Reflectance Modulation Research Articles

MENINGKATKAN LITERASI DAN NUMERASI BERBASIS BIMBEL KEPADA SISWA SD NEGERI NO. 102058 DOLOK MASIHUL

The purpose of this Community Service (PkM) program is to learn about the process of making child-friendly school-based reflective module products that can improve numeracy literacy skills and self-confidence in elementary school students in Dolok Masihul District in grades IV, V, and VI. This activity is carried out by the Serdang Bedagai II team and is carried out every Monday to Wednesday. The PkM activity was held from February 2 – 26, 2022 at SDN 102058 Dolok Masihul. The target of this PkM program is students in grades IV, V and VI of SDN 102058 Dolok Masihul. The form of activities in the implementation of this service includes free tutoring activities for English, Mathematics, Indonesian and PkN subjects which are carried out at SDN 102058 Dolok Masihul. The impact of the implementation of this PkM activity is 1) Produce reflective modules based on child-friendly schools that are ideal for strengthening numeracy literacy abilities and self-confidence of Dolok Masihul District grade IV, V, and VI primary school pupils, 2) Knowing the impact of child-friendly school-based reflective modules on numeracy literacy abilities and self-confidence in Dolok Masihul District grade IV, V, and VI primary school pupils.
 Keywords: Literacy, numeracy, tutoring, improvement

Reconfigurable Intelligent Surface-Aided Quadrature Reflection Modulation for Simultaneous Passive Beamforming and Information Transfer

Reflection modulation based on reconfigurable intelligent surface (RIS) is considered to be a promising information transfer mechanism, which does not require any additional radio frequency chains. However, existing reflection modulation schemes consider manipulating the ON/OFF states of RIS elements, which may result in some power loss. In this paper, we propose a new scheme, called RIS-aided quadrature reflection modulation (RIS-QRM), for better utilizing the reflection power in RIS-aided downlink multiple-input single-output (MISO) wireless systems. To this end, RIS-QRM partitions the RIS elements into two subsets in order to reflected the incident signals towards two orthogonal directions by using passive beamforming and encodes its local data onto the two partitions. A closed-form expression for the unconditional pairwise error probability of RIS-QRM in Rician fading is derived assuming maximum-likelihood detection at the receiver. Moreover, a low-complexity detection method that decouples the joint search of the constellation symbol and the RIS element partition is proposed. Computer simulation results corroborate the effectiveness of RIS-QRM and validate the analytical results. It is shown that RIS-QRM improves the error performance of the additional bits delivered by the RIS without deteriorating the error performance of the bits modulated on the constellation symbol, as compared to ON/OFF-based RIS-aided schemes.

Advantages of External Reflection and Transflection over ATR in the Rapid Material Characterization of Negatives and Films via FTIR Spectroscopy.

The identification of film support material is of utmost importance for evidence-based collection management in cultural heritage institutions, especially the identification of cellulose nitrate for fire safety reasons, as nitrate is highly flammable and deteriorates over time. Cellulose nitrate film was used by photographers and movie filmmakers from its release in the 1880s to the 1950s. Cellulose acetate, being called safety film, gradually began to replace cellulose nitrate, as it is not flammable. Despite its non-flammable properties, cellulose acetate also deteriorates in hazardous ways. Therefore, identification of cellulose nitrate and cellulose acetate in collections is imperative for preservation and risk management to collections and humans. Large photographic collections can easily contain several thousand negatives or more, so a rapid, non-invasive and reliable method is needed. Traditional identification methods, such as destructive chemical tests, are sometimes unreliable, and spectroscopic analyses are normally time-consuming. To overcome these issues, rapid material characterization was performed in transflection mode with a Fourier-transform infrared (FTIR) spectrometer equipped with an external reflectance module and an additional aluminum-foil reflector. With this newly developed method, the support material (cellulose nitrate, cellulose acetate and polyester) of about 99.8% of all films can be determined within two seconds of measuring time, without any further spectral processing. Very distinctive spectral patterns are obtained with this new method, regardless of which side of the film is being analyzed. A simple visual inspection of the raw spectrum is usually sufficient to determine the film support identity. A detailed comparison of the various FTIR techniques shows the advantages of the transflection measurement for the material characterization of film support layers. This newly developed method enables the non-invasive, rapid and unambiguous material identification of even large film collections in a short time.

