Multiple Total Internal Reflections Research Articles

Reflection Mechanism of Dielectric Corner Reflectors: The Role of the Diffraction of Evanescent Waves and the Goos-Hänchen Shift.

Nano- and microstructures have been developed for asymmetric light transmission (ALT) filters operating in a wide wavelength range. One of the most straightforward structures with ALT properties is a dielectric corner reflector (DCR) comprising a one-dimensional grating of a triangular shape on one surface. The DCR possesses strong reflection only for one-way light illumination due to multiple total internal reflections (TIRs) inside the triangular grating. For triangular structures being much larger than the wavelength of light, the reflection properties are expected to be fully described by geometrical optics. However, geometrical optics do not account for the Goos–Hänchen (GH) shift, which is caused by the evanescent wave of the TIR. In this work, the reflection mechanism of DCRs is elucidated using the finite element method and a quantitative model built by considering the GH shift. The reduction in reflection of the DCR is dominated by diffraction of the evanescent wave at the corner of the triangular structure. Our model is based on simple mathematics and can optimize the DCR geometry for applications addressing a wide wavelength range such as radiative cooling.

Analysis of non-idealities in rhomb compensators.

In-line rotatable rhombs that are only weakly chromatic are desired as compensators for a wide variety of applications in spectroscopic polarimetry and Mueller matrix spectroscopic ellipsometry. These devices employ multiple total internal reflections to generate differences in the phase shifts upon reflection for orthogonal fast and slow axis optical electric field components. A framework has been developed for characterization of non-idealities in the performance of rhombs due to dissipation and associated dichroism upon each reflection as well as stress-induced birefringence along each beam path. External oblique reflection measurements by spectroscopic ellipsometry for the internally reflecting interface structures has enabled characterization of the dichroic effects and retardance generated by the reflections. The framework for analysis of the effects of stress relies on simulations demonstrating that the contributions to polarization modification from each beam path depend only on the accumulated stress-induced retardance and average azimuthal angle of the fast principal stress axis along the given path. The overall approach has been applied to straight-through Mueller matrix measurements of a three-reflection rhomb in its operational configuration to establish the set of stress parameters for each of the four beam paths needed to fit the measurements. Thus, device geometry and optical structure, including layer thicknesses and component media optical properties, as well as stress-induced retardances and average stress azimuthal angles, which are all deduced in the analysis, enable a complete description of the polarization modifying properties of the rhomb when serving as a compensator.

Solc filter in optically active anisotropic crystal slabs

This is the first experimental demonstration of the Solc filter action in bulk composed of a slab of an optically active single crystal of left-handed quartz and a slab of right-handed quartz. The total birefringence of slabs and multiple total internal reflections from their external surfaces are used to form retardance of elements of a classic filter. The optical rotation difference of left-handed and right-handed quartz plates is used for mutual orientation of the elements. Precision of plate production ensures compliance with the technological requirements to filter parameters. Spectral transmission curves of the five-element filter, data of contrast measurement, full width at half maximum and angular field of view are presented. The filter potential is discussed.

Mechanism Behind Angularly Asymmetric Diffraction in Phase-Gradient Metasurfaces

Phase-gradient metasurfaces (PGMs) provide remarkable control over the propagation of light. One expects that the number of unit cells $m$ in a supercell should not change the nature of a PGM's diffraction characteristics, yet recent experiments have indicated $m$-dependent asymmetric absorptivity. An analytical description of the relationship between absorptivity and $m$ is needed, but lacking. This study offers a simple, intuitive semianalytical approach to explaining the observed asymmetric absorptivity. Here the phase gradient ensures additional, multiple total internal reflections inside the grating, leading to more dissipation and the asymmetric diffraction response.

Visualizing Light Rays Using Fluorescence

We present a simple and effective experimental setup to help students visualize light rays in optics experiments. When illuminated by a blue-violet laser pointer (typical wavelength [Formula: see text][Formula: see text]nm), tonic water and phosphorescent paper show fluorescence which allows the laser beam to be clearly seen by a large audience under normal ambient lighting. The setup is particularly useful for conducting classroom demonstrations on the reflection, refraction and diffraction of light. Quantitative measurement is also possible, e.g. students can attach a transparent scale to the phosphorescent paper or container holding the tonic water, and perform a quick verification of Snell’s law and the diffraction formula [Formula: see text]. The appeal of the visualization of light beams in multiple total internal reflections and retroreflection could help teachers introduce technological applications such as optical fibers and retroreflectors in road signs. A simple but interesting experiment of scattering laser light to form a light cone in a medium is shown using the fluorescence method. Redoing or modifying other innovative optics experiments using the fluorescence method is also discussed.

