Multiple Total Internal Reflection Research Articles

Suppressing Optical Losses in Solar Cells via Multifunctional and Large-Scale Geometric Arrays.

The occurrence of optical loss on the surface of solar cells is inevitable due to the difference in the refractive index between air and glass, as well as the insufficient absorption of the active layer. To address this challenge, micron-sized geometry arrays, such as hemispheres and hemisphere pits, are prepared on quartz glass through the advanced indirect patterning technology of UV-LIGA. These geometric arrays exhibit multiple mechanisms for controlling light waves, including multiple rebounds, diffraction scattering, and total internal reflection. These synergistic effects suppress optical losses at the device's surface and prolong the photon propagation path in the active layer. After being patterned with this structure, the average transmittance and haze of the quartz glass reach 93.91% and 75%, respectively. Compared to their flat counterpart, the decorated monocrystalline silicon solar cells demonstrated an apparent improvement in photocurrent and produced a 7.2% enhancement in power conversion efficiency.

Optical fluxes propagation in the planar transport layer of multilayer coatings

The article is concerned with peculiarities study of the quasimonochromatic optical fluxes propagation through thin planar transparent layer of multilayer coating. There is shown that these fluxes can be transported by the layer in process of its multiple consequtive total internal reflection or by the waveguide-resonance propagation manner depending on correlation between the layer width and the radiation coherence length half of transported fluxes. Efficiency comparison of these radiation transportation mechanisms showed that the waveguide-resonance propagation approach is more adequate for results description of the optical waveguides functioning. It allowed to conclude that optical waveguides (fibers) function in frame of the waveguide-resonance paradigm and the waveguide-resonance mechanism is responsible for the light fluxes transportation on great distances.

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

Composition and Structure of Complexes Formed in Aqueous Solutions of Trifluoroacetic Acid According to IR Spectroscopy Data

The composition and structure of complexes that formed in aqueous solutions of trifluoroacetic acid were studied by frustrated multiple total internal reflection IR spectroscopy (FMTIR). Two types of complexes with a molecular structure formed: trimers CF3COOH · (H2O)2 and cyclic tetramers (CF3COOH)2 · (H2O)2, in which the molecules of the components are arranged in pairs. In the range of acid concentrations from 100% to [H2O]/[CF3COOH] = 1: 1, only these tetramers formed, and all added water was bound into these hydrates. In more dilute solutions (up to [H2O]/[CF3COOH] = 2: 1), CF3COOH · (H2O)2 complexes formed along with tetramers; at a double excess of H2O, the components of the solution were completely bound into these trimers. In dilute solutions (from 0 to 3.6 M CF3COOH), the acid is completely dissociated into H5O 2 + and CF3COO– ions hydrated with water molecules. In the range of medium concentrations (from 3.6 M to [H2O]/[CF3COOH] = 2: 1), the solutions contain both these ions and CF3COOH · (H2O)2 dihydrates. For this range of compositions of the CF3COOH−H2O system, the concentrations of H5O 2 + ions and CF3COOH · (H2O)2 dihydrates were calculated.

H3O 2 - ions with a strong quasi-symmetrical H-bond and their hydration in aqueous solutions of NaOH and KOH

Ion-molecular interactions in aqueous solutions of NaOH (0–47.8%) and KOH (0–51.95%) are studied by multiple frustrated total internal reflection IR spectroscopy. Interpretation of the spectra and analysis of the spectral data are performed based on the results of DFT calculations (B3LYP/6-31++G(d, p)) of the characteristics of the free and double hydrated H3O2- ion. It is established that the changes in the IR spectra of NaOH and KOH aqueous solutions caused by increasing alkali concentration are due to the formation of H3O2- ions with a strong quasi-symmetrical hydrogen bond and their subsequent hydration by one or two water molecules. The influence of the cation nature on the degree of hydration of H3O2- ions is demonstrated. The equilibrium concentrations of monohydrate (H3O2- ∙ H2O) and dihydrate (H3O2- ∙ 2H2O) are calculated and their IR continuous absorption spectra are isolated.

Powerful Projective Technique: KANEHA-TIR-Ψ

We present a new type of powerful projective method called KANEHA-TIR-Ψ projective Technique. This technique connects traditional projection methods with cognitive and affective domains of persons under projection by processes of introspection, total internal reflection (TIR), structuralism and gestaltism. The multiple TIR processes of thoughts, ideas and their repetitive modifications, synthesis using individual differences, analysis and evaluation by introspection, structuralism and gestaltism processes result into extremely purified and refined outputs. This technique found very useful, result-oriented and productive for various kinds of diagnosis, personality measurements, personality development, training and brain programming purposes. i-KANEHA-TIR-Ψ projective technique delivered quite good, justified and reproducible results among different situations, environments, and cultures. We propose its industrial applications for designing branch-programmed instructions for training and assessments of academic and industrial professionals.

