Sensitivity Of Resonance Wavelength Research Articles

Broadband dual parametric fiber sensor for concentration and temperature sensing with high sensitivity and linearity

A dual parametric sensor is proposed based on photonic crystal fiber (PCF) structure and surface plasmon resonance (SPR) effect in this paper. The proposed SPR-PCF sensor has a broadband spectral response from 1200 to 2400 nm. Detections of the alcohol with different concentrations and temperatures are carried out to demonstrate its dual parametric performance. When the concentration of the alcohol solution changes from 10 % to 87 %, the resonance-wavelength sensitivity is −1588.3 pm/% and the resonance-loss sensitivity is −0.34837 dB/%. While the external temperature is verified in a range of 20 °C and 80 °C, the resonance-wavelength and resonance-loss sensitivities are 2031.8 pm/°C and 0.473 dB/°C, respectively. Its R2 can always be larger than 0.99. Dual-parameter sensing can be realized via using the sensitivities as the coefficients to construct a transfer matrix. The proposed SPR-PCF sensor is expected to have potential applications in chemistry, biology, and environment monitoring.

PH Sensor Through a Self-Assembled Multifunctional Layer With Clitoria Ternatea Based on Long-Period Fiber Gratings

In this study, Clitoria ternatea was used to provide a quantifiable method for pH measurement. The researchers proposed a new pH measurement method that involves the use of a KrF excimer laser to perform laser-assisted etching of the crown structure of long-period fiber gratings. Processing of the front surface of the optical fibers through grating resulted in periodically structured optical fibers with a sensor diameter of 55 μm and a period of 660 μm; these structured optical fibers were encapsulated using glass slides. On the front surface of the optical fibers, functional group modification of the fiber surface was conducted and a nanogold coating was applied using the self-assembly method. Additionally, Clitoria ternatea was bonded to the surface of the optical fibers for the measurement of refractive index. In the pH sensing experiment, the average loss sensitivity detected by the sensors with no nanogold self-assembled coating was 0.0635 dB/pH. By contrast, the average resonant wavelength sensitivity of the sensors with a nanogold self-assembled coating under localized surface plasmon resonance was increased to 0.173 nm/pH. Compared with the sensors with no nanogold self-assembled coating, the sensors with this coating had a wavelength drift sensitivity enhanced by a factor of 37.

Sensitivity investigation of the microfiber-toslab evanescent wave sensors

Microfiber-to-slab sensor is comprised of a tapered fiber in evanescent contact with a multimode slab waveguide. The effects of the sensor configuration parameters on its evanescent wave sensitivity were investigated through theoretical analysis. On the basis of that, the rules for fabricating a microfiber-to-slab sensor with high device sensitivity were presented. By optimizing geometry parameters, it was shown that the resonant wavelength sensitivity can be as high as nearly 20000 nm/RIU. The conclusions derived from our work may be used for design and optimization of microfiber-to-slab devices for practical applications.

Sensing performance analysis on Fano resonance of metallic double-baffle contained MDM waveguide coupled ring resonator

Based on the transmission property and the photon localization characteristic of the surface plasmonic sub-wavelength structure, a metallic double-baffle contained metal-dielectric-metal (MDM) waveguide coupled ring resonator is proposed. Like the electromagnetically induced transparency (EIT), the Fano resonance can be achieved by the interference between the metallic double-baffle resonator and the ring resonator. Based on the coupled mode theory, the transmission property is analyzed. Through the numerical simulation by the finite element method (FEM), the quantitative analysis on the influences of the radius R of the ring and the coupling distance g between the metallic double-baffle resonator and the ring resonator for the figure of merit (FOM) is performed. And after the structure parameter optimization, the sensing performance of the waveguide structure is discussed. The simulation results show that the FOM value of the optimized structure can attain to 5.74×104 and the sensitivity of resonance wavelength with refractive index drift is about 825 nm/RIU. The range of the detected refractive index is suitable for all gases. The waveguide structure can provide effective theoretical references for the design of integrated plasmonic devices.

Nonconcentric triple-microring resonator for label-free on-chip sensing with high figure-of-merit

A nonconcentric triple-microring resonator employing a silicon-on-insulator platform is proposed and analyzed for label-free sensing applications. The numerical simulations are carried out based on the finite-difference time-domain with perfectly matched layer boundary condition and transmission matrix methods. Its physical aspects and specific applications are highlighted. The results show that, in the optimized structure, a Q factor of 3.06×109 is achieved under weak coupling conditions. It is 3 orders of magnitude larger than that of a dual-ring resonator and 6 orders of magnitude larger than that of a single-ring resonator with lossless waveguide. In addition, to validate the proposed scheme, the designed ring resonator-based photonic sensor achieves refractive index sensing with resonance wavelength sensitivity of 101 nm/refractive index unit (RIU) and figure-of-merit of 11,211 RIU−1. Correspondingly, the detection limit of refractive index variation will be improved significantly compared with those of nonconcentric single-/dual-ring resonator and concentric triple-ring resonator. It is very useful for label-free on-chip biochemical sensing.

