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Frequency response study of surface acoustic wave devices with SiO <i> <sub/>x</sub></i> N <i> <sub/>y</sub></i> film using LiTaO <sub/>3</sub> substrate
摘要： In an attempt to suppress the frequency variation of a surface acoustic wave device caused by dielectric ?lm deposition on an interdigital transducer (IDT) electrode, we fabricated a one-port resonator and examined the correlation with frequency response and refractive index when a SiOxNy ?lm is deposited. Our data showed that the resonator frequency changes as the refractive index of the SiOxNy ?lm changes. We also found that the frequency drift caused by the SiOxNy deposition can be suppressed if the refractive index is kept in a certain range. Then, we performed a ?nite element method spectral domain analysis to calculate frequency response using the Young’s modulus obtained in this experiment. The calculated frequency response indicated that the refractive index of the SiOxNy ?lm needs to be altered in accordance with the IDT electrode thickness. We suggest that one of the e?ective ways of controlling the frequency response is to manage the refractive index of SiOxNy.
关键词： SiOxNy ?lm,frequency response,refractive index,IDT electrode,surface acoustic wave device
更新于2025-09-10 09:29:36
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Applied magnetic field effect on core mode properties of MFPCF
摘要： The work investigates a magnetic ?uid ?lled photonic crystal ?bre (MFPCF) at 1557 nm under applied magnetic ?eld. They computed the refractive index change of the MF due to the magnetic ?eld and used it in simulations to ?nd the effective refractive indices of the core and the ?rst cladding modes of the MFPCF. Then, they analytically computed the effective mode area and the con?nement loss. The effective refraction index of the core mode increasing by 0.0341% under the applied ?eld of 0–500 Oe, increases the effective mode area by 128% and the con?nement loss by 866%. Thus, a rather small change in the effective refractive index gives rise to a rather large change in con?nement loss. However, this effect saturates after about 500 Oe because the MF nanoparticles no longer change their magnetic orientation. It is also noteworthy that the con?nement loss changes almost linearly with the effective area as the magnetic ?eld change. These results suggest that MFPCF are suitable for a tunable attenuator and a ?eld sensor.
关键词： con?nement loss,effective mode area,photonic crystal ?bre,refractive index,magnetic ?uid
更新于2025-09-10 09:29:36
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Silicon Photonic Microring Resonator Arrays for Mass Concentration Detection of Polymers in Isocratic Separations
摘要： Molecular weight distribution (MWD) is often the most informative analytical parameter in polymer analysis with gel permeation chromatography (GPC) being the most common approach for determining the MWD for polymer samples. Many industrially relevant polymers lack chromogenic or fluorogenic signatures, precluding use of spectroscopy-based detection. Universal detectors, such as evaporative light scattering and charged aerosol detectors, are nonlinear, limiting quantitative polymer analysis. Differential refractive index (dRI) detectors show linear mass concentration sensitivity but are limited for some analyses given that they are incompatible with gradient-based separations, have limited dynamic range, and require extended thermal equilibration times. In this study, we investigated the utility of silicon photonic microring resonator arrays as a quantitative mass concentration detector for industrial polymer analysis. Microring resonators have optical properties that are sensitive to changes in refractive index, offer an extended dynamic range, broad solvent compatibility, and linear mass concentration detection for a range of molecular weights. Linear mass concentration detection for microrings was demonstrated through a series of isocratic GPC separations using narrow MWD polystyrene (PS) standards. This detection technology was then utilized in conjunction with GPC to analyze a series of broad MWD PS standards, with results in good agreement with dRI and UV. These results demonstrate the potential of the microring resonator platform as a detector for industrial polymer analysis.
