Single Wavelength Light Source Research Articles

Estimating droplet size distribution of emulsions using turbidity measurements: A soft sensor based on artificial neural network

Ability to characterise droplet size distribution (DSD) of emulsions in real-time is essential for on-demand production of customised emulsions. In this work, for the first time, we demonstrate a possibility of estimating full DSD of oil in water emulsions from turbidity measurements using a single wavelength light source. We used recently published data of DSD and turbidity measurements of rapeseed oil in water emulsions (oil volume fractions of 0.15, 0.3 and 0.45) produced with vortex based hydrodynamic cavitation device. Measured DSDs are represented by weighted sum of three log-normal distributions. We developed an approach and a methodology based on artificial neural network (ANN) to estimate DSD from a single measurement of turbidity. A mathematical model is developed to simulate measured turbidity profiles using the known DSDs. The validated model was then used to generate simulated data of turbidity and oil volume fraction pairs (105 pairs). This synthetic data was used to train ANN which used turbidity and volume fraction as input and eight parameters of DSD as output. The developed ANN was able to capture the experimentally measured characteristic diameters and DSDs very well for three oil volume fractions and four different number of passes. The presented methodology and results will be useful for developing an in-line soft sensor based on turbidity measurements for real time estimation of full DSDs of emulsions.

A Self-Calibrated Single Wavelength Biosensor for Measuring Oxygen Saturation.

Traditional methods for measuring blood oxygen use multiple wavelengths, which produce an intrinsic error due to ratiometric measurements. These methods assume that the absorption changes with the wavelength, but in fact the scattering changes as well and cannot be neglected. We found that if one measures in a specific angle around a cylindrical tissue, called the iso-pathlength (IPL) point, the reemitted light intensity is unaffected by the tissue's scattering. Therefore, the absorption can be isolated from the scattering, which allows the extraction of the subject's oxygen saturation. In this work, we designed an optical biosensor for reading the light intensity reemitted from the tissue, using a single light source and multiple photodetectors (PDs), with one of them in the IPL point's location. Using this bio-device, we developed a methodology to extract the arterial oxygen saturation using a single wavelength light source. We proved this method is not dependent on the light source and is applicable to different measurement locations on the body, with an error of 0.5%. Moreover, we tested thirty-eight males and females with the biosensor under normal conditions. Finally, we show the results of measuring subjects in a hypoxic chamber that simulates extreme conditions with low oxygen.

Tapered tip optical fibers for measuring ultra-small refractive index changes with record high sensitivity.

Here we demonstrate an inexpensive, simple, and ultra-sensitive refractive index sensor based on a tapered tip optical fiber combined with a straightforward image analysis method. The output profile of this fiber exhibits circular fringe patterns whose intensity distribution dramatically changes even with ultra-small refractive index variations in the surrounding medium. The sensitivity of the fiber sensor is measured using different concentrations of saline solutions with a transmission setup consisting of a single wavelength light source, a cuvette, an objective lens, and a camera. By analyzing the areal changes in the center of the fringe patterns for each saline solution, we obtain an unprecedented sensitivity value of 24,160 dB/RIU (refractive index unit), which is the highest value reported so far among intensity-modulated fiber refractometers. The resolution of the sensor is calculated to be 6.9 ×10-9. Moreover, we measure the sensitivity of the fiber tip in the backreflection mode using salt-water solutions and obtained a sensitivity value of 620 dB/RIU. This sensor is ultra-sensitive, simple, easy to fabricate, and low-cost, which makes it a promising tool for on-site measurements and point-of-care applications.

A New PM Sampler with a Built-In Black Carbon Continuous Monitor

We introduce a new instrument for sampling the airborne particulate matter (PM) while monitoring the black carbon (BC) atmospheric concentration. The concentration of PM and BC are usually measured by separate instruments with possible systematics differences even in the collecting inlets. The new equipment is based on a low-volume sequential PM sampler, fully compliant with the EU-CEN and US-EPA regulatory standards, with a built-in optical BC monitor. The BC concentration is continuously measured during the sampling in the PM accumulated on the filter while the PM concentration can be obtained off-line by a standard gravimetric analysis. The optical set-up, upstream the collecting filter, is composed by a single wavelength light source (λ = 635 nm) and a photodiode, placed in way to receive the light backscattered by the filter surface at a fixed angle. The mechanical arrangement does not introduce any perturbation to the PM sampling. Thanks to an original calibration curve, the sample absorbance is deduced from the output signal of the photodiode. Finally, the BC concentration is obtained through the Mass Absorption Coefficient (MAC). After the sampling and the PM gravimetric determination, the same filter can be sent to other compositional analyses. Thermo-optical quantification of the Elemental and Organic Carbon (EC and OC) in the filter sample can thus be exploited to tune the MAC value to the PM composition of a particular site. The main features of the new instrument and the set of validation tests against other PM samplers and BC monitors of widespread use (i.e.,: Multi Angle Absorption Photometer and aethalometer) are detailed and discussed.

