Transparent Slab Research Articles

Strategies to enhance the performance of luminescent solar concentrators using colloidal quantum dots

A luminescent solar concentrator (LSC), an optically transparent slab with high refractive index, infused with emissive luminophores, absorbs, re-emits and concentrates solar energy to the edges of a waveguide. This work aims to develop an efficient Monte-Carlo Ray-tracking algorithm to track the photon’s excursion in LSC. The efficiency largely depends upon the optical properties of both luminophores and the slab waveguides. Two frameworks contribute here: (i) luminophores’ optimal optical properties and (ii) design of the waveguide. Three colloidal QD-based systems (AgInS2/ZnS, ClSeS/ZnS and CuInS2) are employed and the ClSeS/ZnS QD-based LSC demonstrates the highest efficiency of 12.5% at a concentration of 200 ppm. Interestingly, a multi-QD approach in a single LSC device yields 17.2% efficiency which is 27.3% improvement over single QDs. By adjusting the luminophore emission angle from 45° to 90° the efficiency enhances by 2%. Future applications of the work include ecofriendly, sustainable renewable energy sources with long-term stability.

Ethylene photocatalytic degradation using TiO2 immobilized in a NETmix mili-photoreactor

Ethylene oxidation by TiO2 photocatalysis was studied in a mili-photoreactor (NETmix), as a potential clean postharvest technology to scavenge ethylene from fruit. The NETmix photoreactor comprises a stainless steel slab imprinted with a network of cylindrical chambers interconnected by prismatic channels, sealed by a UVA transparent borosilicate slab (BS), and a UVA LED plate paced above the reactor window. A thin film of the photocatalyst was immobilized in the NETmix network or on the side of the borosilicate slab in contact with the ethylene gas stream. Ethylene oxidation in single-pass mode (continuous operation) was evaluated as a function of TiO2 crystallinity, TiO2 loading, radiant power, illumination mechanism, feed stream composition (ethylene and water concentration), and flow rate. The catalyst loading and deposition surface, and relative humidity (RH) of the feed stream strongly affected the ethylene conversion, mineralization, and reaction rate. Even under severe conditions (RH = 25% and Qfeed = 571 cm3 min−1 for the back side illumination), the NETmix removed at least 0.11 μmolethylene min−1. The high efficiency of the photocatalytic NETmix reactor allows the removal of ethylene from the storage system at the beginning of fruit ripening, the period of the highest gas production, enabling it to be used as a promising technology in controlling fruit ripening.

The relationship between fingering flow fraction and water flux in unsaturated soil at the laboratory scale

Preferential flow is a widespread process in unsaturated soil and it is important to incorporate preferential flow in mathematical and numerical models to accurately predict subsurface flow and solute transport. In this study we conduct experiments to relate the fraction of fingering flow (f) with water flux (qs) and average active water saturation (Se∗) which is a key constitutive relation in modeling subsurface preferential flow. Infiltration experiments were conducted in a two-dimensional transparent slab chamber, with different soil grain sizes and initial water saturation. Available experimental data from the literature are also compiled and compared with our new data. Results show that the f-qs relationship is independent on grain size of the soil and whether the sand is initially dry or wet. The exponent of the f-qs relationship (a0) varies in a small range (0.39–0.48) and the exponent of the f-Se∗ relationship (γ) can be predicted from a0 and soil grain size. The Richards equation was combined with the f-qs relationship to model the preferential flow experiments. The results show that the constitutive relationship successfully predicts preferential flow velocity in unsaturated soil.