Optically Modulated Passive Broadband Daytime Radiative Cooling Materials Can Cool Cities in Summer and Heat Cities in Winter

Broadband passive daytime radiative cooling (PDRC) materials exhibit sub-ambient surface temperatures and contribute highly to mitigating extreme urban heat during the warm period. However, their application may cause undesired overcooling problems in winter. This study aims to assess, on a city scale, different solutions to overcome the winter overcooling penalty derived from using PDRC materials. Furthermore, a mesoscale urban modeling system assesses the potential of the optical modulation of reflectance (ρ) and emissivity (ε) to reduce, minimize, or reverse the overcooling penalty. The alteration of heat flux components, air temperature modification, ground and roof surface temperature, and the urban canopy temperature are assessed. The maximum decrease of the winter ambient temperature using standard PDRC materials is 1.1 °C and 0.8 °C for daytime and nighttime, respectively, while the ρ+ε-modulation can increase the ambient temperature up to 0.4 °C and 1.4 °C, respectively, compared to the use of conventional materials. Compared with the control case, the maximum decrease of net radiation inflow occurred at the peak hour, reducing by 192.7 Wm−2 for the PDRC materials, 5.4 Wm−2 for ρ-modulated PDRC materials, and 173.7 Wm−2 for ε-PDRC materials; nevertheless, the ρ+ε-modulated PDRC materials increased the maximum net radiation inflow by 51.5 Wm−2, leading to heating of the cities during the winter.

Attosecond electronic delay response in dielectric materials.

The advancement in the attosecond field and the generation of XUV attosecond pulses has enabled the study of electron dynamics in the solid-state by high harmonic generation spectroscopy. Here, we introduce new all-optical attosecond metrology to study the light-field induced electron dynamics in dielectric systems. This new methodology is based on the phase transition of a dielectric material due to its interaction with a strong light field. Hence, the charge carriers undergo an inter- and intraband transition, causing a modification in the electronic structure, dielectric constant, and optical properties of the dielectric system. Consequently, the dielectric material experiences an adiabatic semi-metal phase transition due to the strong polarizability. Therefore, the reflectivity of the dielectric system changes, following the shape of the pump field. Accordingly, the time-resolved reflectivity change measurement provides direct access to the phase transition and the related electronic dynamics of the system in real-time. In the reported experiment, a strong light field (pump pulse) induces the phase transition and modifies the fused silica sample's reflectivity, which is probed by another weak light field (probe pulse). The reflected probe beam spectrum is acquired as a function of the time delay between the pump and probe pulses. This measurement shows that the real-time phase transition dynamic (and reflectivity change) follows the pump field shape. Moreover, the reflectivity measurements have been recorded at different pump field strengths performed under the same conditions. The reflectivity trace shows a retardation phase delay at a higher driver field strength. The delay response-retrieved from the recorded reflectivity traces-is in the order of a few hundred attoseconds. In addition, the results show that the delay response monotonically increases as the trigger field escalates. Furthermore, the reflectivity measurements have been acquired for another dielectric system (CaF2). The electronic delay response shows the same linear behavior increase as that of the SiO2 system. This work establishes a universal new attosecond metrology for measuring the electron dynamics and delay response in different materials.