Investigation of orientational order in a nematic liquid crystal with semiconductor CdSe/Zns QDs by IR spectroscopy

The dichroic ratio and orientational-order parameter of fundamental bands have been studied in the IR spectrum for a nematic liquid crystal based on alkylcyanobiphenyls and its suspensions with semiconductor CdSe/ZnS QDs with a core size of 5 nm. Analyses have been performed by the method of multiple frustrated total internal reflection. It is shown that an increase in the nanoparticle concentration from 0.5 to 1.3 wt % improves the orientation uniformity of the liquid crystal near the interface with the orienting surface. The orientational order parameter in a suspension with 1.3 wt % QDs has increased in comparison with the initial liquid crystal by more than 10% for the fundamental bands in alkylcyanobiphenyl molecules, the stretching vibrations of which correspond to the direction of their long axes.

Electric field induced spin and valley polarization within a magnetically confined silicene channel

We study the electronic structure and transport properties of Dirac electrons along a channel created by an exchange field through the proximity of ferromagnets on a silicene sheet. The multiple total internal reflection induces localized states in the channel, which behaves like an electron waveguide. An effect of spin- and valley-filtering originating from the coupling between valley and spin degrees is predicted for such a structure. Interestingly, this feature can be tuned significantly by locally applying electric and exchange fields simultaneously. The parameter condition for observing fully spin- and valley-polarized current is obtained. These findings may be observable in todays' experimental technique and useful for spintronic and valleytronic applications based on silicene.

Ions with strong symmetric H-bonds and their solvation in aqueous-ethanolic solutions of HCl

Ion-molecular interactions in the HCl-EtOH-H2O system are studied by means of multiple frustrated total internal reflection IR spectroscopy over a wide range of concentrations of the components. It is demonstrated that, in the investigated solutions, the acid is fully bound into ions and uncharged complexes formed by strong symmetric or quasi-symmetric H-bonds. There is a competition between H2O and EtOH molecules during the formation of the (H5C2(H)O…H…O(H)C2H5)+, (H2O…H…OH2)+, and (H2O…H…O(H)C2H5)+ proton disolvates. In dilute solutions of HCl in 2: 1 and 1: 1 EtOH-H2O mixtures, (H2O…H…OH2)+ proton dihydrates are mainly formed, whereas in concentrated HCl solutions, under conditions of a partial solvation of ions by solvent molecules, predominantly (H2O…H…O(H)C2H5)+ mixed proton disolvates arise. In concentrated solutions of HCl in EtOH with low water content, the acid is partially bound into (H5C2(H)O…H+…Cl−) uncharged complexes with the participation of the Cl− anion.

Surface modification of polypropylene materials by the cobalt complex of 5,10,15,20-tetrakis-(4-methylpyridyl)porphyrin tetratosylate

The process of immobilization of cobalt(II) 5,10,15,20-tetrakis(4-methylpyridyl)porphyrin tetratosylate on chemically activated surface of polypropylene materials was studied using infrared spectroscopy of multiple frustrated total internal reflection, electron spectroscopy, and atomic force microscopy. The modified materials were shown to have a sorption activity with respect to nitrogen bases, the structural analogs of blood toxines.

Reflection and refraction of an Airy beam at a dielectric interface

Reflection and refraction of a finite-power Airy beam at the interface between two dielectric media are investigated analytically and numerically. The formulation takes into account the paraxial nature of the optical beams to derive convenient field evolution equations in coordinate frames moving along Snell's refraction and reflection axes. Through numerical simulations, the self-accelerating dynamics of the Airy-like refracted and reflected beams are observed. Of special interest are the cases of critical incidence at Brewster and total-internal-reflection (TIR) angles. In the former case, we find that the reflected beam achieves self-healing, despite the severe suppression of a part of its spectrum, while, in the latter case, the beam remains nearly unaffected except for the Goos-Hänchen shift. The self-accelerating quality persists even if the beam is trapped by multiple TIRs inside a dielectric film. The grazing incidence of an Airy beam at the interface between two media with close refractive indices is also investigated, revealing that the interface can act as a filter depending on the beam scale and tilt. We finally consider reverse refraction and perfect imaging of an Airy beam into a left-handed medium.