Metal ion implantation into transparent dielectric slab: an effective route to high-stability localized surface plasmon resonance sensors

Ag/SiO2 and Au/SiO2 samples were prepared by separately implanting 30 keV Ag and Au ions into 0.5-mm-thick SiO2 slabs at a fluence of 6 × 1016 ion·cm−2, and their optical and structural properties were studied in detail by using a fiber spectrometer and a transmission electron microscope, respectively. Our results showed that the two samples featured by their respective nanocomposite surface layers were asymmetrical in structure, and hence, their characteristic signals in the reflectance spectra excited by the lights incident from the rear surfaces were able to exhibit corresponding blueshifts when the overlays on the implanted surfaces were increased in refractive index with respect to air. Our results also showed that each of characteristic signals was strongly dependent on the localized surface plasmon resonance (LSPR) behavior of the involved Ag or Au nanoparticles (NPs), and it could not appear at a wavelength position smaller than or equal to that of the LSPR absorption peak since the involved Ag or Au NPs were quite small in size. These results meant that the two samples could be regarded as the LSPR sensors with a negative refractive index sensitivity (RIS), although their sensing abilities would lose when the overlays were very large in refractive index. Especially, the two samples were demonstrated to be relatively high in stability because the involved Ag and Au NPs were closely hugged and chemically protected by the matrices of SiO2, and consequently, they could have a chance to become prospective sensing devices in some special fields as long as their RISs and linearities could be improved in the future. The above findings substantially confirmed that the metal ion implantation into transparent dielectric slab was an effective route to the high-stability LSPR sensors.

Quantum sensing of open systems: Estimation of damping constants and temperature

We determine quantum precision limits for estimation of damping constants and temperature of lossy bosonic channels. A direct application would be the use of light for estimation of the absorption and the temperature of a transparent slab. Analytic lower bounds are obtained for the uncertainty in the estimation, through a purification procedure that replaces the master equation description by a unitary evolution involving the system and ad hoc environments. For zero temperature, Fock states are shown to lead to the minimal uncertainty in the estimation of damping, with boson-counting being the best measurement procedure. In both damping and temperature estimates, sequential pre-thermalization measurements, through a stream of single bosons, may lead to huge gain in precision.

Transparent glass slab thickness measurement by binary-spot focus signal

espanolLos sistemas de error de foco basados en el principio astigmatico que utilizan detectores de cuatro cuadrantes como elemento generador de senal han sido usados ampliamente en una gran variedad de aplicaciones. Sin embargo, su principio de funcionamiento no es particularmente adecuado para medidas que involucran mas de un spot. En este trabajo proponemos un nuevo metodo que usa un CCD como dispositivo de deteccion y un metodo de procesar los datos adquiridos. Un efecto secundario de este cambio es la perdida del parametro SEF, clave en estas tecnicas. Para superar este problema se propone un nuevo parametro que llamamos senal de foco. El proceso de medicion de espesor de una muestra transparente con dos caras reflectoras usando esta tecnica tambien es presentado. EnglishFocus error systems based on the astigmatic principle relying on four quadrant photo detectors as the signal generation element have widely been used in many different applications. Nevertheless, its working principle is not particularly suitable for measurements involving more than one spot. In this work we propose a new method that uses a CCD as the detection device as well as a method of processing acquired data. A side effect of this change is the loss of the FES parameter key to these techniques. To overcome this issue a new parameter named focus signal is proposed. The thickness measuring process of a transparent sample with two reflective layers using this technique is also presented.

Laser transmission welding of PMMA using IR semiconductor laser complemented by the Taguchi method and grey relational analysis

Abstract Laser transmission welding involves localized heating and non-contact techniques at the interface of two polymer pieces to be joined. The welding quality is very sensitive to speed welding, thickness and welding line width and depth. This work presents the laser transmission welding of Poly(Methyl Meta acrylate) PMMA polymer transparent and oblique slabs. A semiconductor laser with 808 nm wavelength, 2 W output power and a 2 mm beam diameter was used. Three different transparent slabs with dimensions 40 × 60 mm and thickness (2.6, 3.7, 4.3 mm) were fixed tightly onto oblique slab (dark color). Three different selected speeds (44, 113, 150 mm/min) of the welding process were applied to the prepared samples. Results indicate the welding line width and depth were inversely proportional to the welding speed while the transparent slab thickness have little effect. Nine experiments were performed for the three different thickness at different speeds. Taguchi method and grey relational analysis were used to determine the optimum values for welding speed, width, depth and thickness during these nine experiments. The results exhibit good agreement with those of the Taguchi method and grey relational analysis.

