Evanescent Wave Field Research Articles

CRISPR/Cas12a powered air-displacement enhanced evanescent wave fluorescence fiber-embedded microfluidic biochip for nucleic acid amplification-free detection of Escherichia coli O157:H7

Simple yet ultrasensitive and contamination-free quantification of environmental pathogenic bacteria is in high demand. In this study, we present a portable clustered regularly interspaced short palindromic repeats-associated protein 12a (CRISPR/Cas12a) powered Air-displacement enhanced Evanescent wave fluorescence Fiber-embedded microfluidic Biochip (AEFB) for the high-frequency and nucleic acid amplification-free ultrasensitive detection of Escherichia coli O157:H7. The performance of AEFB was dramatically enhanced upon employing a simple air-solution displacement process. Theoretical assays demonstrated that air-solution displacement significantly enhances evanescent wave field intensity on the fiber biosensor surface and increases the V-number in tapered fiber biosensors. Consequently, light-matter interaction is strengthened, and fluorescence coupling and collection efficiency are improved, considerably enhancing sensitivity. By integrating the CRISPR biosensing mechanism, AEFB facilitated rapid, accurate, nucleic acid amplification-free detection of E.coli O157:H7 with polymerase chain reaction (PCR)-level sensitivity (176 cfu/mL). To validate its practicality, AEFB was used to detect E.coli O157:H7 in surface water and wastewater. Comparison with RT-PCR showed a strong linear relationship (R2 = 0.9871), indicating the excellent accuracy and reliability of this technology in real applications. AEFB is highly versatile and can be easily extended to detect other pathogenic bacteria, which will significantly promote the high-frequency assessment and early-warning of bacterial contamination in aquatic environments.

Acoustic rotation of multiple subwavelength cylinders for three-dimensional topography reconstruction

Accurate rotation of microparticles is of great significance in micro-rotors, multi-angle microscopic observation, microbial three-dimensional phenotyping, and microsystem assembly. However, most methods can only rotate a single object, thus limiting the throughput. In this study, we realized the simultaneous rotation of many trapped and aligned subwavelength glass cylinders inside an evanescent wave field excited by a resonant phononic crystal plate. The unique feature of the rotation lies in its periodic distribution as well as the rotation axis being perpendicular to the acoustic axis. The rotary power originates from viscous torque generated by the evanescent wave-induced near-boundary acoustic streaming's asymmetry distribution on the trapped cylinder. Furthermore, the three-dimensional topographies of rotated cylinders can be reconstructed from the microscopic images under different rotating angles. Our findings can pave the way toward developing simple, disposable, and scalable microfluidic devices for massive subwavelength acoustic rotation by carefully designing acoustic metamaterials.

2.11 GHz all-fiber harmonic mode-locked laser based on highly nonlinear hybrid multimode interference saturable absorber

This paper proposes a harmonic mode-locked fiber laser based on a novel highly nonlinear hybrid multimode interference saturable absorber (SA). The hybrid multimode interference SA is integrated by tapered graded-index multimode fiber (TA-GIMF) and Bi2Te3. The numerical simulation results show that TA-GIMF can improve the stability of nonlinear multimode interference mode-locking by filtering higher-order transverse modes. In addition, the larger evanescent-wave fields generated by TA-GIMF are more beneficial to the light–matter interaction. By depositing Bi2Te3 on TA-GIMF, the nonlinear saturation absorption properties and nonlinear coefficients in the laser cavity are further improved. Based on the hybrid multimode interference SA, the repetition rate of the fiber laser reached 2.11 GHz, corresponding to the 30th harmonic of the fundamental repetition rate of 70.41 MHz. Our results are the highest repetition rate generated based on the NL-MMI effect and provide novel insights into implementing highly integrated, high repetition-rate mode-locked fiber lasers.

