bluuebunny/crossref_metadata_2025_split huggingface dataset:
Model Hamiltonians of open quantum optical systems: Evolvement from hermiticity to adjoint commutativity
Authors: Zloshchastiev Konstantin G. 
Published: December 2022

Abstract
In the conventional quantum mechanics of conserved systems, Hamiltonian is assumed to be a Hermitian operator. However, when it comes to quantum systems in presence of dissipation and/or noise, including open quantum optical systems, the strict hermiticity requirement is nor longer necessary. In fact, it can be substantially relaxed: the non-Hermitian part of a Hamiltonian is allowed, in order to account for effects of dissipative environment, whereas its Hermitian part would be describing subsystem’s energy. Within the framework of the standard approach to dissipative phenomena based on a master equation for the reduced density operator, we propose a replacement of the hermiticity condition by a more general condition of commutativity between Hermitian and anti-Hermitian parts of a Hamiltonian. As an example, we consider a dissipative two-mode quantum system coupled to a single-mode electromagnetic wave, where we demonstrate that the adjoint-commutativity condition does simplify the parametric space of the model.
Effect of accommodation on coma at central and peripheral retina
Authors: Sapkota Kishor , Gomes Jessica , Franco Sandra 
Published: December 2022

Abstract
Coma is one of the most common ocular higher order aberrations and highly affects the quality of image. It is assumed that corneal aberrations are balanced by internal (lenticular) aberrations so that retinal image quality may not have great impact. However, during accommodation, the shape, position, and curvature of the crystalline lens changes which might disrupt this balance between internal and corneal aberration. This study aimed to investigate the effect of accommodation on primary coma (

C
3

−
1

and

C
3
1

) and secondary coma (

C
5

−
1

and

C
5
1

) in relaxed and accommodated eyes. Zernike coefficients were measured in 53 subjects with Hartmann-Shack aberrometer both at the central and peripheral retina up to 30° off-axis in horizontal and vertical meridians. The process was repeated with 2.50 D accommodation stimulus and comas were compared with and without accommodation. Root-mean-square of total coma was also assessed. With accommodation, vertical comas changed to more negative value and horizontal comas changed to more positive values in most of the off-axis positions. In contrast, the secondary vertical comas became less negative and secondary horizontal comas became more negative with accommodation in most of the off-axis fixations. Thus, the results showed that accommodation affects coma which depends up on position of the fixation.
Contribution to the improvement of the correlation filter method for modal analysis with a spatial light modulator
Authors: Benedicto David , Collados M. Victoria , Martín Juan C. , Mendoza-Yero Omel , Vallés Juan A. , Atencia Jesús 
Published: December 2022

Abstract
Modal decomposition of light is essential to study propagation properties of waveguides and photonic devices. Modal analysis can be carried out by implementing a computer generated hologram acting as a match filter in a spatial light modulator. In this work, a series of aspects to be taken into account in order to get the most out of this method are presented, aiming to provide operational procedures. First of all, the influence of the mode normalization in the complex amplitude encoding inherent noise is investigated. Then, a method for filter size adjustment based on the LP-modes symmetry is presented. Finally, a robust method to measure the phase difference between modes is proposed. These procedures are tested by wavefront reconstruction in a conventional few mode fiber.
Coupled two-core integrated waveguides modal analysis
Authors: Benedicto David , Collados M. Victoria , Martín Juan C. , Atencia Jesús , Vallés Juan A. 
Published: December 2022

Abstract
We present a modal analysis of coupled two-core integrated waveguides fabricated by femtosecond laser writing as a function of the core-to-core distance, illuminating position and input light wavelength. In order to do that we use the correlation filter method, implementing the computer generated holograms in a phase-only spatial light modulator. Due to the two-core waveguide symmetry, we prove it is not necessary to encode the complex amplitude in a phase-only device as long as the cores are not strongly coupled. A comparison between experimental and numerical modal weights is presented, showing that simple phase-only match filters allow the modal decomposition of two-core waveguides output beams.
Simulation and development of a prototype for high precision surface metrology
Authors: Costa Sílvia , Abreu Manuel 
Published: December 2022

