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DNA is fundamental for storing and transmitting genetic information. Analyzing DNA or RNA base sequences enables the identification of genetic disorders, monitoring gene expression, and detecting pathogens. Traditional detection techniques like polymerase chain reaction (PCR) and next-generation sequencing (NGS) have limitations, including complexity, high cost, and the need for advanced computational skills. Therefore, there is a significant demand for enzyme-free and amplification-free strategies for rapid, low-cost, and sensitive DNA detection. DNA biosensors, especially those utilizing plasmonic nanomaterials, offer a promising solution. This study introduces a novel DNA-functionalized waveguide-enhanced nanoplasmonic optofluidic biosensor using a nanogold-linked sorbent assay for enzyme-free and amplification-free DNA detection. Integrating plasmonic gold nanoparticles (AuNPs) with a glass planar waveguide (WG) and a microfluidic channel, fabricated through cost-effective, vacuum-free methods, the biosensor achieves specific detection of complementary target DNA sequences. Utilizing a sandwich architecture, AuNPs labeled with detection DNA probes enhance sensitivity by altering evanescent wave distribution and inducing plasmon resonance modes. The biosensor demonstrated exceptional performance in DNA detection, achieving a limit of detection (LOD) of 33.1 fg/mL (4.36 fM) with a rapid response time of approximately 8 min. This ultrasensitive, rapid, and cost-effective biosensor exhibits minimal background nonspecific adsorption, making it highly suitable for clinical applications and early disease diagnosis. The innovative design and fabrication processes offer significant advantages for mass production, presenting a viable tool for precise disease diagnostics and improved clinical outcomes. [ABSTRACT FROM AUTHOR]

Bimetal clad planar waveguide having polyaniline polymer as a guiding layer is proposed and studied for biosensing applications. The dispersion relation and reflectivity of the proposed sensor is obtained using transfer matrix method. The sensing performance and stability of proposed waveguide-based sensor is optimized using different volume fraction of Ag–Au bimetal. The volume fraction 1 represents pure Ag metal coating waveguide that shows maximum sensing performance in our all considered cases. In this case, maximum obtain sensitivity, detection accuracy and quality parameter is 74.140, 11.199 and 559.970°/RIU respectively, at the cover refractive index 1.410. Since, resonance angle and full width at half maxima of resonance peak decreases with increase of Ag metal percentage in Ag–Au bimetal therefore the presence of Au metal decreases the sensing performance of the sensor. Hence, a small volume fraction of Au metal is recommended for higher sensitivity with stability. [ABSTRACT FROM AUTHOR]

The performance of the metamaterial-inspired substrate-integrated waveguide is discussed in this work, concerning a resonator misalignment potentially caused by the fabrication process. Initially, the design parameters of the aforementioned waveguide at the X-band are presented, while its optimal operation is validated to prove the effectiveness of the apparatus. Then, various significant aspects of the polynomial chaos expansion theory are briefly introduced to facilitate the sensitivity analysis due to fabrication errors. The direction of misalignment is, firstly, investigated, while the general case is, also, considered, highlighting a notable immunity, especially at lower frequencies. Additionally, a parametric examination is conducted in terms of the fabrication tolerance, measured as a percentage of the resonator unit cell. All the required simulations are conducted utilizing the non-intrusive approach of the polynomial chaos methodology via the popular Finite-Difference Time-Domain scheme.

Lossy mode resonance (LMR) has garnered significant attention in sensor applications. LMR was primarily explored in fiber-based systems, however, there has been a recent upsurge in its application within planar waveguides. This article compares the LMR phenomenon in planar waveguides with the most employed coatings in the field, specifically SnO2, TiO2, and ITO. Additionally, the experimental findings are compared with simulations conducted using the finite element method (FEM) within the COMSOL Multiphysics environment. The novelty of this research lies in the integration of both experimental results and theoretical calculations, utilizing strong FEM simulation tools, in a single study.

DNA is fundamental for storing and transmitting genetic information. Analyzing DNA or RNA base sequences enables the identification of genetic disorders, monitoring gene expression, and detecting pathogens. Traditional detection techniques like polymerase chain reaction (PCR) and next-generation sequencing (NGS) have limitations, including complexity, high cost, and the need for advanced computational skills. Therefore, there is a significant demand for enzyme-free and amplification-free strategies for rapid, low-cost, and sensitive DNA detection. DNA biosensors, especially those utilizing plasmonic nanomaterials, offer a promising solution. This study introduces a novel DNA-functionalized waveguide-enhanced nanoplasmonic optofluidic biosensor using a nanogold-linked sorbent assay for enzyme-free and amplification-free DNA detection. Integrating plasmonic gold nanoparticles (AuNPs) with a glass planar waveguide (WG) and a microfluidic channel, fabricated through cost-effective, vacuum-free methods, the biosensor achieves specific detection of complementary target DNA sequences. Utilizing a sandwich architecture, AuNPs labeled with detection DNA probes enhance sensitivity by altering evanescent wave distribution and inducing plasmon resonance modes. The biosensor demonstrated exceptional performance in DNA detection, achieving a limit of detection (LOD) of 33.1 fg/mL (4.36 fM) with a rapid response time of approximately 8 min. This ultrasensitive, rapid, and cost-effective biosensor exhibits minimal background nonspecific adsorption, making it highly suitable for clinical applications and early disease diagnosis. The innovative design and fabrication processes offer significant advantages for mass production, presenting a viable tool for precise disease diagnostics and improved clinical outcomes.

