Resonance Peak Wavelength Research Articles

Antibiotic-Mediated Plasmonic Resonance on a Novel Nanopillar Metasurface Array.

This study demonstrates a silicon nanopillar metasurface coupled with localized surface plasmon resonance (LSPR) mediated by the presence of cephalexin antibiotics in solution for biosensing applications. A facile fabrication process was developed to create the metasurface on silicon wafers with a unique resonance signature. The resulting metasurface consists of periodic nanopillars approximately 180 nm in diameter, 210 nm deep, and with a controlled edge-to-edge separation of 200 nm. These dimensions were chosen based on a finite element method simulation that was used to investigate the ideal parameters to produce the desired resonance effect in the metasurface reflection spectra. Optimization of the nanopillar surface properties and the sidewall angle allowed for replication of the simulations. This metasurface was coupled with BSA-coated gold nanospheres (BSANS) to mediate the redshift of peak resonance wavelength values, occurring only in the presence of the antibiotic linker. The device fabricated herein exhibits a significant 22 nm wavelength shift resulting from changes to the local refractive index in the presence of the BSANS-antibiotic coupling. Further enhancement of the binding events is promoted by the LSPR hot spots formed between the nanoparticles and the metasurface allowing for sensitive and real-time detection.

Tunable Plasmon Resonance in Silver Nanodisk-on-Mirror Structures and Scattering Enhancement by Annealing.

In this study, we evaluated the surface plasmon characteristics of periodic silver nanodisk structures fabricated on a dielectric thin-film spacer layer on a Ag mirror substrate (NanoDisk on Mirror: NDoM) through finite difference time domain (FDTD) simulations and experiments involving actual sample fabrication. Through FDTD simulations, it was confirmed that the NDoM structure exhibits two sharp peaks in the visible range, and by adjusting the thickness of the spacer layer and the size of the nanodisk structure, sharp peaks can be obtained across the entire visible range. Additionally, we fabricated the NDoM structure using electron beam lithography (EBL) and experimentally confirmed that the obtained peaks matched the simulation results. Furthermore, we discovered that applying annealing at an appropriate temperature to the fabricated structure enables the adjustment of the resonance peak wavelength and enhances the scattering intensity by approximately five times. This enhancement is believed to result from changes in the shape and size of the nanodisk structure, as well as a reduction in grain boundaries in the metal crystal due to annealing. These results have the potential to contribute to technological advancements in various application fields, such as optical sensing and emission enhancement.

A Simultaneous Measurement Sensor for Temperature and Curvature Based on Congruent Quasi-Helical Long-Period Fiber Grating.

This article presents a long-period fiber-grating sensor based on a congruent quasi-helical structure (CQH-LPFG) with the two-parameter measurement of both temperature and curvature. The CQH-LPFG sensor was manufactured using a high-frequency CO2 laser, and an innovative quasi-helical structure was introduced into the two-parameter measurement of the temperature and curvature of the optical fiber sensor with excellent results. The experiment and analysis demonstrate that the curvature sensitivities of the three resonance peaks in the 1440 nm to 1540 nm transmission spectrum were 11.88 nm/m-1, 8.05 nm/m-1, and 11.11 nm/m-1, and the curvature varied ranging from 0.156 m-1 to 0.494 m-1. The three resonance peaks showed temperature responsivities of 29.87 pm/°C, 24.65 pm/°C, and 36.85 pm/°C, respectively, and the linear fit was of excellent quality. In the case of measuring both curvature and temperature changes simultaneously, the resonant peak wavelength of the CQH-LPFG sensor was demodulated through matrix analysis, with dip A and dip C providing superior simultaneous measurements. These features make it a promising candidate for applications such as engineering machinery and the health inspection of buildings.

Distributed Bragg reflector based ASE noise removal pump wavelength filters for futuristic chip-scale quantum photonic circuits.