Fiber in-line Mach-Zehnder interferometer based on a pair of short sections of waveguide.

A fiber in-line Mach-Zehnder interferometer based on a pair of femtosecond laser inscribed short sections of waveguide is presented. One short waveguide directs part of the propagating light from the fiber core to the cladding-air interface, and experiences multiple total internal reflections before taking back to the fiber core by the other short waveguide. The device is robust in structure, can be fabricated in a fast way and with a flexible manner, and has the capability of ambient refractive index sensing, which makes it highly desirable for many "lab-in-fiber" applications.

Compact multi-projection 3D display system with light-guide projection

We propose a compact multi-projection based multi-view 3D display system using an optical light-guide, and perform an analysis of the characteristics of the image for distortion compensation via an optically equivalent model of the light-guide. The projected image traveling through the light-guide experiences multiple total internal reflections at the interface. As a result, the projection distance in the horizontal direction is effectively reduced to the thickness of the light-guide, and the projection part of the multi-projection based multi-view 3D display system is minimized. In addition, we deduce an equivalent model of such a light-guide to simplify the analysis of the image distortion in the light-guide. From the equivalent model, the focus of the image is adjusted, and pre-distorted images for each projection unit are calculated by two-step image rectification in air and the material. The distortion-compensated view images are represented on the exit surface of the light-guide when the light-guide is located in the intended position. Viewing zones are generated by combining the light-guide projection system, a vertical diffuser, and a Fresnel lens. The feasibility of the proposed method is experimentally verified and a ten-view 3D display system with a minimized structure is implemented.

Efficient optical path folding by using multiple total internal reflections in a microcavity

We propose using an asymmetric resonant microcavity for the efficient generation of an optical path that is much longer than the diameter of the cavity. The path is formed along a star polygonal periodic orbit within the cavity, which is stable and confined by total internal reflection. We fabricated a semiconductor device based on this idea with an average diameter of 0.3 mm and achieved a path length of 2.79 mm experimentally.

A Long Cylindrical Optical Fiber Sensor Based on Multiple Total Internal Reflections in Heterodyne Interferometry

In this paper, a long cylindrical multimode optical fiber sensor (OFS) based on multiple total internal reflections in heterodyne interferometry is proposed. The cladding of the sensing portions of the fiber sensors is removed, but dont be coated with any metal films. With the OFS the phase shift difference due to the multiple total internal reflections (MTIRs) effect between the p-and s-polarizations can be measured by using the heterodyne interferometry. Substituting the phase shift difference into Fresnels equations, the refractive index for the tested medium can be calculated. According to numerical simulations and experimental results, the long cylindrical OFS is with the best resolution of 0.0000028 refractive index unit (RIU). However, the OFS could be valuable for chemical, biological and biochemical sensing. It has some merits, such as, high sensitivity, high resolution, stability, small size and in real-time measurement.

New-Type Biosensor Based on Multiple Total-Internal Reflections in Heterodyne Interferometry

In this paper, a novel biosensor based on multiple total-internal reflections (MTIRs) in heterodyne interferometry (HI) is proposed. The biosensor is made of an elongated prism. As a heterodyne optical light source transmits through the new-type biosensor, it will undergo multiple total-internal reflections (MTIRs). Thus we can obtain the text signal at the output. The phase difference variation due to the different refractive indices of the tested media can be obtained by a Lock-In-amplifier (LIA). By some numerical calculations, we can achieve the related parameters of the tested medium. The resolution of the sensor can reach 4×10-7 refractive index unit (RIU). The electro-optical biosensor has some merits, easy operation, in real-time measurement, and high stability, etc.