Surface plasmon resonance biosensor based on gold-coated side-polished hexagonal structure photonic crystal fiber.

The refractive index sensing characteristics of the side-polished photonic crystal fiber (PCF) surface plasmon resonance (SPR) sensor are detailed investigated in this paper. We used the finite element method (FEM) to study the influences of the side-polished depth, air hole size, lattice constant, and the refractive index (RI) of the PCF material on sensing performance. The simulation results show that the side-polished depth, air hole size, lattice pitch have significant influence on the coupling strength between core mode and surface plasmon polaritons (SPPs), but have little influence on sensitivity; the coupling strength and sensitivity will significant increase with the decrease of RI of the PCF material. The sensitivity of the D-shaped PCF sensor is obtained to be as high as 21700 nm/RIU in the refractive index environment of 1.33-1.34, when the RI of the PCF material is controlled at 1.36. It revealed a new method of making ultra-high sensitivity SPR fiber sensor. Then we experimental demonstrated a SPR refractive sensor based on the side-polished single mode PCF and investigated the sensing performance. The experimental results of the plasmon resonance wavelength sensitivity agree well with the theoretical results. The presented gold-coated D-shaped PCF SPR sensor could be used as a simple, cost-effective, high sensitivity device in bio-chemical detection.

Tuning of whispering gallery modes in a magnetic-fluid-infiltrated silica capillary based on lateral pumping scheme

An all-optical tuning method of whispering gallery modes (WGMs) in a silica capillary based on lateral pumping scheme has been proposed and experimentally demonstrated by exploiting the photo-thermal effect of magnetic fluids (MFs) infiltrated into a micro-capillary. The WGMs are coupled from a tapered fiber perpendicular to the silica capillary. Experimental results indicate that the microresonator integrated with MFs shows a Q-factor of 1.2867 × 104 and its optical tunability reaches 0.0382 nm/(mW · mm−2) under 532 nm laser illumination. Compared with the one infiltrated with pure water, our proposed capillary shows an optical tuning sensitivity increase of about 4270 times. The experimental results on the WGM resonance wavelength sensitivity for the capillaries with different diameters are in accordance with our simulation outcome using radially dependent heat conducting equation. Further experimental studies indicate that the proposed microresonator possesses a good spectral reversibility. Moreover, the dynamic response experiment shows that the rise and fall time of this microresonator is about 231 ms and 255 ms, respectively. The above intriguing features make the proposed WGM resonator a promising candidate for potential applications in optical filtering, microfluidic sensing, and signal processing as well as reconfigurable devices for future all-optical networks.

Combining Two Types of Gratings for Simultaneous Strain and Temperature Measurement

A new optical fiber sensor made of tapered and CO2-laser-notched long-period fiber gratings (LPFGs) is proposed for the simultaneous measurement of strain and temperature. Experiments are run to verify the feasibility of using the proposed sensor for the simultaneous measurement of strain and temperature. Experimental results indicate that after the two LPFGs are connected with each other, the sensitivity of CO2-LPFG to strain deceases from 1.7 to 0 pm/ $\mu \varepsilon $ , and the sensitivity of the tapered LPFG remains unchanged; it is −1.4 and −1.5 pm/ $\mu \varepsilon $ . The sensitivity of resonance wavelength 1280, 1412, and 1545 nm to temperature are 80 pm/°C, 67 pm/°C, and 69 pm/°C. Simultaneous strain and temperature experiments prove the stability of proposed sensor. It is therefore strongly believed that the proposed sensor can be used to achieve simultaneous measurement of strain and temperature.

An ultrasensitive optical label-free polymeric biosensor based on concentric triple microring resonators with a central microdisk resonator

In this paper we propose an optical label-free biosensor based on a polymeric platform. Label-free biosensors have not the drawbacks and stability problems of commercialized devices which are used for detection of labeled molecules. In addition, we choose polymeric platform, due to simple and low cost fabrication process and also high biocompatibility properties. The suggested structure consists of concentric triple ring resonators along with a disk resonator which offers deeper notches, higher sensitivity and vaster detection area with respect to other similar configurations such as single ring resonator, double concentric ring resonators, etc. Our numerical simulations based on the finite difference time domain (FDTD) method, show that in optimized structure, a transmission notch depth of −48.7dB for sensor at rest and a free spectral range of 56nm are achievable. In addition, resonance wavelength sensitivity and output power sensitivity of sensor are 1000nm/RIU and 1.8×104dB/RIU, respectively. The external radius of outer ring resonator is only 5μm, and detection area of the sensor is 40.37μm2. With this small size, to the best of our knowledge, the obtained notch depth and sensitivity parameters are one of the highest values in ring resonator-based biosensors reported to date.

