Lossy Mode Resonance Research Articles

Fiber Optic Sensing With Lossy Mode Resonances: Applications and Perspectives

This review focuses on the recent advances in lossy more resonance (LMR) fiber optic sensors. LMR sensors present many interesting features also in comparison with surface plasmon resonance (SPR), the most widespread resonance-based sensing platform. Two key parameters determine the performance of LMR sensors: geometrical configuration and material supporting the LMR. After reviewing those aspects and some fundamentals of the theory, the review focuses on the sensing mechanisms, mainly based on refractometry, and their possible applications. Many examples from the literature are reported ranging from electric field to pressure sensors and from gas detection to biosensors. Such vibrant activity on LMR sensors confirms the potentiality of this technology making it a very promising platform for sensor development.

Refractive index and salinity sensors by gallium-doped zinc oxide thin film coated on side-polished fibers

This work presents a high-sensitivity refractive index and salinity sensor by using fiber-optic side-polishing and electron-beam evaporation techniques. Thin film coated on the flat surface of side-polished fibers can generate a lossy mode resonance (LMR) effect. A gallium-doped zinc oxide (GZO) thin film was prepared by an electron-beam evaporation with the ion assisted deposition method. The residual thickness of the side-polished fiber was 76.5 μm, and GZO film thickness of 69 nm was deposited on the flat surface of the side-polished fiber to fabricate LMR-based fiber sensors. The variation in the optical spectrum of LMR-based fiber sensors was measured by different refractive index saline solutions. The LMR wavelength shift is caused by the refractive index change, which is nearly proportional to the salinity. The corresponding sensitivity of the proposed fiber-optic sensor was 3059 nm/RIU (refractive index unit) for the refractive index range of 1.333 to 1.398. To evaluate the sensitivity of LMR salinity sensors, the saline solution salinities of 3.6%, 7.3%, 10.9%, 14.6%, 18.2% and 21.9% were measured in this work. The experimental result shows that the sensitivity of the proposed salinity sensor is 9.94 nm/%.

Lossy mode resonance sensor assisted by dual long-period fiber gratings with core-mode blocker

A novel sensor configuration consisting of TiO2 film and dual long-period fiber gratings (LPFG) with an in-between core-mode blocker (CMB) is proposed and numerically investigated. TiO2 film is on the cladding surface of separation fiber between two identical LPFGs and lossy mode resonance (LMR) is induced by a single cladding mode which is coupled from core mode by the first grating. Afterwards, the cladding mode influenced by LMR is recoupled into core mode by the second grating. As a result, the output spectrum is characterized as a dip in the top of a bandpass spectrum curve. The central wavelength of this dip is sensitive to surrounding refractive index and the numerical analysis reveals that the sensitivity reaches 5075 nm/RIU with excellent linearity. In this configuration, the bandwidth of attenuation dip is reduced in a great manner since LMR is induced by a single cladding mode. Moreover, this sensor configuration synthesizes the advantages of both LMR and LPFG, which offers additional degrees of freedom in the sensor design.

Two-Dimensional Transition Metal Dichalcogenides-Based High Sensitivity Lossy Mode Refractive Index Sensor

Two-dimensional transition metal dichalcogenides (TMDs) have very potential properties for sensing applications. Hence, a lossy-mode resonance (LMR) refractive index (RI) sensor based on TMDs- indium-tin-oxide (ITO) configuration is proposed for high imaging sensitivity. A significant advantage of the proposed LMR sensor is that can achieve sharp resonance curves for both the transverse electric (TE) and transverse magnetic (TM) polarizations while the traditional surface plasmon resonance (SPR) sensor can only support TM polarizations. Through theoretical analysis, we found that the imaging sensitivity can be improved to 6438 RIU−1 ( $\text{n}_{s}=1$ .330) and 6695 RIU−1 ( $\text{n}_{s}=1$ .340) for TE and TM polarizations, respectively. It is an existing improvement of about 85.84 times and 11.5 times correspond to the single ITO-based LMR sensor without TMDs, respectively. This article reveals the design rules of the LMR sensor after system research, which provides guidance for further research and applied in environmental monitoring, biomolecules inspection, and so on.

