Optical Resonance Research Articles

Versatile Nanoring Fabrication Assisted by Hole-mask Colloidal Lithography.

Nanomaterials shaped as rings are interesting nanostructures with control of the materials properties at the nanoscale. Nanoring plasmonic resonators provide tunable optical resonances in the near-infrared with application in sensing. Fabrication of nanorings can be carried out via top-down approaches based on electron beam lithography with high control of the ring size parameters but at high cost. Alternatively, fabrication via self-assembly approaches has a higher speed/lower cost but at the cost of control of ring parameters. Current colloidal lithography approaches can provide nanoring fabrication over large areas but only of specific materials and a select set of rings (large ring diameters or small rings with ultrathin walls). We extend Hole-mask Colloidal Lithography to use ring shaped holes, allow the deposition of arbitrary materials, and allow the independent tuning of ring-wall thickness over a large range of values. We present a generic approach for the fabrication of nanorings formed from a range of materials including low cost (e.g., Cu, Al) and nonplasmonic (e.g., W) materials and with control of ring wall thickness and diameter allowing tuning of ring parameters and materials for applications in nanooptics and beyond.

Phonon–Polaritonic Resonances on Nanopillars of Hexagonal Boron Nitride for Surface‐Enhanced Infrared Absorption

Phonon polaritons (PhPs) in hexagonal boron nitride enable sharp midinfrared optical resonance with strong spatial confinement, making them promising for surface‐enhanced infrared absorption (SEIRA) spectroscopy. Here, using colloidal nanosphere lithography, hBN nanopillar antennas are fabricated and their PhP resonances in a cost‐effective way are demonstrated. By varying the diameters of the hBN nanopillars, the PhP resonance can be readily tuned to match the molecular vibrations of CBP (4,4′‐bis(N‐carbazolyl)‐1,1′‐biphenyl) molecules. Upon frequency matching, the coupling between the PhP resonance and the molecular vibration shows pronounced mode splitting, illustrating the SEIRA behavior with a coupling strength approaching the strong coupling regime. However, with slight frequency mismatching around 10 cm−1, the coupling strength decreases significantly, indicating a high sensitivity of the SEIRA activities to the resonance frequency of hBN nanopillar antennas. The findings provide a new method for the fabrication of PhP nanoantennas and may promote the development of PhPs in SEIRA‐based midinfrared sensing applications.

Nanoprobes based on quantum dots and Gd(III) complexes for dual optical and magnetic resonance imaging

The combination of more than one clinical technique has been increasingly explored to improve imaging diagnosis, suppressing the limitations of individual procedures. Quantum dots (QDs) have been associated with paramagnetic complexes (GdDOTA) to develop optical-magnetic nanoprobes for imaging techniques. Herein, we report the preparation of bimodal nanoprobes by conjugating fluorescent QDs with GdDOTA complexes through dative bonds. These nanoprobes showed an enhancement in their emission intensity compared to bare QDs. Moreover, the nanosystems exhibited r1 values up to 69% higher than the clinical GdDOTA. Therefore, the bimodal systems demonstrated promising performance for both optical and magnetic resonance imaging, exhibiting potential as bimodal contrast agents.

Room-temperature tuning of mid-infrared optical phonons and plasmons in W-doped VO2 thin films

The development of mid-infrared nanophotonics relies on the availability of new materials combining metal- and insulator-like optical features. We systematically studied the phase transition of thermochromic vanadium dioxide (VO2) using substitutional tungsten doping at room temperature. Our results reveal that vanadium dioxide thin films, doped with tungsten and grown via pulsed laser deposition techniques on sapphire substrates, can be precisely engineered to exhibit tailored infrared phonon and plasmon polaritonic responses. By controlling the extent of tungsten concentration, starting from VO2-WO3 cold-pressed powder targets, we demonstrate the ability to continuously adjust both the amplitude and frequency of optical phonon resonances. Furthermore, we observe tunable free-electron response due to varying tungsten concentrations. The adopted fabrication technique makes it possible to create multilayer structures by alternating layers with different concentrations of tungsten. Our results pave the way for the development of tunable mid-infrared metamaterial devices operating at room-temperature.

