Optical Principles Research Articles

Optical steelyard: high-resolution and wide-range refractive index sensing by synergizing Fabry–Perot interferometer with metafibers

Refractive index (RI) sensors play an important role in various applications including biomedical analysis and food processing industries. However, developing RI sensors with both high resolution and wide linear range remains a great challenge due to the tradeoff between quality (Q) factor and free spectral range (FSR) of resonance mode. Herein, the optical steelyard principle is presented to address this challenge by synergizing resonances from the Fabry–Perot (FP) cavity and metasurface, integrated in a hybrid configuration form on the end facet of optical fibers. Specifically, the FP resonance acting like the scale beam, offers high resolution while the plasmonic resonance acting like the weight, provides a wide linear range. Featuring asymmetric Fano spectrum due to modal coupling between these two resonances, a high Q value (~ 3829 in liquid) and a sensing resolution (figure of merit) of 2664 RIU−1 are experimentally demonstrated. Meanwhile, a wide RI sensing range (1.330–1.430 in the simulation and 1.3403–1.3757 in the experiment) is realized, corresponding to a spectral shift across several FSRs (four and two FSRs in the simulation and experiment, respectively). The proposed steelyard RI sensing strategy is promising in versatile monitoring applications, e.g., water salinity/turbidity and biomedical reaction process, and could be extended to other types of sensors calling for both high resolution and wide linear range.

Electronic analogue of Fourier optics with massless Dirac fermions scattered by quantum dot lattice

Abstract The field of electron optics exploits the analogy between the movement of electrons or charged quasiparticles, primarily in two-dimensional materials subjected to electric and magnetic (EM) fields and the propagation of electromagnetic waves in a dielectric medium with varied refractive index. We significantly extend this analogy by introducing an electronic analogue of Fourier optics dubbed as Fourier electron optics (FEO) with massless Dirac fermions (MDF), namely the charge carriers of single-layer graphene under ambient conditions, by considering their scattering from a two-dimensional quantum dot lattice (TDQDL) treated within Lippmann–Schwinger formalism. By considering the scattering of MDF from TDQDL with a defect region, as well as the moiré pattern of twisted TDQDLs, we establish an electronic analogue of Babinet’s principle in optics. Exploiting the similarity of the resulting differential scattering cross-section with the Fraunhofer diffraction pattern, we construct a dictionary for such FEO. Subsequently, we evaluate the resistivity of such scattered MDF using the Boltzmann approach as a function of the angle made between the direction of propagation of these charge-carriers and the symmetry axis of the dot-lattice, and Fourier analyze them to show that the spatial frequency associated with the angle-resolved resistivity gets filtered according to the structural changes in the dot lattice, indicating wider applicability of FEO of MDF.

Arduino-Based Non-Invasive Blood Sugar Analyzer Instrumentation System

Arduino-based Non-Invasive Blood Sugar Measurement Instrumentation System is a system designed to measure blood sugar levels without requiring blood samples, as in invasive methods. The system uses photodiodes and LEDs (Light Emitting Diodes) function as a measurement process using optical principles. Arduino as the base of the microcontroller to manage the sensor and measurement process, process the data from the sensor, and send it to the LCD for display. The testing and calibration of the device showed that the average error percentage was around 2.91%, indicating an excellent degree of accuracy in measuring sugar levels non-invasively, although there were slight deviations that were still within acceptable tolerances. By considering the average result of the percentage of error it can be concluded that this system is effective and reliable for blood sugar measurement without invasive.

Complex optical systems for individualized correction of presbyopia

Amultitude of available intraocular lens (IOL) models enable apersonalized approach to presbyopia correction in order to meet each patient's needs. This review article discusses more complex approaches which can be useful in selected cases. The concept of reversible trifocality enables correction of presbyopia using asupplementary intraocular lens (IOL), which can be removed if necessary (e.g., intolerance to multifocal optics). The use of capsulotomy-fixated IOLs enables high precision for positioning of the lens and better stability compared to conventional capsular bag-fixated IOLs, which can be particularly advantageous in multifocal optics. The mix and match concept enables acombination of different IOLs with various optical principles to achieve the desired binocular effect. Binocular IOL systems, which consist of two complementary IOLs, can be seen as afurther development of the mix and match concept. Knowledge of the available options and their application can further improve correction of presbyopia.