Abstract
Optical techniques are used in many applications in the metrology field, namely for high accuracy surface profiling. Although there many techniques are available, a specific measurement methodology must be correctly chosen according to the specifications of the range of measurement, field, and surface characteristics. In this work we simulate and develop a small prototype capable of measuring surfaces of circa 10 by 10 cm with an uncertainty of 20 µm in all directions, using the astigmatic method as baseline. The aim of this paper is then to show a dedicated and optimized optical setup that allow the surface characterization of a sample surface.
Optofluidic Fabry-Perot interferometric sensor for the real-time measurement of refractive index
Authors: Leça JM , Magalhães Y , Antunes P , Pereira V , Ferreira MS 
Published: December 2022

Abstract
In this work, a microfluidic system combined with a fibre-optic extrinsic Fabry-Perot interferometer is proposed to measure refractive index continuously and in real time. A microfluidic platform was designed and created for this purpose through 3D printing. The Fabry-Perot cavity is an integral part of the microfluidic chip and is perpendicular to the sample flow. The light is conducted through a single mode optical fibre and the refractive index measurements were based on the optical power and wavelength shift of the reflected spectra. The developed optofluidic setup was characterised using different concentrations of glucose solutions. A sensitivity of 1102 nm/RIU was obtained when using the wavelength shift, however, when the same solution was analysed over time, the signal for wavelength shift measurements was found to be unstable. The optical power shift was correlated with the refractive index and a sensitivity of -79.6 dB/RIU was obtained, with a good linearity (r2 = 0.996). Good results were verified in terms of stability with a maximum standard deviation of 0.028 dB and a sensor resolution of 4.3×10−4 RIU. This sensor has a great potential for applications in which refractive index real-time measurements are required, such as food and beverages industry process control.
Reducing the impact of the sunlight in urban areas using asphalt mixtures with phase change materials: a review in Scopus in the last three years
Authors: Landi Salmon , Segundo Iran Rocha , Homem Natália , Sousa Jorge , Freitas Elisabete , Costa Manuel F. M. , Carneiro Joaquim 
Published: December 2022

AbstractPhase change materials (PCMs) have been incorporated into asphalt concrete pavements because they can regulate the temperature by absorbing and releasing heat during physical state changes. This effect reduces temperature gradients of pavements and, consequently, increases its service life. This work presents a systematic review of recent articles published in peer-reviewed journals (available in the Scopus database) involving asphalt mixtures with PCMs and focusing on mechanical characterization. It is observed that most of the selected papers investigated the benefits of polyethylene glycol as a PCM. The most common strategy to avoid leakage during the phase transition involved using a porous material that acts as a carrier matrix for the PCMs. Generally, asphalt pavements with PCMs are systems with favourable thermal transferability, thus demonstrating higher heat absorption and dissipation rates. Finally, the asphalt mixtures containing PCMs showed lower mechanical performance than the control mixtures. However, they still satisfy the required criteria. In any case, it is expected that with the incorporation of PCMs into asphalt pavements, the social and environmental effects (Urban Heat Island) of sunlight in urban areas can be mitigated by the thermoregulation phenomena.
Autonomous Optical Tweezers: from automatic trapping to single particle analysis
Authors: Coutinho Felipe , Teixeira Joana , Rocha Vicente , Oliveira João , Jorge Pedro A. S. , Silva Nuno A. 
Published: December 2022