Imaging-based spectrometer-less optofluidic biosensors based on dielectric metasurfaces for detecting extracellular vesicles

Biosensors are indispensable tools for public, global, and personalized healthcare as they provide tests that can be used from early disease detection and treatment monitoring to preventing pandemics. We introduce single-wavelength imaging biosensors capable of reconstructing spectral shift information induced by biomarkers dynamically using an advanced data processing technique based on an optimal linear estimator. Our method achieves superior sensitivity without wavelength scanning or spectroscopy instruments. We engineered diatomic dielectric metasurfaces supporting bound states in the continuum that allows high-quality resonances with accessible near-fields by in-plane symmetry breaking. The large-area metasurface chips are configured as microarrays and integrated with microfluidics on an imaging platform for real-time detection of breast cancer extracellular vesicles encompassing exosomes. The optofluidic system has high sensing performance with nearly 70 1/RIU figure-of-merit enabling detection of on average 0.41 nanoparticle/µm2 and real-time measurements of extracellular vesicles binding from down to 204 femtomolar solutions. Our biosensors provide the robustness of spectrometric approaches while substituting complex instrumentation with a single-wavelength light source and a complementary-metal-oxide-semiconductor camera, paving the way toward miniaturized devices for point-of-care diagnostics.

Paper-Based Multiplex Surface-Enhanced Raman Scattering Detection Using Polymerase Chain Reaction Probe Codification

We construct a multiplex surface-enhanced Raman scattering (SERS) platform based on a plasmonic paper substrate and a double-labeled probe for the detection of multiple fluorescent dyes at high sensitivity in a single-wavelength light source system. Plasmonic paper, made of silver nanodots on three-dimensional cellulose fibers, enables highly sensitive SERS biosensing based on localized surface plasmon resonance (LSPR). The proposed method enables the identification and quantification of a range of fluorescent dyes ranging from picomolar to millimolar concentrations. The use of 5' fluorescent dyes and 3' biotin-modified probes as SERS-coded probes renders possible the separation of fluorescent dyes with streptavidin-coated magnetic beads (SMBs) and the sensitive detection of multiple dyes after the reverse transcription polymerase chain reaction (RT-PCR). This experimental study reveals the multiplex detection capability of PCR-based SERS under existing PCR conditions without modifying primer and probe sequences. The combination of magnetic bead-based separation and paper SERS platform is efficient, economical, and can be used for the simultaneous detection of two or more pathogens.

Near-Infrared Regulated Nanozymatic/Photothermal/Photodynamic Triple-Therapy for Combating Multidrug-Resistant Bacterial Infections via Oxygen-Vacancy Molybdenum Trioxide Nanodots.

Bacterial infections have become a major danger to public health because of the appearance of the antibiotic resistance. The synergistic combination of multiple therapies should be more effective compared with the respective one alone, but has been rarely demonstrated in combating bacterial infections till now. Herein, oxygen-vacancy molybdenum trioxide nanodots (MoO3-x NDs) are proposed as an efficient and safe bacteriostatic. The MoO3-x NDs alone possess triple-therapy synergistic efficiency based on the single near-infrared irradiation (808 nm) regulated combination of photodynamic, photothermal, and peroxidase-like enzymatic activities. Therein, photodynamic and photothermal therapies can be both achieved under the excitation of a single wavelength light source (808 nm). Both the photodynamic and nanozyme activity can result in the generation of reactive oxygen species (ROS) to reach the broad-spectrum sterilization. Interestingly, the photothermal effect can regulate the MoO3-x NDs to their optimum enzymatic temperature (50 °C) to give sufficient ROS generation in low concentration of H2 O2 (100 µm). The MoO3-x NDs show excellent antibacterial efficiency against drug-resistance extended spectrum β-lactamases producing Escherichia coli and methicillin-resistant Staphylococcus aureus (MRSA). Animal experiments further indicate that the MoO3-x NDs can effectively treat wounds infected with MRSA in living systems.