Overview of intraocular lenses with optics for correcting presbyopia

In recent years intraocular lenses (IOLs) for correcting presbyopia have been significantly improved and diversified. There are currently many different IOL models based on awide variety of optical designs. The wide variety of available IOL solutions to correct presbyopia can be challenging for surgeons and patients. In everyday practice, the question is which IOL is best for which patient. This overview describes and categorizes the currently available implants. The respective optical properties are analyzed and clinical study results are discussed, in particular those evaluating visual performance and the occurrence of photic phenomena. Monofocal-plus IOLs provide improved intermediate visual acuity with optimal distant visual acuity and minimal photic phenomena. Extended depth of field (EDoF) IOLs extend the depth of field through different optical principles and provide good distant and intermediate visual acuity. Trifocal lenses enable the greatest independence from spectacles at the price of ahigher probability of dysphotopsia. The selection of the most suitable IOL for correction of presbyopia requires abalance between the patient's visual needs and possible side effects. An adequate knowledge of the currently available implants allows a patient-oriented selection of IOLs.

Simultaneous Multifocal Plane Fourier Ptychographic Microscopy Utilizing a Standard RGB Camera.

Fourier ptychographic microscopy (FPM) is a computational imaging technology that can acquire high-resolution large-area images for applications ranging from biology to microelectronics. In this study, we utilize multifocal plane imaging to enhance the existing FPM technology. Using an RGB light emitting diode (LED) array to illuminate the sample, raw images are captured using a color camera. Then, exploiting the basic optical principle of wavelength-dependent focal length variation, three focal plane images are extracted from the raw image through simple R, G, and B channel separation. Herein, a single aspherical lens with a numerical aperture (NA) of 0.15 was used as the objective lens, and the illumination NA used for FPM image reconstruction was 0.08. Therefore, simultaneous multifocal plane FPM with a synthetic NA of 0.23 was achieved. The multifocal imaging performance of the enhanced FPM system was then evaluated by inspecting a transparent organic light-emitting diode (OLED) sample. The FPM system was able to simultaneously inspect the individual OLED pixels as well as the surface of the encapsulating glass substrate by separating R, G, and B channel images from the raw image, which was taken in one shot.

Image authentication method based on Fourier zero-frequency replacement and single-pixel self-calibration imaging by diffractive deep neural network.

The diffractive deep neural network is a novel network model that applies the principles of diffraction to neural networks, enabling machine learning tasks to be performed through optical principles. In this paper, a fully optical authentication model is developed using the diffractive deep neural network. The model utilizes terahertz light for propagation and combines it with a self-calibration single-pixel imaging model to construct a comprehensive optical authentication system with faster authentication speed. The proposed system filters the authentication images, establishes an optical connection with the Fourier zero-frequency response of the illumination pattern, and introduces the signal-to-noise ratio as a criterion for batch image authentication. Computer simulations demonstrate the fast speed and strong automation performance of the proposed optical authentication system, suggesting broad prospects for the combined application of diffractive deep neural networks and optical systems.

Rapid and high-precision measurement method for fine pitch gears without high-precision installation

To address the measurement issues posed by fine pitch gears, due to the characteristics such as low stiffness and narrow tooth space, this paper proposes a rapid and high-precision measurement method which does not require precise installation by combining optical and visual principles. A calibrated artifact, featuring cylindrical and flat surfaces, was designed to accurately determine the relative positions of the line laser sensor, camera, and rotary table. An experimental setup was constructed, and measurement experiments were conducted on two types of cylindrical gears. To validate the precision of the measurement system, gear profile deviation, helix deviation and pitch deviation were evaluated according to ISO 1328-1:2013. The results were compared with the reference evaluations from Klingelnberg Gear Measuring Center P26, with difference less than 2.4µm. Eight repeatability experiments were conducted, demonstrating that the method proposed satisfies the measurement requirements for fine pitch gears with an accuracy of class 6.

Fourier Ptychographic Microscopy Reconstruction Method Based on Residual Local Mixture Network.

