To Total Internal Reflection Research Articles

Efficient Redirection of Trapped Broad-Band Fluorescence from Substrates into Free Space Using c-Si Metasurfaces.

Fluorescent dye films on transparent substrates are essential for OLEDs, flexible displays, X-ray detection, and wireless optical communications. However, their efficiency is often hampered by fluorescence trapping due to total internal reflection (TIR) and waveguiding. This study tackles this longstanding challenge by reconceptualizing the integration of dye films with nanoantenna metasurfaces. Traditional methods involve directly spin-coating films onto c-Si metasurfaces on quartz substrates, resulting in edge luminescence and weak inner signals. We present a straightforward, adjustable approach by integrating dye films on the opposite side of quartz substrates, reaching a 2.5-fold photoluminescence enhancement and improving the uniformity of the emission compared to the conventional methods. These gains stem from redirecting a significant portion of leaked fluorescence light trapped inside the substrate into free space, surpassing TIR conditions through in-plane diffraction orders of the metasurfaces across the full RGB spectrum. Our findings facilitate the design of more efficient luminescent devices.

Validation of Point-of-Care Device for Rapid Detection of Salmonella enterica in Meat Products.

Accurate and rapid detection of pathogens in foods of animal origin has been a critical part of the One Health Action Plan of the European Union (EU). Biosensors have the potential in bringing required technologies to accomplish this on the field, wherein loop-mediated isothermal amplification (LAMP) and lab-on-a-chip have proven to be ideal. We have developed a LAMP-based point-of-care (POC) device, the VETPOD, as a solution to the contemporary challenges in the rapid detection of Salmonella spp. The core technology in the VETPOD is a ready-to-use cartridge that included an injection-molded polymer chip with pyramid-shaped optical structures embedded within the chip. These pyramid-shaped optical structures direct the incident light, due to total internal reflection (TIR), through the reaction chambers to the phototransistor. The VETPOD was validated against the ISO 6579-1 reference method. A total of 310 samples were tested that included 180 Salmonella spiked samples in 6 different meat categories and 130 strains to determine the specificity. The overall results were satisfactory, wherein the VETPOD had an acceptable sensitivity (96.51%) compared to the reference (98.81%) and near perfect agreement with ISO 6579-1 with an overall Cohen's kappa of 0.94. The relative level of detection (RLOD) for the VETPOD was 1.38 CFU/25 g that was found to be 1.17 times higher than the reference. The VETPOD showed 98% precision for inclusivity and 100% precision for the exclusivity samples. The VETPOD proved as a useful alternative to detect Salmonella spp. that can be adaptable to a broader spectrum of pathogens in future.

30‐3: Student Paper: Polarization State Exploration and Management in Waveguide Display with Polarization Volume Gratings

In this work, we focus on the polarization state input, propagation and output of waveguide display device using polarization volume holographic gratings (PVH) as couplers. First, a detailed study of the transmissive PVH (T‐PVH) is presented in terms of diffraction efficiency, polarization selectivity and polarization output, which is expected to be used as the waveguide input/output couplers. The configuration here called “Slanted T‐PVH” has the advantageous property of maintaining orthogonal circular output polarization states. Then, the polarization state management of light propagating in waveguide is considered. The issue that the polarization state of the light can change as it propagates in the waveguide due to total internal reflection (TIR) is made clear, that has a negative effect on the waveguide PVH input/output couplers efficiency, image uniformity, and the polarization multiplexing capability. Finally, it is shown that applying compensators to correct the polarization state change can solve the polarization state change in a waveguide.

Compensator design for polarization state management in waveguide displays based on polarization volume gratings.

In this work, we focus on the polarization state management in optical devices using optical elements based on circular polarization. As an example, we point out the issue in a waveguide display using circular polarization optical elements as input/output couplers, where the polarization state of the light can change as it propagates in the waveguide due to total internal reflection (TIR). This has a negative effect on the waveguide output coupler efficiency, image uniformity, and the polarization multiplexing capability. To address this problem, we discussed two different methods to compensate the polarization state change. With the compensator applied to correct the polarization state change in the waveguide, the optical elements based on circular polarization can be used with their advantages as input/output couplers for waveguide displays.