Diagnostic dilemma of papilledema and pseudopapilledema.

Papilledema is the optic disc swelling caused by increased intracranial pressure (ICP) that can damage the optic nerve and cause subsequent vision loss. Pseudopapilledema refers to optic disc elevation without peripapillary fluidthatcan arise from several optic disc disorders, with optic disc drusen (ODD) being the most frequent cause. Occasionally, pseudopapilledema patients are mistakenly diagnosed as papilledema, leading to the possibility of unneeded procedures. We aim to thoroughly examine the most current evidence on papilledema and pseudopapilledema causes and several methods for distinguishing between both conditions. An extensive literature search was conducted on electronic databases including PubMed and google scholar using keywords that were relevant to the assessed pathologies. Data were collected and then summarized in comprehensive form. Various techniques are employed to distinguish between papilledema and pseudopapilledema. These techniques include Fundus fluorescein angiography, optical coherence tomography, ultrasonography, and magnetic resonance imaging. Lumbar puncture and other invasive procedures may be needed if results are suspicious. Papilledema is a sight-threatening condition that may lead to visual affection. Many disc conditions may mimic papilledema. Accordingly, differentiation between papilledema and pseudopailledema is crucial and can be conducted through many modalities.

Continuous-wave quasi-single-mode random lasing in CH3NH3PbBr3 perovskite films on patterned sapphire substrates.

We report intriguing continuous-wave quasi-single-mode random lasing in methylammonium lead bromide (CH3NH3PbBr3) perovskite films synthesized on a patterned sapphire substrate (PSS) under excitation of a 532-nm laser diode. The random laser emission evolves from a typical multi-mode to a quasi-single-mode with increasing pump fluences. The full width at half-maximum of the lasing peak is as narrow as 0.06 nm at ∼547.8 nm, corresponding to a high Q-factor of ∼9000. Such excellent random lasing performance is plausibly ascribed to the exciton resonance in optical absorption at 532 nm and the enhanced optical resonance due to the increased likelihood for randomly scattered light to re-enter the optical loops formed among the perovskite grains by multi-reflection at the perovskite/PSS interfaces. This work demonstrates the promise of single-mode perovskite random lasers by introducing the exciton resonance effect and ingeniously designed periodic nano/micro optical structure.

Corrosive Pseudomonas aeruginosa detection by measuring pyocyanin with a lab-on-fiber optical surface plasmon resonance biosensor in aquatic environments

Oceanic facilities and equipment corrosion present considerable economic and safety concerns, predominantly due to microbial corrosion. Early detection of corrosive microbes is pivotal for effective monitoring and prevention. Yet, traditional detection methods often lack specificity, require extensive processing time, and yield inaccurate results. Hence, the need for an efficient real-time corrosive microbe monitoring technology is evident. Pseudomonas aeruginosa, a widely distributed microorganism in aquatic environments, utilizes its production of quinone-like compounds, specifically pyocyanin (PYO), to corrode metals. Here, we report a novel fiber optic surface plasmon resonance (SPR) sensor modified by the C-terminal of BrlR protein (BrlR-C), which is a specific receptor of PYO molecule, to detect P. aeruginosa in aquatic environments. The results showed that the sensor had a good ability to recognize PYO in the concentration range of 0–1 μg/mL, and showed excellent sensing performance in real-time monitoring the growth status of P. aeruginosa. With a strong selectivity of PYO, the sensor could clearly detect P. aeruginosa against other bacteria in seawater environment, and exhibited excellent anti-interference ability against variations in pH, temperature and pressure and other interfering substances. This study provides a useful tool for monitoring corrosive P. aeruginosa biofilm in aquatic environments, which is a first of its kind example that serves as a laboratory model for the application of fiber optic technology in real-world scenarios to monitoring biofilms in microbial corrosion and biofouling.

Sub-ppt level detection of carbon monoxide and nitrous oxide enabled by mid-infrared doubly resonant photoacoustic spectroscopy.