This article reports a novel design of a compact tunable resonance filter with a highly extinguished and ultra-broad out-of-band rejection for on-chip amplified spontaneous noise suppression from pump lasers highly demanding for generating pure/entangled photon pairs via χ(3) process in a CMOS compatible silicon photonics technology platform. The proposed device is designed with two identically apodized distributed grating structures for guided Fabry-Perot resonant transmissions in a silicon-on-insulator rib waveguide structure. The device design parameters are optimized by theoretical simulation for a low insertion loss singly-resonant transmission peak at a desired wavelength. We observed that a device length of as low as ∼ 35 µm exhibits a rejection band as large as ∼ 60 nm with an extinction of ∼ 40 dB with respect to the resonant wavelength peak at λr ∼ 1550 nm (FWHM ∼ 80 pm, IL ∼ 2 dB). The experimental results have been shown to be closely matching to our theoretical simulation and modeling results in terms of its stop bandwidth and resonance wavelength for noise suppressed pump laser wavelength filtering. As expected from the theoretical prediction, the trend pertaining to the trade-off between passive insertion loss and Q-value of the resonances has been observed depending on the device parameters. The thermo-optic tuning characteristics of resonant wavelengths have been obtained by integrating microheaters. The resonance peak could be tuned at a rate of 96 pm per mW of consumed thermal power. Noise associated with an amplified pump wavelength (λP ∼ 1550 nm) has been shown to be suppressed (∼ 40-dB), up to the detector noise floor.

Optical fiber sensor for curvature and temperature simultaneous measurement based on an anti-resonance mechanism

Based on an anti-resonance mechanism, we propose and experimentally demonstrate an optical fiber sensor for simultaneous measurement of curvature and temperature. The sensor structure consists of a hollow fiber and a twisted graded index multimode fiber spliced between two single-mode fibers. By using the twisted graded index multimode fiber to change the energy distribution of the mode field, not only improve the coupling efficiency of the sensor but also the sensitivity of the curvature measurement. The experimental results show that the intensity of the resonance peak based on the anti-resonance mechanism decreases with the increase of curvature, while the resonance peak wavelength is insensitive to curvature. In addition, due to the thermal expansion and thermo-optic effect of the fiber, the wavelength of the resonance peak is red-shifted with increasing temperature, and the intensity of the resonance peak is insensitive to temperature. Therefore, the intensity and wavelength signals of the resonance peak are monitored separately, and the simultaneous measurement of displacement and temperature is realized. The maximum sensitivity of the proposed curvature sensor can reach −2.84 dB/m−1, the dynamic range of curvature is 0 m−1 to 20.18 m−1, and the temperature sensitivity of 20 pm/∘C is realized. The proposed sensor has a compact structure, simple preparation, high coupling efficiency, and good repeatability, making it an ideal choice for simultaneous measurement of curvature and temperature in structural monitoring, mechanical manufacturing, and other fields.

Design and analysis of a fiber Bragg grating-based foot pressure assessment system.

This research presents a comprehensive study focused on the design, implementation, and analysis of an innovative fiber Bragg grating (FBG) based foot pressure assessment system. FBG sensors strategically placed on the great toe, metatarsal 1, metatarsal 2, and heel provided distinct peak resonant wavelengths, strains, and pressures during experimental cycles. Participant 1 exhibited peak resonant wavelength of 1537.745 nm for great toe, 1537.792 nm for metatarsal 1, 1537.812 nm for metatarsal 2, and 1537.824 nm for heel. Participant 2 showcased distinct graphical representations with peak resonant wavelengths ranging from 1537.903 to 1537.917 nm. In a fracture patient condition, the FBG-based system monitored weight-bearing capacity, integrated with real-time X-ray imaging for dynamic insights of rehabilitation as distinct approach. The strains and pressures at each position exhibited notable variations along with the sensitivity of 1.31με obtained across all positions, underscoring the FBG-based system's reliability in capturing subtle foot pressure.