Abstract
Optical trapping is a versatile and non-invasive technique for single particle manipulation. As such, it can be widely applied in the domains of particle identification and classification and thus used as a tool for monitoring physical and chemical processes. This creates an opportunity for integrating the method seamlessly into optofluidic chips, provided it can be automatized. Yet even though OT is well established in multiple scientific domains, a full stack approach to its integration into other technological devices is still lacking. This calls for solutions in tasks such as automatic trapping and signal analysis.
In this manuscript, we describe the implementation of an algorithm seeking autonomous particle location and trapping. The methodology is based upon image-processing, allowing for particle location using real time image segmentation. A local thresholding algorithm is applied, followed by morphological techniques for closing shapes and excluding non-bounded regions - after which only the particles remain on the image. Once the centroid is identified, the stage is translated accordingly by piezo-electric actuators, followed by the laser activation. In this way, trapping is achieved, and one may proceed to analyze the forward scattered optical signal, after which a new particle inside the actuators range may be automatically trapped.
This development, when compared with existent solutions involving holographic optical tweezers, allows for similar capabilities without using a spatial light modulator, thus dramatically reducing the setup costs of autonomous OT solutions. Therefore, when combined with particle classification techniques, this method is well suited for integration into possible optofluidic chips for autonomous sensing and monitoring of biochemical samples.
Label-Free Multiplexed Analysis Using Photonic Crystal-Based Biosensors
Authors: Nifontova Galina , Fleury Fabrice , Nabiev Igor , Sukhanova Alyona 
Published: December 2022

Abstract
Label-free bioanalytical methods have been widely employed in biomedical research, in particular, in drug screening and discovery, diagnostics, and proteomics. Photonic crystals (PCs) represent a modern alternative to surface plasmon resonance (SPR) techniques. Imaging of PC surface modes has been demonstrated as a promising label-free approach allowing for multiplexed detection. Surface modification of PC sensors is an important stage determining the effectiveness of the analysis of biomolecule interactions. Here, we describe the results of the development of a label-free PC-based sensor, the key steps of the modification and functionalization of the PC surface with proteins, as well as the evaluation of its suitability for sensing via 2D imaging of binding events. Our data demonstrate the efficiency of the designed PC-based sensor for analysis of proteins interactions and pave the way for the engineering of a label-free biosensing platform based on PCs.
Influence of absorptive tinted filter lenses on contrast sensitivity in healthy participants under three different environmental conditions
Authors: Perez-Baladron Adrian , Salgado-Núñez Andrea , Garcia-Queiruga Jacobo , Pena-Verdeal Hugo , Yebra-Pimentel Eva 
Published: December 2022

Abstract
Purpose: The present study aimed to analyse the influence of absorptive tinted filter lenses on Contras Sensitivity (CS) in healthy participants under three different environmental conditions. Methods: 10 Healthy qualified volunteers who fulfilled the inclusion/exclusion criteria were recruited: refractive spherical error between +2.00 and -4.00D, refractive cylindrical error less than 1.00 D, Best Corrected Visual Acuity (BCVA) ≥ 1.0 and Low Vision Quality of Life (LVQOF) score ≥ 50. Participants were scheduled for three-session under different environmental conditions where CS was measured with a Pelli-Robson chart with and without five (ML Filters 450, 500, 511, 527 and 550) absorptive tinted filters lenses: 1) indoor, 2) outdoor on a sunny day, 3) outdoor on a rainy day. The filters were always introduced in the same order, from the higher absorption filter (ML Filter 550) to the lower (ML Filter 450). Results between filters and environmental conditions were compared. Results: There was a statistical difference in the CS values obtained with and without a filter in the measurements performed in all environmental conditions (Friedman test: all p < 0.001) with no differences in the pairwise analysis between filters (Wilcoxon test; all ≥ 0.009). There was no statistically difference in the CS values between environmental conditions without filters or with any of the filters (Friedman test: all p ≥ 0.097). Conclusions: The present study found that coloured filter lenses between 450 and 550 nm wavelength absorption had minimal impact on CS in healthy participants.
Analysis of power transfer between two multi-core fibers with long-period gratings
Authors: Sousa Liliana M. , Facão Margarida , Nogueira Rogério N. , Rocha Ana M. 
Published: December 2022