Continuously Geometric Phase Modulation by using a reflective liquid crystal structure

Distinguished from the dynamical phase gained by optical path difference, the geometric phase (GP) is an additional phase delay produced by the variation of polarization states when light propagates in an anisotropic medium. Its modulation amount does not depend on the thickness of the medium or the wavelength of the light, therefore, it is expected to realize smaller and faster phase modulation unit. Based on the principle that the geometric phase generated by two passes through a wave plate of circularly polarized light with the same rotation direction is four times the rotation angle of optical axis of the wave plate, a reflective phase modulation structure composed of an In-plane Switching (IPS) liquid crystal (LC) cell, a mirror and two quarter wave plates is proposed in this paper. Under the action of IPS electrodes, the LC director can rotate nearly 80°in-plane to realize a 320°GP modulation. Finite Difference Time Domain (FDTD) method is used to simulate the GP modulation, and an optical path for interferometric measurement is built. The experimental results are in good agreement with the simulation results. This method uses only a single layer of driving electrodes and a LC cell to achieve 320°GP modulation, which avoids the alignment problem and provides a new idea for the spatial light dynamic modulator.

Bloch Surface Wave‐Assisted Ultrafast All‐Optical Switching in Graphene

AbstractGraphene has ultrafast charge carrier dynamic and shows strong light–matter interaction allowing the use in photovoltaic devices, fast photodetectors, saturable absorbers, and electro‐optical modulators. However, despite the high nonlinear optical susceptibilities, the small amount of material significantly limits the use of graphene for nonlinear optical applications. In this work, Bloch surface waves (BSWs) are employed, enhancing the graphene–light interaction, for all‐optical switching realization. By placing a graphene monolayer on top of a 1D photonic crystal, it is shown that for the wavelength corresponding to the BSW resonance, the reflection coefficient is modulated on the sub‐picosecond time scale by an order of magnitude larger than that for bare graphene. The magnitude of the reflection change reaches 0.3% at the fluence of 40 µJ cm−2. The reported results are proof of priciple possibility of BSW‐assisted enhancing the reflection modulation of any 2D materials and transparent thin films while maintaining their inherent ultrafast dynamics, which is useful for the further development of all‐optical switches.

Star-Shaped Wheel for Mechanical Micro-Doppler Modulation

This letter investigates the possibility of using deliberated geometries for rotating targets, which may improve the detectability and classification by means of its micro-Doppler signature. Beyond the signature provided by the rotation rate of the target, every particular geometry leads to specific and unique modulation waveforms that increase the information related to this target. Different star-shaped wheels with particular geometries have been designed demonstrating different reflection characteristics and modulation waveforms. The signature of these rotating star-shaped wheels has been measured in an anechoic chamber using a general-purpose 24 GHz frequency-modulated continuous wave (FMCW) radar platform and a detection algorithm based on the derivative of the cross-correlation is proposed to validate the proposed approach.

Modulating visible-near-infrared reflectivity in ultrathin graphite by reversible Li-ion intercalation

Two-dimensional materials with optical turnability have wide prospect in related applications such as electrochromic coating and thermal camouflage. Here we report a Li-intercalated ultrathin graphite device with tunable visible-near-infrared reflectivity. After Li-ion intercalation, the Fermi surface of ultrathin graphite will move to a higher level, which prevents the interband optical transitions below it. Therefore, it is possible to change the absorptivity or emissivity of ultrathin graphite through reversible Li-ion intercalation, which accomplishes the modification to reflectivity indirectly. In our experiment, the strong fluorescence background and Peak shifts in Raman spectra, as well as the enlarged layer spacing in XRD spectra, together confirmed that Li-ions were successfully intercalated into the graphite layers. The relative reflectivity of ultrathin graphite increased sharply in a wide range from 460 nm to 1500 nm after complete Li-ion intercalation. At a typical near-infrared wavelength 1500 nm for instance, the relative reflectivity is 0.28 for pristine graphite while 0.70 for fully lithiated graphite. Such reversible intercalated modulation in visible-near-infrared reflectivity of ultrathin graphite might provide a new way to design electrochromic coating, thermal camouflage or radar stealth systems, which also promotes further understanding and optical applications of graphene and other 2D materials. • Systematic investigation into visible-near-infrared reflectivity modulation of intercalated ultrathin graphite. • The relative reflectivity of ultrathin graphite increased sharply in a wide wavelength range after Li-ion intercalation. • Such prominent modulation of ultrathin graphite might be ascribed to uplifted Fermi level in intercalated graphene layers.