Investigation of a Pyramid-like Optical Absorber with High Absorptivity in the Range of Ultraviolet A to Middle Infrared

In this study, a simple pyramid-like ultra-wideband absorber was designed to explore high absorptivity across a wide bandwidth. The absorber consisted of eight layers organized into four groups, and each group comprised a metal layer followed by an oxide layer, both of which were square with equal side lengths. Specifically, the chosen oxides, arranged from bottom to top, included SiO2 (t7 layer), Al2O3 (t5 layer), SiO2 (t3 layer), and Al2O3 (t1 layer). In the initial design phase, the thickness of the t8 Ti layer was set to 50 nm and assigned initial values to the thicknesses of the t7-t1 layers, and the widths of the four groups w4, w3, w2, and w1, decreased successively from bottom to top, creating a structure reminiscent of a pyramid. Comsol (version 6.0) was utilized to simulate and systematically vary one parameter at a time, ranging from the thicknesses of the t7-t1 layers to the widths of w4-w1, in order to identify the most suitable structural parameters. Our analyses demonstrated that multimode resonance arose due to the emergence of absorption peaks at lower wavelengths between larger and smaller areas. Additionally, surface plasmon resonance and interference effects between various layers and materials were attributed to the alternating arrangement of metal and oxide layers. The enhancements in the electric field observed at different resonance peak wavelengths illustrated the Fabry–Perot cavity effect, while the impedance matching effect was observed through variations in the real and imaginary parts of the optical impedance with respect to the wave vector. After simulating using these optimally found thicknesses and widths, the aforementioned effects manifested in the pyramid-like ultra-wideband absorber we designed, with its absorptivity surpassing 0.900 across the spectrum from ultraviolet A (335 nm) to middle infrared (4865 nm).

Dynamically manipulation of anisotropic coherent perfect absorption in borophene metasurface

This paper proposed a borophene-based metamaterial device to achieve the anisotropic coherent perfect absorption (CPA) effect in the two-port device. By simply adjusting the polarization angle of the incident light, the dynamic switching of the CPA resonance peak wavelength can be achieved. Besides, by simultaneously modulating the electron doping concentration of borophene and the relative phase of the incident light, the coherent absorption efficiency of borophene can be continuous modulated for both polarization directions. Furthermore, the theorem of scattering matrix is utilized to elucidate the physical mechanism of CPA, and the analytical results demonstrate remarkable accordance with the numerical computations. Owing to the flexible continuous tunability, the proposed borophene CPA device is expected to open up new opportunities for optical modulators and all-optical logic chips.

Machine learning enabled 2D photonic crystal biosensor for early cancer detection

In this paper, a novel 2D Photonic Crystal (PC)-based cancer biosensor is proposed for the detection of different types of cancer cells HeLa, PC12, MDA, MCF, and Jurkat. The sensor is designed using Silicon-on-insulator (SOI) substrate in a triangular lattice with holes in the slab. The proposed design is optimized to provide a high-quality factor of 15,000, high sensitivity and a low detection limit that are highly effective in cancer detection. Proposed biosensor uses a series of resonant cavities that slice the resonant wavelength to a high peak resonant wavelength with a spectral linewidth of 0.1 nm. The integration of 2D PC biosensors with machine learning techniques for early and accurate cancer detection is optimized for the data set. The performance analysis of Multiple Linear Regression (MLR) and Support Vector Machine (SVM) is studied by repeating training, testing, and optimization of target values (Resonant Wavelength) with dependent and independent features of a 2D PC biosensor system. The SVM modelprovides an R squared value of 0.99 for the biosensor, and the MLR model gave an R squared value of 0.88. TheSVM model provides excellent accuracy in predicting the target values with all the trained input features of a 2D PC biosensing system.

Tunable Mie resonance in complex-shaped gadolinium niobate

Nanoscale particles described by Mie resonance in the UV–vis–NIR region are in high demand for optical applications. Controlling the shape and size of these particles is essential, as it results in the ability to control the wavelength of the Mie resonance peak. In this work, we study the extensive scattering properties of gadolinium niobate particles with complex bar- and cube-like shapes in the UV–vis–NIR region. We perform our experimental analysis by characterizing the morphology and extinction spectra, and our theoretical study by implementing a Mie scattering model for a distribution of spherical particles. We can accurately model the size distribution and extinction spectra of complex shaped particles and isolate the contribution of aggregates to the extinction spectra. We can separate the contributions of dipoles, quadrupoles, and octupoles to the Mie resonances for their respective electric and magnetic parts. Our results show that we can tune the broad Mie resonance peak in the extinction spectra by the nanoscale properties of our system. This behavior can aid in the design of lasing and luminescence-enhanced systems. These dielectric gadolinium niobate submicron particles are excellent candidates for light manipulation on the nanoscale.