We report highly sensitive detection of carbon monoxide (CO) and nitrous oxide (N2O) using doubly resonant photoacoustic spectroscopy paired with a quantum cascade laser (QCL) at 4.57 μm. The butterfly-packaged QCL is used to exploit the CO absorption line at 2190.02 cm-1 and the N2O absorption line at 2191.42 cm-1 by scanning the injection current. Leveraging the simultaneous acoustic and optical resonances and adopting a lower photoacoustic detection frequency, we achieve a minimum detection limit of 0.85 part-per-trillion (ppt) for CO over the 500 s averaging time, and 0.7 ppt for N2O over the 200 s averaging time. Our approach demonstrates record sensitivity for CO and N2O detection compared to state-of-the-art optical gas sensors.

Continuous beam scanning by transverse mode-locking in a Pound-Drever-Hall stabilized resonator

Mode-locking, i.e., the phase-locked superposition of resonator modes, enables ultrafast laser beam dynamics. Here, high-speed beam scanning at 79.6 MHz is achieved by generating sets of phase-locked transverse resonator modes. Such transverse mode-locked (TML) beams are obtained via conversion in an empty, optical resonator from incident longitudinal mode-locked beams. In this conversion scheme the modal power and phase distributions can be controlled to alter the dynamics of the emerging scanning beams. It is shown, that the Pound-Drever-Hall stabilization scheme is applicable to compound TML resonances and it is used to maintain resonance between the incident beam’s spectral components and the transverse mode resonances. This way, TML states are reliably generated and continuously emitted.

Longitudinal Mode Number Estimation of External Cavity Diode Laser Using Dual Periodic Grating for Optical Profiler System.

The concept of an optical profiler based on optical resonance was proposed, highlighting the initial requirements for mode number estimation. We proposed a method for estimating the longitudinal mode number of a laser propagating in an external cavity diode laser with high accuracy, utilizing dual-periodic diffraction gratings. These gratings were fabricated using interference lithography. To estimate the mode number, the wavelengths of two different modes are compared. Therefore, the greater the difference between the wavelengths, the higher the accuracy of the mode number determination. While the mode number difference was approximately 35 when using a conventional diffraction grating, this could be increased by a factor of 20 to around 700 using the dual-periodic grating. The relative accuracy achieved was 1.4 × 10-5.

Optical nuclear electric resonance in LiNa: selective addressing of nuclear spins through pulsed lasers

Optical nuclear electric resonance (ONER), a recently proposed protocol for nuclear spin manipulation in atomic systems via short laser pulses with MHz repetition rate, exploits the coupling between the nuclear quadrupole moment of a suitable atom and the periodic modulations of the electric field gradient generated by an optically stimulated electronic excitation. In this theory paper, we extend the scope of ONER from atomic to molecular systems and show that molecular vibrations do not interfere with our protocol. Exploring the diatomic molecule LiNa as a first benchmark system, our investigation showcases the robustness with respect to molecular vibration, and the ability to address and manipulate each of the two nuclear spins independently, simply by adjusting the repetition rate of a pulsed laser. Our findings suggest that it might be possible to shift complicated spin manipulation tasks required for quantum computing into the time domain by pulse-duration encoded laser signals.

Hydrogel binding sodium alginate based optical fiber surface plasmon resonance for calcium ion trace detection

A plasmonic tilted fiber Bragg grating (TFBG)-based sensor for the detection of calcium ion (Ca2+) was proposed and demonstrated experimentally. Hydrogel material was synthesized by utilizing hydrogen bond recombination between cellulose nanocrystals (CNC) and polyvinyl alcohol (PVA). Sodium alginate (SA) was incorporated into this hydrogel material, resulting in a composite membrane with specific binding properties for Ca2+. The membrane was applied as a coating on the surface of a gold-coated TFBG. The CNC/PVA-SA modified gold on the TFBG surface enhanced the localized refractive index changes caused by variations of Ca2+ concentrations. The experimental results demonstrated an impressive limit of detection (LOD) of approximately 0.025 fM, which is five orders of magnitude better than the current LODs of similar Ca2+ sensors. And the proposed Ca2+ sensor exhibited a wide dynamic range of 10−16 M to 10−6 M.

