mathematically analogous phenomenon serves as a mere tool for explaining quantum tunneling while aiding our understanding of it and facilitating its visualization. The experimental demonstration shall prove that quantum tunneling is a daily occurring phenomenon and that it is possible once the barrier is thin enough. If these arguments are indeed met with a successful visual demonstration a wavelike character of the photons happens to be confirmed as well.

Automated preclinical detection of mechanical pain hypersensitivity and analgesia.

The lack of sensitive and robust behavioral assessments of pain in preclinical models has been a major limitation for both pain research and the development of novel analgesics. Here, we demonstrate a novel data acquisition and analysis platform that provides automated, quantitative, and objective measures of naturalistic rodent behavior in an observer-independent and unbiased fashion. The technology records freely behaving mice, in the dark, over extended periods for continuous acquisition of 2 parallel video data streams: (1) near-infrared frustrated total internal reflection for detecting the degree, force, and timing of surface contact and (2) simultaneous ongoing video graphing of whole-body pose. Using machine vision and machine learning, we automatically extract and quantify behavioral features from these data to reveal moment-by-moment changes that capture the internal pain state of rodents in multiple pain models. We show that these voluntary pain-related behaviors are reversible by analgesics and that analgesia can be automatically and objectively differentiated from sedation. Finally, we used this approach to generate a paw luminance ratio measure that is sensitive in capturing dynamic mechanical hypersensitivity over a period and scalable for high-throughput preclinical analgesic efficacy assessment.

Microwave Soil Heating with Evanescent Fields from Slow-Wave Comb and Ceramic Applicators

Microwave soil heating deactivates weed seeds; however, in many modern agricultural settings, weed seeds are mostly found in the top 1–2 cm of the soil profile. Until recently, microwave soil heating has been achieved using various antennas, which project the microwave energy deeply into the soil. The aim of this research was to develop new microwave applicators that provide shallow heating (less than 50 mm). This paper presents two applicator designs, one based on a comb slow-wave structure and the other on the frustrated total internal reflection (FTIR) principle, which utilise evanescent microwave fields to restrict the depth of microwave heating. The background theory to their performance is presented, followed by experimental evidence of their constrained heating performance under different soil moisture scenarios. Experimental measurements of the heating performance of these applicators, in soils of varying moisture content, demonstrate that the evanescent microwave fields restrict the depth of heating, so that most of the energy is manifested in the top 50 mm of soil. The evanescent field decay rate for the FTIR applicator changes from 44.0 ± 0.7 m−1 to 30 ± 1.2 m−1 as the soil moisture changes from 32% to 174% (dry weight basis). This is higher than the evanescent field decay rate for the comb slow-wave applicator (17.6 ± 0.7 m−1 to 19.9 ± 1.5 m−1). The FTIR applicator has a wider and shallower heating pattern than the comb slow-wave applicator. Because of the double heating lobes of the FTIR applicator, the effective half temperature heating width is approximately 150 mm. This is wider than the half temperature heating width of the comb slow-wave applicator (95 mm).

Biologically Inspired Ultrathin Contact Imager for High‐Resolution Imaging of Epidermal Ridges on Human Finger

AbstractCompound eyes exhibit compelling vision schemes due to their unique visual ultrastructures. Here, a biologically inspired ultrathin contact imager (BUCI) for high‐resolution contact fingerprint imaging is reported. The BUCI contains ultrathin arrayed camera, light‐emitting diode arrays, and light guide plate (LGP). The ultrathin arrayed camera is fully packaged with microlens arrays, variable micropinhole arrays (MLA‐VMA), and a single complementary metal oxide semiconductor image sensor. The ultrathin arrayed camera shows a large field of view of 77.3° and a constant MTF50 of 89.4 cycles mm–1, relatively higher than a comparable single lens camera at the distance less than 36.8 mm. The channel images of a human fingertip are directly obtained by using frustrated total internal reflection and stitched to a single and high‐resolution full‐field image for a fingertip of 5.7 mm × 4.9 mm. The BUCI provides a new platform for high‐resolution contact imaging in biometric or healthcare applications.