Highly sensitive refractive index and magnetic field sensor based on long-period fiber grating inscribed in tapered optical fiber

A refractive index (RI) and magnetic field sensor based on tapered long period fiber grating (LPFG) is proposed. We prepared two different periods of LPFGs (LPFG1 and LPFG2) using high-frequency CO2 laser point by point method on tapered single-mode fiber. Firstly, LPFG1 is used to measure the RI of sodium chloride solution. LPFG1 is immersed in sodium chloride solutions with different RI to measure the sensitivity of LPFG to RI. The experimental results indicate that LPFG1 is particularly sensitive to changes in environmental RI, with a sensitivity of 381.820 nm/RIU. Due to the special sensitivity of tapered LPFG to environmental RI, in order to eliminate the influence of residual sodium chloride on the surface of LPFG1 on magnetic field measurement, we use LPFG2 with similar parameters to measure the environmental magnetic field. LPFG2 was encapsulated in a glass capillary tube filled with the magnetic fluid (MF). After the environmental magnetic field changed, the RI of MF changed, causing the resonance peak wavelength of LPFG2 to drift. We measured the magnetic field using LPFG2 within the magnetic field range of 0.66 mT to 20 mT. Only in the magnetic field range of 1.95 mT to 4.6 mT, good linear fitting was achieved, with a magnetic field sensitivity of 1.242 nm/mT and a fitting coefficient of 0.9852. The experimental results indicate that LPFG inscribed in tapered optical fiber has high sensitivity to environmental RI and magnetic field. The sensor has a simple structure, small volume, easy production, and high sensitivity, which has certain practical application prospects.

Detection of viral and bacterial diseases using 2D photonic crystal-based elliptical ring resonator sensor

Our proposed work analyzes and models the photonic crystal (PhC)-based elliptical ring resonator for detecting viral and bacterial infections. Optical sensors show extreme results as sensing devices. So, they are broadly accepted in the medical field for the rapid and effective diagnosis of diseases. Optical biosensors are designed to detect cancer, malaria, typhoid, tuberculosis, etc. The principle behind the working of optical biosensors is a shift in the peak resonance wavelength corresponding to the small changes in the refractive index values. Due to the rapid mutation and replication of viral pathogens in the human cell nucleus, there is high demand for sensors that provide accurate results for viral and bacterial diseases in seconds. Hence, optical biosensors can give results in a short amount of time with a high sensitivity. The proposed sensor achieved a high sensitivity of 881.25 nm / RIU for tuberculosis and 555.55 nm / RIU for hepatitis B. The quality factor and figure of merit is also calculated, and their values come out to be 624.37 and 346.38, respectively, in the case of typhoid and Bacillus cereus. The platform used for simulating the analytes is the finite-difference time-domain.

Photonic crystal with magnified resonant peak for biosensing applications

A theoretically and numerically photonic crystal structure with parity-time symmetry is investigated to realize the design of a biomedical sensor for biosensing applications. The transmittance spectra of the structure are investigated, and various performance parameters are evaluated. Different structure parameters such as the unit cell number, the thickness of the sample layer, macroscopic Lorentz oscillation intensity in the PT-symmetry unit cell, the porosity of gallium nitride, and incident angle are theoretically and numerically investigated. To improve the performance of the device, an optimization technique is used. The relatively high sensitivities of 496 nm RIU (the change in the resonant peak wavelength per refractive index unit) and 1002142%/RIU (the change in the transmittance of the resonant peak per refractive index unit) are achieved. The proposed device can be a relatively high-precision detection device for biosensing applications.