Numerical investigation of a Ge1-xSnx-on-AlN waveguide and its sensing mechanism for the detection of trace gases in the mid-infrared regime

This work reports the integration of a Ge1−xSn x -on-AlN optical waveguide (WG) on SiO2 substrate to facilitate mid-infrared (MIR) trace gas detection. Here, the proposed structure makes use of Ge1−xSn x in the core of the WG and the AlN cladding; this enables the effective guidance and confinement of a broad spectrum of MIR light waves within the GeSn WG. The gas detection mechanism of the device is based on the evanescent wave field component of a guided mode to examine particular molecular absorption/trace gas characteristics of the upper cladding environment. The designed WGs exhibit high power confinement (∼90%) and low propagation loss of 0.61–1.18 dB/cm at λ=4.3−4.74µm with x=6% in the Ge1−xSn x core. We also discuss the capability of the proposed WG to detect trace gases such as CO, CO2, and N2O. The results show that the minimum detectable concentrations (Cmin) of these gases are ∼0.42, 0.12, and 0.16 ppm, respectively, for x=6%. These encouraging results enable a new sensor platform for GeSn-based MIR trace/atmospheric gas detection.

Silicon Photonics Sensors for Biophotonic Applications—A Review

In the last two decades, biosensors have made a remarkable development in the area of food quality monitoring, drug discovery, environmental monitoring, soil quality monitoring, the healthcare industry, and medical point of care diagnosis. The integrated silicon photonic-based biosensors using the evanescent wave (EW) field and their advantages in terms of high sensitivity, high reliability, compactness, robustness, and miniaturization are discussed in this review. Specifically, different silicon photonic device configurations based on the EW field, such as interferometer-, resonator-, photonic crystal-, and Bragg grating-based biosensors, are discussed in detail. Moreover, various performance improvement strategies, such as advance and fundamental approaches, including Vernier effect-based systems in the cascaded form of the Mach–Zehnder interferometer (MZI)-ring resonator, are also reviewed. This article further reviews the usage of silicon-photonic biosensors for lab-on-chip (LOC) applications, including optoelectronic integrated circuits (OEICs). The state-of-the-art performance of different biosensors technologies is also comparatively discussed.

Fiber Optic Sensor with a Gold Nanowire Group Array for Broad Range and Low Refractive Index Detection

To achieve high performance and wide range detection, we propose an ultra-wide range high sensitivity plasmonic fiber optic sensor with a gold (Au) nanowire group array, which has both propagating surface plasmon resonance (PSPR) and local surface plasmon resonance (LSPR) sensing characteristics. The PSPR, LSPR, and PSPR+LSPR are presented as Au thin layers, Au spheres (or Au nanowires), and Au nanowire group arrays, respectively, and their respective properties are analyzed from theoretical, simulated, and numerical aspects. When detection is performed, the presence of both evanescent wave and electric field forces in the Au nanowire group array combines to significantly improve the sensor’s detection capability. Detection simulation analysis was performed using COMSOL Multiphysics software. The range of refractive indices that can be detected is 1.08 to 1.37 in the optical band from 1210 nm to 2140 nm. In the detection range, the maximum sensitivity of the detected wavelength is 13,000 nm/RIU. Our proposed sensor has a broad range, high sensitivity, and low refractive index detection, and has good research value and application prospects.

Reusable smartphone-facilitated mobile fluorescence biosensor for rapid and sensitive on-site quantitative detection of trace pollutants

Increasing exposure to toxic pollutants highlights the need for their sensitive detection technologies that can be rapidly adapted and deployed in various settings. Optical biosensors are an excellent solution due to their outstanding features. However, the sophisticated and expensive optical design limits their scalability and actual application. Herein, an innovative reusable smartphone-facilitated mobile fluorescence biosensor (s-MFB) was built through integrating miniaturized all-fiber optical system and microfluidic system with smartphone. An asymmetric Y-shaped fiber optic coupler (Y-FOC) is constructed for simultaneous transmission of excitation light and the collected fluorescence. In particular, the incidence rays are introduced into the fiber bio-probe at a specific angle through the single-mode fiber of the Y-FOC, which enhances the evanescent wave field and the number of total internal reflections. The s-MBF showed a LOD for free Cy5.5 of 0.1 nM. Combining indirect competitive immunoassay with the s-MFB, this new assay, which achieve quantitative detection of bisphenol A and norfloxacin in 15 min with high sensitivity and reusability, substantially reduces the complexity and improves the scalability of trace pollutants detection. The adjunctive smartphone application allows on-site real-time quantitative detection, automated interpretation of reporting results, and early-warning of pollution accidents.

