Peak Wavelength Research Articles

A Simultaneous Measurement Sensor for Temperature and Curvature Based on Congruent Quasi-Helical Long-Period Fiber Grating.

This article presents a long-period fiber-grating sensor based on a congruent quasi-helical structure (CQH-LPFG) with the two-parameter measurement of both temperature and curvature. The CQH-LPFG sensor was manufactured using a high-frequency CO2 laser, and an innovative quasi-helical structure was introduced into the two-parameter measurement of the temperature and curvature of the optical fiber sensor with excellent results. The experiment and analysis demonstrate that the curvature sensitivities of the three resonance peaks in the 1440 nm to 1540 nm transmission spectrum were 11.88 nm/m-1, 8.05 nm/m-1, and 11.11 nm/m-1, and the curvature varied ranging from 0.156 m-1 to 0.494 m-1. The three resonance peaks showed temperature responsivities of 29.87 pm/°C, 24.65 pm/°C, and 36.85 pm/°C, respectively, and the linear fit was of excellent quality. In the case of measuring both curvature and temperature changes simultaneously, the resonant peak wavelength of the CQH-LPFG sensor was demodulated through matrix analysis, with dip A and dip C providing superior simultaneous measurements. These features make it a promising candidate for applications such as engineering machinery and the health inspection of buildings.

Manipulating excited states for constructing ultraviolet hybridized local and charge transfer fluorophores and non-doped OLEDs with high color purity

The development of efficient ultraviolet (UV) organic light-emitting materials and devices holds paramount significance for their practical applications. Nonetheless, attaining a short-wavelength electroluminescence peak of less than 390 nm while maintaining high color purity in non-doped devices remains a formidable challenge. In this work, we have successfully designed and synthesized two UV hybridized local and charge transfer fluorophores, specifically 4DBF-CZCN and 2DBF-CZCN, which are comprised of cyanide-modified phenylcarbazole and a weak electron donor dibenzofuran. And the properties of excited state are well regulated through the different linking site of dibenzofuran. The resulting non-doped devices exhibit not only emission peak wavelengths of 390 and 388 nm, accompanied by narrow full-width-at-half-maximums of 42 and 38 nm, respectively, corresponding to color coordinates of (0.164, 0.034) and (0.164, 0.036), but also admirable external quantum efficiencies of 3.00 % and 2.86 % at high luminance levels of 1910 and 1252 cd m−2, respectively.

Super-Spectral-Resolution Raman spectroscopy using angle-tuning of a Fabry-Pérot etalon with application to diamond characterization

Raman spectroscopy is an extremely powerful laser-based method for characterizing materials based on their unique inelastic scattering spectrum. Ultimately, the power of the technique is limited by the resolution of the spectrometer. Here we introduce a new method for achieving Super-Spectral-Resolution Raman Spectroscopy (SSR-RS), by angle-tuning a Fabry–Pérot (F-P) etalon filter that we incorporated in a micro-Raman setup. A monolithically coated F-P etalon structure, only 1.686 mm in thickness, was mounted onto an angle-tunable motorized stage, and Raman spectra were automatically acquired for many different angles of the etalon. Using a low-resolution grating of 150 g/mm by itself, without the F-P etalon, we obtained a best-case regular Raman spectral linewidth of 44 cm−1 for the characteristic Raman peak from a diamond sample. When we applied the SSR-RS technique to diamond, we obtained a super-spectral resolution peak that was 27x narrower, namely 1.63 cm−1, and a Raman shift of 1331.3 cm−1. To baseline SSR-RS, we applied the super-spectral-resolution method to extract the linewidth and peak wavelength of the laser excitation itself and obtained a laser linewidth of better than 0.014 cm−1, with a laser wavelength centered at 531.962 nm, close to the stated wavelength of 532 nm. This extracted laser linewidth is 3300x times narrower compared to its measured linewidth of 46 cm−1. Thus, our work suggests that SSR-RS can be very generally applied to greatly improve the resolution and precision of Raman instrumentation, and potentially lower the cost of obtaining high-resolution Raman spectroscopic capabilities.