Fabrication, microstructure and optical properties of large-sized Nd:YAG and composite Yb:YAG transparent ceramic slabs

Abstract Large-sized Nd:YAG and composite Yb:YAG transparent ceramic slabs of high quality were fabricated by the conventional solid-state reaction sintering technique. The Yb:YAG transparent ceramic slabs were surrounded by undoped YAG transparent ceramics and this composite structure was built in the process of ceramic shaping. The difference in microstructure between Yb:YAG and YAG transparent ceramics was not observed and the composite Yb:YAG slabs showed fully dense and pore-free microstructure. The in-line transmittances at 400 nm reached 81.7% and 79.7 % for YAG and Yb:YAG transparent ceramics, respectively, indicating good optical quality of the composite ceramic slab. And the optical transmission micrograph was very homogeneous with only a few isolated scattering centers. These results suggested that building composite structure in the process of ceramic shaping was a simple and reliable technical scheme. Moreover, the large-sized Nd:YAG transparent ceramic slab with size of 150.0 mm × 50.0 mm × 4.0 mm was also prepared. The calculated absorption coefficient was about 0.002 cm-1 @1064 nm, which suggested that the optical quality of this Nd:YAG transparent ceramic slab had reached the level of Nd:YAG crystals.

Overcoming limitations in photochemical UVC/H2O2 systems using a mili-photoreactor (NETmix): Oxytetracycline oxidation

This study focuses on the intensification of a photochemical UVC/H2O2 system using a mili-photoreactor (NETmix) for a better and faster elimination of oxytetracycline (OTC) from urban wastewater. This mili-photoreactor comprises a network of small cylindrical chambers and prismatic transport channels sealed by a UVC transparent quartz slab allowing unique properties. Since light has a profound effect on the photochemical process, UVC photons distribution over the reaction medium was investigated using a multiple UVC lamp design (4, 6 or 11 W) allocated in parallel or perpendicular to the solution movement. In addition, the effect of other operating variables, such as oxidant dosage (100–900 mg L−1), oxidant feed configuration (single entry or continuous multi-injection) and flow rate (50–100 L h−1) was studied. A kinetic model able to describe the OTC oxidation by the UVC/H2O2 photochemical system in the mili-photoreactor was also developed. Moreover, matrix effect was evaluated by spiking OTC in a secondary effluent from an urban WWTP. In this case, OTC degradation was inhibited in about 2 to 3 times due to the presence of organic/inorganic substances (soluble and particulate), inherent to the real matrix, that act as scavenger of oxidant species and as UVC light filter. The NETmix mili-photoreactor presented high photochemical space time yield (PSTY) values when compared with a conventional tubular photoreactor. This highlights the NETmix capacity to enhance UVC/H2O2 processes through an homogeneous light distribution over the entire reaction medium.

Anomalous refraction of a low divergence monochromatic light beam in a transparent slab.

An exact formulation for the propagation of a monochromatic wave packet impinging on a transparent, homogeneous, isotropic, and parallel slab at oblique incidence is given. Approximate formulas are derived for low divergence light beams. These formulas show the presence of anomalous refraction phenomena at any slab thickness, including negative refraction and flat lensing effects, induced by reflection at the rear face.

Thin and thick dielectric films for THz surface plasmon control

Propagation of a broadband (λ = 0.3–3 mm) THz surface plasmon (SP) through a long transparent slab of thickness d varying from d ≪ λ through d ≈ λ to d ≫ λ is experimentally studied and theoretically analyzed. It is demonstrated that the temporal and spectral shapes of the transmitted SP pulse differ considerably for those three regimes of plasmon–layer interaction. Optimal dielectric film thickness (20 μm) for SP confinement without much attenuation and dispersion is estimated.