Addressing learner anxiety via reflective practice.

Medical students experience anxiety when learning the pelvic, breast and male genitourinary exam (also known as sensitive physical exams). Reflection can help students process emotionally challenging learning experiences and help give those experiences meaning. We describe the development of a reflection module to enhance reflection during sensitive exam instruction. We developed this module following Kern's Six Step Method for curriculum development, including a targeted needs assessment. Informed by educational reflection theory, the module addressed all elements of reflection. The module was optional, asynchronous and administered online, requiring minimal administrative support. Prior to sensitive exam instruction, participants identified goals and values and named emotions. Following exam instruction, participants again named their emotions and then self-evaluated whether they had met their goals and upheld their values. Participants found the module to be a useful modality to reflect. Most notably, they identified the naming of emotions, goals and values clarification and the opportunity to reflect both prior to and after an educational experience as helpful. Younger students found the module particularly helpful. An online, low-resource, asynchronous reflection module is feasible and can be a way for students to reflect on challenging learning experiences. In addition to using with sensitive exam instruction, the module can be applied to activities such as anatomic dissection, ethics workshops or clinical learning.

Damage characteristics of a triple-junction GaAs cell with a subwavelength structured antireflective film

A theoretical model of temperature and stress damage of a triple-junction GaAs solar cell with a conical subwavelength structure antireflection film is proposed to analyze the influence of subwavelength structure on damage characteristics. The distribution of temperature and stress under different cone structure parameters are calculated. Results show that the subwavelength structure will significantly modulate the light field, temperature field, and stress field inside the solar cell. Under the simultaneous influence of reflectivity and conical structure modulation, the melting damage and stress damage thresholds reach the minimum values of 2.485 × 10 7 and 0.49 × 10 7 W / c m 2 when the cone height and bottom diameter are 500 and 750 nm, respectively.

Performance Enhancement of All-Inorganic Carbon-Based CsPbIBr2 Perovskite Solar Cells Using a Moth-Eye Anti-Reflector.

All-inorganic carbon-based CsPbIBr2 perovskite solar cells (PSCs) have attracted increasing interest due to the low cost and the balance between bandgap and stability. However, the relatively narrow light absorption range (300 to 600 nm) limited the further improvement of short-circuit current density (JSC) and power conversion efficiency (PCE) of PSCs. Considering the inevitable reflectance loss (~10%) at air/glass interface, we prepared the moth-eye anti-reflector by ultraviolet nanoimprint technology and achieved an average reflectance as low as 5.15%. By attaching the anti-reflector on the glass side of PSCs, the JSC was promoted by 9.4% from 10.89 mA/cm2 to 11.91 mA/cm2, which is the highest among PSCs with a structure of glass/FTO/c-TiO2/CsPbIBr2/Carbon, and the PCE was enhanced by 9.9% from 9.17% to 10.08%. The results demonstrated that the larger JSC induced by the optical reflectance modulation of moth-eye anti-reflector was responsible for the improved PCE. Simultaneously, this moth-eye anti-reflector can withstand a high temperature up to 200 °C, and perform efficiently at a wide range of incident angles from 40° to 90° and under various light intensities. This work is helpful to further improve the performance of CsPbIBr2 PSCs by optical modulation and boost the possible application of wide-range-wavelength anti-reflector in single and multi-junction solar cells.