This paper introduces a novel design of a tapered rib waveguide utilizing Hybrid Chalcogenide material. The waveguide is 4 mm in length and has a core of GAP-Se. GAP-Se is a combination of GeSe2, As2Se3, and PbSe. The upper and lower cladding are made of SiO2. The varying height of the rib layer results in a reduced effective mode area and an increased nonlinear coefficient. To achieve a desirable and intended supercontinuum spectrum in this waveguide, we utilize a pump pulse with a pulse duration of 100 fs and a power of 1 kW at a wavelength of 3.1 µm. We can change the waveguide dimensions to control and engineer the dispersion properties, which give us two zero dispersion wavelengths at 2.81 µm and 4.91 µm. As a result, we get a supercontinuum spectrum from 2.2 to 5 µm with a bandwidth of 2.8 µm. This design can be useful for different purposes such as biomedical, sensors, and optical coherence tomography. [ABSTRACT FROM AUTHOR]

Microwave sensors offer appealing features such as susceptibility, quick response, and non-invasiveness, making them valuable tools for highly accurate measurements of material characterisation. A wide range of techniques, including cavity waveguide, planar transmission line, cavity waveguide perturbation, open-ended coaxial probe, and free-space transmission, have been employed to characterise materials that are essential for their costeffectiveness, ease of manufacturing, high sensitivity, good quality factor (Q-factor), and compact size, allowing them to be applied to different material types. Among the microwave sensor types, the substrate-integrated waveguide (SIW) has emerged as a promising technology in order to characterise materials in an efficient manner. This paper presents a review of the current state and potential opportunities of SIW microwave sensors in the characterisation of dielectric materials. It provides insights into various design principles, techniques, and applications of SIW microwave sensors across different sectors, highlighting their advantages and limitations compared to conventional waveguide-based sensors. Furthermore, the paper summarises several fabrication methods that can be implemented for SIW microwave sensors to enable the production of efficient and reliable sensors. Additionally, the future directions provided in this paper aim to contribute to the ongoing development and optimisation of SIW-based microwave sensors for accurate and efficient dielectric material characterisation. Overall, this review article serves as a beneficial resource for new researchers seeking to understand the role of SIW microwave sensors in material characterisation. It outlines the current status, opportunities, and potential advancements of SIW sensors, shedding light on their significance and potential impact in the field of material characterisation. [ABSTRACT FROM AUTHOR]

Composite silica-titania waveguide films of refractive index ca. 1.8 are fabricated on glass substrates using a sol-gel method and dip-coating technique. Tetraethyl orthosilicate and tetraethyl orthotitanate with molar ratio 1:1 are precursors. Fabricated waveguides are annealed at 500 °C for 60 min. Their optical properties are studied using ellipsometry and UV-Vis spectrophotometry. Optical losses are determined using the streak method. The material structure and chemical composition, of the silica-titania films are analyzed using transmission electron microscopy (TEM) and electron dispersive spectroscopy (EDS), respectively. The surface morphology was investigated using atomic force microscopy (AFM) and scanning electron microscopy (SEM) methods. The results presented in this work show that the waveguide films are amorphous, and their parameters are stable for over a 13 years. The optical losses depend on their thickness and light polarization. Their lowest values are less than 0.06 dB cm−1. The paper presents the results of theoretical analysis of scattering losses on nanocrystals and pores in the bulk and interfaces of the waveguide film. These results combined with experimental data clearly indicate that light scattering at the interface to a glass substrate is the main source of optical losses. Presented waveguide films are suitable for application in evanescent wave sensors. [ABSTRACT FROM AUTHOR]

Microwave sensors offer appealing features such as susceptibility, quick response, and non-invasiveness, making them valuable tools for highly accurate measurements of material characterisation. A wide range of techniques, including cavity waveguide, planar transmission line, cavity waveguide perturbation, open-ended coaxial probe, and free-space transmission, have been employed to characterise materials that are essential for their cost-effectiveness, ease of manufacturing, high sensitivity, good quality factor (Q-factor), and compact size, allowing them to be applied to different material types. Among the microwave sensor types, the substrate-integrated waveguide (SIW) has emerged as a promising technology in order to characterise materials in an efficient manner. This paper presents a review of the current state and potential opportunities of SIW microwave sensors in the characterisation of dielectric materials. It provides insights into various design principles, techniques, and applications of SIW microwave sensors across different sectors, highlighting their advantages and limitations compared to conventional waveguide-based sensors. Furthermore, the paper summarises several fabrication methods that can be implemented for SIW microwave sensors to enable the production of efficient and reliable sensors. Additionally, the future directions provided in this paper aim to contribute to the ongoing development and optimisation of SIW-based microwave sensors for accurate and efficient dielectric material characterisation. Overall, this review article serves as a beneficial resource for new researchers seeking to understand the role of SIW microwave sensors in material characterisation. It outlines the current status, opportunities, and potential advancements of SIW sensors, shedding light on their significance and potential impact in the field of material characterisation.

In recent years, the technology of waveguide-based planar solar concentrators has been getting more attention in the Concentrated Photovoltaics (CPV) sector due to its compact design and performance versatility and its extended potential applicability from large power plants to built environments, such as Building Integrated Photovoltaics (BIPV). Within the last two decades, geometric design-based Planar Light Concentrator (PLC) and diffraction grating-based PLC have been developed with versatile design architectures along with luminescent PLC, which relies primarily on the development of concerned luminescent optical materials. However, congregating and evaluating the technical advancement gained in the field seems challenging due to the segregated state-of-the-art approaches. Hence, this review attempted to organise the present state of waveguide-based PLC in the frame of reference of PLC optics and optical material design. A systematic comparison of optics and optical material design parameters and the merit of the different PLC systems have been explored within this review to serve as a ready reference for its adoption to develop compact planar waveguide-based CPV systems.

In mode division multiplexing (MDM) optical system, the mode filter has become an inseparable part to reduce modal crosstalk and transmit the desired modes unabatedly. As filtering out lower-order mode is difficult, here we propose a reconfigurable structure of a higher-order mode pass filter consisting of two tunable mode converters and a directional coupler (DC) in a three-mode planar waveguide platform. By switching the working states of the mode converters, the structure can also be used as a fundamental mode (TE0) pass filter and hence dynamic output signals can be achieved. For the second-order mode (TE2) transmission, the simulated excess loss is ∼0.61 dB at 1.550 μm and the extinction ratio remains ≥24 dB (power ratio of TE0 & TE2 Launch) and ≥25 dB (power ratio of TE1 & TE2 Launch) at the entire C-band (1.530–1.565 μm). The device has negligible polarization dependence and hence the TM polarization exhibits similar results.