关键词： polymers,refractive index,mass concentration detection,isocratic separations,silicon photonic microring resonator arrays,GPC
更新于2025-09-10 09:29:36
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Gas Sensing Mechanism of Silica with Photonic Bandgap Shift
摘要： Two physical models, Replacing model and Filling model, have been proposed to explain the mechanism of effective refractive index change of photonic crystals (PCs). Theoretically, photonic bandgap (PBG) would shift when PCs are exposed to different environment, which leads to change of effective refractive index of PCs. However, the mechanism of effective refractive index change is distinct when PCs are placed in different gases or vapors. Here, silica PCs were successfully fabricated by self-assembled method. The PGB of silica PCs exhibit similar redshift in volatile organic compounds (VOCs) or small-molecule gases. We propose Replacing model to elaborate silica PCs exposed to VOCs, while Filling model to explain silica PCs exposed to small-molecule gases. Additionally, the redshift of PBG was transformed into volume fraction of adsorbed gas in order to achieve selective sensing of silica PCs. The approach could be exploited for application in sensing.
关键词： refractive index,photonic crystals,photonic bandgap,silica,gas sensing
更新于2025-09-10 09:29:36
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Modeling the Temperature Dependent Material Dispersion of Imidazolium Based Ionic Liquids in the Vis-NIR
摘要： A thorough analysis of the refractive index of eleven 1-alkyl-3-methylimidazolium based ionic liquids with three different anions, tetrafluoroborate BF4, bis(trifluoromethylsulfonyl)imide NTf2 and trifluoromethanesulfonate OTf, is reported. Refractive indices were estimated, in the temperature interval from 298.15 K to 323.15 K, using an Abbe refractometer to determine the value at the sodium D line and white light spectral interferometry to obtain dispersion in the range of wavelengths from 400 to 1000 nm. The first part of the manuscript is focused on the dependence of refractive index with wavelength, temperature, cation alkyl chain length and anion nature. Once the main features are detailed, and in order to explain the experimental trends, a model for the refractive index is considered where its square is expressed by a single resonance Sellmeier dispersion formula. This formula has two coefficients, the first one identifies the position of the resonance in the spectral axis, and the second one specifies its strength. It was found that, for a given compound, the resonance's position is independent of temperature, while the strength varies linearly with it. This model reproduces successfully the experimental data within the refractive index uncertainty. Furthermore, the model allows calculating the thermo-optic coefficient and its wavelength dependence.
关键词： ionic liquids,refractive index,thermo-optic coefficient
更新于2025-09-10 09:29:36
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Spectroscopic Microtomography in the Visible Wavelength Range
摘要： We demonstrate spectroscopic microtomography in the visible wavelength range (450–700 nm) using digital holographic tomography, a wavelength-scanning source, and a variable-optical-path-length strategy. This multidimensional imaging system can directly measure the absorption-coefficient and refractive-index spectra of a three-dimensional specimen. We apply the system developed to characterize three types of polystyrene beads (undyed, blue dyed, and red dyed) as well as oxygenated and deoxygenated single red blood cells.
关键词： visible wavelength range,absorption-coefficient,digital holographic tomography,refractive-index spectra,spectroscopic microtomography
更新于2025-09-10 09:29:36
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[IEEE 2018 IEEE 38th International Conference on Electronics and Nanotechnology (ELNANO) - Kiev (2018.4.24-2018.4.26)] 2018 IEEE 38th International Conference on Electronics and Nanotechnology (ELNANO) - Efficient Geometry of Surface Plasmon Resonance Based Fiber Optic Sensor
摘要： The efficient structure for optical fiber based surface Plasmon resonance sensor has been investigated. The sensor structure is based on removing the cladding of a multimode optical fiber and replacing it with thin film of gold. The incident light inside the fiber will excite surface plasmons which will be resulted in the absorption in specific wavelengths. The absorption behavior is dependent on the dielectric constants at the vicinity of the metallic thin film. Based on the amount of removed cladding and deposition regions on the core structure of the fiber, different configurations can be considered. Based on the computational analysis, we have studied performance of sensor for three different configurations. Our method of study is based on solving wave equation in different sensor geometry and calculating absorption for different available modes using Finite Element Method in COMSOL environment. The results of our study show that, the optimum configuration of sensor considering wavelength sensitivity is for a fiber which half of core and cladding has been removed and the gold thin film is deposited on its surface.
