Approximate model for analyzing band structures of single-ring hollow-core anti-resonant fibers

Precise knowledge of modal behavior is of essential importance for understanding light guidance, particularly in hollow-core fibers. Here we present a semi-analytical model that allows determination of bands formed in revolver-type anti-resonant hollow-core fibers. The approach is independent of the actual arrangement of the anti-resonant elements, does not enforce artificial lattice arrangements and allows determination of the effective indices of modes of preselected order. The simulations show two classes of modes: (i) low-order modes exhibiting effective indices with moderate slopes and (ii) a high number of high-order modes with very strong effective index dispersion, forming a quasi-continuum of modes. It is shown that the mode density scales with the square of the normalized frequency, being to some extent similar to the behavior of multimode fibers

On-chip fluorescence detection using photonic bandgap guiding optofluidic hollow-core light cage

The on-chip detection of fluorescent light is essential for many bioanalytical and life-science related applications. Here, the optofluidic light cage consisting of a sparse array of micrometer encircling a hollow core represents an innovative concept, particularly for on-chip waveguide-based spectroscopy. In the present work, we demonstrate the potential of the optofluidic light cage concept in the context of integrated on-chip fluorescence spectroscopy. Specifically, we show that fluorescent light from a dye-doped aqueous solution generated in the core of a nanoprinted dual-ring light cage can be efficiently captured and guided to the waveguide ports. Notably, the fluorescence collection occurs predominantly in the fundamental mode, a property that distinguishes it from evanescent field-based waveguide detection schemes that favor collection in higher-order modes. Through exploiting the flexibility of waveguide design and 3D nanoprinting, both excitation and emission have been localized in the high transmission domains of the fundamental core mode. Fast diffusion, detection limits comparable to bulk measurements, and the potential of this approach in terms of device integration were demonstrated. Together with previous results on absorption spectroscopy, the achievements presented here suggest that the optofluidic light cage concept defines a novel photonic platform for integrated on-chip spectroscopic devices and real-time sensors compatible with both the fiber circuitry and microfluidics. Applications in areas such as bioanalytics and environmental sciences are conceivable, while more sophisticated applications such as nanoparticle tracking analysis and integrated Raman spectroscopy could be envisioned

3D-nanoprinted on-chip antiresonant waveguide with hollow core and microgaps for integrated optofluidic spectroscopy

Here, we unlock the properties of the recently introduced on-chip hollow-core microgap waveguide in the context of optofluidics which allows for intense light-water interaction over long lengths with fast response times. The nanoprinted waveguide operates by the antiresonance effect in the visible and near-infrared domain and includes a hollow core with defined gaps every 176 µm. The spectroscopic capabilities are demonstrated by various absorption-related experiments, showing that the Beer-Lambert law can be applied without any modification. In addition to revealing key performance parameters, time-resolved experiments showed a decisive improvement in diffusion times resulting from the lateral access provided by the microgaps. Overall, the microgap waveguide represents a pathway for on-chip spectroscopy in aqueous environments

Coherent interaction of atoms with a beam of light confined in a light cage

Controlling coherent interaction between optical fields and quantum systems in scalable, integrated platforms is essential for quantum technologies. Miniaturised, warm alkali-vapour cells integrated with on-chip photonic devices represent an attractive system, in particular for delay or storage of a single-photon quantum state. Hollow-core fibres or planar waveguides are widely used to confine light over long distances enhancing light-matter interaction in atomic-vapour cells. However, they suffer from inefficient filling times, enhanced dephasing for atoms near the surfaces, and limited light-matter overlap. We report here on the observation of modified electromagnetically induced transparency for a non-diffractive beam of light in an on-chip, laterally-accessible hollow-core light cage. Atomic layer deposition of an alumina nanofilm onto the light-cage structure was utilised to precisely tune the high-transmission spectral region of the light-cage mode to the operation wavelength of the atomic transition, while additionally protecting the polymer against the corrosive alkali vapour. The experiments show strong, coherent light-matter coupling over lengths substantially exceeding the Rayleigh range. Additionally, the stable non-degrading performance and extreme versatility of the light cage provide an excellent basis for a manifold of quantum-storage and quantum-nonlinear applications, highlighting it as a compelling candidate for all-on-chip, integrable, low-cost, vapour-based photon delay

Modeling public acceptance of demand-responsive transportation: An integrated UTAUT and ITM framework

Demand-responsive transportation (DRT) is a flexible form of shared mobility in which service provision is shaped by the user demand. DRT has been considered a sustainable mobility solution, as it reduces CO2 emissions from fixed-route services and encourages a mode shift from private cars to shared mobility. Given that public acceptance is a key for the wider diffusion of DRT, this study explored the factors affecting usage intention for DRT in the Republic of Korea. Drawing on the unified theory of acceptance and use of technology (UTAUT) and the initial trust model (ITM), a conceptual framework was developed that linked attitudinal and psychological factors to behavioral intention for DRT usage. 1168 valid observations were collected from adults aged 19–64 years in the Republic of Korea using a structured online survey, and analyzed using structural equation modeling. The results showed that the four UTAUT constructs (performance expectancy, social influence, facilitating conditions, and environmental concerns) were directly related to intention for DRT usage. Indirect impacts of perceived safety, structural assurance, familiarity, performance expectancy, and effort expectancy on initial trust were also found. Consequently, the constructs with the greatest total effect on usage intention were (in order of relevance) initial trust, performance expectancy, social influence, and structural assurance. As one of the few attempts to examine public acceptance of DRT, it is expected that findings from this study could contribute to the literature by providing insights into potential users’ attitudes toward DRT. This study further offers guidance on designing interventions intended to promote a transition toward increased operational efficiency through policy developments for DRT, thereby achieving sustainable development