A double-layer metal superlens was rigorously analyzed and systematically designed to improve subwavelength imaging ability. It was revealed that transmission properties of the imaging system could be accurately interpreted by the five-layer waveguide mode theory—each amplification peak among the spatial frequency range of evanescent waves was associated with a corresponding surface plasmon polariton (SPP) mode of an insulator-metal-insulator-metal-insulator (IMIMI) structure. On the basis of such physical insight, evanescent waves of higher spatial frequency were effectively amplified via increasing propagation constants of symmetrically coupled short-range SPP (s-SRSPP) and antisymmetrically coupled short-range SPP (a-SRSPP), and evanescent waves of lower spatial frequency were appropriately diminished by approaching to cut off symmetrically coupled long-range SPP (s-LRSPP). A flat and broad optical transfer function of the imaging system was then achieved, and improved subwavelength imaging performance was validated by imaging an ideal thin object of two slits with a 20-nm width distanced by a 20-nm spacer, under 193-nm illumination. The resolution limit of the designed imaging system with double-layer superlens was further demonstrated to be at least ~λ/16 for an isolated two-slit object model. This work provided sound theoretical analysis and a systematic design approach of double-layer metal superlens for near-field subwavelength imaging, such as fluorescent micro/nanoscopy or plasmonic nanolithography. [ABSTRACT FROM AUTHOR]

The development of resonance phenomena-based optical biosensors has gained relevance in recent years due to the excellent optical fiber properties and progress in the research on materials and techniques that allow resonance generation. However, for lossy mode resonance (LMR)-based sensors, the optical fiber presents disadvantages, such as the need for splicing the sensor head and the complex polarization control. To avoid these issues, planar waveguides such as coverslips are easier to handle, cost-effective, and more robust structures. In this work, a microfluidic LMR-based planar waveguide platform was proposed, and its use for biosensing applications was evaluated by detecting anti-immunoglobulin G (anti-IgG). In order to generate the wavelength resonance, the sensor surface was coated with a titanium dioxide (TiO2) thin-film. IgG antibodies were immobilized by covalent binding, and the detection assay was carried out by injecting anti-IgG in PBS buffer solutions from 5 to 20 μg/mL. The LMR wavelength shifted to higher values when increasing the analyte concentration, which means that the proposed system was able to detect the IgG/anti-IgG binding. The calibration curve was built from the experimental data obtained in three repetitions of the assay. In this way, a prototype of an LMR-based biosensing microfluidic platform developed on planar substrates was obtained for the first time. [ABSTRACT FROM AUTHOR]

We present a tunable planar groove gap waveguide (PGGWG) resonant cavity at Ka-band. The cavity demonstrates varactor loading and biasing without bridging wires or annular rings, as commonly is required in conventional substrate-integrated waveguide (SIW) resonant cavities. A detailed co-simulation strategy is also presented, with indicative parametric tuning data. Measured results indicate a 4.48% continuous frequency tuning range of 32.52–33.98 GHz and a Qu tuning range of 63–85, corresponding to the DC bias voltages of 0–16 V. Discrepancies between simulated and measured results are analyzed, and traced to process variation in the multi-layer printed circuit board stack, as well as unaccounted varactor parasitics and surface roughness. [ABSTRACT FROM AUTHOR]

Chalcogenide glass (ChG) has been fabricated into on-chip integrated waveguides owing to its high nonlinear refractive index. However, the systematic research of Ge-Sb-S glass shows that Ge25Sb10S65 glass has greater hardness and stronger resistance to laser damage than other component glasses considered in this study. Additionally, the high nonlinear refractive index of Ge25Sb10S65 glass makes it a suitable base material for on-chip integrated devices. To further verify the application potential of this glass in integrated photonics, a waveguide based on Ge25Sb10S65 glass, with width W = 2 μm and thickness H = 1.4 μm, was engineered for supercontinuum generation (SCG). A monolithically integrated SCG spanning from 870 nm to 2480 nm is obtained, when pumped by a femtosecond laser at a central wavelength of 1.55 μm, with a repetition rate of 1 MHz. The results indicated that the Ge25Sb10S65 glass has great prospects of utilization in on-chip integrated devices for application in optical frequency combs (OFCs) or SCG.

Composite silica-titania waveguide films of refractive index ca. 1.8 are fabricated on glass substrates using a sol-gel method and dip-coating technique. Tetraethyl orthosilicate and tetraethyl orthotitanate with molar ratio 1:1 are precursors. Fabricated waveguides are annealed at 500 °C for 60 min. Their optical properties are studied using ellipsometry and UV-Vis spectrophotometry. Optical losses are determined using the streak method. The material structure and chemical composition, of the silica-titania films are analyzed using transmission electron microscopy (TEM) and electron dispersive spectroscopy (EDS), respectively. The surface morphology was investigated using atomic force microscopy (AFM) and scanning electron microscopy (SEM) methods. The results presented in this work show that the waveguide films are amorphous, and their parameters are stable for over a 13 years. The optical losses depend on their thickness and light polarization. Their lowest values are less than 0.06 dB cm−1. The paper presents the results of theoretical analysis of scattering losses on nanocrystals and pores in the bulk and interfaces of the waveguide film. These results combined with experimental data clearly indicate that light scattering at the interface to a glass substrate is the main source of optical losses. Presented waveguide films are suitable for application in evanescent wave sensors.