Design of a Reflective Type Optical Fiber Sensor Based on Multiple Total-Internal Reflections Theory in Heterodyne Interferometry

In this paper, a reflective type optical fiber sensor (OFS) based on multiple total internal reflections in heterodyne interferometry is proposed. The sensor is made of a multimode optical fiber which cladding was removed and polished as a top shape. And the end surface of the sensor is designed as a micro-mirror. As a heterodyne optical source is launched into the optical fiber sensor at a suitable incident angle, we can obtain the phase difference between s-and p-polarizations at the output of the optical fiber sensor. By numerical simulation, it is clear that the resolution of the system by using the intensity method can reach refractive index unit (RIU) at least in the measurement range of. The OFS could be valuable for chemical, biological and biochemical sensing. It has some merits, such as, high resolution and stability, small size and real-time measurement.

New Type Small-Angle Sensor Based on Multiple Total Internal Reflections and Attenuated Total Reflections in Heterodyne Interferometry

In this paper, a new type small-angle sensor based on multiple total internal reflections and attenuated total reflections in heterodyne interferometry is presented. The small-angle sensor is designed as a reflective elongated prism that is made of BK7 glass. The shorter-side surface of the reflective elongated prism was coated with 2nm Ti-film and 45.5nm Au-film, but the longer-side surface of that was not coated with metal films. With the new type small-angle sensor, the small rotation angle can be obtained only by measuring the phase difference between the p-and s-polarization lights due to the multiple attenuated total-internal reflections (MATRs) and total-internal reflections (TIRs) effects. Its angular resolution can reach 0.000000295 radian at least. The new type small-angle sensor has some merits, e.g., high resolution, high sensitivity, stability, and in real-time test, etc.

Slab waveguide sensor based on amplified phase change due to multiple total internal reflections

We present theoretically an optical slab waveguide sensor based on amplified phase change due to multiple total internal reflections (TIRs). Compared with the conventional waveguide sensors, the proposed approach provides higher sensitivity. In this sensor, we adopt the change in the ellipsometric total phase change \Delta as the measuring probe of changes in the refractive index (RI) of the cladding. The change in \Delta is calculated for large number of alternating total reflections. Numerical calculations show that \Delta is strongly dependent on the RI variations of the cladding. Moreover, theoretical simulations show that the resolution of this sensor is predicted to be \approx 10^{-8} refractive index units (RIU). The proposed sensor could be used as a RI and a pressure sensor.

Spin and momentum filtering of electrons on the surface of a topological insulator

We investigate theoretically the transport properties of Dirac fermions on the surface of a three-dimensional topological insulator. Dirac electrons can be totally reflected in front of a magnetic/electric p-n junction. For a p-n-p structure, multiple total internal reflections at the interfaces result in the bound states in the channel, which behaves like an electronic waveguide. This p-n-p like structure exhibits spin and momentum filtering features and could be used as a spin and/or charge diode.

Fiber-optic particle plasmon resonance sensor for detection of interleukin-1β in synovial fluids

A facile and label-free biosensing method has been developed for determining an osteoarthritis concerned cytokine, interleukin-1β (IL-1β), in synovial fluids. The biosensing technique, fiber-optic particle plasmon resonance (FOPPR), is based on gold nanoparticles-modified optical fiber where the gold nanoparticle surface has been modified by a mixed self-assembled monolayer for further conjugation of anti-IL-1β antibody and minimization of nonspecific adsorption. Upon binding of IL-1β to anti-IL-1β on the gold nanoparticle surface, the absorbance of the gold nanoparticle layer on the optical fiber changes and the signal change is enhanced through multiple total internal reflections along the optical fiber. Results show that the detection of IL-1β in synovial fluid by this sensor agrees quantitatively with the clinically accepted enzyme-linked immunosorbent assay (ELISA) method but a much shorter analysis time is required (<10 min). The sensor response versus log concentration of IL-1β was linear ( r = 0.9947) over the concentration range of 0.050–10 ng/mL and a limit of detection (LOD) of 21 pg/mL (1.2 pM) was achieved. Such a LOD for IL-1β (17 kDa) represents a major advancement in the field of real-time monitoring of low molecular weight proteins in complex biological fluids.