Pumping of electromagnetic energy via multiple total internal reflection from active media

An experiment for strong light amplification at multiple total reflections from active gaseous media is proposed.

Relationship Between Interfacial Water Layer Adhesion Loss of Silicon/Glass Fiber–Epoxy Systems: A Quantitative Study

Water at the polymer/substrate interface is often the major cause of adhesion loss in coatings, adhesives, and fiber-reinforced polymer composites. This study critically assesses the relationship between the interfacial water layer and the adhesion loss in epoxy/siliceous substrate systems. Both untreated and silane-treated Si substrates and untreated and silane-treated E-glass fibers were used. Thickness of the interfacial water layer was measured on epoxy/Si systems by Fourier transform infrared–multiple total internal reflection (FTIR-MTIR) spectroscopy. Adhesion loss of epoxy/Si systems and epoxy/E-glass fiber composites was measured by peel adhesion and short-beam shear tests, respectively. Little water accumulation at the epoxy/Si substrate interface was observed for silane-treated Si substrates, but about 10 monolayers of water accumulated at the interface between the epoxy and the untreated Si substrate following 100 h of exposure at 24 °C. More than 70% of the initial epoxy/untreated Si system peel strength was lost within 75 h of exposure, compared with 20% loss after 600 h for the silane-treated Si samples. Shear strength loss in composites made with untreated E-glass fiber was nearly twice that of composites fabricated with silane-treated fiber after 6 months of immersion in 60 °C water. Further, the silane-treated composites remained transparent, but the untreated fiber composites became opaque after water exposure. Evidence from FTIR-MTIR spectroscopy, adhesion loss, and visual observation strongly indicated that a water layer at the polymer/substrate interface is mostly responsible for the adhesion loss of epoxy/untreated siliceous substrate systems and epoxy/untreated glass fiber composites and that FTIR-MTIR is a viable technique to reliably and conveniently assess the adhesion loss attributable to water sorption at the interface.

Infrared spectroscopy of bonded silicon wafers

Infrared spectra of multiple frustrated total internal reflection and transmission for silicon wafers obtained by direct bonding in a wide temperature range (200–1100°C) are studied. Properties of the silicon oxide layer buried at the interface are investigated in relation to the annealing temperature. It is shown that the thickness of the SiO2 layer increases from 4.5 to 6.0 nm as the annealing temperature is increased. An analysis of the optical-phonon frequencies showed that stresses in the SiO2 relax as the annealing temperature is increased. A variation in the character of chemical bonds at the interface between silicon wafers bonded at a relatively low temperature (20–400°C) is studied in relation to the chemical treatment of the wafers’ surface prior to bonding. Models of the process of low-temperature bonding after various treatments for chemical activation of the surface are suggested.

Development of a monolithic total internal reflection-based biochip utilizing a microprism array for fluorescence sensing

This paper proposes a monolithic integration method to fabricate a total-internal-reflection (TIR) based biosensor for fluorescence sensing. The monolithic TIR-based biosensor integrates a microfluidic chamber, polymer-based optics and planar waveguides into a high-throughput platform. The polymer-based optics, fabricated by SU-8 resist, include cylindrical microlenses and a microprism array for effectively conducting the excitation light into the planar waveguide. Two kinds of substrate materials, namely quartz and SU-8 resist, are used to fabricate the planar optical waveguides for efficiency comparison. To fabricate the microprism array, a technology employing glycerol-compensated oblique exposure is employed, and microprism arrays with inclined surface angles from 25° to 35° on the planar optical waveguide have been successfully fabricated. Multiple total internal reflection spots can be observed through this monolithically integrated optical system simultaneously. The real-time Brownian motion of fluorescent microspheres excited by the evanescent wave under this system is captured for motion analysis. The results demonstrate the feasibility of this system on the study of nanoscale phenomena. The unique fabrication and integration aspects of the monolithic biosensor including on-chip micro-optics simplify current TIR optical configurations and could potentially be integrated into a lab-on-a-chip microsystem.

