Submillisecond Response Time Research Articles

The Role of AI/ML in Enhancing Security and Fraud Detection in Digital Payments

As digital payment systems continue to evolve and gain widespread adoption, the need for robust security measures and effective fraud detection mechanisms has become paramount. This article explores the transformative role of Artificial Intelligence (AI) and Machine Learning (ML) in revolutionizing fraud detection and prevention within the digital payment ecosystem. Through comprehensive analysis of implementation strategies and performance metrics, we demonstrate how AI-powered solutions achieve fraud detection rates of up to 99.9% while maintaining false positive rates below 0.1%. The article reveals that modern fraud detection systems must process transaction volumes exceeding 100,000 per second during peak periods, with real-time decision-making latency under 50 milliseconds. Integration of advanced ML models, including deep learning and federated learning approaches, has shown a 50% reduction in fraud losses within the first year of deployment. Our analysis of stream processing architectures and edge computing implementations demonstrates how organizations can achieve sub-millisecond response times while maintaining regulatory compliance. As global digital transaction values are projected to reach $8.26 trillion by 2024, these AI/ML solutions prove crucial in combating sophisticated fraud attempts, which are expected to reach $38.5 billion by 2027. The study examines specific case studies, algorithms, and models, demonstrating how AI-powered solutions offer more accurate, efficient, and adaptive mechanisms to safeguard digital transactions while maintaining system performance and user experience.

Scattering-Free and Fast Response Polymer Brush-Stabilized Liquid Crystals Beam Steering Using Surface-Initiated Polymerization Technique.

Nonmechanical fast response optical beam steering technology is increasingly essential for telecommunications, imaging systems, optical sensing, displays, and military applications. Polymer network liquid crystal (PNLC) beam steering can achieve submillisecond response times but faces limitations due to scattering issues arising from the refractive index mismatch between the polymer network and the liquid crystals (LCs). In this article, we demonstrate a scattering-free, fast-response LC beam steering by using polymer brushes to stabilize the gradient refractive index. First, the initiator is incorporated into the alignment layer and the monomer is mixed into the LC layer. Surface-initiated polymerization (SIP) is then employed to grow the polymer brushes exclusively on the substrate's surface, thus confining the polymer network's growth to the LC bulk and reducing interfacial scattering. For polymer brush stabilized liquid crystal (PBSLC) beam steering device with a period size of 225 μm and a cell gap of 7.2 μm, the average transmission rate reaches 88% in the visible light spectrum with a haze value of only 6.91. The steering angle is 0.16, and the diffraction efficiency is 80.3%. When a voltage of 35 Vrms is applied, the primary energy can be tuned to the zeroth order, with a response time close to 1 ms. By cascading two PBSLC beam steering devices with opposite steering directions, the primary energy of the beam can be adjusted between zeroth, +1, and -1 order. This method requires only a UV light source, a precision displacement stage, a power supply, and a mask, avoiding the need for expensive equipment and complex electrode fabrication. By adjustment of the phase change period, step width, and number of steps during fabrication, the steering angles and diffraction efficiency of the PBSLC beam steering device can be easily controlled, highlighting its significant potential for industrial production.

Submillisecond Electric Field Sensing with an Individual Rare-Earth Doped Ferroelectric Nanocrystal.

Understanding the dynamics of electrical signals within neuronal assemblies is crucial to unraveling complex brain functions. Despite recent advances in employing optically active nanostructures in transmembrane potential sensing, there remains room for improvement in terms of response time and sensitivity. Here, we report the development of such a nanosensor capable of detecting electric fields with a submillisecond response time at the single-particle level. We achieve this by using ferroelectric nanocrystals doped with rare-earth ions that produce upconversion (UC). When such a nanocrystal experiences a variation of surrounding electric potential, its surface charge density changes, inducing electric polarization modifications that vary, via a converse piezoelectric effect, the crystal field around the ions. The latter variation is finally converted into UC spectral changes, enabling optical detection of the electric potential. To develop such a sensor, we synthesized erbium and ytterbium-doped barium titanate crystals of ≈160 nm in size. We observed distinct changes in the UC spectrum when individual nanocrystals were subjected to an external field via a conductive atomic force microscope tip, with a response time of 100 μs. Furthermore, our sensor exhibits a remarkable sensitivity of 4.8 kV/cm/, enabling time-resolved detection of a fast-changing electric field of amplitude comparable to that generated during a neuron action potential.