Fourier Ptychographic Microscopy (FPM) is a microscopy imaging technique based on optical principles. It employs Fourier optics to separate and combine different optical information from a sample. However, noise introduced during the imaging process often results in poor resolution of the reconstructed image. This article has designed an approach based on a residual local mixture network to improve the quality of Fourier ptychographic reconstruction images. By incorporating channel attention and spatial attention into the FPM reconstruction process, the network enhances the efficiency of the network reconstruction and reduces the reconstruction time. Additionally, the introduction of the Gaussian diffusion model further reduces coherent artifacts and improves image reconstruction quality. Comparative experimental results indicate that this network achieves better reconstruction quality, and outperforming existing methods in both subjective observation and objective quantitative evaluation.

Angular Deviations, Lateral Displacements, and Transversal Symmetry Breaking: An Analytical Tutorial

The study of a Gaussian laser beam interacting with an optical prism, both through reflection and transmission, provides a technical tool to examine deviations from the optical path as dictated by geometric optics principles. These deviations encompass alterations in the reflection and refraction angles, as predicted by the reflection and Snell laws, along with lateral displacements in the case of total internal reflection. The analysis of the angular distributions of both the reflected and transmitted beams allows us to understand the underlying causes of these deviations and displacements, and it aids in formulating analytic expressions that are capable of characterizing these optical phenomena. The study also extends to the examination of transverse symmetry breaking, which is a phenomenon observed in the laser beam as it traverses the oblique interface of the prism. It is essential to underscore that this analytical overview does not strive to function as an exhaustive literature review of these optical phenomena. Instead, its primary objective is to provide a comprehensive and self-referential treatment, as well as give universal analytical formulas intended to facilitate experimental validations or applications in various technological contexts.

Dual-Function Wearable Hydrogel Optical Fiber for Monitoring Posture and Sweat pH.

In recent years, wearable devices have been widely used for human health monitoring. Such monitoring predominantly relies on the principles of optics and electronics. However, electronic detection is susceptible to electromagnetic interference, and traditional optical fiber detection is limited in functionality and unable to simultaneously detect both physical and chemical signals. Hence, a wearable, embedded asymmetric color-blocked optical fiber sensor based on a hydrogel has been developed. Its sensing principle is grounded in the total internal reflection within the optical fiber. The method for posture sensing involves changes in the light path due to fiber bending with color blocks providing wavelength-selective modulation by absorption changes. Sweat pH sensing is facilitated by variations in fluorescence intensity triggered by sweat-induced conformational changes in Rhodamine B. With just one fiber, it achieves both physical and chemical signal detection. Fabricated using a molding technique, this fiber boasts excellent biocompatibility and can accurately discern single and multiple bending points, with a recognition range of 0-90° for a single segment, a detection limit of 0.02 mm-1 and a sweat pH sensing linear regression R2 of 0.993, alongside great light propagation properties (-0.6 dB·cm-1). With its extensive capabilities, it holds promise for applications in medical monitoring.

Construction of a High-Temperature Sensor for Industry Based on Optical Fibers and Ruby Crystal.

This paper presents the construction of an innovative high-temperature sensor based on the optical principle. The sensor is designed especially for the measurement of exhaust gases with a temperature range of up to +850 °C. The methodology is based on two principles-luminescence and dark body radiation. The core of this study is the description of sensing element construction together with electronics and the system of photodiode dark current compensation. An advantage of this optical-based system is its immunity to strong magnetic fields. This study also discusses results achieved and further steps. The solution is covered by a European Patent.

Uricase biofunctionalized plasmonic sensor for uric acid detection with APTES-modified gold nanotopping

Current uric acid detection methodologies lack the requisite sensitivity and selectivity for point-of-care applications. Plasmonic sensors, while promising, demand refinement for improved performance. This work introduces a biofunctionalized sensor predicated on surface plasmon resonance to quantify uric acid within physiologically relevant concentration ranges. The sensor employs the covalent immobilization of uricase enzyme using 1-Ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) and N-Hydroxysuccinimide (NHS) crosslinking agents, ensuring the durable adherence of the enzyme onto the sensor probe. Characterization through atomic force microscopy and Fourier transform infrared spectroscopy validate surface alterations. The Langmuir adsorption isotherm model elucidates binding kinetics, revealing a sensor binding affinity of 298.83 (mg/dL)−1, and a maximum adsorption capacity of approximately 1.0751°. The biofunctionalized sensor exhibits a sensitivity of 0.0755°/(mg/dL), a linear correlation coefficient of 0.8313, and a limit of detection of 0.095 mg/dL. Selectivity tests against potentially competing interferents like glucose, ascorbic acid, urea, D-cystine, and creatinine showcase a significant resonance angle shift of 1.1135° for uric acid compared to 0.1853° for interferents at the same concentration. Significantly, at a low uric acid concentration of 0.5 mg/dL, a distinct shift of 0.3706° was observed, setting it apart from the lower values noticed at higher concentrations for all typical interferent samples. The uricase enzyme significantly enhances plasmonic sensors for uric acid detection, showcasing a seamless integration of optical principles and biological recognition elements. These sensors hold promise as vital tools in clinical and point-of-care settings, offering transformative potential in biosensing technologies and the potential to revolutionize healthcare outcomes in biomedicine.