Analyzing the Effects of Monochromatic Lights on the Fungal Growth to Control the Progression of Microbial Deterioration on Animal Collections Preserved in the Zoological Museum of Naples, Italy

ABSTRACT Exposing artworks and artifacts in museums is fundamental to disseminate culture and knowledge but is also risky since the exposure to environmental conditions can deteriorate exhibited objects. Light is crucial, being able to trigger photochemical effects, and jointly responsible (with temperature and humidity) for biological risk generation. In this context, fungal growth in museum artifacts is a damaging factor that should not be underestimated. Consequently, the study of lighting effects on fungi development is essential. In this work, five different fungal strains (Aspergillus fumigatus, Bjerkandera adusta, Fusarium oxysporum, Penicillium chrysogenum, and Penicillium granulatum) isolated from samplings on animal exhibits hosted in the Zoological Museum of Naples, Italy, are cultivated inside four experimental boxes, equipped with monochromatic LEDs with different peak wavelengths (460 nm, 518 nm, 594 nm, and 638 nm). The growth rate, the protein and carbohydrate contents are analyzed and compared to results obtained in darkness (typical growth conditions for studies about fungi). Results demonstrate that, even if fungi are heterotrophic organisms and do not need light to grow and develop, their growth rate, and their protein and carbohydrate contents are affected by the exposure to monochromatic radiation, but the spectral sensitivity strictly depends on the analyzed species. For this reason, it is not possible to infer general practical guidelines for lighting applications, and it becomes urgent to establish accurate and shared analysis protocols to be applied case by case, to study the effects of the environmental conditions on microorganisms and drive-specific design choices.

Revealing the Filler-Matrix Interfacial Interactions: Real-Time Observation with Mechano-Responsive Spiropyran Microbeads.

Interfacial interactions between polymers and fillers play a crucial role in determining the performance of composite materials. In this study, mechano-responsive spiropyran (SP) beads, which exhibit fluorescence changes under stress, serve as force probes to evaluate force transfer efficiency across two types of interfaces: noncovalent and covalent. These interfaces are engineered by respectively employing physical blending and grafting polymerization to integrate hydroxyl SP beads with a polyurethane (PU) matrix. A custom-built in situ opto-mechanical setup quantitatively assesses force transfer by monitoring changes in fluorescence intensity and peak wavelength during specimen stretching. The analysis reveals that the covalent interface significantly outperforms the noncovalent interface, demonstrating a 100% improvement in force magnitude and transfer rate from the PU matrix to the SP beads. Direct observation of SP beads within the PU matrix during tension unveils that enhanced force transfer efficiency is closely linked to changes in the SP beads' aspect ratio. Fluorescence changes in SP beads are solely a function of aspect ratio, making them effective independent force probes.

M13 bacteriophage-based high-sensitivity Fabry-Pérot etalon for detecting humidity and volatile organic compounds

Various sensor applications have been developed for protection against hazardous environments, and research on functional materials to enhance performance has also been pursued. The M13 bacteriophage (M13) has found utility in sensor applications like disease diagnosis and detection of harmful substances due to its potential for controlling interaction with target substances through adjustments in electrochemical and mechanical properties via genetic engineering technology. However, while optimizing reactivity or binding affinity between M13 and target materials is crucial for sensor performance enhancement, precise dynamic measurement methods for this were lacking. This study demonstrates the application of an M13-based dynamic actuator in a Fabry–Pérot etalon (M13-FPE) as a spacer for precise measurement of humidity and reactivity to volatile organic compounds (VOCs). The transmission spectrum is optimized by adjusting the reflectance and cavity gap size (dM13) of the two mirrors comprising the M13-FPE, and changes are measured in a rainbow-color-dotted (RCD) pattern using a customized spectrometer. Utilizing the peak wavelengths of the RCD pattern, the change in dM13 is dynamically and precisely measured, revealing approximately 3% and 0.3% swelling for ethanol and isopropyl alcohol, respectively. M13 demonstrates binding affinities of 827 ppb and 158 ppb for ethanol and isopropyl alcohol, respectively, with its low reactivity measured precisely, exhibiting an error of 0.03 nm using the peak wavelength change rate.