Features of the vibrational spectra of diamond-like and polymer-like a-C:H films

Comparative analysis of the IR spectra of multiple frustrated total internal reflection (MFTIR) in the range 4000–1000 cm−1 is performed for diamond-like and polymer-like a-C:H films with the refractive indices n ≥ 2.0 and n ≤ 1.7, respectively. The films are obtained by chemical-vapor deposition from octane, cyclohexane, toluene, and acetylene under various conditions using a dc glow discharge plasma. Characteristic features are found in the vibrational spectra of a-C:H films with different refractive indices. A peak at 1250 cm−1, which is independent of the initial hydrocarbon, is observed in the spectra of the diamond-like films. Additional peaks at 3400 and 1700 cm−1, due to O-H and C=H vibrations, are present in the spectra of the polymer-like films. It is shown that the integrated intensity of the band of CH vibrations peaked at ∼2900 cm−1 decreases exponentially by an order of magnitude with an increase in n from 1.55 to 2.4.

Static solar concentrator with vertical flat plate photovoltaic cells and switchable white/transparent bottom plate

A new type of static solar concentrator is proposed to match the aesthetic features of towns. The concentrator consists of vertical plate solar cells and white/transparent switchable bottom plate, which is operated with external power. The bottom is switched to be a diffuse reflection white surface when the cell generates electric power, and switched to be a light transmissible transparent surface when the cell does not deliver power. The light collection of this concentrator was analyzed by using multiple total internal reflection model and ray tracing simulation. For the same ratio of the area of the solar cells to that of the collector surface, the collection efficiency for the proposed concentrator is about half of that of the conventional concentrator for flat plate cell, and nearly equal to that of the concentrator for the embedded spherical silicon solar cells.

Hydrogen in Si–Si bond center and platelet-like defect configurations in amorphous hydrogenated silicon

Hydrogen and deuterium in bond-centered (BC) and platelet-like configurations were detected in hydrogenated (and deuterated) amorphous silicon thin films deposited from SiH4 and SiD4 plasmas. Infrared absorptions due to these configurations were measured using in situ multiple total internal reflection Fourier transform infrared spectroscopy in a differential mode, where changes in the as-deposited a-Si:H(D) films were observed during D2(H2) plasma exposure. This method coupled with preferential replacement of H(D) by D(H) in BC and platelet-like configurations over the isolated bulk SiH(SiD) configurations enabled detection of these modes without interference from the strong SiH(SiD) absorptions. The Si–H(D) stretching modes for BC hydrogen and BC deuterium were observed at ∼1950 and ∼1420cm−1, respectively, while those for platelet-like hydrogen and deuterium were detected at ∼2033 and ∼1480cm−1, respectively.

Surface Processes during Growth of Hydrogenated Amorphous Silicon

ABSTRACTHydrogenated amorphous silicon films for photovoltaics and thin film transistors are deposited from silane containing discharges. The radicals generated in the plasma such as SiH3 and H impinge on the surface and lead to silicon film growth through a complex network of elementary surface processes that include adsorption, abstraction, insertion and diffusion of various radicals. Mechanism and kinetics of these reactions determine the film composition and quality. Developing deposition strategies for improving the film quality requires a fundamental understanding of the radical-surface interaction mechanisms. We have been using in situ multiple total internal reflection Fourier transform infrared spectroscopy and in situ spectroscopic ellipsometry in conjunction with atomistic simulations to determine the elementary surface reaction and diffusion mechanisms. Synergistic use of experiments and atomistic simulations elucidate elementary processes occurring on the surface. Herein, we review our current understanding of the reaction mechanisms that lead to a-Si:H film growth with special emphasis on the reactions of the SiH3 radical.

Modeling and experimental verification of the performance of TIRF-sensing systems for oligonucleotide microarrays based on bulk and integrated optical planar waveguides

The detection of hybridization events on oligonucleotide microarrays in real time can be performed, using the optical principle of total internal reflection fluorescence (TIRF). We have investigated and compared three TIRF-sensing configurations using two bulk and one integrated optical planar waveguide as transducer platforms for oligonucleotide microarrays, which have been brought in contact with flow cells. Based on the ray optics model, expressions were derived for the calculation of the intensity of the CCD-camera signal generated by solved fluorophores in the flow cell volume. A noise analysis was performed and expressions for the calculation of the detection limit of the surface fluorophore density were derived. With a bulk optical single total internal reflection configuration a detection limit of 3.74 molecules/μm 2, with a bulk optical multiple total internal reflection configuration a detection limit of 1.83 molecules/μm 2 and with the integrated optical waveguide (IOW) configuration a detection limit of 0.013 molecules/μm 2 was numerically estimated based on background data of the bulk volume signal. The derived analytical expressions address the full system, including light source, optical waveguide and the detection unit and can serve as a tool for TIRF-system design.