Lights, camera, path splitter: a new approach for truly simultaneous dual optical mapping of the heart with a single camera

BackgroundOptical mapping of transmembrane voltage and intracellular calcium is a powerful tool for investigating cardiac physiology and pathophysiology. However, simultaneous dual mapping of two fluorescent probes remains technically challenging. We introduce a novel, easy-to-use approach that requires a path splitter, single camera and excitation light to simultaneously acquire voltage and calcium signals from whole heart preparations, which can be applied to other physiological models – including neurons and isolated cardiomyocytes.ResultsComplementary probes were selected that could be excited with a single wavelength light source. Langendorff-perfused hearts (rat, swine) were stained and imaged using a sCMOS camera outfitted with an optical path splitter to simultaneously acquire two emission fields at high spatial and temporal resolution. Voltage (RH237) and calcium (Rhod2) signals were acquired concurrently on a single sensor, resulting in two 384 × 256 images at 814 frames per second. At this frame rate, the signal-to-noise ratio was 47 (RH237) and 85 (Rhod2). Imaging experiments were performed on small rodent hearts, as well as larger pig hearts with sufficient optical signals. In separate experiments, each dye was used independently to assess crosstalk and demonstrate signal specificity. Additionally, the effect of ryanodine on myocardial calcium transients was validated – with no measurable effect on the amplitude of optical action potentials. To demonstrate spatial resolution, ventricular tachycardia was induced –resulting in the novel finding that spatially discordant calcium alternans can be present in different regions of the heart, even when electrical alternans remain concordant. The described system excels in providing a wide field of view and high spatiotemporal resolution for a variety of cardiac preparations.ConclusionsWe report the first multiparametric mapping system that simultaneously acquires calcium and voltage signals from cardiac preparations, using a path splitter, single camera and excitation light. This approach eliminates the need for multiple cameras, excitation light patterning or frame interleaving. These features can aid in the adoption of dual mapping technology by the broader cardiovascular research community, and decrease the barrier of entry into panoramic heart imaging, as it reduces the number of required cameras.

Porphyrin-based covalent organic framework nanoparticles for photoacoustic imaging-guided photodynamic and photothermal combination cancer therapy

Combination of photodynamic therapy (PDT) and photothermal therapy (PTT) generally requires different components to build a composite irradiated with different excitation lights. One component photoactive agent for enhanced combination of PDT and PTT under the excitation of a single wavelength light source is more urgent in tumor phototherapy via adjusting spatial arrangement of photoactive units. Herein, porphyrin-based covalent organic framework nanoparticles (COF-366 NPs) were synthesized to control the orderly spatial arrangement of the photoactive building units and firstly used for antitumor therapy in vivo. COF-366 NPs provide the simultaneous therapy of PDT and PTT under a single wavelength light source with the monitoring of photoacoustic (PA) imaging, which makes the operation simpler and more convenient. COF-366 NPs had achieved good phototherapy effect even in the face of large tumors. The prepared multifunctional COF-366 NPs open up a new avenue to phototherapeutic materials and expand the application range of covalent organic framework.