Effect of Aggregated Lysozyme on Fluorescence Properties of Rose Bengal.

Protein aggregates cause abnormal states and trigger various diseases, including neurodegenerative disorders. This study examined whether the xanthene dye derivative Rose Bengal could track a series of conformational changes in protein aggregates. Using lysozyme as a model protein, aggregated proteins were prepared by heating under acidic conditions. The absorption spectra, steady-state fluorescence spectra, fluorescence quantum yield, fluorescence lifetime, and phosphorescence lifetime of a solution containing Rose Bengal in the presence of aggregated lysozyme were measured to identify their spectroscopic characteristics. The absorption spectrum of Rose Bengal changed significantly during the formation of agglomerates in heated lysozyme. Additionally, the fluorescence intensity decreased during the initial stages of the aggregation process with an increase in heating time, followed by an increase in intensity along with a red-shift of the peak wavelength. The decrease in quantum yield with a fixed fluorescence lifetime supported the formation of a nonfluorescent ground-state complex between Rose Bengal and the aggregated lysozyme. Based on the characteristic changes in absorption and fluorescence properties observed during the aggregation process, Rose Bengal is considered an excellent indicator for the sensitive discernment of aggregated proteins.

Coumarin-aurone based fluorescence probes for cysteine sensitive in-situ identification in living cells

The quantification of cysteine (Cys) levels in the organisms holds paramount significance in biological research and disease diagnosis, which can give the correlation between abnormal Cys levels and diseases. In this study, two fluorescent probes, designated as DEA-OH and DEA-AC, featuring a coumarin-aurone backbone specifically engineered for Cys detection, were meticulously designed and synthesized. The diethylamino coumarin-aurone probe DEA-OH and the acrylate-substituted probe DEA-AC demonstrated remarkable sensitivity in detecting cysteine by means of copper displacement (DEA-OH) and acrylate hydrolysis mechanisms (DEA-AC) with fluorescence detection limits of 7.25 μM and 1.65 μM, respectively. Moreover, the fluorescence peak wavelength of the two probes displayed a linear relationship with solvent polarity in the ET (30) range of 30–65 kcal•mol−1, indicating the potential for monitoring changes in environmental polarity within this ET (30) range. The outstanding attributes exhibited by DEA-AC including superior photostability, remarkable selectivity, and swift response (kinetic rate constant: 0.00747 s−1), coupled with the exceptional anti-interference ability, have significantly broadened its scope of applications, for example detecting alterations in Cys within biological systems.

Characterization of composition dependence of properties of a MgNiO-based MSM structure

In this study, the effect of Mg composition on structural and optical properties of MgxNi1-xO alloy thin film single crystal semiconductors as well as their implementation into Metal-Semiconductor–Metal (MSM) photodetector are studied. An 850 meV blue-shift of the bandgap is observed from 3.65 eV to 4.50 eV with increasing Mg composition from 0% to 67%. The deep ultraviolet/visible rejection ratio, which is the ratio of photosensitivity at a peak wavelength of 360 nm to that at 450 nm is found to be ∼58 for Mg composition of 67%. Mg rich (%67 Mg) alloy-based photodetector is found to have two orders smaller dark current and have higher spectral response compared to NiO-based one. Spectral responsivities for MgxNi1-xO photodetectors are determined as 415 mA W−1, 80 mA W−1, and 5.6 mA W−1 for Mg compositions of 67%, 21%, and 0% (reference-NiO), respectively. Furthermore, the detectivity of the photodetectors enhances as Mg composition increases and the highest detectivity of a magnitude of ∼1011 Jones is found for the photodetector with Mg composition of 67%.