Laser-tuned whispering gallery modes in a solid-core microstructured optical fibre integrated with magnetic fluids.

A laser-assisted tuning method of whispering gallery modes (WGMs) in a cylindrical microresonator based on magnetic-fluids-infiltrated microstructured optical fibres (MFIMOFs, where MF and MOF respectively refer to magnetic fluid and microstructured optical fibre) is proposed, experimentally demonstrated and theoretically analysed in detail. The MFIMOF is prepared by infiltrating the air-hole array of the MOF using capillary action effect. A fibre-coupling system is set up for the proposed MFIMOF-based microresonator to acquire an extinction ratio up to 25 dB and a Q-factor as large as 4.0 × 104. For the MF-infiltrated MOF, the light propagating in the fibre core region would rapidly spread out and would be absorbed by the MF-rod array cladding to induce significant thermal effect. This has been exploited to achieve a WGM resonance wavelength sensitivity of 0.034 nm/mW, which is ~20 times higher than it counterpart without MF infiltration. The wavelength response of the resonance dips exhibit linear power dependence, and owing to such desirable merits as ease of fabrication, high sensitivity and laser-assisted tunability, the proposed optical tuning approach of WGMs in the MFIMOF would find promising applications in the areas of optical filtering, sensing, and signal processing, as well as future all-optical networking systems.

Bend-insensitive long period fiber grating-based high temperature sensor

A novel bend-insensitive long period fiber grating (LPFG) is presented and applied in high temperature measurement. This LPFG is formed by periodically arranging three micro-core-offsets fabricated by employing the cleaving–splicing method in the standard single mode fiber. As bend is applied onto the LPFG along the most bend-insensitive orientation, the resonant wavelength sensitivity of the transmission spectrum is 0.0097nm/m−1 for a curvature range of 0–3.5m−1, which is about three orders lower than those of the conventional gratings. For other orientations of the LPFG, the bend sensitivities are also one or two orders lower than those of conventional ones. This better bend characteristic could be used to improve the sensing performances of the LPFG, such as improving the measurement accuracy and resolving cross sensitivity issue between bend and other parameters. Moreover, since the mode coupling of the LPFG results from the fiber geometry deformation which indicates a better thermal stability, the LPFG could be used for high temperature measurement occasions.

Performance of wavelength modulation surface plasmon resonance biosensor

Surface plasmon resonance (SPR) is a rapid, label-free, high-precision technique of biological sensing and analysis. The investigation on the characteristics of provides theoretical basis and instructions for the applications of SPR A Kretschmann-structure surface plasmon resonance (SPR) biosensor based on wavelength modulation was developed, and also its sensing performances in the bulk solution was investigated. Measurements with different concentrations of bulk ethanol and ethylene glycol solutions show that the resonant wavelength shows a low sensitivity, but a higher linear response to the change in refractive index (RI), when RI is relatively smaller. With increasing refractive index , the sensitivity of resonance wavelength to changes in the refractive index increases. In the refractive index range of 1. 407 0-1. 430 RIU, sensitivity reaches to 11 487 nm RIU-1. The sensor resonance wavelength stability is 0. 213 8 nm, and the minimum resolution of refractive index approaches to 10-6 RIU. The advantages of the surface plasmon resonance sensor developed here results in simple operation, high sensitivity, wide detection range, low resolution, makes it an important candidate in chemical and biological sensing.

Long period grating in/on planar and channel waveguides: A theory description

A comprehensive, complete theory suitable for a long period grating (LPG) on/in a planar or channel waveguide is described on the basis of coupled mode theory. The theory aims at key characteristic parameters with respect to the effect of the LPG, including resonance wavelength, transmission power of the guided mode in the waveguide, full-width at half-maximum (FWHM) of the power attenuation band in transmission spectrum of the guided mode, and coupling coefficient between a guided and a coupled mode. The type of the grating including relief and index modulation, different polarization state combinations of the guided mode and the resonant mode, and slanted grating structure are considered in this theory. The influences of the coupling between two guided modes and between a guided mode and a substrate mode are discussed. The role of cladding layer in a long period waveguide grating is demonstrated in particular. Finally, the expressions for the sensitivity of resonance wavelength as a function of external temperature, pressure and surrounding refractive index are derived.