Horizontal white light flat-topped beams produced by the diffraction mask

The flat-topped beam is a special beam with wide applications in the directional backlight autostereoscopic display, and it is used as a directional backlight in the horizontal direction. However, it is still challenge to white light flat-topped beams with the traditional flat-topped beam shaper. In this paper, it is proposed that diffraction mask with butterfly-shaped hole arrays and cylindrical lens be used to produce the horizontal flat-topped white beams. The surface of the LCD backlight mask is covered by a layer of diffraction mask, where the butterfly-shaped holes are arranged in line along the vertical direction. Simultaneously, the height and width, hole center height are kept identical, and the ratio between the center depth and the perimeter of butterfly-shape hole is defined as the concavity. A flat convex cylindrical lens is placed in front of diffraction mask gaplessly. The uniform light field from LCD backlight is transformed into the white light flat-topped beams and projected on the receiving screen by the diffraction mask and cylindrical lens. Based on the Huygens-Fresnel diffraction integral, the intensity distribution formula of diffraction of the single wavelength light source on the receiving screen is derived. Furthermore, the intensity distribution formula on the screen is derived by super positioning the multiple wavelengths. The proposed method is verified by both numerical simulation and experimental validation. Numerical simulations elucidate the effects of the different transmission distance and butterfly hole concavity on the white light flat-topped beam flat-topped factor. The stimulated results show that the propagation distance does not influence the white light beam transverse intensity distribution characteristics of flat top. With the beam propagation distance increasing, the horizontal width of flat-topped beam becomes larger. When the concavity of the butterfly hole decreases, light intensity distribution shifts from Gaussian to flat type. However, the flat-topped factor decreases when the butterfly concavity is too small. The optimal concavity varies from 0.4 to 0.6, where the flattened factor of the transverse flat-topped beams reaches 0.89. In the experiments, films are produced with the diffraction of butterfly hole array mask. The height and width of butterfly are both 48 μm, and the concavities of the butterfly are 1, 0.83, 0.66 and 0.83 respectively. The cylindrical lens adopts PMMA cylindrical lens grating plate, with a thickness of 8 mm, a grating density for 18 line/inch, and the cylindrical lens curvature radius R is 2.67 mm. The experimental results show that the beam transmission is consistent with the result of numerical simulation. When concavity of the butterfly is 0.5, the flat factors of the white light horizontal of flat-topped beams are higher than 0.89 in a range from 500 mm to 2000 mm. Moreover, we also discuss the dispersion effects of shaft flat-topped beams and off-axis flat-topped beams, showing that the refraction and dispersion of the cylindrical lens can cancel out each other, so that the horizontal flat-toped white beams is basically dispersionless.

Macrobending Loss Measurements of G.657 Fiber with Suppression of Ripple Effect Induced by Whispering Gallery Modes

During the macrobending loss performance tests of ITU-T G.657 fiber under small bending radius, the test results show big differencesin many tests for the same test samples and conditions. Research shows that the main reason for the difference is Whispering gallery modes phenomenon in small bending radius [1]. The inappropriate test conditions can affect the accuracy of macrobending loss test results. In the test of product validation and field application, single wavelength light source and optical power meter were often used. How to judge whether there is effect existing and how to remove the Whispering gallery modes influence in the testing process has become the key to correctly test macrobending loss by light source and optical power meter. This paper introduces the method of eliminating Whispering gallery modes effect during the macrobending test under small bending radius by single wavelength light source and optical power meter.

Full-Color Light-Emitting Carbon Dots with a Surface-State-Controlled Luminescence Mechanism.

Carbon dots (CDs) with tunable photoluminescence (PL) and a quantum yield of up to 35% in water were hydrothermally synthesized in one pot and separated via silica column chromatography. These separated CDs emitted bright and stable luminescence in gradient colors from blue to red under a single-wavelength UV light. They exhibited high optical uniformity; that is, every sample showed only one peak in the PL excitation spectrum, only one peak in the excitation-independent PL emission spectrum, and similar monoexponential fluorescence lifetimes. Although these samples had similar distributions of particle size and graphite structure in their carbon cores, the surface state gradually varied among the samples, especially the degree of oxidation. Therefore, the observed red shift in their emission peaks from 440 to 625 nm was ascribed to a gradual reduction in their band gaps with the increasing incorporation of oxygen species into their surface structures. These energy bands were found to depend on the surface groups and structures but not on the particle size, not as in traditional semiconductor quantum dots. In addition, because of their excellent PL properties and low cytotoxicity, these CDs could be used to image cells in different colors under a single-wavelength light source, and the red-emitting CDs could be used to image live mice because of the strong penetration capability of their fluorescence.

The Effect of Low-level Laser Therapy on Trigeminal Neuralgia: A Review of Literature.