A double-layer metal superlens was rigorously analyzed and systematically designed to improve subwavelength imaging ability. It was revealed that transmission properties of the imaging system could be accurately interpreted by the five-layer waveguide mode theory—each amplification peak among the spatial frequency range of evanescent waves was associated with a corresponding surface plasmon polariton (SPP) mode of an insulator-metal-insulator-metal-insulator (IMIMI) structure. On the basis of such physical insight, evanescent waves of higher spatial frequency were effectively amplified via increasing propagation constants of symmetrically coupled short-range SPP (s-SRSPP) and antisymmetrically coupled short-range SPP (a-SRSPP), and evanescent waves of lower spatial frequency were appropriately diminished by approaching to cut off symmetrically coupled long-range SPP (s-LRSPP). A flat and broad optical transfer function of the imaging system was then achieved, and improved subwavelength imaging performance was validated by imaging an ideal thin object of two slits with a 20-nm width distanced by a 20-nm spacer, under 193-nm illumination. The resolution limit of the designed imaging system with double-layer superlens was further demonstrated to be at least ~λ/16 for an isolated two-slit object model. This work provided sound theoretical analysis and a systematic design approach of double-layer metal superlens for near-field subwavelength imaging, such as fluorescent micro/nanoscopy or plasmonic nanolithography.

• Fabrication of high energy band gap composite SiO x :TiO y layers of refractive index ca. 1.65. • Resulting composite SiO x :TiO y layers are amorphous and optically homogeneous. • Surface roughness of SiO x :TiO y layers is below 0.2 nm and autocorrelation length is ca. 7 nm. • Elaborated composite SiO x :TiO y waveguide layers have ultra-low optical losses (<0.25 dB/cm). • The influence of SiO x :TiO y waveguide layers surface parameters on optical losses have been determined. This work reports a study on low-loss waveguide layers for planar evanescent wave sensor applications. Crack-free SiO x :TiO y composite layers with refractive indices of ∼1.65, in the visible spectra range, were fabricated using a sol-gel method and a dip-coating technique. Layers of thickness in the 220–360 nm range were produced in a single coating process. By multiple coatings, SiO x :TiO y composite layers of thickness up to 1000 nm were produced. Fabricated layers demonstrated good waveguide properties in the Vis spectral range. The dispersion characteristics of the developed layers refractive index were determined using the spectroscopic ellipsometry method. Spectrophotometric tests validated their optical homogeneity. Using the Tauc method, the widths of optical band gaps were determined, and their high values (E g > 3.7 eV) attest to the amorphous nature of the layer material. The FT-IR studies testified to Si-O-Ti bonds, an attribute of amorphous SiO x :TiO y composites. The tests of surface morphology of the SiO x :TiO y layers, using atomic force microscopy, scanning electron microscopy, and optical profilometry, confirmed their high smoothness. Using the m -line method, waveguide properties and optical losses were examined. To facilitate the interpretation of the experimental results, the mode characteristics and the calculated impact of surface morphology of the waveguide layer. [ABSTRACT FROM AUTHOR]

The development of resonance phenomena-based optical biosensors has gained relevance in recent years due to the excellent optical fiber properties and progress in the research on materials and techniques that allow resonance generation. However, for lossy mode resonance (LMR)-based sensors, the optical fiber presents disadvantages, such as the need for splicing the sensor head and the complex polarization control. To avoid these issues, planar waveguides such as coverslips are easier to handle, cost-effective, and more robust structures. In this work, a microfluidic LMR-based planar waveguide platform was proposed, and its use for biosensing applications was evaluated by detecting anti-immunoglobulin G (anti-IgG). In order to generate the wavelength resonance, the sensor surface was coated with a titanium dioxide (TiO2) thin-film. IgG antibodies were immobilized by covalent binding, and the detection assay was carried out by injecting anti-IgG in PBS buffer solutions from 5 to 20 μg/mL. The LMR wavelength shifted to higher values when increasing the analyte concentration, which means that the proposed system was able to detect the IgG/anti-IgG binding. The calibration curve was built from the experimental data obtained in three repetitions of the assay. In this way, a prototype of an LMR-based biosensing microfluidic platform developed on planar substrates was obtained for the first time.

We present a unified formalism about spatial and angular Goos-Hänchen (GH) and Imbert-Fedorov (IF) shifts. When a horizontally polarized Gaussian beam is reflected from guided-wave resonance structure, the photonic spin Hall effect (PSHE) caused by both spatial and angular IF shifts is theoretically investigated with consideration of beam propagation. When PSHE is observed at Rayleigh range of the reflected beam, the maximum total IF shift is larger than the maximum spatial IF shift. Meanwhile, total IF shift varies faster with the incident angle than the spatial IF shift. The formalism also shows that the spatial and angular IF shifts increase with the increase of the width of the resonant absorption dip. Theoretical predictions agree well with numerical calculations. Those results provide a new way to improve PSHE and have potential application of improving the accuracy of sensors based on PSHE of this structure. [ABSTRACT FROM AUTHOR]

A planar waveguide consisting of a coverslip for a microscope glass slide was deposited in one of its two faces with two materials: silver and indium tin oxide (ITO). The incidence of light by the edge of the coverslip permitted the generation of both surface plasmon and lossy mode resonances (SPRs and LMRs) in the same transmission spectrum with a single optical source and detector. This proves the ability of this optical platform to be used as a benchmark for comparing different optical phenomena generated by both metal and dielectric materials, which can be used to progress in the assessment of different sensing technologies. Here the SPR and the LMR were compared in terms of sensitivity to refractive index and figure of merit (FoM), at the same time it was demonstrated that both resonances can operate independently when silver and ITO coated regions are surrounded by different refractive index liquids. The results were supported with numerical results that confirm the experimental ones.