Abstract
Here, we numerically propose and demonstrate a technique to couple light between two multi-core fibers (MCFs) using long-period gratings (LPGs). The light is coupled from one core of the input MCF to all cores of the output MCF. For that, an LPG is inscribed in the input core of the input MCF and identical LPGs are inscribed in all cores of the output MCF. First, the light is launched into the input core of the MCF and the optical power is transferred to the cladding due to the LPG inscribed in that core. The optical power in the cladding is then transferred to the other MCF cladding by evanescent field coupling. The optical power in the cladding of the output MCF is distributed by all its cores due to the identical LPGs inscribed in them. We optimized the LPGs period, their lengths and offset distance to increase the power transfer at 1480 nm. We achieved a power transfer of 92% of the input power, distributed by all MCF cores, in 10.6 cm of length. We also studied the power transfer sensitivity to the LPGs period.
Comparison between central corneal thickness, anterior chamber depth and axial length values with and without contact lenses
Authors: Noya-Padin Veronica , Nores-Palmas Noelia , Giraldez Maria Jesus , Pena-Verdeal Hugo , Yebra-Pimentel Eva 
Published: December 2022

Abstract
Purpose: To compare the values of central corneal thickness (CCT), the anterior chamber depth (ACD) and the axial length (AL) on measurements performed with and without contact lenses (CL) in healthy subjects. ACD was measured with two different devices (Visionix 120+ and EchoScan US-800) and the values were also compared between them. Material and methods: 20 volunteer participants (6 men and 14 women, 24.8 ± 2.73 years) were recruited. In a single visit, participants underwent autorefraction, biometry, topography and pachymetry with the naked eye (without CL). Then, biometry and pachymetry were repeated twice wearing two different CL (Somofilcon A and Nesofilcon A) of -3.00D lens power fitted in random order. Data were compared using t-tests for related samples. Results: CCT values wearing CL were significantly higher than those obtained with the naked eye (Paired t-test; both p ≤ 0.001). On the other hand, no significant differences were found between the ACD or AL values with the naked eye versus any of the CL studied (Paired t-test, all p ≥ 0.111). The ACD values comparing Visionix120+ to EchoScan US-800 measurements were significantly different with both the naked eye and with any CL (Paired t-test; all p ≤ 0.001). Conclusion: CCT measurements cannot be performed while wearing CL. In contrast, ACD and AL measurements were not affected by the use of any CL. In addition, it was observed that ACD results from both devices are not interchangeable neither when measured with the naked eye nor using any CL.
Optical fiber sensors for monitoring cement paste carbonation
Authors: da Silva P M , Mendes J P , Coelho L C C , de Almeida J M M M 
Published: December 2022

Abstract
The use of concrete has been widespread in our society in housing and infrastructure, despite the environmental cost associated with its production. Its decay poses a social, economic, and environmental problem. Currently, the carbonation of cement paste is monitored through the measurement of its pH, with several optical fiber sensors (OFS) have been produced for this purpose. In the current work the focus is, also, on the carbonation monitoring of cement paste through an OFS, but not through pH measurements. Single fiber reflectance spectroscopy, previously employed to measure cement paste durability, is used to monitor the discoloration of cement paste caused by carbonation. As the carbonation front reaches the fiber tip embedded in the cement paste, the signal reflected onto the fiber increases. The accelerated carbonation of two limestone cement paste samples in an atmosphere of 100% CO2 was successfully monitored. The applicability of the sensor for operational use with ambient CO2 was confirmed through the measurement of carbonation at 3% CO2. The cross interference from water ingress and egress was also evaluated, and it didn’t hinder the measurements of carbonation. Therefore, a novel OFS capable of measuring cement paste carbonation and durability, was achieved.
A Fiber Bragg Grating based Accelerometer for Monitoring the Vibration of an Industrial Engine Prototype: A Preliminary Study
Authors: Silveira Mariana , Avellar Leticia , Cruzeiro Filipe , Macedo Leandro , Leal-Junior Arnaldo , Garcia Guilherme , Frizera Anselmo , Díaz Camilo 
Published: December 2022