Temperature-insensitive optical fiber strain sensor fabricated by two parallel connection Fabry–Perot interferometers with air-bubbles

A strain sensor formed by a parallel connection of two Fabry–Perot interferometers (FPI) is proposed. The femtosecond laser is used to process a micro groove on the end face of a single-mode fiber (SMF), and then, it is welded with another SMF to form a small air bubble at the fusion point, fabricating an FPI. When the axial strain acts on the air bubble, the transverse length of the air bubble will change, causing the air cavity of the FPI to be easily deformed, and FPI can obtain high strain sensitivity. Three FPIs were manufactured with the air bubble sizes of 63, 78, and 93 µm, respectively, and the strain sensitivities of the three FPIs are 2.9, 2.0, and 1.5 pm/µε, respectively. The experimental results show that the smaller the air bubble, the higher the strain sensitivity of FPI. Since the free spectral ranges of the three FPIs are relatively similar, we, respectively, paralleled them to form two Vernier effect strain sensors, and their sensitivities are −14.9 and −14.5 pm/µε, respectively. Their sensitivities are increased by 5.1 times and 7.3 times, respectively. In addition, because three FPIs are composed of air cavities, they have very low temperature sensitivities. When they are connected in parallel, their resonance peak wavelength moves in the same direction with an increase in temperature, forming a reduced Vernier effect, and the temperature sensitivity amplification is very small. Therefore, the temperature cross-sensitivity of the sensor is extremely low and can be ignored.

Enhancement of Quantum Dot Fluorescence by a Metal Nanoparticle/Porous Silicon Microcavity Hybrid System

Enhancement of quantum dot (QD) fluorescence in a hybrid system of a porous silicon microcavity (pSiMC) and silver nanoplatelets (AgNPs) has been estimated using numerical simulation. The system was simulated as a periodic unit cell made of a pSiMC with a resonant wavelength peak at 605 nm, an AgNP with a resonance at 604 nm and a quantum dot (QD) with an emission peak at 605 nm. For comparison, simulations were performed for an AgNP and a QD in a reference single-layered system with a high refractive index. The QD fluorescence was enhanced in the AgNP/pSiMC hybrid system, mainly due to the higher excitation rate.

Silver nanoparticle as an alternate to antibiotics in cattle semen during cryopreservation.

The proposed study was to determine if the silver nanoparticles can be used as potential antimicrobial agents and can replace the use of conventional antibiotics in semen without affecting the motility and fertility of semen. The silver nanoparticles prepared by chemical reduction method were confirmed by determination of the wavelength of surface plasmon resonance peak and further characterized using Zetasizer by determining their size, polydispersity index, and zeta potential. The nanoparticles were assessed for antibacterial activity and their concentration was optimized for use in semen extender for cryopreservation. Cryopreserved semen was further evaluated for seminal parameters, antioxidant parameter, and microbial load. Prepared silver NPs showed a plasmon resonance peak at 417 nm wavelength. NPs were found to possess antibacterial activity and were supplemented in semen extender @ 125 and 250 µg/ml for semen cryopreservation. There was a significant increase in pre and post-freezing motility and other seminal parameters. The microbial load of frozen-thawed semen of control and supplemented groups were well within the permissible limits. Lipid peroxidation levels were reduced in NPs supplemented groups, and reactive oxygen species (ROS) levels were significantly reduced in semen supplemented with 125 µg/ml NPs. Thus it can be conclude that silver NPs can be successfully used as a substitute for antibiotics in cattle bull semen cryopreservation with good antimicrobial activity and no adverse effects on sperm characteristics.

In situ reversible tuning of chemical interface damping in mesoporous silica-coated gold nanorods via direct adsorption and removal of thiol.

Chemical interface damping (CID) is a recently proposed plasmon decay channel in gold nanoparticles. However, thus far, a very limited number of studies have focused on controlling CID in single gold nanoparticles. Herein, we describe a new simple method for reversible tuning of CID in single gold nanorods coated with a mesoporous silica shell (AuNRs@mSiO2). We used 1-alkanethiols with two different carbon chain lengths (1-butanethiol and 1-decanethiol) as adsorbates to induce CID. In addition, NaBH4 solution was used to remove the attached thiol from the AuNR surface. We confirmed the adsorption and removal of 1-alkanethiols on single AuNRs@mSiO2 and the corresponding changes in localized surface plasmon resonance (LSPR) peak wavelengths and linewidths. Furthermore, we investigated the effect of immersion time in NaBH4 solution on thiol removal from AuNRs@mSiO2. Therefore, the LSPR properties and CID can be controlled, thereby paving the way for in situ reversible tuning of CID by repeated adsorption and desorption of thiol molecules on single AuNRs@mSiO2.