Directional thermal emission and display using pixelated non-imaging micro-optics

Thermal radiation is intrinsically broadband, incoherent and non-directional. The ability to beam thermal energy preferentially in one direction is not only of fundamental importance, but it will enable high radiative efficiency critical for many thermal sensing, imaging, and energy devices. Over the years, different photonic materials and structures have been designed utilizing resonant and propagating modes to generate directional thermal emission. However, such thermal emission is narrowband and polarised, leading to limited thermal transfer efficiency. Here we experimentally demonstrate ultrabroadband polarisation-independent directional control of thermal radiation with a pixelated directional micro-emitter. Our compact pixelated directional micro-emitter facilitates tunable angular control of thermal radiation through non-imaging optical principles, producing a large emissivity contrast at different view angles. Using this platform, we further create a pixelated infrared display, where information is only observable at certain directions. Our pixelated non-imaging micro-optics approach can enable efficient radiative cooling, infrared spectroscopy, thermophotovoltaics, and thermal camouflaging.

Photonic Crystal-Integrated Semitransparent Solar Cell for Solar Greenhouse Application

Solar greenhouse technology emerges as a solution that intensifies crop yields and allows utilities to generate energy from photovoltaic cells. Here, we demonstrate a photonic crystal-integrated solar cell that selectively transmits photosynthetic light for plant cultivation and reflects the remaining light to the adjacent solar cells to generate electricity. The photonic crystal is fabricated using an e-beam evaporation method by nonperiodic stacking of TiO2 and SiO2 layers to transmit light at 400–500 nm (blue) and 600–700 nm (red) and reflect green (500–600 nm), ultraviolet, and infrared light. The photonic crystal-integrated solar cell is constructed with the vertically arranged copper indium gallium diselenide (CIGS) solar cell and the tilted photonic crystal with respect to the CIGS cell. By controlling the tilting angle of the photonic crystal film, it achieves the generated electric power of 40.2 W m-2 and the irradiance of 124.6 W m-2 for transmitted photosynthetic lights (400–500 and 600–700 nm). In contrast, a conventional horizontal CIGS cell shows a power generation of 55.6 W m-2 without any light transmission. This work provides a new optical strategy and design principle for the development of a wavelength-selective semitransparent solar cell.

Optical performance investigation for spatially separated non-imaging concentrator with congruent plane concentrating surface

The thermal deformation on the concentrating surface of traditional CPC (Compound Parabolic Concentrator, CPC) is effectively addressed by SCSA-CPC (Separation of Concentrating Surface and Absorber CPC, SCSA-CPC). However, the energy flux density distribution on the absorber of SCSA-CPC is uneven and the concentrating surface is still a curved paraboloid structure, which hinders practical engineering applications and lacks significant economic benefits. In the present research, five kinds of SS-CPCs (Spatially Separated CPC, SS-CPC) with different numbers of congruent plane concentrating surfaces, namely SS-CPC2, SS-CPC3, SS-CPC4, SS-CPC5 and SS-CPC6 were constructed based on non-imaging optics principles. The optical performances of the SS-CPCs were investigated and compared to SCSA-CPC with the same specification. It is found that SS-CPC allows for an increased acceptance angle of up to 41° while effectively improving the uniformity of energy flux density distribution on the absorber. The results also showed that the annual beam radiation collection time can be extended by 43.11 % and SS-CPC has a particular advantage in collecting diffuse radiation, indicating its high adaptability to weather changes. Moreover, due to the congruent planar structure of the concentrating surface, SS-CPC holds promising prospects for practical engineering applications.