Cloaking, trapping and superlensing of lamb waves with negative refraction

We report on experimental and numerical implementations of devices based on the negative refraction of elastic guided waves, the so-called Lamb waves. Consisting in plates of varying thickness, these devices rely on the concept of complementary media, where a particular layout of negative index media can cloak an object with its anti-object or trap waves around a negative corner. The diffraction cancellation operated by negative refraction is investigated by means of laser ultrasound experiments. However, unlike original theoretical predictions, these intriguing wave phenomena remain, nevertheless, limited to the propagating component of the wave-field. To go beyond the diffraction limit, negative refraction is combined with the concept of metalens, a device converting the evanescent components of an object into propagating waves. The transport of an evanescent wave-field is then possible from an object plane to a far-field imaging plane. Twenty years after Pendry’s initial proposal, this work thus paves the way towards an elastic superlens.

Evanescent field interaction of 1550 nm pulsed laser with silver nanomaterial coated D-shape fiber

The paper presents a newly developed fiber-based saturable absorber (SA) operating at 1550 nm waveband. The fiber-based-SA constructed from side-polished fiber called D-shape fiber and with deposited silver nanoparticles act as a nonlinear material for ultrafast laser generation. The interaction between silver nanoparticles and exposed oscillated laser light in cavity were due to evanescent wave (EW) field phenomenon with 1.44% of modulation depth recorded. Stable pulse train of ∼ 1.00 MHz with 2.24 ps pulse width, 10.73 nJ pulse energy, 77.83 dB high signal to noise ratio and 11 mW output power at 1563.24 nm were achieved. Our findings suggests that the properties owned by silver-coated D-shaped fiber via EW can be a great alternative towards conventional film saturable absorber.

Interference caused by electromagnetic interactions

We consider interference fluxes of energy, momentum and angular momentum, describing the interaction of electric charges with constant and variable electromagnetic fields. Absorption and stimulated emission of atoms in the field of free and evanescent waves are described. It is shown that in the case of interaction with reactive fields, the momentum of an atom during absorption and stimulated emission does not change. A wave derivation of Planck’s formula based on the interference of the fields of classical thermal radiation and quantum zero-point oscillations is presented.

Time-delayed acoustic sink for extreme sub-wavelength focusing

After a sound wave enters a Helmholtz resonator, it will be multiply reflected in the cavity and gradually overflow from the opening, just like water slowly flowing out from a water sink. In particular, if such a resonant cavity was arranged near the focus position in a time reversal focusing experiment, the cavity is equivalent to an acoustic sink, and an extreme sub-wavelength focus with a focal size much smaller than the sample size can be achieved. The physical mechanism of this sub-wavelength focusing is that after the sound wave reaches the focus, due to the fact that the arranged cavity has a perfect sound absorbing ability, a large part of the acoustic energy would enter the cavity and then be lost. However, in the loss stage, the localized high-intensity sound energy in the resonant cavity will continuously overflow to the opening. These sounds belong to evanescent wave, and can only be localized near the orifice, so that a very small focus with the size as aperture will be formed. Theoretically, the realization of this extreme sub-wavelength focus resolution depends on the modification of the evanescent wave field. This time-delayed sub-wavelength focusing effect was visually demonstrated by time reversal measurement results in time domain, and the extreme sub-wavelength feature was intuitively demonstrated by results in frequency domain.

Plasmonic field guided patterning of ordered colloidal nanostructures

Abstract Nano-patterned colloidal plasmonic metasurfaces are capable of manipulation of light at the subwavelength scale. However, achieving controllable lithography-free nano-patterning for colloidal metasurfaces still remains a major challenge, limiting their full potential in building advanced plasmonic devices. Here, we demonstrate plasmonic field guided patterning (PFGP) of ordered colloidal metallic nano-patterns using orthogonal laser standing evanescent wave (LSEW) fields. We achieved colloidal silver nano-patterns with a large area of 30 mm2 in <10 min by using orthogonal LSEW fields with a non-focused ultralow fluence irradiation of 0.25 W cm−2. The underlying mechanism of the formation of the nano-patterns is the light-induced polarization of the nanoparticles (NPs), which leads to a dipole-dipole interaction for stabilizing the nano-pattern formation, as confirmed by polarization-dependent surface-enhanced Raman spectroscopy. This optical field-directed self-assembly of NPs opens an avenue for designing and fabricating reconfigurable colloidal nano-patterned metasurfaces in large areas.