The effect of low intensity laser radiation in the treatment of acute and chronic pain is now established in many studies. Tri-geminal neuralgia is a pain passes through nerve's branches and its trigger is located in skin or mucosa that could lead to pain with a trigger stimulus. The pain involved branches of trigeminal nerve that sometimes has patients to seek the treatment for several years. Nowadays different treatments are used for relief of pain that most of them cause tolerance and various side effects. This paper reviews and summarizes scientific papers available in English literature publishedin PubMed, Scopus, Science Direct, Inter science, and Iran Medex from 1986 until July 2011 about the effect of these types of lasers on trigeminal neuralgia which is one of the most painful afflictions known. In different studies, the effect of laser therapy has been compared with placebo irradiation or medicinal and surgical treatment modalities. Low-level laser therapy (LLLT) is a treatment strategy which uses a single wavelength light source. Laser radiation and monochromatic light may alter cell and tissue function. However, in most studies laser therapy was associated with significant reduction in the intensity and frequency of pain compared with other treatment strategies, a few studies revealed that between laser and placebo group there was not any significant difference according to the analgesic effect. Low-level laser therapy could be considered in treatment of trigeminal neuralgia without any side effects.

Step height measurement using lateral shearing cyclic path optical configuration setup and polarization phase-shifting interferometry

We present a step height measurement technique using a lateral shearing cyclic path optical configuration (CPOC) setup and polarization phase shifting interferometry (PPSI). In the technique, the CPOC setup generates two orthogonally polarized, laterally sheared, converging beams that get focused at the back focal plane of a positive lens placed at the input beam of the CPOC setup. These focusing beams are reflected back into the CPOC setup by the step optics, positioned in such a way that one of the surfaces of the step optics coincides exactly with the focus point of one of the laterally sheared focusing beams. The CPOC recombines the beams reflected from the step surfaces and the beams re-pass through the lens, which produces collimated and spherical interfering wave fronts for the respective beams. Using PPSI, the radius of the spherical wavefront emerging from the lens, which is related to the focal shift introduced between the reflected beams due to the step height, is determined. The novelty of the technique is the introduction of the CPOC setup and the use of a single wavelength light source to determine the large step height. Results obtained for a step height of 1.340 mm are presented.

Determination of Optical Constants of Thin Films from Measurements of Reflectance and Transmittance

A new approach to determine the optical constants of thin films using a single wavelength light source without measurement of film thickness has been introduced in this paper. From the reflectance and transmittance measured over a range of film thicknesses, the optical constants of as-deposited GeSbTe alloy films at a wavelength of 685 nm as well as the film thickness at each point of measurement have been obtained by use of a nonlinear fitting. A self-consistent validation of the approach is also presented by comparing the optical constants obtained in both cases of film-incidence and substrate-incidence.

System for detecting environmental ppb-level nitrogen dioxide I

Coloration reactions have been found between nitrogen dioxide (NO 2) and organic compounds, such as aromatic amine derivatives, impregnated in porous glass. A single absorption peak in the visible region was detected after the reactions for all compounds. Linear relationships were obtained between environmental NO 2 concentrations and absorbance changes at peak wavelength for some compounds. A system is proposed for detecting low-levels of NO 2 using these coloration reaction in porous glass. Our designed system is composed of an organically-impregnated porous glass sensor and a simple absorbance meter having a single-wavelength light source. It was clarified that environmental ppb-levels of NO 2 could be detected using our system and that values for hourly average concentrations of NO 2 obtained by our system agreed well with those obtained using commercial analytical instruments. A coloration reaction mechanisms are also proposed based on the experimental results obtained.

Nonlinear influence on PM-AM conversion measurement of group velocity dispersion in optical fibres

The authors propose a method for measuring the group velocity dispersion, including the polarity, of optical fibre by using a single wavelength light source. The method is based on the interplay between phase modulation-amplitude modulation (PM-AM) conversion and self-phase modulation (SPM).

1.5-µm λ/4-shifted InGaAsP/InP DFB lasers

A single wavelength light source in 1.5-μm range was developed using InGaAsP/InP \lambda/4 -shifted distributed feedback (DFB) semiconductor heterostructures. Superiority of the \lambda/4 -shifted DFB structure in terms of stability of the main mode at the Bragg wavelength was shown theoretically, in which the threshold, the output, and the polarization characteristics were taken into account. A \lambda/4 -shifted corrugated grating was made by a newly developed negative and positive photoresists technique. Buried heterostructure (BH) diode lasers with nonreflective window ends were fabricated and highly stable single-mode operation with a low threshold was obtained reproducibly. Direct modulation properties and life-tests results indicated that the \lambda/4 -shifted DFB lasers could be a reliable single-mode light source in a long span lightwave transmission system in 1.5-μm range.