Coupling between a planar waveguide (PWG) mode in an organic single crystal and a surface plasmon polariton (SPP) mode is investigated in this paper. Anticrossing behavior appearing under the strong coupling regime was observed in the dispersion curves of the coupled modes. Although previous studies have utilized spin-coated organic waveguides, to date, there have been no reports on the use of single-crystalline waveguides. The so-called Fano line shapes have been observed in spectra in numerous studies related to PWG–SPP coupled systems, which are expected to find utility in surface plasmon resonance sensors. Meanwhile, transitions from Fano line shapes to Rabi splitting have been observed with increase in coupling and have attracted considerable attention in fundamental physics. As organic single crystals exhibit strong optical anisotropy, the influence of directional dispersions on coupling strength is expected to be significant. In the present study, we have developed angle-resolved transmission microspectroscopy that enables optical measurements of an organic single crystal with an in-plane dimension of hundreds of micrometers even in the nonradiative region. Because measuring such a small sample using conventional attenuated total reflection measurements is difficult, the transmission spectra in the nonradiative region were measured by rotating the sample in index-matching oil. Accordingly, dispersion curves reflecting the coupling between the PWG and SPP modes were obtained. [ABSTRACT FROM AUTHOR]

Sepsis, a life-threatening inflammatory response, demands economical, accurate, and rapid detection of biomarkers during the critical "golden hour" to reduce the patient mortality rate. Here, we demonstrate a cost-effective waveguide-enhanced nanogold-linked immunosorbent assay (WENLISA) based on nanoplasmonic waveguide biosensors for the rapid and sensitive detection of procalcitonin (PCT), a sepsis-related inflammatory biomarker. To enhance the limit of detection (LOD), we employed sandwich assays using immobilized capture antibodies and detection antibodies conjugated to gold nanoparticles to bind the target analyte, leading to a significant evanescent wave redistribution and strong nanoplasmonic absorption near the waveguide surface. Experimentally, we detected PCT for a wide linear response range of 0.1 pg/mL to 1 ng/mL with a record-low LOD of 48.7 fg/mL (3.74 fM) in 8 min. Furthermore, WENLISA has successfully identified PCT levels in the blood plasma of patients with sepsis and healthy individuals, offering a promising technology for early sepsis diagnosis.

We present, experimental broadband propagation characterization of a planar groove gap waveguide (PGGWG) from 29 to 40 GHz. The transmission line Q‐factor is found to vary from 110 to 130 over the band, which is shown by comparison of measurement data to be comparable to substrate integrated waveguide (SIW). PGGWG is found to have a phase constant of nearly double that of SIW using the same materials and manufacturing process. This is a significant result for system miniaturization. [ABSTRACT FROM AUTHOR]

Purpose: Showing the possibility in principle of the use of a screened dielectric resonator excited by the planar waveguide to stabilize the frequency of solid-state sources in the millimeter wavelength range. Design/methodology/aproach: A wiring diagram of the high-Q resonator oscillator included into the self-excited oscillator system is used. To connect the generator to the resonator and the load, using the planar waveguides is suggested. Using just a planar waveguide for power supply from the generator to the resonator can significantly rarefy the spectrum and excite in dielectric resonator a high-Q whispering gallery mode. Findings: The possibility of mm-wave oscillator frequency stabilization by an external high-Q shielded dielectric resonator driven by a planar waveguide is considered. The effective drive of whispering gallery modes of shielded resonator is shown to be achieved by changing the position of the output slot of the oscillator in a planar waveguide. Conclusions: We succeeded in stabilization of the oscillator frequency by an external high-Q shielded dielectric resonator.

Abstract. We report in this paper the result of thin film fabrication of MEH-PPV and MEH-PPB having good optical transparency and low surface roughness suitable for planar waveguide application. The linear optical properties of the polymers were characterized using reflectometry and prism coupling, while the non-linear optical property was measured by means of optical third harmonic generation (THG). The waveguide attenuation of the polymer films was determined by employing prism coupling set-up equipped with a photodiode array detector. The MEH-PPV waveguide film was shown to have a very low attenuation of 0.5 dB cm-1 at 1064 nm yielding an unprecedentedly high figure of merits of 11 at 1 GW/cm2. Pandu Gelombang Planar dari Turunan PPV Sari. Dalam tulisan ini dilaporkan fabrikasi film tipis polimer MEH-PPV dan MEH-PPB yang mempunyai transparansi optik tinggi dan permukaan yang halus sehingga cocok untuk aplikasi pandu gelombang planar. Sifat optic linier dari polimer yang bersangkutan diukur dengan teknik reflektometri dan kopling prisma dan sifat optic nonlinier diukur dengan metoda third harmonic generation (THG). Selanjutnya, atenuasi pandu gelombang dari film polimer yang bersangkutan diukur dengan konfigurasi kopling prisma dan detector diode arrat. Film pandu gelombang yang dihasilkan dalam eksperimen ini memiliki atenuasi rendah sebesar 0.5 dB cm-1 pada panjang gelombang 1064 nm dan menghasilkan "figure of merits" (FOM) sebesar 11 pada intensitas 1 GW/cm2 yang merupakan nilai tertinggi sejauh ini.

• A concept of flat, spectrum splitting concentrator photovoltaic system for electric vehicle roof is presented. • The flat structure and the lateral displacement of sun tracking mechanism allow installation on EV's roof. • Simulations show the system can harvest 4.48 kWh on a summer day. A car, Kia Ray can travel 37.7 mk using this amount of energy. • Simulations for different climates show the proposed system is more suitable with high DNI area. In this paper, we present a novel design and an optical simulation of a flat concentrator photovoltaic (CPV) system for electric vehicle application. The sunlight concentration component is comprised of a planar waveguide integrated dichroic mirror-coated cone prisms and a mirror-coated lens array. Sunlight reflects firstly at the mirror-coated lens array and then strikes the cone prism of the planar waveguide. The prisms are coated by the dichroic mirrors to divide the solar spectrum into two bands. The low-energy band is transmitted and reaches the GaInAsP/GaInAs dual-junction solar cells. The mid-energy band is reflected at the prism surface and coupled inside the waveguide. The exit port of the waveguide is attached with GaInP/GaAs dual-junction solar cells. The simulation results demonstrated a maximum electricity conversion efficiency of 32.88% at the high concentration ratio. The system thickness is 35 mm, which is as thin as the conventional flat photovoltaic panel and system allow for a lateral sun-tracking mechanism. This is suitable for installation on the vehicle's roof. The results showed that the presented flat CPV system is a new approach for a highly efficient application of solar energy to the electrical vehicle. [ABSTRACT FROM AUTHOR]