Abstract
Monitoring the vibration of industrial engines is essential for running diagnostics that can detect faults and point out the feasibility of predictive maintenance. Therefore, this paper describes an optical accelerometer based on a fiber Bragg grating to monitor the vibration of the gearbox of an industrial engine prototype. Experimental tests were performed varying the motor’s rotation speed during normal operation. To validate the proposed system, two electronic accelerometers were attached to the motor’s gearbox and bearing. The natural frequency response of the optical accelerometer was simulated and good agreement with the experimental results was obtained (0.83% of error). The proposed sensor was able to correctly identify the operation speeds of 20, 25, 35, 40, 45 and 50 rps with a maximum error of 0.05%. The mean signal-to-noise ratio (SNR) of the optical accelerometer was 64.05% higher than the SNR of one of the electronic solutions. The experimental results show that the vibration signals have different characteristics when measured at the bearings and at the gearbox, indicating the feasibility of multi-signals analysis for fault detection.
Subwavelength structures for taper waveguides
Authors: Lourenço Paulo , Fantoni Alessandro , Costa João , Fernandes Miguel , Vieira Manuela 
Published: December 2022

Abstract
In Photonic Integrated Circuits (PICs) it is often necessary some sort of mismatch adaptation between waveguides of different cross-sections. There are several instances of such a designing constraint, being the vertical coupling between the PIC and an optical fibre probably the most representative of all examples. Here, the beam of electromagnetic energy inside the PIC must be inserted/extracted through/to an optical fibre. Typical core diameters are approximately 10 μm and 5 μm, for single mode optical fibres operating in the near infrared and visible wavelengths, respectively. On the other hand, the optical interconnects linking individual structures in PICs are usually single mode waveguides, 400 to 500 nm wide and a few hundreds of nanometres thick. This presents a bidimensional mismatch between the optical fibre and the single mode waveguide within the PIC, that requires both lateral and longitudinal beam expansions. In this work, we have approached the lateral expansion of the fundamental mode propagating in a single mode waveguide, at the operating wavelength of 1550 nm and being coupled out into an optical fibre, through a grating structure 14.27 μm wide. To this end, we have designed and simulated a subwavelength metamaterial planar structure, which is able to expand laterally the fundamental mode’s profile from 450 nm to 14.27 μm, within 11.1 μm. Furthermore, we will be presenting the results obtained when comparing this structure with several linear inverted taper waveguides, regarding coupling and propagation efficiencies. Namely, we compared the coupling efficiencies of the modes propagating in an 100 μm long waveguide, when being excited by the analytically calculated fundamental mode and the fields obtained at the end of the designed structure. The results obtained for the designed structure 11.1 μm long and the calculated fundamental mode showed a coupling efficiency of -1.53 dB and -1.20 dB, respectively.
Towards real-time identification of trapped particles with UMAP-based classifiers
Authors: Teixeira Joana , Rocha Vicente , Oliveira João , Jorge Pedro A. S. , Silva Nuno A. 
Published: December 2022

Abstract
Optical trapping provides a way to isolate, manipulate, and probe a wide range of microscopic particles. Moreover, as particle dynamics are strongly affected by their shape and composition, optical tweezers can also be used to identify and classify particles, paving the way for multiple applications such as intelligent microfluidic devices for personalized medicine purposes, or integrated sensing for bioengineering. In this work, we explore the possibility of using properties of the forward scattered radiation of the optical trapping beam to analyze properties of the trapped specimen and deploy an autonomous classification algorithm. For this purpose, we process the signal in the Fourier domain and apply a dimensionality reduction technique using UMAP algorithms, before using the reduced number of features to feed standard machine learning algorithms such as K-nearest neighbors or random forests. Using a stratified 5-fold cross-validation procedure, our results show that the implemented classification strategy allows the identification of particle material with accuracies up to 80%, demonstrating the potential of using signal processing techniques to probe properties of optical trapped particles based on the forward scattered light. Furthermore, preliminary results of an autonomous implementation in a standard experimental optical tweezers setup show similar differentiation capabilities for real-time applications, thus opening some opportunities towards technological applications such as intelligent microfluidic devices and solutions for biochemical and biophysical sensing.