Scattering Effect on Optical Performance of Quantum Dot White Light-Emitting Diodes Incorporating SiO₂ Nanoparticles

The scattering effect plays an important role in improving the optical performance of the quantum dot (QD) white light-emitting diodes (LEDs). A majority of the previous studies have focused on the planar packaging structure only with respect to total internal reflection (TIR). In this study, SiO2 nanoparticles are incorporated into QD-silicone encapsulation of LEDs with semi-spherical lens packaging (SSLP) to exploit their scattering effect. The results show that the radiant efficacy (31.35%@100 mA) and luminous efficacy (87.56 lm/W@100 mA) of QD white LEDs can be optimized using SiO2 nanoparticle concentration (0.1 wt%) and that they increase by 5.04% and 11.08%, respectively, as compared to the conventional structure. A comprehensive ray-tracing simulation validates that the nanoparticles in the SSLP structure lead to severe loss of chip light. On the contrary, the fluorescence light increases due to the enhancement of conversion by QDs. The transmission electron microscopy images and the finite-difference time-domain simulation have been introduced to investigate the surface adsorption of SiO2 nanoparticle. This study indicates that SiO2 incorporation is an effective method to improve the efficiency of QD white LEDs, and provides a better understanding on the scattering effect based on TIR, color conversion, and surface adsorption.

Structured planar laser-induced fluorescence (S-PLIF) for the accurate identification of interfaces in multiphase flows

Annular flows are employed in numerous engineering and industrial processes relating to the chemical, oil and gas, solar and nuclear energy industries. Yet, the reliable and detailed (i.e., time- and space-resolved) measurement of film thickness in these flows continues to elude us, as the moving and wavy interface renders the application of optical diagnostics, such as planar laser-induced fluorescence (PLIF), particularly challenging. In this research article, we present a novel adaptation of PLIF, which we refer to as structured PLIF (S-PLIF), which can suppress the errors in PLIF-derived film thickness measurements that arise due to total internal reflection (TIR) of the emitted fluorescence at the phase boundary. The proposed measurement approach relies on the periodic modulation of the laser-light intensity and angled illumination of the examined region of the flow, in order to generate fluorescence images with alternating bright and dark regions at an angle to the channel wall and film interface. An image-processing methodology capable of recovering the location of the true gas-liquid interface from such images is presented, and the application of S-PLIF is demonstrated in liquid films in a vertical pipe over the Reynolds number range ReL≈150−1500. The results from this technique are compared to simultaneously recovered, “conventional” (uncorrected) PLIF data, as well as data from other techniques over the same range of conditions, demonstrating the efficacy of S-PLIF. A comparison amongst S-PLIF data obtained with the observation angle between the laser-sheet plane and the camera’s observation axis set to β=70∘ and 90 ∘ is also performed, showing that the employment of β=70∘ is highly advantageous in avoiding distortions caused by optical interactions of the emitted fluorescence at the free surface of circumferentially non-uniform films. The instantaneous and average film-thickness uncertainties of S-PLIF are estimated to be below 10% and 5%, respectively, when measuring smooth films; an improvement over the other optical measurement techniques considered in this work. Finally, the application of S-PLIF is demonstrated in the presence of a gas-shear flow with gas entrainment in the liquid, and simultaneously with particle image velocimetry (PIV).