Voltage-modulated surface plasmon resonance biosensors integrated with gold nanohole arrays.

Surface plasmon resonance (SPR) has emerged as one of the most efficient and attractive techniques for optical sensors in biological applications. The traditional approach of an EC (electrochemical)-SPR biosensor to generate SPR is by adopting a prism underneath the sensing substrate, and an angular scan is performed to characterize the reflectivity of target analytes. In this paper, we designed and investigated a novel optical biosensor based on a hybrid plasmonic and electrochemical phenomenon. The SPR was generated from a thin layer of gold nanohole array on a glass substrate. Using C-Reactive Protein (CRP) as the target analyte, we tested our device for different concentrations and observed the optical response under various voltage bias conditions. We observed that SPR response is concentration-dependent and can be modulated by varying DC voltages or AC bias frequencies. For CRP concentrations ranging from 1 to 1000 µg/mL, at the applied voltage of -600 mV, we obtained a limit of detection for this device of 16.5 ng/mL at the resonance peak wavelength of 690 nm. The phenomenon is due to spatial re-distribution of electron concentration at the metal-solution interface. The results suggest that CRP concentration can be determined from the SPR peak wavelength shift by scanning the voltages. The proposed new sensor structure is permissible for various future optoelectronic integration for plasmonic and electrochemical sensing.

An Organic Electro‐Mechanical Cavity Emitting Efficiently Tunable, Continuous‐Wave‐Pumped Nonlinear‐Optical Modes

AbstractOrganic polar crystals are a promising material platform for achieving unique nonlinear nanophotonic properties. Mainly, tunable second‐harmonic generation (SHG) with continuous‐wave (CW) pump sources is considered as breakthrough technology for optical switching, actuation, sensing, chip‐integrated coherent light sources, and low‐threshold tunable microlasers. Here, the discovery of tunable CW SHG in a polar (non‐centrosymmetric) electro‐mechanical microcrystal cavity of 4‐(4‐(methylthio)phenyl)‐2,6‐di(1H‐pyrazol‐1‐yl)pyridine (UOH1) is demonstrated. As a result of total internal reflection in mirror‐like light‐reflecting facets and its high second‐order nonlinear susceptibility, the octahedron‐shaped cavities exhibit both bright femtosecond and CW‐pumped SHG with coherent whispering gallery mode (WGM) and bow‐tie‐like (BT) optical modes excited in its spectrum. Moreover, for an external dc electric field of about 23 kV cm−1 the microcavity displays 0.18 nm resonant wavelength peak shift in the second harmonic signal due to electrostriction (strain effect).

A simple green synthesis of pure and sterling silver nanoparticles via pulsed laser ablation in deionized water: characterization and comparison

Pure silver (Ag) and its alloy nanoparticles (NPs) with intense and tunable SPR bands in the visible region are widely exploited for biosensors, information storage, and solar energy systems. Pure Ag and Sterling silver (Ag92.5Cu7.5) NPs were synthesized by the laser ablation method in deionized water using a pulsed Nd:YAG laser. The prepared NPs were characterized and compared for their structural, morphological, and optical properties. The x-ray diffraction (XRD) and selected area electron diffraction (SAED) results revealed that the NPs have polycrystalline nature with five lattice directions. The diffraction peak positions for Ag92.5Cu7.5 NPs exhibited an average redshift of 0.1 ̊ compared to pure Ag NPs due to the presence of copper atoms in the composite crystal unit cell structure. The formation of spherical NPs with an average size of 9.1 nm and 8.4 nm for Ag and Ag92.5Cu7.5 NPs was confirmed using transmission electron microscopy (TEM) and high-resolution TEM (HRTEM). It was found that the concentration of synthesized Ag92.5Cu7.5 alloy NPs was considerably higher than that of pure Ag NPs. Going from pure to alloy silver NPs, the wavelength of surface plasmonic resonance (SPR) peak shifted from 400 nm to 395 nm. The UV–vis absorption spectra at different aging times revealed that pure Ag colloidal solution is relatively stable. Both colloidal solutions exhibited a similar pattern of photoluminescence (PL) emission spectra with peaks in the blue region.