A differentiated plane wave: its passage through a slab

Differentiating a monochromatic uniform plane electromagnetic wavefield with respect to its direction produces, from a field that is completely lacking in localized specific features, one that contains a straight vortex-like line, a ‘C-line’ of defined circular polarization. There is also a second separate C-line of opposite handedness; indeed, in a sense, a straight line of every polarization is realized. Because of its primitive construction it is analytically simple to study the passage of a differentiated wave obliquely through a plane interface into a medium of different refractive index, to trace its C-line. This was done in an earlier paper. Here we extend the method to passage through a parallel-sided transparent slab. There are multiple reflections within the slab, as in a Fabry–Pérot interferometer. The exiting wave, as a single differentiated plane wave, has a straight oblique C-line. Inside the slab, and in front of it, there is wave interference. The result is a coiled, helix-like, C-line in front of the slab and another inside it. The two coils wrap around separate hyperboloids of one sheet, like cooling towers. The emerging straight C-line is shifted (with respect to a C-line in a notional undisturbed incident plane wave) both in the plane of incidence and transversely to it, and the second C-line behaves similarly. The analysis is exact and could be extended in a straightforward way to a general stratified medium.

Deducing radiation pressure on a submerged mirror from the Doppler shift

Radiation pressure on a flat mirror submerged in a transparent liquid, depends not only on the refractive index n of the liquid, but also on the phase angle psi_0 of the Fresnel reflection coefficient of the mirror, which could be anywhere between 0^{\circ} and 180^{\circ}. Depending on the value of psi_0, the momentum per incident photon picked up by the mirror covers the range between the Abraham and Minkowski values, i.e., the interval (2\hbarw_0/nc,2n\hbarw_0/c). Here \hbar is the reduced Planck constant, w_0 is the frequency of the incident photon, and c is the speed of light in vacuum. We argue that a simple experimental setup involving a dielectric slab of refractive index n, a vibrating mirror placed a short distance behind the slab, a collimated, monochromatic light beam illuminating the mirror through the slab, and an interferometer to measure the phase of the reflected beam, is all that is needed to deduce the precise magnitude of the radiation pressure on a submerged mirror. In the proposed experiment, the transparent slab plays the role of the submerging liquid (even though it remains detached from the mirror at all times), and the adjustable gap between the mirror and the slab simulates the variable phase-angle psi_0. The phase of the reflected beam, measured as a function of time during one oscillation period of the mirror, then provides the information needed to determine the gap-dependence of the reflected beam's Doppler shift and, consequently, the radiation pressure experienced by the mirror.

The Optomotor Maze: A Population Assay for Visual Perception in Drosophila: Figure 1.

Vision is a major sensory modality in Drosophila behavior, with more than one-half of the Drosophila brain devoted to visual processing. The mechanisms of vision in Drosophila can now be studied in individuals and in populations of flies by using various paradigms. The optomotor maze, described here, is a novel and efficient approach for querying visual perception in Drosophila populations. The optomotor maze setup is very simple: An eight-choice maze consisting of 3-mm paths grooved into a transparent Plexiglas or acrylic slab is placed over an upturned cathode ray tube (CRT) monitor on which visuals are displayed. The placement or movement of the visuals on the CRT, which the flies can see through the flat bottom of the maze, influences their turning behavior at each choice point. This paradigm can be adapted for visual learning by simply rerunning flies in the maze (habituation) or as a more sophisticated version of the aversive phototaxic suppression (APS) paradigm.

Wide-Range Calibration of Corneal Backscatter Analysis by In Vivo Confocal Microscopy

To report intra- and interinstrument calibration methods for corneal backscatter analysis by in vivo confocal microscopy. Applicability of two reference standards was evaluated for corneal backscatter calibration. Repeated measurements of four concentrations of AMCO Clear (GFS Chemicals, Inc., Powell, OH) suspension and three transparencies (26%, 49%, and 65%) of polymethylmethacrylate (PMMA) slabs were performed to assess image intensity acquisition in a wide backscatter range. Intra- and intersession repeatability and lot-to-lot variation were determined for both standards. The effect of light intensity (LI) variation on image intensity acquisition was evaluated by examination of PMMA slabs with nonreference (60% and 80%) and reference (72%) LIs. Both reference standards were implemented in the protocol. Intrainstrument calibration was verified by measuring three normal corneas with 60%, 72%, and 80% LIs. Interinstrument calibration was tested by measuring PMMA slabs on a second, similar confocal microscope. AMCO Clear was used to express image intensity in absolute scatter units (SU), whereas the 49% transparent PMMA slab showed best repeatability, without image saturation, to adjust for LI variation. Intrainstrument calibration for LI variation reduced mean differences from -38.3% to 1.7% (60% LI) and from 33.9% to -0.6% (80% LI). The mean difference between similar microscopes decreased from 18.4% to 1.2%, after calibration of the second microscope. Large interinstrument differences necessitate calibration of corneal backscatter measurements. With AMCO Clear suspension and PMMA slabs, standardization was achieved in a wide backscatter range corresponding to normal and opaque corneas. These methods can easily be applied in ophthalmic practice.