Lossy Mode Resonance Sensors Based on Double ITO/TiO2 and Triple TiO2/ITO/TiO2 Thin Film Coated Single Mode Fiber Taper

Based on the previously developed computer program for rigorous calculation of modes in optical fibers containing layers of various materials of arbitrary, including nanometer, thickness, the calculation and optimization of single-mode double adiabatic tapers covered with one, two and three-layer films: ITO, ITO/TiO2, TiO2/ITO/TiO2 of equal thickness is performed, with the aim of their application as the environment refractive index sensors. It is shown that in the range of wavelengths 1.00–1.6 µm, two, and in particular, three-layer coatings not only can increase the sensitivity, but also significantly reduce the width of the lossy mode resonance (LMR), which, in turn, leads to a significant increase in the figure of merit (FOM) of the sensor, defined as the sensitivity/width of the LMR.

Lossy mode resonance-based highly sensitive fiber optic refractive index sensor using the bilayer of FTO/HfO2 for operation in the visible region

A lossy mode resonance (LMR) based fiber optic refractive index (RI) sensor utilizing a layer of fluorine-doped tin oxide (FTO) over the unclad core of the fiber is theoretically analyzed. To enhance its sensitivity, the thickness of the FTO layer is optimized. For further sensitivity enhancement, an over-layer of two different materials, T i O 2 and H f O 2 , is used. The sensitivity of F T O / T i O 2 and F T O / H f O 2 bilayer based LMR sensors increases with the increase in the thickness of the over-layer for a fixed thickness of the bilayer. Further, the sensitivity of the sensor utilizing the F T O / H f O 2 bilayer is found to be more than the sensitivity of the F T O / T i O 2 bilayer sensor. To keep the operating spectral range of the sensor in the visible region, the total thickness of the bilayer is adjusted. It is found that a total bilayer thickness of 30 nm with 90% thickness of H f O 2 gives the maximum sensitivity of 4400 nm/RIU for 1.33 RI of the sensing medium, which is more than three times the sensitivity of the FTO coated LMR sensor. The sensitivity of the proposed LMR sensor utilizing the F T O / H f O 2 bilayer is compared with the other LMR sensors reported in the literature, and it is found that the proposed sensor possesses the highest sensitivity. The other advantage of the proposed sensor is that it works in the visible region, which reduces the cost of the sensor.

High Figure of Merit in Lossy Mode Resonance Sensors with PtSe2 Thin Film

Lossy mode resonance (LMR) sensors not only support transverse magnetic mode (TM) but also respond to transverse electric (TE) polarization, which has the advantage over traditional surface plasmon resonance sensing supporting only a single TM polarization. We theoretically propose an LMR sensor that can detect the refractive index (RI) changes based on the Kretschmann configuration with PtSe2 material. The refractive index parameter of PtSe2 film is fitted through experimental measurements, and the performance of LMR sensor with PtSe2 is theoretically calculated. The figure of merit (FOM) of the sensor performance has been significantly improved, and the maximum FOM with 626 RIU−1 has been acquired.

Lossy mode resonance in an etched-out optical fiber taper covered by a thin ITO layer.

The results of the rigorous calculation of mode fields in double adiabatic, single-mode etched-out optical fiber tapers coated with thin indium tin oxide films are discussed in the context of their application as environment refractive index sensors. It is shown that at only two particular thicknesses covering the homogeneous section of the taper ITO film about 100 nm and 177 nm, the lossy mode resonance is observed in the wavelength range of 1.50-1.55 µm. Moreover, the sensitivity of a sensor based on a 177 nm coating is significantly higher, and the resonance width is significantly lower than that of a sensor with a 100 nm coating. Optimal from the viewpoint of the figure of merit, values for the diameter of a homogeneous section of the etched fiber are defined.

Generation of lossy mode resonances in a broadband range with multilayer coated coverslips optimized for humidity sensing

Coverslips deposited with a metallic oxide can be employed for generating lossy mode resonances by lateral incidence of light on the coverslip. Here it is demonstrated that with copper oxide the fading observed with other materials in the near infrared (NIR) wavelength range is avoided and LMRs can be obtained in a broadband range from 400 to 1700 nm, which permitted to observe the better performance in the NIR region compared to the visible region: the sensitivity to humidity is improved by more than a factor of two. However, copper oxide is not adequate for sensing humidity. The sensitivity of the device was optimized initially with a tin oxide coating and later with an additional layer of agarose, specifically adequate for the detection of humidity. The best performance was obtained with an agarose concentration 1% w/v, which permitted to observe a 10-fold sensitivity increase compared to the same device without agarose. This opens the path towards the development of environmental, chemical or biological sensors with an optimized sensitivity to a specific parameter to detect.

