Research on a fiber sensing system for metal ion detection based on SPF-PCF-SPF structure and coated LPFG

In order to provide a method for accurately detecting the concentration and types of heavy metal ions in water,a fluid ion detection system is designed.It consists of a side-polished fiber-assisted fluid structure and a long-period fiber grating(LPFG)coated with a metal chelating agent membrane.In this study,both theoretical and experimental investigations are conducted to examine the sensing characteristics of the system towards copper ion and iron ion solutions.The results demonstrate that under the premise of ensuring solution flow,the system can achieve specific identification of different types of heavy metal ions.Furthermore,it exhibits concentration sensing sensitivities of 9.23×10^(4) mL·nm/mol and 7.13×10^(4) mL·nm/mol for copper sulfate(CuSO_(4))and ferric chloride(FeCl_(3))solutions,respectively.Therefore,this sensing system offers the potential for real-time detection of metal ions.

Enhancement of magnetic and dielectric properties of low temperature sintered NiCuZn ferrite by Bi_(2)O_(3)-CuO additives

With a series of 1.0 wt%Bi_(2)O_(3)-x wt%CuO(x=0.0,0.2,0.4,0.6,and 0.8)serving as sintering additives,Ni_(0.23)Cu_(0.32)Zn_(0.45)Ee_(2)O_(4)ferrites are successfully synthesized at a low temperature(900℃)by using the solid state reaction method.The effects of the additives on the phase formation,magnetic and dielectric properties as well as the structural and gyromagnetic properties are investigated.The x-ray diffraction(XRD)results indicate that the added Bi_(2)O_(3)-CuO can lower the synthesis temperature significantly without the appearing of the second phase.The scanning electron microscope(SEM)images confirm that Bi_(2)O_(3)is an important factor that determines the sintering behaviors,while CuO affects the grain size and densification.With CuO content x=0.4 or 0.6,the sample shows high saturation magnetization,low coercivity,high real part of magnetic permeability,dielectric permittivity,and small ferromagnetic resonance linewidth(ΔH).The NiCuZn ferrites are a promising new generation of high-performance microwave devices,such as phase shifters and isolators.

Design and characteristic research on side-polished fiber fluid sensing system

A novel fluid sensing system based on side-polished optical fiber(SPOF)is proposed,which realizes the fluid replaceability and effective refractive index(RI)sensing characteristics.Numerical investigations demonstrate that the photonic bandgap effect can be obtained if the RI of liquid is higher than that of substrate material in the wavelength range studied.The relationship between bandgap edge wavelength and RI is studied theoretically.The SPOF with a depth of 57μm is used in the experiment to realize the construction of the fluid channel.After filling three different liquids,the result shows that the wavelength of the bandgap edge has a red shift with RI increased,which is nearly linear in the RI range of 1.56—1.6 with a sensitivity about 5543.64 nm/RIU.The proposed sensing system can be flexibly applied to the field of fluid characteristic sensing such as biochemical solution characteristic detections.

Design and numerical simulation of SPF-PCF-SPF fluid sensing system based on photoelectric oscillator

In this paper,an optical fiber fluid sensing system based on optoelectronic oscillator(OEO)was proposed and studied numerically.The fluid sensor head is constructed by splicing two sections of side-polished fiber(SPF)to one section of photonic crystal fiber(PCF).Fluid sample can flow continuously through the holes of PCF.The refractive index(RI)change of the fluid sample can lead to the effective RI change of the fiber,resulting in frequency change of microwave signal generated by OEO.By monitoring the oscillation frequency using an electronic spectrum analyzer(ESA),the RI of fluid sample can be measured.Thanks to the fast interrogation speed of ESAs,the measuring speed can be increased significantly compared to traditional optical fiber RI sensing systems using optical spectrometers.The sensing principle of the system was studied.The sensitivity of the proposed system was evaluated by simulation,and an RI sensitivity of-14.20 MHz/RIU can be achieved.The results show that with proper system design,real-time RI measurement with high sensitivity can be achieved.Increasing the length of the PCF while under the premise of the fluid parameters will be the most reasonable way to improve the sensitivity.The proposed design and simulation results can provide suggestions for the fabrication and optimization of fluid sensing systems used for real-time detection and measurement of biological elements and heavy metal ions in liquid environment.

Bioimaging of Dissolvable Microneedle Arrays: Challenges and Opportunities

The emergence of microneedle arrays(MNAs)as a novel,simple,and minimally invasive administration approach largely addresses the challenges of traditional drug delivery.In particular,the dissolvable MNAs act as a promising,multifarious,and well-controlled platform for micro-nanotransport in medical research and cosmetic formulation applications.The effective delivery mostly depends on the behavior of the MNAs penetrated into the body,and accurate assessment is urgently needed.Advanced imaging technologies offer high sensitivity and resolution visualization of cross-scale,multidimensional,and multiparameter information,which can be used as an important aid for the evaluation and development of new MNAs.The combination of MNA technology and imaging can generate considerable new knowledge in a cost-effective manner with regards to the pharmacokinetics and bioavailability of active substances for the treatment of various diseases.In addition,noninvasive imaging techniques allow rapid,receptive assessment of transdermal penetration and drug deposition in various tissues,which could greatly facilitate the translation of experimental MNAs into clinical application.Relying on the recent promising development of bioimaging,this review is aimed at summarizing the current status,challenges,and future perspective on in vivo assessment of MNA drug delivery by various imaging technologies.