Light-Responsive, Shape-Switchable Block Copolymer Particles

A robust strategy is developed for preparing light-responsive block copolymer (BCP) particles in which shape and color can be actively controlled with high spatial and temporal resolution. The key to achieving light-responsive shape transitions of BCP particles is the design and synthesis of surfactants containing light-active groups (i.e., nitrobenzyl esters and coumarin esters) that modulate the amphiphilicity and interfacial activity of the surfactants in response to light of a specific wavelength. These light-induced changes in surfactant structure modify the surface and wetting properties of BCP particles, affording both shape and morphological transitions of the particles, for example from spheres with an onion-like inner morphology to prolate or oblate ellipsoids with axially stacked nanostructures. In particular, wavelength-selective shape transformation of the BCP particles can be achieved with a mixture of two light-active surfactants that respond to different wavelengths of light (i.e., 254 and 420 nm). Through the use of light-emitting, photoresponsive surfactants, light-induced changes in both color and shape are further demonstrated. Finally, to demonstrate the potential of the light-triggered shape control of BCP particles in patterning features with microscale resolution, the shape-switchable BCP particles are successfully integrated into a patterned, free-standing hydrogel film, which can be used as a portable, high-resolution display

Orbit Determination of KOMPSAT-1 and Cryosat-2 Satellites Using Optical Wide-field Patrol Network (OWL-Net) Data with Batch Least Squares Filter

The optical wide-field patrol network (OWL-Net) is a Korean optical surveillance system that tracks and monitors domestic\ud satellites. In this study, a batch least squares algorithm was developed for optical measurements and verified by Monte\ud Carlo simulation and covariance analysis. Potential error sources of OWL-Net, such as noise, bias, and clock errors, were\ud analyzed. There is a linear relation between the estimation accuracy and the noise level, and the accuracy significantly\ud depends on the declination bias. In addition, the time-tagging error significantly degrades the observation accuracy, while\ud the time-synchronization offset corresponds to the orbital motion. The Cartesian state vector and measurement bias were\ud determined using the OWL-Net tracking data of the KOMPSAT-1 and Cryosat-2 satellites. The comparison with known\ud orbital information based on two-line elements (TLE) and the consolidated prediction format (CPF) shows that the orbit\ud determination accuracy is similar to that of TLE. Furthermore, the precision and accuracy of OWL-Net observation data\ud were determined to be tens of arcsec and sub-degree level, respectively

Orbit Determination of KOMPSAT-1 and Cryosat-2 Satellites Using Optical Wide-field Patrol Network (OWL-Net) Data with Batch Least Squares Filter

The optical wide-field patrol network (OWL-Net) is a Korean optical surveillance system that tracks and monitors domestic\ud satellites. In this study, a batch least squares algorithm was developed for optical measurements and verified by Monte\ud Carlo simulation and covariance analysis. Potential error sources of OWL-Net, such as noise, bias, and clock errors, were\ud analyzed. There is a linear relation between the estimation accuracy and the noise level, and the accuracy significantly\ud depends on the declination bias. In addition, the time-tagging error significantly degrades the observation accuracy, while\ud the time-synchronization offset corresponds to the orbital motion. The Cartesian state vector and measurement bias were\ud determined using the OWL-Net tracking data of the KOMPSAT-1 and Cryosat-2 satellites. The comparison with known\ud orbital information based on two-line elements (TLE) and the consolidated prediction format (CPF) shows that the orbit\ud determination accuracy is similar to that of TLE. Furthermore, the precision and accuracy of OWL-Net observation data\ud were determined to be tens of arcsec and sub-degree level, respectively

Bicontinuous Block Copolymer Morphologies Produced by Interfacially Active, Thermally Stable Nanoparticles

Polymeric bicontinuous morphologies were created by thermal annealing mixtures of poly(styrene-<i>b</i>-2-vinylpyridine) (PS-<i>b</i>-P2VP) block copolymers and stabilized Au-core/Pt-shell (Au–Pt) nanoparticles. These Au–Pt nanoparticles have a cross-linked polymeric shell to promote thermal stability and are designed to adsorb strongly to the interface of the PS-<i>b</i>-P2VP block copolymer due to the favorable interaction between P2VP block and the exterior of the cross-linked shell of the nanoparticle. The interfacial activity of these Au–Pt nanoparticles under thermal annealing conditions leads to decrease in domain size of the lamellar diblock copolymer. As nanoparticle volume fraction ϕ_p was increased, a transition from a lamellar to a bicontinuous morphology was observed. Significantly, the effect of these shell-cross-linked Au–Pt nanoparticles under thermal annealing conditions was similar to those of traditional polymer grafted Au nanoparticles under solvent annealing conditions reported previously. These results suggest a general strategy for producing bicontinuous block copolymer structures by thermal processing through judicious selection of polymeric ligands, nanoparticle core, and block copolymer