Improving the width of lossy mode resonances in a reflection configuration D-shaped fiber by nanocoating laser ablation.

The full width at half maximum (FWHM) of lossy mode resonances (LMRs) in the optical spectrum depends on the homogeneity of the thin film deposited. In this Letter, a method for improving the FWHM is applied for an LMR generated by a D-shaped optical fiber in reflection configuration. For this purpose, three samples with different attenuation were deposited with DC sputtering thin films of SnO2-x, and a further controlled immersion of the samples in water was performed. A laser-cleaner method was used to improve the FWHM characteristics of one of the samples from 106 to 53 nm. This improvement can be applied to thin-film-based sensors where there is a problem with the inhomogeneity of the coating thickness. Moreover, with this technique, it was proved that a coated length of just 3-4 mm permits the generation of an LMR, with implications for the miniaturization of the final device.

Lossy mode resonance-based uniform core tapered fiber optic sensor for sensitivity enhancement

A lossy mode resonance (LMR)-supported fiber optic sensor in which a uniform fiber core is placed among two identical tapered regions, is investigated numerically. Indium tin oxide (ITO) and aluminum-doped zinc oxide (AZO) are considered as LMR active materials used to excite several lossy modes and gold and silver are used as surface plasmon resonance (SPR) active materials. In this probe design, a central uniform core coated with ITO/AZO is the active sensing region, whereas tapered regions are meant for bringing the incident angle close to the critical angle. The sensitivity of the present fiber optic bio-sensor is evaluated for first two LMRs utilizing both ITO and AZO separately, along with its variation with the taper ratio (TR). For ITO, the maximum sensitivity values are observed to be 18.425 μm RIU−1 (refractive index unit) and 0.825 μm RIU−1, corresponding to the first and second LMRs, respectively, at a TR of 1.6 and for AZO, equivalent values are 0.79 μm RIU−1 and 0.35 μm RIU−1, respectively, at a TR of 2.0. The results illustrate that the first LMR is more sensitive than the second LMR and the ITO-coated probe possesses greater sensitivity than the AZO-coated probe for both LMRs. Similarly, for the fiber optic SPR sensor, the maximum value of sensitivity is 5.6425 μm RIU−1, in the case of gold and 5.0615 μm RIU−1 in the case of silver, at a TR of 1.6. Hence, the result shows that the sensor with the present fiber optic probe design has around a 3-fold enhancement in sensitivity compared with conventional SPR sensors. This study will have applications in many sensing schemes where the requirement of large sensitivity is vital.

Effect of thermal annealing on sensing properties of optical fiber sensors coated with indium tin oxide nano-overlays

In this work we discuss an effect of thermal annealing on optical and electrical properties of indium tin oxide (ITO) thin films deposited on a short section of multimode polymer-clad silica (PCS) optical fiber core. ITO films were deposited using different configuration of high power impulse magnetron sputtering (HiPIMS) and radio frequency magnetron sputtering (RF MS) cathodes. Due to tuned ITO film thickness it was possible to observe for these structures a lossy-mode resonance (LMR) and trace changes in properties of the films. Electrical resistance of the ITO overlays was also measured. Both optical and electrical measurements were repeated after annealing at 200°C in a tube furnace and nitrogen atmosphere. The measurements have shown that thermal annealing changes optical response to external refractive index (RI) of the fiber sensor and also changes the ITO layer resistivity. As an effect of thermal annealing we observed a shift of the LMR towards longer wavelengths. In addition as a result of annealing, the resistivity of the ITO layer was reduced. Full Text: PDF ReferencesM. Sobaszek et al., "Optical monitoring of thin film electro-polymerization on surface of ITO-coated lossy-mode resonance sensor", Proc. SPIE, vol. 10323, pp. 103234W, 2017. CrossRef I. Del Villar et al., " Generation of lossy mode resonances by deposition of high-refractive-index coatings on uncladded multimode optical fibers", J. Opt., vol. 12, no. 9, pp. 95503, 2010. CrossRef M. Śmietana et al., "Simultaneous optical and electrochemical label-free biosensing with ITO-coated lossy-mode resonance sensor", Biosensors and Bioelectronics, vol. 154, pp. 112050, 2020. CrossRef P. Niedziałkowski et al., " Electrochemical performance of indium-tin-oxide-coated lossy-mode resonance optical fiber sensor", Sensors and Actuators B: Chemical, vol. 301, no. 12, pp. 1-10, 2019. CrossRef V. Stranak et al., "Effect of mid-frequency discharge assistance on dual-high power impulse magnetron sputtering", Surface & Coatings Technology, vol. 206, no. 11-12. pp. 2801-2809, 2012. CrossRef I. Del Villar et al., "Design rules for lossy mode resonance based sensors", Appl. Opt., vol. 51, no. 19, pp. 4298-4307, 2012. CrossRef W. F. Wu and B. S. Chiou, "Effect of annealing on electrical and optical properties of RF magnetron sputtered indium tin oxide films", Appl. Surf. Sci., vol. 68, no. 4, pp. 497-504, 1993. CrossRef M. Smietana et al., "Optical Monitoring of Electrochemical Processes With ITO-Based Lossy-Mode Resonance Optical Fiber Sensor Applied as an Electrode", J. Light. Technol., vol. 36, no. 4, pp. 954-960, 2018. CrossRef M. Śmietana et al., "Study on Combined Optical and Electrochemical Analysis Using Indium‐tin‐oxide‐coated Optical Fiber Sensor", Electroanalysis, vol. 31, no.2, pp. 398-404, 2019. CrossRef