We consider the Laplace operator in a planar waveguide, i.e. an infinite two-dimensional straight strip of constant width, with Robin boundary conditions. We study the essential spectrum of the corresponding Laplacian when the boundary coupling function has a limit at infinity. Furthermore, we derive sufficient conditions for the existence of discrete spectrum. [ABSTRACT FROM AUTHOR]

Abstract We describe a new sensitive method for the investigation of weakly magnetic films placed inside a tri-layer planar waveguide. Polarized neutrons tunnel into the waveguide through the surface, channel along the layers and are emitted from the end face as a narrow and slightly divergent microbeam. Polarization analysis permits to detect very small magnetization in the order of a few 10 Gauss. The magnetic film containing the rare-earth element Tb was investigated using both fixed wavelength and time-of-flight polarized neutron reflectometers. The experimental results are presented and discussed. [ABSTRACT FROM AUTHOR]

To overcome the limitations of low sensitivity and instability of metal-medium-metal tunable surface plasmon resonance (SPR) sensors excited by planar waveguides, a silver-graphene-medium-graphene-silver film symmetrical SPR sensing structure excited by planar waveguides is proposed. And optimize sensor performance through modeling. The principle of symmetry structure for sensing tunability is analysed, finding that sensing with a silver film has a higher sensitivity than a gold film. However, since the silver film is easily oxidized, it affects the stability and repeatability of the sensor. To solve this problem, the graphene layer is added to the silver film to improve the disadvantage of easy oxidation of the silver film. A plane waveguide with a refractive index distribution of the residual error function of the excitation is prepared by ion exchange. The sensor structure was modeled and analyzed, and the influence of metal material, metal thickness, graphene layer number and thickness of the detection medium on the performance of the sensor was studied, and the sensing structure was better optimized. The results show that the silver film has a better sensing performance and higher sensitivity than the gold film. By adjusting the thickness of the detection medium, the refractive index range of the detection medium has a certain tunability: the choice of graphene thickness optimises sensor stability and detection sensitivity. [ABSTRACT FROM AUTHOR]

Abstract Planar waveguide LuAG/10 at.%Yb:LuAG/LuAG laser ceramics were fabricated by the tape casting method combined with the vacuum pre-sintering and hot isostatic pressing (HIP) post-treatment. The morphologies of the raw materials, tapes and green bodies were observed. The microstructure, optical transmittance and the Yb3+ ions distribution of the LuAG/10 at.%Yb:LuAG/LuAG ceramics with different pre-sintering temperatures after HIP post-treatment were mainly studied. The experimental results showed that the average grain size and in-line transmittance of the HIPed ceramics increased with the increase of pre-sintering temperature. For the LuAG/10 at.%Yb:LuAG/LuAG ceramics pre-sintered at 1825 °C for 20 h and then HIPed at 1700 °C for 3 h under 200 MPa Ar atmosphere, the in-line transmittance of the sample with the thickness of 2 mm was about 74% at 1100 nm and the maximum diffusion distance of Yb3+ was about 166 μm. The bulk and grain boundary diffusion coefficients of Yb3+ ions for the samples pre-sintered at 1775 °C–1825 °C after HIP post-treatment were calculated by Fick's second law by using the LA-ICP-MS. What's more, CW laser at 1030 nm was demonstrated and the maximum output power of 0.4 W with a slop efficiency of 9.4% was achieved. Highlights • Planar waveguide LuAG/10 at.%Yb:LuAG/LuAG laser ceramics were fabricated by the tape casting and two-step sintering method. • Laser oscillation of planar waveguide LuAG/Yb:LuAG/LuAG ceramics was demonstrated for the first. • The diffusivity of Yb3+ increased with increasing the pre-sintering temperature, especially for the grain boundary diffusion. [ABSTRACT FROM AUTHOR]

Abstract Neutron planar waveguides are focusing devices generating a narrow neutron beam of submicron width. Such a neutron microbeam can be used for the investigation of local microstructures with high spatial resolution. The essential parameter of the microbeam is its angular width. The main contribution to the microbeam angular divergence is Fraunhofer diffraction on a narrow slit. We review and discuss various ways to characterize the angular divergence of the neutron microbeam using time-of-flight and fixed wavelength reflectometers. Highlights • Planar waveguides transform neutron macrobeam into a narrow microbeam. • Neutron microbeam is used for scan of microstructures with high spatial resolution. • Fraunhofer diffraction on a narrow slit contributes to a microbeam angular divergence. • Microbeam divergence depends on neutron wavelength and waveguiding layer width. • Experimental results and calculations are presented and discussed. [ABSTRACT FROM AUTHOR]

We describe the design and performance characterization of spectrally tunable microengineered notch filters operating in the longwave infrared from 8 to 12 micron using quantum cascade lasers (QCLs) tunable over the full spectral range. The filter design is based on the guided mode resonance phenomenon. The device structure consists of a subwavelength dielectric grating on top of a planar waveguide using high-index transparent dielectric materials, i.e., germanium (Ge) and zinc selenide (ZnSe) with refractive indices of 4.0 and 2.4, respectively. The filters are designed to reflect the incident broadband light at one (or more) narrow spectral band while fully transmitting the rest of the light. Spectral tuning of the reflected wavelength is achieved by changing the angle of incidence by mechanically tilting the filter. Filters based on one-dimensional (1-D) gratings are polarization dependent and those based on two-dimensional (2-D) gratings are close to polarization independent. Simple two-layer antireflection coatings were applied to minimize reflections from the nonpatterned side of the filter substrate. Our experimental setup consisted of a commercial QCL system operating at room temperature, a microengineered filter, and an uncooled broadband sensor. We present the filter design and detailed characterization experiment, and compare the theoretical and experimental results for 1-D filters. [ABSTRACT FROM AUTHOR]