Wavelength-Dependent Bragg Grating Sensors Cascade an Interferometer Sensor to Enhance Sensing Capacity and Diversification through the Deep Belief Network

Fiber-optic sensors, such as fiber Bragg grating (FBG) sensors and fiber-optic interferometers, have excellent sensing capabilities for industrial, chemical, and biomedical engineering applications. This paper used machine learning to enhance the number of fiber-optic sensing placement points and promote the cost-effectiveness and diversity of fiber-optic sensing applications. In this paper, the framework adopted is the FBG cascading an interferometer, and a deep belief network (DBN) is used to demodulate the wavelength of the sampled complex spectrum. As the capacity of the fiber-optic sensor arrangement is optimized, the peak spectra from FBGs undergoing strain or temperature changes may overlap. In addition, overlapping FBG spectra with interferometer spectra results in periodic modulation of the spectral intensity, making the spectral intensity variation more complex as a function of different strains or temperature levels. Therefore, it may not be possible to analyze the sensed results of FBGs with the naked eye, and it would be ideal to use machine learning to demodulate the sensed results of FBGs and the interferometer. Experimental results show that DBN can successfully interpret the wavelengths of individual FBG peaks, and peaks of the interferometer spectrum, from the overlapping spectrum of peak-overlapping FBGs and the interferometer.

Blue thermally activated delayed fluorescence excimers with high external quantum efficiency and accelerated reverse intersystem crossing

This study reports for the first time the development of an efficient blue excimer with thermally activated delayed fluorescence (TADF) properties using a multi-resonance TADF-type fused indolo[3,2,1-jk]carbazole-derived compound with a planar structure for facile excimer formation. The blue excimer was efficiently generated by doping the indolo[3,2,1-jk]carbazole-derived emitter at a high doping concentration. The photophysical analysis demonstrated that the photoluminescence quantum yield (PLQY), rate coefficients of reverse intersystem crossing (RISC), and horizontal emitting dipole orientation values were improved by excimer formation in the solid film compared with the monomer-dominant solid film by suppressing the concentration-quenching effect. Specifically, the delayed PLQY increased because of the efficient RISC process at high doping concentrations. Consequently, an enhanced maximum external quantum efficiency of 26.3% was obtained in the excimer device (15 wt%) compared with 15.2% in the monomer prevalent device (1 wt%). Moreover, the excimer device showed a peak wavelength of 473 nm and color coordinate of (0.13, 0.19). This demonstration is the first of excimer TADF organic light-emitting diodes with a blue emission and a high external quantum efficiency of 26.3%.

Emission mechanisms in low-threshold UV random laser based on ZnO microrod array

Despite rather extensive study of the random lasing effect in ZnO structures, the issue of the optical gain mechanisms in microstructured ZnO random lasers remains poorly understood. In this work, the radiative properties of an array of vertically aligned ZnO microrods, synthesized by a modified thermal evaporation method, were studied. The microrods exhibited lengths up to 60 μm and diameters ranging from 1 to 5 μm. Random lasing from a microrod array was observed in the near-UV range (with a laser emission peak wavelength of ∼391 nm) with a threshold down to 40 kW/cm2 under optical excitation. An analysis of the nature of optical gain in the grown structure was conducted at various temperatures. It was found that at room temperature, two-phonon-assisted exciton recombination is the main process leading to light amplification.

Isomorphism of Sr[Li3AlO4] and Sr[Li3GaO4] - Syntheses, Crystal Structure, and Europium(II) Luminescence.