An Optical Biosensor-Based Quantification of the Microcystin Synthetase A Gene: Early Warning of Toxic Cyanobacterial Blooming.

The monitoring and control of toxic cyanobacterial strains, which can produce microcystins, is critical to protect human and ecological health. We herein reported an optical-biosensor-based quantification of the microcystin synthetase A (mcyA) gene so as to discriminate microcystin-producing strains from nonproducing strains. In this assay, the mcyA-specific ssDNA probes were designed in silico with an on-line tool and then synthesized to be covalently immobilized on an optical-fiber surface. Production of fluorescently modified target DNA fragment amplicons was accomplished through the use of Cy5-tagged deoxycytidine triphosphates (dCTPs) in the polymerase chain reaction (PCR) method, which resulted in copies with internally labeled multiple sites per DNA molecule and delivered great sensitivity. With a facile surface-based hybridization process, the PCR amplicons were captured on the optical-fiber surface and were induced by an evanescent-wave field into fluorescence emission. Under the optimum conditions, the detection limit was found to be 10 pM (S/N ratio = 3) and equaled 103 gene copies/mL. The assay was triumphantly demonstrated for PCR amplicons of mcyA detection and showed satisfactory stability and reproducibility. Moreover, the sensing system exhibited excellent selectivity with quantitative spike recoveries from 87 to 102% for M. aeruginosa species in the mixed samples. There results confirmed that the method would serve as an accurate, cost-effective, and rapid technique for in-field testing of toxic Microcystis sp. in water, giving early information for water quality monitoring against microcystin-producing cyanobacteria.

High-throughput biomolecular interaction analysis probing by an array fluorescent biosensor platform

Interactions between biomolecules have been extensively investigated in versatile applications, such as biosensing, medical diagnosis and drug screening. In this study, an improved biomolecular interaction analysis probing with an integrated array fluorescent biosensor platform is proposed to overcome the limitations of surface plasmon resonance (SPR), such as a small number of reactions that can be simultaneously analysed and weak reusability of biospecific active surfaces. Reactions between biological molecules at twenty-four individual biosensing spots are monitored in real time by measuring the changes in fluorescence intensity excited by an evanescent wave field at a biospecific active surface. A sensor chip with the biospecific active surface is reusable with over 200 test cycles. The interaction between bisphenol A (BPA) and anti-BPA antibody is chosen as a paradigm to validate this assay. With a wide range of low to high concentrations of anti-BPA antibody, twenty-four response curves at the individual biosensing spots can be generated in real time and simultaneously provide further information about the interactions between antibody and surface-tethered antigen. This system is also characterised by its high-throughput cross-reactivity analysis between antigens and antibodies on the patterned waveguide with a shortened time-to-result.

Fabrication and evaluation of evanescent wave absorption based polyaniline-cladding modified fiber optic urea biosensor

The fabrication and study of cladding modified intrinsic fiber optic urea biosensor has been reported in the present investigation. A simple cladding modification technique was used to construct the sensor by uncladding the small portion from optical fiber. Further bare core was decorated by supportive porous, chemically and optically sensitive matrix material polyaniline (PANI) as an active cladding for enzyme residency. Enzyme-urease (Urs) was cross-linked on the active cladding region via glutaraldehyde solution. Confirmation of the prepared PANI in proper form determined by ultraviolet-visible and Fourier transform infrared spectroscopic techniques. X-ray diffraction technique was employed for nature and compatibility examination of PANI. Sensor parameters such as sensitivity, selectivity, stability and lower detection limit have been analyzed by absorption variation study in evanescent wave field. The response of prepared sensor was studied towards urea in the wide concentration range 100 nM–100 mM and confirmed its lowest detection limit as 100 nM. The stability of sensor was found 28 days with little variation in response. The fabricated sensor has not shown any response towards interference species like glucose, ascorbic acid, l-alanine, l-arginine and their combination with urea solution and hence found selective for urea solution only.