In this paper, we researched the growth mechanism of solid-state crystal growth (SSCG) method in planar waveguide. The effect of tetraethyl orthosilicate (TEOS) inside YAG (yttrium aluminum garnet) ceramic matrixes on the YAG single-crystal growth was studied. The results indicated that the crystal growth increased with increasing TEOS content. Theoretical analysis confirmed that the solid-state crystal growth kinetics could be fitted by the Lifshitz–Slyozov–Wagner law. Additionally, the segregation of silicon was observed, the SSCG process with SiO 2 effectively eliminated the pores in the YAG ceramic matrices via diffusion to the growth interface between the crystal and the ceramic. We successfully obtained high transparency YAG single crystal using the SSCG method, which transmittance value reached 83.62% at 1064 nm. [ABSTRACT FROM AUTHOR]

A reliable method is presented for the computation of the propagation constants and the corresponding hybrid modal fields in multilayered planar dielectric stacks comprising multiple anisotropic conducting sheets. The appropriate dispersion functions (DFs) are formulated and evaluated using a numerically stable scattering matrix methodology. The roots of the DFs are computed by the Cauchy integration method with automatic differentiation of the DF. [ABSTRACT FROM AUTHOR]

A robust and efficient method is presented for the computation of the electromagnetic modes supported by planar multilayer waveguides that may comprise lossy, active, plasmonic, and uniaxial media, including graphene sheets. Pole-free and numerically stable dispersion functions (DFs) are developed for various shielding configurations using the $S$ -matrix formulation. The modal propagation constants are computed by the Cauchy integration method on the four-sheeted Riemann surface, using the derivative of the DF for greater reliability. Since analytical derivatives of the S-parameters are difficult to obtain, automatic differentiation is employed, implemented by operator overloading in modern Fortran. The method is validated using various benchmark problems found in the literature. [ABSTRACT FROM AUTHOR]

A mutual coupling of a surface plasmon polariton (SPP) with an optical mode excited in a planar waveguide (WG) is discussed. A planar layered structure is studied consisting of a coupling prism, an Au film and a high-index interlayer for SPPs generation, and a dielectric waveguide composed of a ferromagnetic garnet on a (CaMgZr)-doped gallium–gadolinium garnet substrate (GGG) separated by an air gap. The dependence of coupling resonances on the gap thickness and the interlayer refractive index is analyzed to obtain an optimal field intensity enhancement for future designs of plasmonic and magneto-plasmonic sensing elements. [ABSTRACT FROM AUTHOR]

Ge28Sb12Se60 waveguides and microresonators were fabricated by thermal evaporation and dry etching technology. The low loss waveguides and high-index-contrast Ge28Sb12Se60 microring resonators were developed and demonstrated using the optimal parameters of CF4/CHF3 etching recipe. An intrinsic quality factor (Q-factor) of 2.3 × 105 with propagation loss of 2.4 dB/cm at 1550 nm was obtained in this microring resonator with 800 × 400 nm cross-sectional dimension. Critically coupled resonator showed extinction ratio of >30 dB. Nonlinear refractive index (n 2) of 5.12 × 10−18 m2/W for Ge28Sb12Se 60 glass was measured and nonlinear coefficient (γ) of 24 W−1 m −1 asfabricated waveguide was also estimated. This paper illustrates the potential of Ge28Sb 12Se60 glass as a low loss and large nonlinearity material for integrated photonics applications. [ABSTRACT FROM AUTHOR]

Characteristics of propagation of bright pyroelectric quasi-solitons are studied in a photorefractive waveguide. These solitons considered are supported solely by the pyroelectric effect. The investigation is performed under Wentzel-Kramers-Brillouin-Jefferys approximation and a Gaussian ansatz for the soliton is used instead of numerical solutions. The planar waveguide structure intensifies the self-focussing while decreasing the minimum or threshold power required for self trapping. The waveguide structure embedded in the crystal can self trap a soliton of power lower than the threshold power. As the waveguide parameter increases, minimum required power to self trap the beam decreases. The existence of bistable states is also predicted. Four regimes of power are identified and investigated in which the quasi-solitons behaviour is distinct. [ABSTRACT FROM AUTHOR]

Aiming at alleviating the adverse effect of poor light penetrability on microalgae growth, planar waveguide modules functioned as diluting and redistributing the intense incident light within microalgae culture more homogeneously were introduced into a lab-scale open raceway pond (ORP) for Nannochloropsis oculata cultivation. As compared to the conventional ORP, the illumination surface area to volume ratio and effective illuminated volume percentage in the proposed ORP were respectively improved by 5.53 times and 19.68–172.72%. Consequently, the superior light distribution characteristics in the proposed ORP contributed to 193.33% and 443.71% increase in biomass concentration and lipid yield relative to those obtained in conventional ORP, respectively. Subsequently, the maximum biomass concentration (2.31 g L −1 ) and lipid yield (1258.65 mg L −1 ) was obtained when the interval between adjacent planar waveguide modules was 18 mm. The biodiesel produced in PWM-ORPs showed better properties than conventional ORP due to higher MUFA and C18:1 components proportions. [ABSTRACT FROM AUTHOR]

Transverse electric (TE) modes in symmetrical planar slot waveguides are analytically solved, and a comprehensive knowledge about them is provided. It has been shown that there are four types of TE modes in planar slot waveguides just as the TM modes. Their field solutions, characteristic equations and cut-off conditions are derived. The cut-off conditions and the power confinement factors of the TE and TM modes are compared. It is demonstrated that there may be degeneration points between TE and TM modes. Because a three-dimensional waveguide has similar modal characteristics as its planar counterpart, our work presents a foundation of recognizing and utilizing the three-dimensional slot waveguides. [ABSTRACT FROM PUBLISHER]