关键词： Refractive Index Sensor,Surface Plasmon Resonance,SPR Fiber,Fiber Based Sensor,Finite Element Method,COMSOL
更新于2025-09-10 09:29:36
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Propagation of Electromagnetic Waves through an Invisible Gradient-Index Lens with Negative Refractive Index
摘要： A radially inhomogeneous (gradient-index) lens made of material with a negative refractive index, invisible from the viewpoint of geometrical optics, is proposed and designed. The design includes derivation and solution of an equation for determining the refractive index profile, as well as derivation of an expression allowing calculation of the ray trajectories in the lens. Propagation of a plane wave through a cylindrical modification of the proposed lens both for the case of E-polarization and for the case of H-polarization is analyzed numerically using the hybrid projection method. The results obtained for the RCS of the lens are compared to the similar performance of a positive-index lens described in the previous publications.
关键词： numerical methods,RCS,geometrical optics,invisible lens,Electromagnetic wave propagation,negative refractive index,gradient-index lens
更新于2025-09-09 09:28:46
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All solid quasi-single material supermode microstructure fiber with flattened dispersion and single mode transmission
摘要： An all solid quasi-single material microstructure fiber (AS-QSM-MSF) with flattened dispersion and single mode transmission is presented in this paper. Besides microstructured cladding, six-core configuration is also employed to incorporate mode coupling mechanism into light transmission control in our proposed fiber. By doing this, flattened dispersion in the range of ? 1.03–0.75 ps/(nm km) can be achieved from 1.52 to 2.01 μm, while refractive index difference Δn between matrix and doped inclusions is less than 0.016. Numerical results also show that the fundamental supermode has a flat top power density distribution with effective mode area 48.4 μm2 at 1.55 μm. Compared with the fibers of Gaussian power distribution, our fiber has a more uniform power distribution, which means that our fiber is less susceptible to nonlinear effect under same input power and effective mode area. In addition, simulation results show that the proposed AS-QSM-MSF has a wide single mode regime with cutoff wavelength at 1.197 μm. And the confinement loss and bending loss of the fiber at 45 mm bending radius are as low as 2.6 × 10?7 dB/km and 9.7 × 10?2 dB/km at 1.55 μm, respectively.
关键词： Microstructure fiber,All solid structure,Supermode,Flattened dispersion,Low refractive index difference
更新于2025-09-09 09:28:46
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The effect of Nb2O5 on fast neutron removal cross section, optical, and structural properties of some calcium borate oxide glasses containing Bi3+ ions
摘要： Background In recent years, the preparation of transparent glass in the visible region has led to the development of radiation shielding materials with measuring structure and optical properties. Also, the study on the interaction of neutron radiation with matter is important in the field of radiation protection. Purpose Preparation of transparent calcium and bismuth borate oxide glasses containing Nb5+ ions can be used as a neutron radiation shield and determine refractive index with different methods for this glass. Methods Niobium bismuth borate glasses with composition 60B2O3–20CaO–(20 ? x)Bi2O3–xNb2O5, where (x is in mol%, 0 ≤ x ≤ 10), have been prepared using conventional melt-quenching technique; the structure of each sample was studied by XRD, FTIR, and UV spectra chart analysis. Results XRD and FTIR showed that all glass samples were highly homogeneous and had structured with short-range-order/amorphous solids. The refractive index of each sample was estimated by charts of UV–Vis and FTIR, in addition to an empirical method, and we obtained values very close to each other. The refractive index values are relatively high, so this glass can be used in nonlinear studies as well as luminescence characterization. The macroscopic fast neutron removal cross sections ((cid:2)R/ρ) have calculated, for all samples, and the highest value was in sample containing 2.5% niobium pentoxide. Conclusion Bismuth borate glass containing a few niobium pentoxide can be used as a protective shield of neutrons.
关键词： Borate glass,Refractive index,UV–Vis,Oxide glasses,Optical properties
更新于2025-09-09 09:28:46