Electrochemically directed biofunctionalization of a lossy-mode resonance optical fiber sensor.

In this work, we present a direct electrochemical biofunctionalization of an indium-tin-oxide-coated lossy-mode resonance optical fiber sensor. The functionalization using a biotin derivative was performed by cyclic voltammetry in a 10 mM biotin hydrazide solution. All stages of the experiment were simultaneously verified with optical and electrochemical techniques. Performed measurements indicate the presence of a poly-biotin layer on the sensor's surface. Furthermore, dual-domain detection of 0.01 and 0.1 mg/mL of avidin confirms the sensor's viability for label-free detection.

Lossy Mode Resonance Based Fiber Optic Creatinine Sensor Fabricated Using Molecular Imprinting Over Nanocomposite of MoS2/SnO2

Creatinine (CR) produced through the muscle metabolism acts as biomarker to monitor the kidney functioning of the human body. In this study, a successful effort has been made to develop a fast and easy detection method for the monitoring of CR concentration in an aqueous solution as well as in the artificial urine sample. The sensor has been developed over a lossy mode resonance (LMR) based optical fiber platform using MoS2@SnO2 nanocomposite as LMR supporting material and MoS2@SnO2 nanocomposite along with CR imprinted polymer film as artificial antibodies. The sensor’s performance has been studied for the CR concentration range from 0 to $2000~\mu \text{g}$ /mL which lies within the physiological range found in human blood and urine. The maximum sensitivity and detection limit of the sensor have been found to be 0.41 nm/( $\mu \text{g}$ /mL) and $1.86~\mu \text{g}$ /mL, respectively. The sensor has several advantages such as high selectivity, long-term stability, repeatability and fast response. The recovery of the sensor probes close to 100% with the artificial urine sample shows its potential use in the biomedical application.

A Comprehensive Review: Materials for the Fabrication of Optical Fiber Refractometers Based on Lossy Mode Resonance.

Lossy mode resonance based sensors have been extensively studied in recent years. The versatility of the lossy mode resonance phenomenon has led to the development of sensors based on different configurations that make use of a wide range of materials. The coating material is one of the key elements in the performance of a refractometer. This review paper intends to provide a global view of the wide range of coating materials available for the development of lossy mode resonance based refractometers.

Generation of leaky mode resonance by metallic oxide nanocoating in tilted fiber-optic gratings.

This work investigates the excitation of dense comb-like enhanced leaky mode resonance (eLMR) in tilted fiber Bragg grating (TFBG) integrated with indium tin oxide (ITO) nanocoating. The ITO overlay leads to a large reduction in mode loss and a great increase of propagation length for s-polarized leaky modes, which means the leaky modes become guided. The guidance of leaky modes enhances significantly the interaction with the core guided mode, which leads to the generation of strong dense comb-like eLMR. The results show that the ultra-narrow eLMR bands present promising sensing performance with an extended measurement range and provide advantages of high Q measurement over the case of surface plasmon resonance (SPR) and lossy mode resonance (LMR). The similarities and differences between the eLMR and SPR and LMR are also discussed. This study offers new opportunities to develop eLMR-based multifunctional fiber-optic devices with high performance.