An assessment of Saunderson corrections to the diffuse reflectance of paint films

We revise basic concepts behind the surface correction terms to the diffuse reflectance of a paint coating and its measurement with an integrating sphere. We question the validity of using the Fresnel relationships to calculate the surface reflectance terms in the case of paint films. Results of measurements on a white paint covered with an index-matched transparent slab are presented. From these results we infer the internal diffuse reflectance of the surface and obtain noticeable discrepancies from the prediction of Fresnel relationships.

Thickness measurement of transparent plates by a self-mixing interferometer

We introduce a technique to measure transparent glass slab thickness. It employs a very simple setup combining two interferometers: a forward-going beam scheme and a self-mixing readout of the beam reflected back to the laser source. Interestingly, the difference of the two readouts provides a quantity related to thickness measurement, irrespective of refractive index. We demonstrate this method using samples on a range of thickness from 30 to 1000microm.

Light transmission in thermal stress-induced birefringent medium

In this paper the temperature and thermal stress distribution in a simplified-mode transparent slab is calculated and then variation of refractive index is acquired based on the photo-elastic theory. Using the vector differential algorithm the refractive behavior of rays in such media is simulated, and luminous intensity distribution and shape of fringes at the receiving plane is predicted. The output of the program is in coincidence with the check experiment based on photo-elasticity technique, which indicates the correctness of our analysis method and light transmission calculation method. This research provides a practical means for improving the imaging quality of optical instruments.

The Dual‐microfacet Model for Capturing Thin Transparent Slabs

AbstractWe present a new model, called the dual‐microfacet, for those materials such as paper and plastic formed by a thin, transparent slab lying between two surfaces of spatially varying roughness. Light transmission through the slab is represented by a microfacet‐based BTDF which tabulates the microfacet's normal distribution (NDF) as a function of surface location. Though the material is bounded by two surfaces of different roughness, we approximate light transmission through it by a virtual slab determined by a single spatially‐varying NDF. This enables efficient capturing of spatially variant transparent slices. We describe a device for measuring this model over a flat sample by shining light from a CRT behind it and capturing a sequence of images from a single view. Our method captures both angular and spatial variation in the BTDF and provides a good match to measured materials.

Interplay between optical nonlinearity and localization in a finite disordered Fibonacci chain

Both the average transmission coefficients and dimensionless optical resistances of a nonlinear disordered Fibonacci chain are calculated as functions of the photon flux of an incident light field with various types of chains of scatters, numbers of embedded nonlinear-optical scatterers, and energies of incident photons. If the incident optical field is very weak, the nonlinear-optical scattering in the chain becomes negligible and the chain behaves just like a transparent dielectric slab. As for the interplay between the optical nonlinearity and localization effect in the finite disordered Fibonacci chain, it is found that the localization effect introduced in the disordered Fibonacci chain exhibits a reduction in the transmission only when the incident optical field is strong. The localization effect, which increases with the number of scatterers in the chain, is found to yield an enhanced optical nonlinearity of the system. The localization effect on the incident optical wave in the chain can be accelerated by an intense light illumination in the presence of a large number of nonlinear-optical scatterers. When energetic photons fly through the chain, they tend to ignore most of the deeply embedded optical scatterers. When the number of scatterers in the system is ${F}_{16}=1597$, a complete localization in the chain is reached for an incident field amplitude as low as $50\phantom{\rule{0.3em}{0ex}}\mathrm{kV}∕\mathrm{cm}$.