Temperature self-compensated fiber-optic Pb(II) sensor with improved selectivity by Resorcylaldehyde post-modified organic metal framework

Post-modification of metal-organic framework (MOF) materials is an effective means to enhance their efficient and selective adsorption for heavy metal ions. In this article, we presented a reflection-type optical fiber surface plasmon resonance (SPR) sensor based on dual core fiber (DCF) coated with UiO-66-RSA (UiO-66-NH2 post-modified with resorcinol aldehyde) film for the specific detection of Pb(II) in aqueous media. The composite material UiO-66-RSA exhibits stronger affinity and specificity for Pb(II) than UiO-66-NH2. The adsorption of Pb(II) can change the equivalent refractive index (RI) of UiO-66-RSA film, causing a regular shift in SPR spectra. Experiments have shown that the limit of detection (LOD) of the SPR Pb(II) sensor can reach 0.1 nM. Meanwhile, research has found that the SPR sensor is accompanied by temperature crosstalk of 0.356 nm/°C. Therefore, we constructed a Michelson temperature interferometer using polymer micro tips on the end face of the fiber core to achieve temperature compensation. Based on the above two sensing channels, dual parameter demodulation of Pb(II) concentration and temperature can be achieved with an error rate of less than 0.5 %. This article has potential research value in exploring the application of post modification techniques of MOF in fiber optic lead ion detection.

Enhancing cooperativity of molecular J-aggregates by resonantly coupled dielectric metasurfaces

Abstract J-aggregates are supramolecular assemblies of dyes exhibiting strong absorption and fluorescence with narrow linewidths, as well as large optical nonlinearities, induced by the formation of largely delocalized molecular excitons. The degree of cooperativity achievable in J-aggregates ensembles, however, is limited by local disorder and thermally induced decoherence effects. A way to overcome these limitations and increase molecular exciton delocalization and coherence is to couple the ensemble of highly ordered molecular dipoles to a common electromagnetic mode in an optical resonator. In this work, we use dielectric metasurfaces to alter the radiative properties of coupled J-aggregate films and demonstrate a 5-fold Purcell enhancement of the luminesce intensity and narrowing of the emission directivity down to ∼300 mrad around the normal. These results highlight the potential of designer dielectric metasurfaces to foster the emergence of cooperative phenomena in excitonic systems, including optical nonlinearities and superradiance.

Microwave power self-coherent reference measurement based on ensembles of nitrogen-vacancy centers in diamond

Microwave detection based on optical detection magnetic resonance technology (ODMR) of nitrogen-vacancy (NV) centers is simple and non-invasive. However, in high microwave power ranges, saturation appears and cannot be used for accurate power measurement. The self-coherent reference measurement for high-power microwave based on ODMR of NV centers has been demonstrated. Firstly, by introducing the principle of microwave self-coherent reference, that is, by adjusting the phase difference to achieve power regulation of microwave, a conversion model by phase modulation between enhancement and attenuation of microwave power is introduced. Then, the microwave self-coherent reference measurement is established under combinations of microwave power with different phase settings. Combined with the frequency modulation technology, the sensitivity of measurement is significantly improved from 4.59 nT/Hz1/2 to 67.69 pT/Hz1/2. The maximum measurement range of microwave power can be extended to 2×104 times the initial saturated power of direct measurement with ODMR. The results show that the method efficiently overcomes saturation under the direct measurement of ODMR and provides useful technical assistance for near-field detection, performance monitoring, and problem diagnostics for microwave devices.

High-quality quasi-bound state in the continuum enabled single-nanoparticle virus detection.

Bound states in the continuum (BICs) have emerged as a powerful platform for boosting light-matter interactions because they provide an alternative way of realizing optical resonances with ultrahigh quality(Q-) factors, accompanied by extreme field confinement. In this work, we realized an optical biosensor by introducing a quasi-BIC (qBIC) supported by an elaborated all-dielectric dimer grating. Thanks to the excellent field confinement within the air gap of grating enabled by such a high-Q qBIC, the figure of merit (FOM) of a biosensor is up to 18,908.7 RIU-1. Furthermore, we demonstrated that such a high-Q grating can help push the limit of optical biosensing to the single-particle level. Our results may find exciting applications in extreme biochemical sensing like COVID-19 with ultralow concentration.