Enhancing images for vision measurement in hazy tunnel construction

To address the negative impacts of image degradation on vision measurement in hazy tunnel construction, this paper presents a unified enhancement method of color and grayscale images in tunnel haze environments. Firstly, a tunnel haze environment light scattering model is introduced utilizing geometric optics principles and the conventional atmospheric scattering model. Secondly, a model for perceiving image haze is established within the image feature space to estimate ambient light and transmission. The efficacy of the method is assessed by constructing a tunnel haze simulation chamber and a platform for measurement of tunnel boring machine (TBM) cutter wear. Comparative experiments demonstrate the method reduces the error in 3D point cloud reconstruction by 77% and improves the measurement precision of TBM cutter wear by 62%. The results demonstrate the potential application of this method in automated tunnel construction. However, further research is needed to enhance its efficacy in dense haze images.

Formation of homogeneous pyridinic emission states in carbon dots via solid-state carbonization of aminoquinoline: Optical design principles and light-emitting diode applications

Developing carbon dots (CDs) for practical applications faces significant hurdles due to non-homogeneity in their chemical structure, leading to broad spectral distribution and the excitation-energy-dependent behavior of their fluorescence (FL) emission properties. To address this challenge, we implemented solid-state carbonization of 6-aminoquinoline (6-AQ) devoid of any additives that could induce chemical non-homogeneity. This process yielded pyridinic-nitrogen-doped CDs (PN-CDs) characterized by homogenous, uniform emission states arising from pyridine-incorporated heteroatomic structures. Notably, these PN-CDs exhibited excitation-energy-independent FL at 520 nm with a full-width-half-maximum of 70 nm. To elucidate the structure-property relationship in PN-CDs, a comprehensive analysis encompassing time-resolved spectroscopy and ab initio calculations was conducted. Furthermore, we performed a comparative study by manipulating synthesis parameters and utilizing six AQ isomers, offering valuable insights to optimize the optical properties of PN-CDs. Finally, we successfully demonstrated high-color-purity and efficient green light-emitting diodes utilizing PN-CDs, highlighting their potential for future display applications. This paves the way for advancement in optical materials with enhanced performance and reduced environmental impact.

Research on the efficient EM modeling method from multilayered anisotropic medium-metal composite targets

The paper presents a high-frequency modeling approach tailored for the electromagnetic (EM) scattering characteristics from electrically large radar targets coated with multi-layered anisotropic mediums (MLAMs). The approach begins by deriving the plane-wave spectrum expression for the incident EM field within MLAMs. It then employs spectral domain full-wave analysis method (SDFWAM) to obtain an analytical representation of the scattering field, further leveraging saddle point evaluation (SPE) to derive asymptotic solutions in the spatial domain. By integrating principles of physical optics (PO) and the tangent plane approximation, the far-field scattering characteristics of target enveloped in the specified medium are efficiently delineated. Validations against standard structure and the Misty satellite model reveal the method's pronounced alignment with the method of moments – finite element method (MoM-FEM) hybrid numerical algorithm, underscoring its notable computational efficiency. Furthermore, in conjunction with scattering sources decomposition technique, the approach is applied to optimize the radar cross-section (RCS) of the Su-57 aircraft, achieving precise and intelligent RCS control at minimal material cost. In conclusion, this research offers pivotal technological and theoretical foundations for EM scattering prediction, stealth design, and performance assessment in radar target domains.

OmniSR-M: A Rock Sheet with a Multi-Branch Structure Image Super-Resolution Lightweight Method

With the rapid development of digital core technology, the acquisition of high-resolution rock thin section images has become crucial. Due to the limitation of optical principles, thin section imaging involves a contradiction between resolution and field of view. In order to solve this problem, this paper proposes a lightweight, fully aggregated network with multi-branch structure for super resolution of rock thin section images. The experimental results on the rock thin section dataset demonstrate that the improved method, called OmniSR-M, achieves significant enhancement compared to the original OmniSR method and also surpasses other state-of-the-art methods. OmniSR-M effectively recovers image details while maintaining its lightweight nature. Specifically, OmniSR-M reduces the number of parameters by 26.56% and the computation by 27.66% compared to OmniSR. Moreover, this paper quantitatively analyzes both the facies porosity rate and grain size features in the application scenario. The results show that the images generated by OmniSR-M successfully recover key information about the rock thin section.