Simulation and experimental verification of off-axis fiber Bragg grating bending sensor with high refractive index modulation

Off-axis FBG simulations were performed in this paper using a finite element method in conjunction with the conformal mapping technique to study the bending sensing characteristics of the off-axis FBG with high index modulation.The refractive index(RI)increase of the grating region is taken into consideration for the mode field simulation.The influences of high RI increase and the offset distance of the grating on the bending sensitivity were analyzed.Off-axis FBGs with different offset distances were fabricated using femtosecond laser with phase mask technique in standard single-mode fiber.The simulation results were verified by the experiment.A bending sensitivity of 0.055 d B/m^(-1) was achieved with an offset distance of 4μm.The simulation and experiment results suggest that the grating offset distance has a greater influence on the sensitivity of the off-axis FBG with high RI modulation than that with low RI modulation.The proposed sensor structure and simulation results can provide suggestion for the design and processing of off-axis FBG bending sensors.

Multi-matrix opto-electronic system for measuring deformation of the millimeter range radiotelescope elements

A novel optical instrument is proposed and studied to measure the deformation of each connection point for a mirror, which includes 24 multi-matrix base units and can be used in millimeter-scale signal reflection systems.Experimental investigations reveal that the error of measurement is σ=8.7×10^(-3) mm at a distance of 5 500 mm, which allows to measure the linear deformation of a radiotelescope with the mirror diameter of 70 m.

Phase-sensitive manipulation of squeezed state by a degenerate optical parametric amplifier inside coupled optical resonators

In this paper, we investigate the quantum fluctuations of subharmonic reflected field from a triple-resonant degenerate optical parametric amplifier(OPA) inside coupled optical resonators, which is driven by the squeezed beam at signal frequency. By controlling the relative phase between the pump beam and the injected signal beam, we can see the quantum fluctuation in the phase direction and amplitude direction due to the parametric down-conversion process in the cavity. Thus, the phase sensitive operation of the compression field is realized due to the quantum interference between the harmonic field of the down converter of OPA and the inner field of the coupled optical resonator. We verified the quantum coherent phenomena of OPA in coupled optical resonators and phase-sensitive manipulations of quantum entanglement for quantum information processing. We realized the electromagnetically induced transparency-like(EIT-like) effect and the optical parameter conversion process at the same time in one optical device. These properties can favor higher manipulation precision and control efficiency, which is more suitable for the integration of quantum-on-chip systems, laying a foundation for the practical application of quantum information.

Roll angle of autocollimator measurement method based on hollow cube corner reflector

In this paper, a method of measuring roll angle with hollow cube corner reflector(HCCR) is proposed. Firstly, the space coordinate vector relationship between the mirror and the autocollimator is established by using the Euler rotation relationship, and the structure of the HCCR is designed. Secondly, through the actual measurement of the HCCR reflector’s angle sensitivity, the specific formula of roll angle measurement is obtained. The experimental results show that the method can be used to measure the roll angle, and the maximum root mean square(RMS) error is 15" in the range of 350", and the repeatability of the experiment is better than 2.7". On the basis of retaining the traditional autocollimator, the plane mirror is replaced with HCCR, which realizes the measurement of the roll angle of the autocollimator. This method does not change the internal structure of the autocollimator system, and there is no process error caused by special processing technology, so as to retain the autocollimator’s own long measurement distance, high measurement accuracy, high system stability, and large range of measurement performance, and it can also be used in industrial production.

A biological fluid fiber Sagnac sensor based on SPF-PCF-SPF structure

A biological solution concentration sensor based on a side-polished fiber(SPF)assisted fluid system is presented.The birefringence properties of the asymmetrically filled fluid in this structure and the relationship between the concentration of the biological solution and the refractive index are theoretically analyzed.It was found that the interference peaks had red-shifted with increasing concentration.A sensing sensitivity of 1.3871×10^(4)nm·mL/mol at 14.68×10^(-4)mol/mL was achieved within the experimental range after different concentrations of arginine solutions were injected into the sensing system.This sensing system can also be applied to measure the concentration of other biological solutions,providing the feasibility of real-time detection of biological solutions.

A whispering gallery mode strain sensor based on microtube resonator

A novel whispering gallery mode(WGM) strain sensor based on microtube has been proposed, where perceiving strain variations are reported via the dynamical regulation of a whispering gallery mode. The WGMs in the microtube resonator were evanescently excited by a micro-nano fiber fabricated by the fusion taper technique. The structural changes of microtubes under axial strain were simulated with finite element software, and the effect of microtube wall thickness on strain sensitivity was systematically studied through experiments. The experimental results show that the strain sensitivity of thin-walled microtube is found to be 1.18 pm/με and the Q-factor in the order of 4.4× 104. Due to its simple fabrication and easy manipulation as well as good sensing performance, the microtube strain sensor has potential applications in high-sensitivity optical sensing.

A 2D quadrangular pyramid photoelectric autocollimator with extended angle measurement range

A photoelectric autocollimator with high accuracy and extended measurement range based on the quadrangular pyramid is proposed,and the corresponding algorithms are also deduced.A new image processing algorithm has been proposed to improve the accuracy,and the corresponding errors are also estimated,the error does not exceed half a pixel when the distance between the marks more than two radii.The experimental results have verified that the measurement range of the proposed two-dimensional(2D)quadrangular pyramid photoelectric autocollimator can be increased 2 times than that of the flat mirror photoelectric autocollimator from 10′to 15′.The accuracy is better than 1″when the deflection is less than 15′.