Deep Contrast and Companion Detection Using the EvWaCo Test Bed Equipped with an Achromatic Focal Plane Mask and an Adjustable Inner Working Angle

Abstract The evanescent wave coronagraph uses the principle of frustrated total internal reflection (FTIR) to suppress the light coming from the star and study its close environment. Its focal plane mask is composed of a lens and a prism placed in contact with each other to produce the coronagraphic effect. In this paper, we present the experimental results obtained using an upgraded focal plane mask of the Evanescent Wave Coronagraph (EvWaCo). These experimental results are also compared to the theoretical performance of the coronagraph obtained through simulations. Experimentally, we reach a raw contrast equal to a few 10−4 at a distance equal to 3 λ/D over the full I band (λ c = 800 nm, Δλ/λ ≈ 20%) and equal to 4 λ/D over the full R band (λ c = 650 nm, Δλ/λ ≈ 23%) in unpolarized light. However, our simulations show a raw contrast close to 10−4 over the full I band and R band at the same distance, thus confirming the theoretical achromatic advantage of the coronagraph. We also verify the stability of the mask through a series of contrast measurements over a period of 8 months. Furthermore, we measure the sensitivity of the coronagraph to the lateral and longitudinal misalignment of the focal plane mask and to the lateral misalignment of the Lyot stop.

Visiflex: A Low-Cost Compliant Tactile Fingertip for Force, Torque, and Contact Sensing

We present the Visiflex, an inexpensive compliant tactile fingertip capable of contact localization and 6 degree-of-freedom (dof) contact force and torque measurement. Because manipulation of rigid or nearly-rigid objects requires compliance at the contact, we build compliance directly into the Visiflex in the form of a well-characterized 6-dof flexure between the fingertip and the base of the Visiflex. This compliance also allows the use of a 6-dof position sensor to measure forces and torques transmitted through the fingertip. The position sensor is a camera, and the same camera is used to detect contact locations on the fingertip via frustrated total internal reflection (FTIR). Our tests indicate that typical errors in contact location detection are less than 1 mm and typical errors in force sensing are less than 0.3 N. A video of the Visiflex can be found online.

Frustrated Total Internal Reflection Spectra of Diazoquinone–Novolac Photoresist Films

Radiation-induced effects in thin films of diazoquinone–novolac photoresists on silicon irradiated with high-energy electrons (~5 MeV) were investigated by frustrated total internal reflection (FTIR) IR Fourier spectroscopy. It was found that irradiation with electrons at a dose of more than 3·1015 cm–2 leads to decrease of the integral absorption at wave numbers in the region of 3700–400 cm–1. The intensity of bands due to the –O–H– and particularly aliphatic –C–H– bonds is increased most strongly during electron irradiation. At a dose of Φ = 1·1017 cm–2 the intensity of the bands due to the methylene (–CH2–) and methyl (–CH3) groups is comparable with the noise level. The intensity of the band at ~1600 cm–1, due to the vibrations of the aromatic ring, does not change at radiation doses in the range of 3·1014–1·1017 cm–2. The obtained experimental data indicate strong cross-linking of the polymeric components during irradiation with electrons. It was found that the radiation-induced changes in the FTIR spectra depend on the type of photoresist (FP9120 and S1813 G2 SP15). The experimental relationships of change in the optical characteristics of thin films of photoresists due to electrons are explained in terms of the radiation chemistry of diazoquinone–novolac resins.

3D Touch Surface for Interactive Pseudo‐Holographic Displays

Herein, the design and implementation of a transparent 3D touch‐enabled surface for richer user interaction with midair 3D virtual objects in a touch‐interactive pseudo‐holographic display are presented. Frustrated total internal reflection (FTIR)‐based touch sensing is used in combination with a four‐sided pyramidal pseudo‐holographic projection. The developed system allows gesture‐based control and smooth touch interaction through facile and inexpensive hardware and open‐source software tools. A software application is also developed as the interface between the touch/gesture‐sensing system and the optical display. By bringing the virtual and real world closer through touch‐based interaction, the presented system will enrich user experience and enable advances in areas such as education, entertainment, gaming, retail, and museums where holograms are currently used.

Splitting the bandwidth of a frustrated total internal reflection filter with nanoparticle inclusions

The frustrated total internal reflection (FTIR) spatial-frequency thin-film filter with metamaterial inclusions operating in a visible spectral range is investigated. Influence of nanoparticles embedded into a resonator layer is analyzed taking into account the frequency dispersion. Narrow band spectral lines and highly directional transmitted light beams for s- and p- polarizations are demonstrated at different values of refractive indices and thicknesses of layers. It is shown that the dispersion causes splitting of the filter bandwidth and spatial splitting of incidence beam into three angularly separated output beams. The type of thin-film filter considered should be useful in many applications, such as high-resolution spectroscopy and color imaging systems.