5CB-doped polymer-stabilised sphere-phase liquid crystal smart window with fast response and high transmittance

ABSTRACT Smart windows have become increasingly popular due to their ability to provide privacy protection, energy efficiency, and user control. Therefore, this technology has a wide range of applications in various fields such as construction, automotive, aviation, and renewable energy. However, commercialisation faces two significant challenges due to the slow response speed and low transmittance. This work demonstrates a 5CB-doped polymer-stabilised sphere-phase liquid crystal (PS-SPLC) smart window with sub-millisecond response time, which can be switched between transparent and scattering states by an electric field. The transmittance exceeds 90% when the voltage is on in the visible light range. This 5CB-doped PS-SPLC smart window has the potential to usher in a new era of smart window research.

Exploring 6G Wireless Communication: Application Technologies, Challenges and Future Direction

The data traffic has increased significantly along with the quick development of smart wireless technologies, and current 5G networks are still not completely prepared to handle future huge data traffic in the areas of services, data transfer, data storage, and processing. 6G is expected to offer very high-level extended 5G capabilities, such as a Tbps data transfer rate and a sub-millisecond response time. The main objective of this study is to be aware of new technologies being enhanced day by day and provide existing research content, issues, and directions for the future regarding 6G wireless networks. Therefore, a systematic literature review of research articles is provided by categorizing the selected studies published between 2019 and 2022 in terms of enabling technologies. First, the researcher discussed the need for 6G by predicting the explosive growth of mobile traffic from 2022 to 2030. Second, 6G requirements, trends, and services are addressed and contrasted with 5G in terms of a group of key performance indicators. Third, conduct a comparative analysis of 6G challenges and gaps, such as security and privacy, the need for a decentralized network, Omnipresent service coverage, and storage efficiency. So, it is essential to develop an accurate, faster, and well-organized system for the 6G wireless network. We have presented an efficient and secure mode R6GS, which combines blockchain and 6G to improve security from the lower to upper layers while also improving storage efficiency. Cybertwin technologies are used at the edge layer of the 6G network in the proposed model R6GS to improve security. The smart contracts, IPFS and Ethereum blockchain are used in the proposed R6GS model to enhance the 6G network's data integrity and data storage. It also processes and stores massive amounts of data at various network layers, which removes the large storage capacity issue of traditional P2P and Client/Server (C/S) networks due to centralized servers in 6G technology. For the performance evaluation, the model is evaluated through expert opinion. Moreover, the proposed R6GS model also improves time efficiency through the edge layer, because if a task is available at the edge layer, there is no need to send a request to the core layer. The server at the edge layer efficiently delivers data to end nodes. Furthermore, a taxonomy is presented in this study. To the best of our knowledge, the proposed methodology worked efficiently.

52‐4: Distinguished Student Paper: Switchable polarization volume gratings for augmented reality waveguide displays

A new electrically driven polymer stabilized polarization volume grating (PVG) is developed. Such a switchable PVG exhibits submillisecond response time, large range of diffraction efficiency modulation, and high see‐through quality. Its potential applications, including significantly suppressed rainbow effect and enhanced light efficiency for a waveguide‐based augmented reality display are demonstrated.

Switchable polarization volume gratings for augmented reality waveguide displays

AbstractA new electrically driven polymer‐stabilized polarization volume grating (PVG) is developed. The diffraction efficiency can be modulated by a vertical electric field. A small amount of liquid crystal monomer is doped into the host cholesteric liquid crystal to form a stabilized polymer network to make the unwinding process reversible. The fabricated device exhibits submillisecond response time, a large range of diffraction efficiency modulation, and clear see‐through capability. Some potential applications are demonstrated, including a significantly suppressed rainbow effect, enhanced light efficiency, and expanded field of view for a waveguide‐based augmented reality display. The unique properties and benefits of switchable PVGs could open a new space in near‐eye display research, especially novel optical systems for augmented reality waveguide displays.

Electrically tuned active metasurface towards metasurface-integrated liquid crystal on silicon (meta-LCoS) devices.