Applications of optical technology in gas concentration detection

Seven common optical methods for gas concentration detection are described. The basic principles, advantages and disadvantages of each method are given in detail. The improvement work and some novel ideas are presented. The applications of combined methods are discussed. These optical methods include some con-ventional gas concentration detection technologies, such as optical interferential method, photoacoustic detection (PAS), correlation spectroscopy, and some novel gas concentration detection technologies, such as tunable diode laser absorption spectroscopy (TDLAS), evanescent wave field sensing technology, hollow core photonic bandgap fiber (HC-PBF) sensing technology and fiber loop ring-down spectroscopy (FLRDS). The prospect of optical gas sensing is listed at the end of the paper, which mainly refers to miniaturization, intelligence, portability, low power consumption, high accuracy, fast response and distributed multi-component telemetry technology.

Study of Evanescence Wave Absorption in Lindane

Evanescent wave field has been studied for the purpose of tailoring fiber sensor capable of detecting lindane concentration in a solution. The mounted fiber was optically polished such that part of the fiber clad is stripped off. To study the evanescent wave field absorption in lindane solution, the unclad fiber was immersed in the solution. Light coming out of the fiber was studied at different wavelength each for different lindane concentration. It was shown that evanescent wave field absorption is stronger at wavelength corresponding to lindane absorption band as has been shown from absorption studies lindane in UV-VIS-NIR spectrophotometer.

Circular synthetic aperture sonar imaging of simple objects illuminated by an evanescent wavefield.

This paper is motivated by the case where an underwater object located within the sediment is illuminated by a grazing acoustic beam below the critical angle. The included experimental work uses a liquid-liquid interface and vertically inverted geometry as a stand-in for the water-sediment boundary. In the super-critical regime sound in the water column refracts into the sediment before scattering. However, for sub-critical illumination a rapidly decaying evanescent wavefield is generated in the sediment near the water-sediment interface. For compact objects located in the sediment near the interface this can result in strong backscattering signals suitable for acoustic image reconstruction using synthetic aperture sonar techniques. Certain properties of the evanescent wavefield such as the vertical phase-locking behavior, the rapid amplitude decay with distance from the interface, and the low-pass filter effect have understandable ramifications for the image formation process and for characteristics of the reconstructed image. In particular, circular imaging techniques require correct placement of the imaging plane to properly focus an object; however, for backscattering (monostatic) evanescent image formation the imaging plane may be placed at the interface and the target will remain in focus regardless of burial depth. A laboratory experiment using simple scatterers is presented.

Polarizing phase shifting interferometry of total internal reflection light for measurement of refractive index and its spatial variation in liquid samples

It is well known that the phase change in total internal reflection (TIR) is a function of the refractive indices of the pair of media involved. The spatial phase variations in a totally internally reflected beam are accurately measured using a Mach Zehnder interferometer employing polarization phase shifting technique. The evaluated phase change is then related to the refractive index variations of the rarer medium. One of the salient features of the proposed technique is that, unlike most interferometric methods where the measured phase is a function of the sample thickness, TIR phase is independent of the sample thickness as long as the evanescent wave field is fully confined within the sample. The theory of the technique is discussed and experimental results showing the three-dimensional profiles of the measured refractive indices and its spatial variations are presented.

Modeling and experimental validation of an evanescent wavefield using a wavenumber integration method

When sound is incident on the boundary between two media, where the first medium has a lower sound speed than the second (such as sound in water incident on some sediments), a critical angle exists. If the incident angle is below this critical angle an evanescent wavefield is formed in the second medium. Experimental work measured the structure of such a wavefield at an oil-water interface insonified by an appropriately oriented transducer, where the region of interest is not in the transducer far-field [Osterhoudt et al., IEEE J. Ocean. Eng. 33, 397–404 (2008)]. Several features of note within the wavefield were observed. This work attempts to model those observations using wavenumber integration techniques. In the incident plane wave approximation, the evanescent wavefield is vertically phase-locked and the characteristic exponential spatial decay is constant across the wavefield. However, the contribution of many wavenumber components across the region of interest is key to understanding the wavefield structure seen in experiments. This model will be compared to the experimental results, and the details of phase, amplitude, and the overall wavefield structure discussed. An improved approximation of the transducer orientation used in experiments may also be inferred from these results. [Work supported by ONR.]