Asymmetric all-dielectric active metasurface for efficient dual reflection modulation

Active metasurface provides an efficient way to achieve optical response in the subwavelength range, dielectric metasurface has attracted much attention due to its low-loss mode and excitable electric/magnetic resonance mode, resulting in a far wider range of applications. However, the resonance spectrum is relatively broad due to the strong radiative loss of the symmetric dielectric metasurface, which limits its application in large modulation extinction ratio. Hence, an active metasurface integrated with the phase change material Ge2Sb2Te5 (GST) is proposed. The active metasurface can support the symmetry-protected quasi bound states in the continuum (QBIC) and excite resonance modes with extremely high quality-factors. As an active medium, the GST layer undergoes a transition from the amorphous state to the crystalline state when the temperature increases, leading to a change in the amplitude/phase of the reflection spectrum. It is demonstrated that dual reflection modulation and the figure-of-merit (FoM) can reach up to 92.0% at the wavelength of 1.45 μm and 92.5% at the wavelength of 1.52 μm as the GST layer is in the middle of nanodisks. An extremely high FoM of 98.5% is also realized when the surface of silicon nanodisks is coated with the GST layer. In addition, the modulation mechanism of the optical response of the active metasurface has been investigated, which is of great significance to the design of the active metasurface. The proposed active all-dielectric asymmetric metasurface has a huge potential in tunable nonlinear optical devices.

Reconfigurable plasmonic nanoslits and tuneable Pancharatnam-Berry geometric phase based on electromechanical nano-kirigami [Invited

Reconfigurable three-dimensional (3D) nanostructures possess additional spatial freedom and rich physical characteristics compared with their two-dimensional (2D) counterparts. Here we demonstrate a facile and automated nano-kirigami method to create the 3D deformed spiral metasurfaces, which can flexibly manipulate optical waves by simply applying external voltages. Through etching Archimedean spirals into Au/SiO2/Si layer, multi-order localized surface plasmon resonances are excited within the spiral nanoslits and are dynamically tuned by floating the nanopatterns and employing the electrostatic forces, which induces a reflection modulation contrast as high as 189%. The 2D-to-3D transformation induces a strong modification of the optical chirality in both aspects of spatial distributions and strength. Importantly, the Pancharatnam-Berry (PB) geometric phase can be carefully designed and dynamically broken in the 2π range by rotating the direction of the spiral units, which results in the dynamic construction and erasing of metasurface holograms. The proposed scheme of tuning plasmonic nanoslits and breaking PB geometric phase by employing the electromechanical deformation provides a new degree of freedom for reconfigurable photonic systems, as well as dynamic applications in quasi-flat optical platforms.

An exploratory study of a work-based learning reflection module and the potential links between student attendance and engagement and student success as an indication of the mastery of reflection

ABSTRACT Reflection is pivotal in Work-Based Learning to enable learning to be gained from experience. Effective reflection also aids self-efficacy and agency. However, more can be known regarding how reflection works in Work-Based Learning contexts and whether attendance, engagement, age and gender are important factors. An exploratory archival research complimented with an unstructured interview was conducted with a class of 27 business students studying a module on reflection on a Work-Based Learning programme. Descriptive statistics and a thematic analysis revealed that the probability of mastering reflection depended upon more than six weeks attendance as well as active engagement in reflective activities. Receiving feedback on journal entries enhanced understanding and application. Women were more likely to engage in feedback opportunities.

Electrochemical Impedance Imaging on Conductive Surfaces

Electrochemical impedance spectroscopy (EIS) is a powerful tool to measure and quantify the system impedance. However, EIS only provides an average result from the entire electrode surface. Here, we demonstrated a reflection impedance microscope (RIM) that allows us to image and quantify the localized impedance on conductive surfaces. The RIM is based on the sensitive dependence between the materials' optical properties, such as permittivity, and their local surface charge densities. The localized charge density variations introduced by the impedance measurements will lead to optical reflectivity changes on electrode surfaces. Our experiments demonstrated that reflectivity modulations are linearly proportional to the surface charge density on the electrode and the measurements show good agreement with the simple free electron gas model. The localized impedance distribution was successfully extracted from the reflectivity measurements together with the Randles equivalent circuit model. In addition, RIM is used to quantify the impedance on different conductive surfaces, such as indium tin oxide, gold film, and stainless steel electrodes. A polydimethylsiloxane-patterned electrode surface was used to demonstrate the impedance imaging capability of RIM. In the end, a single-cell impedance imaging was obtained by RIM.