Extending Polymer Opal Structural Color Properties into the Near-Infrared

We report the fabrication and characterisation of near-IR reflecting films and coatings based on shear-assembled crystalline ensembles of polymer composite microspheres, also known as “polymer opals”. Extension of the emulsion polymerisation techniques for synthesis of tractable larger core-interlayer-shell (CIS) particles, of up to half a micron diameter, facilitates the engineering and processing of thin-film synthetic opals, with a tunable photonic stopband spanning an extended spectral range of λ ≈ 700–1600 nm. Samples exhibit strong “scattering cone” interactions, with considerable angular dependence and angle tuning possible, as measured with a goniometric technique. These intense optical resonances in the near-IR, particularly within the important region around λ ~ 800 nm, combined with an appreciable translucency within the visible light spectrum, is indicative of the potential applications in coatings technologies and solar cells.

Monolithic optical resonator for ultrastable laser and photonic millimeter-wave synthesis

Optical resonators are indispensable tools in optical metrology that usually benefit from an evacuated and highly-isolated environment to achieve peak performance. Even in the more sophisticated design of Fabry-Perot (FP) cavities, the material choice limits the achievable quality factors. For this reason, monolithic resonators are emerging as promising alternative to traditional designs, but their design is still at preliminary stage and far from being optimized. Here, we demonstrate a monolithic FP resonator with 4.5 cm3 volume and 2 × 105 finesse. In the ambient environment, we achieve 18 Hz integrated laser linewidth and 7 × 10−14 frequency stability measured from 0.08 s to 0.3 s averaging time, the highest spectral purity and stability demonstrated to date in the context of monolithic reference resonators. By locking two separate lasers to distinct modes of the same resonator, a 96 GHz microwave signals is generated with phase noise -100 dBc/Hz at 10 kHz frequency offset, achieving orders of magnitude improvement in the approach of photonic heterodyne synthesis. The compact monolithic FP resonator is promising for applications in spectrally-pure, high-frequency microwave photonic references as well as optical clocks and other metrological devices. ©2024. All rights reserved.

Temperature dependence of magnetic sensitivity in ensemble NV centers

The magnetic sensitivity of the ensemble NV centers is directly related to temperature. In this study, we systematically investigated the temperature dependence of photoluminescence properties and optical detection magnetic resonance in ensemble NV centers from 1.6 K to 300 K. The magnetic sensitivity of the ensemble NV centers increases with the temperature rising in the range of 1.6 K to 75 K due to changes in contrast and linewidth, reaching a minimum near 40 K. Furthermore, the decrease in sensitivity is attributed to laser intensity overload at low temperatures by studying the influence of laser power on contrast and linewidth. These results offer valuable insights into NV magnetic sensing applications.

In situ construction of Ag/Bi2O3/Bi5O7I heterojunction with Bi-MOF for enhance the photocatalytic efficiency of bisphenol A by facet-coupling and s-scheme structure

In this study, Ag/Bi2O3/Bi5O7I with s-scheme heterostructures were successfully synthesized in situ by nano-silver modification of CUA-17 and halogenated hydrolysis.The growth rate of Bi2O3 crystals was effectively controlled by adjusting the doping amount of Ag, resulting in the formation of a facet-coupling heterojunctions. Through the investigation of the microstructure and compositional of catalysts, it has been confirmed that an intimate facet coupling between the Bi2O3 (120) facet and the Bi5O7I (312) facet, which provides robust support for charge transfer. Under visible light irradiation, the AgBOI.3 heterojunction photocatalyst exhibited an outstanding degradation rate of 98.2% for Bisphenol A (BPA) with excellent stability. Further characterization using optical, electrochemical, impedance spectroscopy, and electron spin resonance techniques revealed significantly enhanced efficiency in photogenerated charge separation and transfer, and confirming the s-scheme structure of the photocatalyst. Density functional theory calculations was employed to elucidate the mechanism of BPA degradation and the degradation pathway of BPA was investigated by LC-MS. Finally, the toxicity of the degradation intermediates was evaluated using T.E.S.T software.