While highly efficient red-emitting inorganic phosphors have been discovered in the substance class of alkaline earth oxo(nitrido)lithoaluminates, new narrow-band green- and yellow-emitting components are being sought to improve the performance of phosphor-converted light-emitting diodes (pc-LEDs). Various solid-state reactions were carried out under protective gas atmosphere in nickel crucibles and sealed tantalum ampules to synthesize Sr[Li3AlO4], Sr[Li3GaO4], and five substitutional derivates of Sr[Li3(Al1-x Ga x )O4] at moderate temperatures. The observation of a linear increase in the unit cell parameters as a function of the increasing gallium mole fraction x in Sr[Li3(Al1-x Ga x )O4] revealed Vegard behavior in the solid-solution series, which was derived from powder X-ray diffraction data. The isomorphic crystallization of the new oxolithogallate Sr[Li3GaO4] and the known oxolithoaluminate Sr[Li3AlO4] in an ordered variant of the U[Cr4C4] aristotype was verified on the basis of powder and single-crystal X-ray diffraction data. Photoluminescence spectroscopy was used to investigate the narrow-band emissions in the substitution series of Eu2+-activated Sr[Li3(Al1-x Ga x )O4] under blue-light excitation. The emission maximum was shifted to higher energies as the gallium mole fraction increased. Peak wavelengths were observed at λem = 572 nm (fwhm equals 47 nm, 1446 cm-1, 0.18 eV) for yellow-emitting Sr[Li3AlO4]:Eu2+ and at λem = 554 nm (fwhm equals 49 nm, 1589 cm-1, 0.20 eV) for green-emitting Sr[Li3GaO4]:Eu2+. Sr[Li3AlO4]:Eu2+ has excellent thermal quenching resistance with a photoluminescence emission intensity of >93% at T = 423 K relative to the room temperature value, making this inorganic phosphor a potential candidate for solid-state lighting applications.

Dealing with plasmonic crystal biosensors: Sensitivity assessment of nanodisks/nanoholes arrayed plasmonic system for label-free DNA detection

Label-free optical deoxyribonucleic acid (DNA) sensing with arrayed plasmonic nanostructures (plasmonic crystals) is a promising technology for biomedical diagnosis and bioanalytical science. Plasmonic biosensors can detect target biomolecules by utilizing the shift in plasmonic resonance caused by changes in the surrounding refractive index (RI) attributed to the capture of target biomolecules using a recognizer. Conventional explanations for the sensitivity of plasmonic crystals are based on bulk (BRIS) and surface RI sensitivities (SRIS) for basic plasmonic nanoparticles despite their unique properties such as surface lattice resonances (SLRs), wherein localized surface plasmons (LSPs) cooperatively oscillate with their pitch. Therefore, investigating the sensitivity of SLRs is imperative for improving sensing performance. In this study, the sensitivity of adenomatous polyposis coli (APC) gene-related DNA hybridization detection of complementary plasmonic crystals composed of nanodisks (PNDs) on or under plasmonic nanoholes (PNHs) was investigated considering the SLR properties. The BRIS was measured using the conventional definition of the peak wavelength shift per unit RI increment (nm/RIU) followed by the SRIS measurement using the layer-by-layer method. The BRIS and SRIS measurements reflect the practical sensitivity for DNA detection. PNHs had higher sensitivity than PNDs, with a limit of detection of 0.30 nM. Further, only the SLR-based mode responded to localized RI changes because of DNA hybridization, whereas both the LSPs- and SLR-based modes responded to uniform RI changes caused by layer-by-layer coating. Our investigation will open up possibilities and opportunities for plasmonic crystal biosensors.

(Invited) Blue Organic Light-Emitting Diode Using Dynamic Exciton for Low Driving Voltage

Among the three primary colors, blue emission in organic light-emitting diodes (OLEDs) are highly important but very difficult to develop. OLEDs have already been commercialized; however, blue OLEDs have the problem of requiring a high applied voltage due to the high-energy of blue emission. Herein, an ultralow voltage turn-on at 1.47 V for blue emission with a peak wavelength at 462 nm (2.68 eV) is demonstrated in an OLED device. This OLED reaches 100 cd/m2, which is equivalent to the luminance of a typical commercial display, at 1.97 V. Blue emission from the OLED is achieved by the selective excitation of the low-energy triplet states at a low applied voltage by using the charge transfer (CT) state as a precursor and the triplet-triplet annihilation, which forms one emissive singlet from two triplet excitons. We found that the essential component for efficient blue emission is a smaller energy difference between the CT state and triplet exciton, accelerating the energy transfer between the two states and achieving the optimal performance by avoiding direct decay from the CT state to the ground state. Our study demonstrates that the developed OLED allows for a much longer operation lifetime than that from a typical blue phosphorescent OLED because the blue emission originates from a stable low-energy triplet exciton that avoids degrading the constituent materials.