Neutron planar waveguides produce a narrow neutron beam of submicron width which can be used to scan local microstructures with high spatial resolution. The important parameter of a planar waveguide is the distance over which the neutron wave density decays exponentially during the neutron channeling inside a guiding layer. We review various ways to experimentally characterize neutron channeling lengths. Experimental results are presented and advantages and drawbacks of the different methods are discussed. [ABSTRACT FROM AUTHOR]

• New strategy to improve the sensitivity of refractometers based on lossy-mode resonances. • High sensitivity sensing platform can be used for the development of LMR based chemical sensors and biosensors. • Simple disposable planar configuration. In this work a new strategy to improve the sensitivity of refractometers based on lossy-mode resonances has been proved. The proximity of the PFA (tetrafluoroethylene-perfluoro polymer) substrate refractive index to that of water has permitted to implement an optical refractometer with a sensitivity of 41,034 nm per refractive index unit (nm/RIU) for refractive indices ranging from 1.3318 to 1.3347. The work is supported with both theoretical and experimental results. This high sensitivity can be used for the development of LMR based chemical sensors and biosensors, where a low limit of detection is required, with the additional advantage of a simple disposable planar configuration. [ABSTRACT FROM AUTHOR]

Even and odd modes propagating along the symmetrical planar waveguide, which is a film embedded in a nonlinear medium, are described analytically. The dielectric function of the film is characterized by a linear spatial profile symmetrical about its center in transverse direction. The dielectric function of the nonlinear medium changes stepwise its value when the electric field amplitude exceeds the threshold value. Exact solutions of even and odd symmetry to the wave equation with such compound dielectric function are found. The solutions describe the waveguide modes existing with the discrete spectrum of the effective refractive index. Waveguide modes can be excited at certain discrete values of the angle of incidence of the exciting beam. Low-order modes are excited at large angles of incidence, and high-order modes are excited at small ones. The number of excited modes is limited and is determined by the parameters of the waveguide system, in particular, by the film thickness and the wavelength of the exciting radiation. Excitation of an even mode of certain order requires a wavelength longer than that of an odd mode of the same order. The intensity of the mode increases with an increasing film thickness, and it decreases with an increasing wavelength. The power flux and the radiation confinement factor are calculated analytically. The radiation confinement factor behaves in the same way as the intensity of the waveguide mode. It is shown that the minimum value of the radiation power required to excite the mode is reached at the critical value of the film thickness (or the critical wavelength), at which the radiation confinement factor is equal to a half. [ABSTRACT FROM AUTHOR]

The development of accurate, intuitive, and easy-to-handle devices to detect different types of allergens is on the rise, as these are useful tools to guarantee consumer safety, which should be a priority for any food industry. Gliadin, one of the main proteins present in gluten, is the one responsible for triggering the immune system to produce autoantibodies in celiac disease, the most dangerous pathology related to gluten. Lossy Mode Resonance (LMR) based biosensors are lately known as a promising sensing technology and its implementation on planar waveguides has been shown to result in manageable, sustainable and robust structures. In this work, an LMR based microfluidic biosensor for gliadin detection is proposed, by coating a coverslip with Titanium Dioxide (TiO 2) by Atomic Layer Deposition (ALD) to generate the resonance phenomena and functionalizing the sensor surface with anti-gliadin antibody (AGA) through covalent bond. The sensor was exposed to different gliadin concentrations in ultrapure water, in the range of 0.1–100 ppm with an accuracy of ±0.14 ppm, for a sensitivity of 1.35 ppm/ml. The calibration curve was obtained from the experimental data corresponding to three repetitions of the assay and a limit of detection (LOD) of 0.05 ppm was achieved. Moreover, the sensor was exposed to commercial flour samples, some of them labeled as gluten free (GF) and the response agreed with the expected results according to product label. Biosensor specificity to gliadin was demonstrated by injecting chicken egg white albumin without obtaining any significant response. • An LMR based immunosensor on planar waveguide for gliadin detection is proposed. • The gliadin biosensor is label-free and provides real time measurements. • The gliadin concentration detection is 100 times below the gluten-free threshold. • Easy and portable method to use in food industry when quantifying gluten proteins. [ABSTRACT FROM AUTHOR]

Surface plasmon resonance has become a widely accepted optical technique for studying biological and chemical interactions. Among others, detecting small changes in analyte concentration in complex solutions remains challenging, e.g., because of the need of distinguishing the interaction of interest from other effects. In our model study, the resolution ability of plasmonic sensing element was enhanced by two ways. Besides an implementation of metal-insulator-metal (MIM) plasmonic nanostructure, we suggest concatenation with waveguiding substructure to achieve mutual coupling of surface plasmon polariton (SPP) with an optical waveguiding mode. The dependence of coupling conditions on the multilayer parameters was analyzed to obtain optimal field intensity enhancement.

Interval between adjacent planar waveguides and light intensity emitted from waveguide surface were the primary two factors affecting light distribution characteristics in the planar waveguide flat-plate photobioreactor (PW-PBR). In this paper, the synergy effect between light and nitrate in the PW-PBR was realized to simultaneously enhance microalgae growth and lipid accumulation. Under an interval of 10 mm between adjacent planar waveguides, 100% of microalgae cells in regions between adjacent waveguides could be illuminated. Chlorella vulgaris growth and lipid accumulation were synchronously elevated as light intensities emitted from planar waveguide surface increasing. With an identical initial nitrate concentration of 18 mM, the maximum lipid content (41.66% in dry biomass) and lipid yield (2200.25 mg L −1 ) were attained under 560 μmol m −2 s −1 , which were 86.82% and 133.56% higher relative to those obtained under 160 μmol m −2 s −1 , respectively. The PW-PBR provides a promising way for microalgae lipid production. [ABSTRACT FROM AUTHOR]