Impact of size upon lasing in ZnO microtetrapods

High optical quality, well end leg faceted ZnO microtetrapods with leg length between 1 and 12 μm have been grown by carbothermal chemical vapor deposition. Lasing with mode quality factors of 2500–3000 is demonstrated. The origin of laser resonator cavity is discussed as a function of the tetrapod size. It is shown that in big tetrapods with legs of 12 μm in length the laser emission lines are well explained by longitudinal Fabry–Perot modes generated in cavities formed by individual tetrapod legs. The dispersion of the ZnO refractive index is experimentally determined from the position of lasing modes in the temperature interval from 10 to 300 K. It is shown that the lasing mode structure is seriously affected by the decrease of the tetrapod size. For a small tetrapod with a leg length of 1 μm, the lasing modes cannot be explained anymore by the formation of longitudinal Fabry–Perot modes in separate tetrapod legs, and the generation of guided modes by multiple total internal reflections in single tetrapod legs or in pairs of legs should be taken into account. The correlations between the lasing threshold and the tetrapod size are discussed.

Small-displacement sensing system based on multiple total internal reflections in heterodyne interferometry

A small-displacement sensing system based on multiple total internal reflections in heterodyne interferometry is proposed. In this paper, a small displacement can be obtained only by measuring the variation in phase difference between s- and p-polarization states for the total internal reflection effect. In order to improve the sensitivity, we increase the number of total internal reflections by using a parallelogram prism. The theoretical resolution of the method is better than 0.417 nm. The method has some merits, e.g., high resolution, high sensitivity, and real-time measurement. Also, its feasibility is demonstrated.

U-shaped optical fiber sensor based on multiple total internal reflections in heterodyne interferometry

In this paper, an optical fiber sensor based on multiple total internal reflections (MTIRs) in heterodyne interferometry is proposed. With the optical fiber sensor the phase shift difference due to the multiple total internal reflections effect between the p- and s-polarizations is measured by using heterodyne interferometry. Substituting the phase shift difference into Fresnel's equations, the refractive index for the tested medium can be calculated. The resolution of the sensor can reach 1.6×10 −6 refractive index unit (RIU). The optical fiber sensor could be valuable for chemical, biological and biochemical sensing. It has some merits, such as, high resolution and stability, high sensitivity, high resolution and real-time measurement.

Förster resonance energy transfer-based total internal reflection fluorescence reader for apoptosis

A fluorescence reader for the detection of Forster resonance energy transfer (FRET) on surfaces of living cells is described. The method is based on multiple total internal reflections (TIR) of an incident laser beam within a glass slide, such that individual samples on top of the glass slide are illuminated simultaneously by an evanescent electromagnetic field. Enhanced cyan fluorescent protein (ECFP) anchored to the inner leaflet of the plasma membrane is optically excited and transfers its excitation energy via the peptide linker Asp-Glu-Val-Asp (DEVD) to an enhanced yellow fluorescent protein. Upon apoptosis, DEVD is cleaved, and energy transfer is disrupted, as proven by an increase of fluorescence intensity as well as of fluorescence lifetime of the donor ECFP. Due to selective excitation of membrane-associated fluorophores, intracellular fluorescence and background luminescence from the surrounding medium are eliminated. Therefore, this test system appears to be a sensitive device for the detection of apoptosis and more generally for drug screening or in vitro diagnosis on a nanometer scale.

Total internal reflection fluorescence lifetime and anisotropy screening of cell membrane dynamics

A high content screening (HCS) system for fluorescence measurements at surfaces, in particular the plasma membrane of living cells, is described. The method is based on multiple total internal reflections (TIRs) of an incident laser beam within the glass bottom of a microtiter plate such that up to 96 individual samples could be illuminated by an evanescent electromagnetic field. Fluorescence lifetimes and time-resolved fluorescence anisotropies of these samples were assessed. While fluorescence lifetime represents a general measure for the interaction of a marker molecule with its microenvironment, the rotational diffusion time corresponds to the relaxation time of a molecule from a position with a defined orientation into a position with an arbitrary orientation. Thus, time-resolved fluorescence anisotropy reflects the viscosity of the microenvironment, i.e., membrane fluidity in the case of living cells. For all measurements in this study, either human glioblastoma cells incubated with the fluorescent membrane marker NBD-cholesterol or human breast cancer cells expressing a membrane-associating fluorescent protein were used.