Calibration of Haptic Sensors Using Transfer Learning

This paper introduces a novel sensor calibration scheme, the Hybrid Analytical and Network (HAN) model, which is especially suitable for regression based on neural networks with small training datasets. Through the HAN model, qualitative physical knowledge can be used to facilitate network training so that the demand on training data can be significantly reduced. Furthermore, training results can be transferred to the calibration of other types of sensors. The HAN model has been used to calibrate two haptic sensors, namely, the balance sensor and the skin sensor, which both operate on the principle of Frustrated Total Internal Reflection (FTIR), but for two different applications. The balance sensor is designed for human balance ability assessment, while the skin sensor is designed for evaluation of human skin properties. The calibration results using the HAN model are far more accurate and faster than other neural network training methods, especially for a small experiment dataset. The strong transfer ability of the HAN model is also demonstrated by the transfer attempt from balance sensor calibration to that of the skin sensor. The HAN model provides a new method to integrate model-based and data-driven sensor calibration methods, and shows greater efficacy. Its application is not restricted to sensor calibration but has broader potential value in all neural network regression tasks.

Spin Hall effect of tunneling mode in one-dimensional photonic crystal based on frustrated total internal reflection

The spin Hall effect of light (SHEL) upon reflection and refraction of p and s waves in one-dimensional photonic crystal (1DPC) tunneling mode based on frustrated total internal reflection (FTIR) is investigated in this paper. We discuss the SHEL in three different cases based on both theoretical derivation and simulation. These results have demonstrated that the SHEL in 1DPC can be enhanced significantly when the designed 1DPC structure simultaneously satisfies both high reflection coefficient of p-wave and high transmission rate of s-wave. A transverse shift of 28.47 μm (equivalent to 45λin length) can be achieved in the structure without any amplification method, which is much larger than those previously reported in literature.

A Hidden Fingerprint Device on an Opaque Display Panel

In recent years, fingerprint recognition has become more and more widely used in mobile phones. A fingerprint recognition device hidden under an opaque display panel designed based on a waveguide and frustrated total internal reflection (FTIR) is proposed and demonstrated herein. In order to meet the demand for a high screen ratio for mobile phone displays, we use a symmetrical zoom-in and zoom-out coupler design. With this comprehensive coupler and waveguide design, not only can fingerprint recognition be achieved using an opaque display panel, but it also meets the appearance requirements for a mobile phone with a high screen ratio.

Экспресс-анализ жидких смесей методом последовательного испарения компонентов на ИК-фурье-спектрометре ФТ-801 с приставкой МНПВО

Экспресс-анализ жидких смесей методом последовательного испарения компонентов на ИК-фурье-спектрометре ФТ-801 с приставкой МНПВО

On the Design of Force Sensors Based on Frustrated Total Internal Reflection

Frustrated total internal reflection (FTIR) of light is a physical phenomenon which can be used to accomplish several measurement tasks. This paper deals with the design and modeling of pressure field or force sensors based on FTIR. In fact, it is possible to convert the value of contact pressure into a light intensity signal, owing to the frustration of reflection of a dedicated medium. In this sense, it is possible to measure pressure/forces with a camera system or a photosensitive sensor. In this paper, the physical principles of the technique are recalled. Then, an experiment will document the behavior of FTIR at micromechanical level. Consequently, a Greenwood–Williamson (GW) model is proposed as a tool to predict the response of the FTIR-based pressure sensor. Experimental data and uncertainty analysis show that the design methodology is able to predict the behavior of the sensor with an uncertainty that is about ±10% of the actual specimen response, thus providing an effective tool to optimize the FTIR experiments.

Preparation of metal-doped Cu–Mn/HTS-1 catalysts and their mechanisms in efficient degradation of toluene

In order to study their synergistic catalytic effects in toluene degradation, CuMn2O4/HTS-1 (HTS-1 was a titanium silicon molecular sieve), Cu0.7Mn2Y0.3Ox/HTS-1 and Cu0.7Mn2Ce0.3Ox/HTS-1 catalysts were prepared by the impregnation method. The textural properties, redox properties and acidity of the catalysts were characterized by X-ray diffractometer (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), H2 temperature-programmed reduction (H2-TPR), X-ray photoelectron spectroscopy (XPS), frustrated total internal reflection (FT-IR), ammonium temperature-programmed desorption (NH3-TPD) and pyridine adsorption internal reflection (Py-IR) measurements. The potential roles of Lewis acid sites (activating dioxygen) were discussed, and the experimental results indicated that the most efficient route for toluene degradation over Cu0.7Mn2Ce0.3Ox/HTS-1 (toluene conversion rate of 90% (T99)=295°C) was ascribed to regulation of the synergistic effects of redox properties (activating molecular toluene) and Lewis acid sites (activating dioxygen). The Mars–Van–Krevelen (MVK) model was adopted to describe the reaction process of toluene oxidation, which gave an in-depth view into the toluene degradation over CuMn2O4/HTS-1, Cu0.7Mn2Y0.3Ox/HTS-1 and Cu0.7Mn2Ce0.3Ox/HTS-1. In addition, the synergistic effects between redox properties and Lewis acid sites were studied in detail.