Anomalous Brewster effect and evanescent modes at an achiral/chiral dielectric boundary under planar electromagnetic propagation

ABSTRACTFresnel coefficients are examined for electromagnetic (EM) propagation across an achiral/chiral (ACC) boundary. It is found that upon both transmission and reflection, the incident plane (specifically perpendicularly or s-polarized) wave transforms into two modes (right circular polarization (RCP) and left circular polarization (LCP)), propagating non-collinearly and collinearly for the transmitted and reflected modes respectively. This paper focuses on certain anomalous properties pertinent to the chirality itself which provide novel insights into chiral materials. Thus, it is found that the Brewster effect manifests itself anomalously in this chiral scenario within specific ‘bands’ of the (dimensionless) chirality coefficient (). Thus, under appropriate chirality, the Brewster angle (θB) and the reflection coefficient profile may be adjusted via tuning, resulting in zero or low reflections under any linear s polarization. The paper also highlights anomalies relative to total internal reflection (TIR), non-complementarity, mode evanescence, and also possible effective negative-index-like behaviour in the chiral material.

Effect of periodic array on the on-state resistances of GaAs photoconductive semiconductor switch based on total reflection theory

GaAs-based 5-mm-gap photoconductive semiconductor switches (PCSSs), with a thickness of 1 mm, are fabricated. A 60° beveling angle is used to make a periodic array of grooves on the surface of GaAs by mechanical processing. The laser beam should be reflected back when a vertical laser is illuminated on these grooves according to total internal reflection (TIR), which leads to an improvement of the light use efficiency (LUE) for the PCSS. The on-state resistance, ranging from 5.17 Ω to 2.14 Ω for the PCSSs, decreases in proportion with an increase of the duty cycle from 0% to 87.8%, where the pulse laser energy is 6.1 mJ at 1064 nm.

A PHOTONIC CRYSTAL FIBER BASED ON SURFACE PLASMON RESONANCE TEMPERATURE SENSOR WITH LIQUID CORE

A Photonic Crystal Fiber based on Surface Plasmon Resonance (PCF-SPR) temperature sensor with liquid core is proposed in this paper. Glycerin liquid with a high refractive index is filled in the central air hole of the hollow core photonic bandgap (PBG) PCF, the transmission type of PCF will change to total internal reflection (TIR), which will significantly broaden its transmission bands. The refractive index of glycerin changes with temperature within a certain temperature range and can be detected by measuring the transmission spectra, thus the accurate ambient temperature can be obtained. Numerical results indicate that the plasmon on the surface of the gold-coated channels containing glycerin liquid can be intensively excited by the core-guided mode and the excitation of the plasmon mode is sensitive to the change of the temperature. Resolution of the PCF-SPR temperature sensor with liquid core is demonstrated to be as low as 4 × 10-6 RIU, where RIU means refractive index unit.

Light extraction beyond total internal reflection using one-dimensional plasmonic crystals

We demonstrate the application of plasmonic crystals for extracting light trapped in the substrate due to total internal reflection (TIR). The broadband transmission properties of one-dimensional plasmonic crystals have been investigated, both experimentally and numerically, beyond the TIR critical angle in order to reveal the role of plasmonic modes in this process. Through optimisation of the traditional square slit unit cell geometry of the crystals, transmission coefficients of up to 47% were obtained in the TIR regime. An U-shaped cell geometry with a few nm thick continuous film was found to significantly modify the plasmonic modes of the crystal in addition to exhibiting highly tuneable, structurally dispersive transmission peaks, further increasing transmission in the TIR regime up to 56%. Such structures exhibit better than glass transparency at the design wavelength when integrated over all incident angles.

Resolution of the photon scanning tunneling microscope: influence of physical parameters

The photon scanning tunneling microscope (PSTM) is the photon analogue of the electron scanning tunneling microscope (ESTM). It uses the evanescent field due to total internal reflection (TIR) of a light beam in a prism modulated by a sample placed on the base of the prism. Our experimental results shown details which present a lateral size as small as 200 Å. The PSTM axial resolution is more difficult to evaluate. It is a function of the roughness of the sample. For very smooth samples, images shown an axial resolution of about 10 Å. At last we discuss how both lateral and axial resolution can be affected by several parameters such as the tip surface distance and the roughness of the sample itself. This paper shows the necessity to find for each sample a good working distance where the profile follows as close as possible the shape of the sample.