Lossy mode resonance generated by titanium dioxide nanoarray: a comprehensive theoretical research

The lossy mode resonance (LMR)-based optical fiber waveguide based on titanium dioxide nanoarrays was discovered and researched for the first time in this paper. Two kinds of waveguide coating structures, titanium dioxide nanoarrays and nanofilms-nanoarrays systems, were researched using finite element method, where the localized field distribution, the mode transmission characteristics and measurement sensitivities of surrounding refractive index were researched in detail. In the former structure, there exists a localized electromagnetic field that can be generated by both TE and TM polarization modes around nanoarrays. By increasing the diameters of nanoparticles and decreasing the intervals of nanoarrays, the resonance wavelength will redshift and the measurement sensitivity will be enhanced. In the latter structure, the localized electromagnetic field can be obviously enhanced due to the mode coupling between nanofilms and nanoarrays. In addition, the measurement sensitivity of refractive index was 5179 nm/RIU in the range of 1.333–1.343, which is two times higher than that of the structure without TiO2 nanoarrays. This paper opened up a door to study the LMR generated by semiconductor nanoparticles, which is useful in the research of electromagnetic resonance-based sensors in nanoscales.

Lossy Mode Resonance-Based Refractive Index Sensor for Sucrose Concentration Measurement

A detailed analysis of Prism/LiF/ZnO structure based lossy mode resonance sensor is presented for measurement of sucrose concentration. Theoretical and experimental studies using angular interrogation technique has been carried out to achieve high sensitivity for a range of surrounding medium refractive indices (1.33-1.45). Simulation outcomes reveal that a low refractive index layer of LiF may be introduced between substrate and the absorbing film of ZnO to develop a high sensitivity refractive index sensor. Various sensor configurations at different thicknesses of LiF are investigated for both s- and p- polarizations of light at the wavelength of 632.8 nm. The best obtained sensor configurations have been developed experimentally to measure concentration of sucrose solution. The maximum sensitivities of 61.92 °/RIU for s- polarization and 68.80 °/RIU for p-polarization are obtained experimentally, which are found to be in close agreement with the theoretically simulated results.

Simultaneous optical and electrochemical label-free biosensing with ITO-coated lossy-mode resonance sensor

In this work we discuss a new label-free biosensing device based on indium tin oxide (ITO) overlaid section of a multimode optical fiber fused silica core. The sensor has been used to optical measurements also simultaneously interrogated electrochemically (EC). Due to optimized thickness and optical properties of ITO film, a lossy-mode resonance (LMR) could be observed in the optical domain, where electrical properties of the film allowed for application of the sensor as a working electrode in an EC setup. It has been confirmed that the LMR response depends on optical properties of the external medium, as well as potential applied to the electrode during cyclic voltammetry. After the ITO surface functionalization with amine groups and covalently attached biotin, the device has been applied for label-free biosensing of avidin in both the domains simultaneously. On the example of biotin-avidin detection system it was demonstrated that when avidin concentration increases a decrease in current and increase in LMR wavelength shift were recorded in EC and optical domain, respectively. Both optical and EC responses follow the protein interaction process, and thus can be used as cross-verification of the readouts. Moreover, an extended information has been achieved comparing to solely EC interrogation, i.e., the grafting process of biotin and avidin was directly monitored optically displaying individual steps of an incubation procedure.

All-Fiber Multifunctional Electrooptic Prototype Device with a Graphene/PMMA (Poly(methyl methacrylate)) Hybrid Film Integrated on Coreless Side-Polished Fibers

All-fiber optical devices with the merits of easy compatibility, strong anti-interference ability, and high robustness haven been extensively studied in the past years. However, the fabricating processes of these devices are complex and costly, and most of them are usually single-functional. Here, we demonstrate an all-fiber electro-optic prototype device with graphene/PMMA (polymethyl methacrylate) hybrid film integrated on the CSPF (coreless side-polished fiber) for the first time. The as-fabricated GP-CSPF can be used as an electro-optic modulator with the amplitude modulation efficiency of 1.13 dB/V at the wavelength of 1540 nm, which is comparable with the state-of-the-art modulators based on graphene. The internal working mechanism of the GP-CSPF was analyzed theoretically and experimentally. The results indicate the LMR (lossy mode resonance) and electro-thermo-optic effects work together on the device to achieve the electro-optic modulation. Meanwhile, the GP-CSPF also can be used as a photoconduc...