A New Technology for Industrial Strain Mapping Using Single-Wall Carbon Nanotube Sensors

Measurements of mechanical strain are widely used in heavy industry to design and test new structures and to ensure the safety of installed infrastructure. However, the few practical methods for strain measurement all have serious limitations. To complement these methods, we have developed a new strain technology, called S4 for “strain-sensing smart skin,” which uses single-wall carbon nanotubes (SWCNTs) as microscopic sensors. Nanotubes dilutely embedded in a polymer are applied as a thin film to specimen surfaces of interest. Subsequent strains in the specimen are transmitted by load transfer through the film to the nanotubes, inducing axial compression or extension. Those small structural deformations of the SWCNTs alter the semiconducting band gaps in predictable ways, causing proportional shifts in the peak wavelengths of their near-infrared fluorescence emission. Shifts are quantified by optically exciting the specimen surface and spectrally analyzing the resulting fluorescence to deduce strain values at the probed locations. The S4 method has recently been implemented using hyperspectral imaging. We demonstrate measurements in less than one minute of strain maps containing hundreds of thousands of pixels with 50 microstrain noise levels and 0.2 mm spatial resolution. This technology has promising potential to become a large-scale commercialized application of carbon nanotechnology.

Mimicking Axons by Conductive Metal Lines Formed by Photocatalytically Grown Gold

Nanoionic memristive devices based on the field−driven migration of metal cations and oxygen vacancies have gathered high interest in the scientific community for their capability to technically mimic synaptic connections. Less attention has been given to long−range global plasticity in artificial neuronal networks. The aim of our research is to use light−stimulated growth of gold metal lines to technically mimic the growth of long−range axonal connections for neuromorphic computing architectures. For this purpose, we investigate the formation of metal lines by UV−light−stimulus−driven photocatalytic deposition of gold on titanium dioxide layers. In this study, we present a significant contribution that stems from our active involvement in CRC 1461- Neurotronics, a pivotal initiative funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation). Our research falls under Project-ID 434434223 – SFB 1461, within the broader context of Bio-inspired information pathways.0.8-mm wide photoactive titanium dioxide lines are defined by photolithography on a Sodalime glass substrate. We deposited a 70 nm thick titanium dioxide line on a 10 nm thick indium tin oxide adhesion layer by DC sputtering. The substrate was then heat treated for 90 minutes at 400°C and subsequently cooled on a metal plate to achieve the photocatalytically active anatase phase of titanium dioxide [1]. The growth process is conducted in a beaker by reduction from an aqueous gold chloride precursor solution (HAuCl4). In each step of the growth process, the substrate is placed in a beaker containing 15 ml of the precursor. The solution is obtained by dissolving 15 mg of HAuCl4 powder in 60 ml of deionized water. We utilize a UV LED with the peak wavelength of 365 nm and an approximate intensity of 1.8 - 2.7 mW/cm² to illuminate the sample in the beaker. The illumination time and UV intensity are crucial for this dynamic process. Here, we illuminated the sample for 12 hours and refreshed the solution every 2 hours. After each refreshment of the solution, the substrate is washed thoroughly with deionized (DI) water and is dried under nitrogen gas. We analyze the surface properties of grown gold utilizing scanning electron microscopy (SEM) and measure the conductance of the grown lines by applying voltage via the needles of a hard contact probe station.In the first experiments the growth of gold clusters on the surface is observed instead of the homogeneous gold coverage of the photolithographically defined titanium dioxide lines, which are needed for long-range electrical connections. Then, we coincidentally observed that the presence of a scratch on the titanium dioxide line led to the growth of continuous gold lines on the damaged area. Subsequently, deliberate scratches were introduced manually using tweezers, varying in both size and thickness. SEM images depict islands and covered areas, with notable growth observed on the scratched regions. Remarkably, wider scratches exhibit a proportionally increased width of the grown lines, and a uniform line devoid of any gaps is distinctly visible on broader scratches. We observed particle growth on thinner lines. However, unlike the uniform alignment observed in wider scratches, these particles did not coalesce into a continuous line. Instead, they remained separated from each other, exhibiting small gaps between individual particles. The morphological analysis of the grown gold line using SEM reveals a crystalline morphology of particles.As the primary objective of this research is to mimic axons with gold lines, ensuring conductivity is crucial for obtaining long−range electrical connections mimicking axons. To achieve this, voltage was applied using the needles of a hard contact probe station, and the resulting current was measured. The linear behavior observed in the I–V diagram of the wider line serves as a confirmation of its conductance (≈0.003 S).