Lock-in thermoreflectance as a tool for investigating spin caloritronics

We report lock-in thermoreflectance (LITR) measurements of spin-caloritronic phenomena in magnetic hybrid structures. In the LITR measurements, the temperature modulation signals due to the spin Peltier effect (SPE) and anomalous Ettingshausen effect (AEE) were detected through the temperature dependence of the optical reflectivity of the sample surface. By using the lock-in technique, the reflectivity modulation in response to an alternating charge current applied to the samples can be detected sensitively, which allows us to clarify the transient responses of the SPE and AEE and gives a clue to separate these phenomena. We applied this method to a junction system comprising a ferromagnetic metal film formed on a magnetic insulator substrate and found that the transient response unique to the SPE can be observed even when the SPE and AEE coexist. We also checked that the lock-in signals of the reflected light intensity exhibit no light polarization rotation; the observed temperature modulation is free from parasitic magneto-optical effects. The SPE and AEE can thus be measured not only by the conventional laser-based LITR but also by light-emitting-diode-based LITR, which enables versatile and cost-effective measurements.

Magnetic Control of Optical Reflectance from Metallic Thin Film Using Surface Plasmon Resonance and Faraday Rotation.

We demonstrate magnetic control of optical reflectance with no ferromagnetic material via combining the Faraday rotation and the surface plasmon resonance (SPR) in a Kretschman configuration under magnetic fields < 0.5 T. The SPR produces the polarization sensitive reflectance from the Au or Ag thin film coated on a N-BK7 prism in which the Faraday rotation occurs. The gold (Au) or silver (Ag) metal film as a plasmonic film somewhat acts as an incident angle-dependent reflection polarizer that can sensitively sense the polarization change induced by the Faraday rotation that occurs in a prism. We find that combination of Faraday rotation and the surface plasmon can induce a significant magnetic modulation of reflectance normalized with respect to that obtained with no magnetic fields at a specific incident angle of light. The magnetic control of optical reflectance presented may find an application in polarizer-free photonic devices with no ferromagnetic material for magneto-optical modulation.

Examining the Necessity of Reflective Module: Literacy Numeracy Skill of Students Elementary School

The research aims to describe the need for reflective modules in building literacy skills of primary school students. The research used a quantitative descriptive method. The population was the fifth-grade primary school students that implement the 2013 curriculum with A accreditation—the data collection technique used non-test with observation instruments, questionnaires, interview guidelines, and literature review. The sample was taken using a purposive random sampling technique. The sample in this study was 126 students. The results showed that students and teachers need a reflective module to build numeracy literacy. The reflective module has the potential to build numeracy literacy skills. Literacy skill is closely related to reflective thinking processes, in which reflective thinking is a critical thinking process for making an assessment. Self-assessment aims to measure the extent of an individual's abilities to encourage the individual to develop self-potential.

Bio-inspired electrochromic skin based on tungsten oxide

Some animals, such as the chameleon, have great capability of camouflage by changing their skin color to avoid detection. This outstanding property have inspired researchers to develop the ability of the materials and devices to mimic chameleon for applications in intelligent wearable and camouflage devices. Tungsten oxide (WO3), switching between blue and transparent, is widely studied due to its large optical modulation but it is difficult to obtain multicolor and flexibility. Here, we design a bio-inspired chameleon skin electrochromic device (ECD) assembled by inorganic electrochromic materials WO3, which can achieve the reversible color changes from yellow, light green to dark green according to subtractive color mixture theory. The flexible ECD exhibits a high optical reflectance modulation of 38.9% at voltage of ± 1.5 V in the wavelength range of 250–2500 nm. Fast response speed of 0.32 s for both coloring and bleaching process is obtained which can be attributed to the porous structure of the WO3 electrochromic layer. The ECD keeps excellent electrochromic performance even under bending conditions, indicating the great flexibility. The inorganic bio-inspired chameleon skin ECD opens new avenues for the design of intelligent and wearable devices.