Generation of extremely strong accelerating electric field by focusing radially polarized THz pulses with a paraboloid ring

Efficient acceleration of electrically charged particles by focused electromagnetic pulses requires a strong accelerating electric field as well as a sufficiently large interaction region. Single-cycle terahertz pulses are promising candidates for such applications due to their advantageous wavelength and available peak electric field at the MV/cm level. We propose and characterize a focusing optics for a possible electron vacuum accelerator. This consists of a reflaxicon for beam shaping and a ring-like segment of an on-axis parabolic mirror for tight focusing of the radially polarized THz pulse in order to reach a strong accelerating electric field. The electric field distribution in the focal region was determined by the Stratton–Chu vector diffraction method. Semi-analytical and purely analytical formulae were also derived, simplifying the computation procedure. By focusing radially polarized single-cycle terahertz pulses with 3mJ pulse energy, calculations predict accelerating electric field component in the order of 100MV/cm, well suitable for particle acceleration.

Fiber optic probe integrated with colloidal nanoparticles with directional diffraction selectivity for magnetic field vector detection

A fiber optic probe integrated with colloidal nanoparticles with directional diffraction selectivity is proposed for wide-bandwidth magnetic field vector detection. The probe is constructed with the multimode fiber in which the end-surface is integrated with the Fe3O4@C colloidal nanoparticles by a silicone tube. The colloidal nanoparticles form a three-dimensional photonic crystal structure by magnetic field for diffraction selectivity. The lattice constant and diffraction angle are adjusted by the intensity and direction of the magnetic field, respectively. Obtaining the directional diffraction light through the magnetic field-induced photonic band gap shift with the wavelength blue shift and reflectivity change is confirmed by theory and experiment. The results show that the maximum sensitivity reaches up to 19.7 nm/mT in response range from 13 mT to 200 mT. For vector detection, the peak wavelength shift from 740 nm to 485 nm and reflectance shift from 71% to 7% covering the 0–45° region is verified. In addition, the proposed method could decouple intensity and direction of the magnetic field completely. The fiber optic probe integrated with colloidal nanoparticles has wide detection range and high sensitivity with rapid response. It will open up new horizons for inspiring design and application of magnetic field vector detection in robot posture control and motion perception.

High‐Performance Flexible PbS Nanofilm Wavelength Sensor with Detection Region Ranging from DUV to NIR

AbstractIn this study, on the fabrication of a flexible wavelength sensor is reported, which is achieved by growing a layer of lead sulfide (PbS) nanofilm on both sides of a polyethylene terephthalate substrate using the chemical bath deposition method, followed by the deposition of two parallel Au interdigital electrodes. Experimental result shows that the photocurrent ratio of the two photodetectors monotonically decreases with increasing wavelength in the range from 265 nm (UV) to 2000 nm (NIR), indicating that the incident light wavelength can be distinguished by the photocurrent ratio. Notably, the as‐constructed wavelength sensor exhibits superior performance compared to most previously reported filter‐less designs, achieving an average absolute error of 11.5 nm and an average relative error of 1.1%. It is also found that the sensor exhibits excellent mechanical flexibility and environmental stability. Furthermore, by introducing the back‐end circuit, real‐time detection of the wavelength of monochromatic light and the peak wavelength of LED light are achieved, with detection errors not exceeding 2.8% and 2.6%, respectively. It is believed that the flexible PbS nanofilm wavelength sensor prepared in this study has potential application in future portable and flexible optoelectronic devices.