Active metasurfaces add a new dimension to static metasurfaces by introducing tunability, and this has received enormous attention from industry. Although various mechanisms have been proposed over the past few years in literature, solutions with good practicality are limited. Liquid crystal (LC)-based active metasurface is one of the most promising approaches due to the well-established LC industry. In this paper, an electrically tunable active metasurface was proposed and experimentally demonstrated using photoaligned nematic LC. The good quality of the LC photoalignment on the metasurface was demonstrated. Tunable transmission was obtained for telecommunication C band and the modulation depth in transmission amplitude of 94% was realized for 1530 nm. Sub-millisecond response time was achieved at operating a temperature of 60°C. The progress made here presents the potential of LC-based active metasurfaces for fast-switching photonic devices at optical communication wavelengths. More importantly, this work lays the foundations for the next-generation liquid crystal on silicon (LCoS) devices that are integrated with metasurfaces (meta-LCoS).

Research Progress on Blue-Phase Liquid Crystals for Pattern Replication Applications.

Blue-Phase Liquid Crystals (BPLCs) are considered to be excellent 3D photonic crystals and have attracted a great deal of attention due to their great potential for advanced applications in a wide range of fields including self-assembling tunable photonic crystals and fast-response displays. BPLCs exhibit promise in patterned applications due to their sub-millisecond response time, three-dimensional cubic structure, macroscopic optical isotropy and high contrast ratio. The diversity of patterned applications developed based on BPLCs has attracted much attention. This paper focuses on the latest advances in blue-phase (BP) materials, including applications in patterned microscopy, electric field driving, handwriting driving, optical writing and inkjet printing. The paper concludes with future challenges and opportunities for BP materials, providing important insights into the subsequent development of BP.

Supramolecular Tools for the Stabilisation of Blue-Phase Liquid Crystals

Blue phases (BPs), a unique manifestation of chirality in the liquid crystalline state, have gained considerable attention due to the unusual combination of properties such as sub-millisecond response times to electrical fields and Bragg reflection of circularly polarised light. Initially they were regarded as promising materials for the development of the next-level display technologies. However, in recent years, they have gained increasing attention as responsive photonic materials with sensing or optoelectronics properties (photonic mirrors and filters). A major limitation so far has been their narrow temperature range in which they usually exist. The aim of the present review is to summarise the recent efforts made to stabilise BPs by employing specific non-covalent bonds and the principles of supramolecular chemistry.1 Introduction2 Stabilisation of Blue Phases by Supramolecular Methods2.1 Doping Approach2.2 Design Approach3 Conclusions and Outlook

Elastic Instability of Cubic Blue Phase Nano Crystals in Curved Shells.

Many crystallization processes, including biomineralization and ice-freezing, occur in small and curved volumes, where surface curvature can strain the crystal, leading to unusual configurations and defect formation. The role of curvature on crystallization, however, remains poorly understood. Here, we study the crystallization of blue phase (BP) liquid crystals under curved confinement, which provides insights into the mechanism by which BPs reconfigure their three-dimensional lattice structure to adapt to curvature. BPs are a three-dimensional assembly of high-chirality liquid crystal molecules arranged into body-centered (BPI) or simple cubic (BPII) symmetries. BPs with submicrometer cubic-crystalline lattices exhibit tunable Bragg reflection and submillisecond response time to external stimuli such as an electric field, making them attractive for advanced photonic materials. In this work, we have systematically studied BPs confined in spherical shells with well-defined curvature and boundary conditions. The optical behavior of shells has also been examined at room temperature, where the cholesteric structure forms. In the cholesteric phase, perpendicular anchoring generates focal conic domains on the shell's surface, which transition into stripe patterns as the degree of curvature increases. Our results demonstrate that both higher degrees of curvature and strong spatial confinement destabilize BPI and reconfigure that phase to adopt the structure and optical features of BPII. We also show that the coupling of curvature and confinement nucleates skyrmions at greater thicknesses than those observed for a flat geometry. These findings are particularly important for integrating BPs into miniaturized and curved/flexible devices, including flexible displays, wearable sensors, and smart fabrics.

Fast-Response Flexible Temperature Sensors with Atomically Thin Molybdenum Disulfide.

Real-time thermal sensing on flexible substrates could enable a plethora of new applications. However, achieving fast, sub-millisecond response times even in a single sensor is difficult, due to the thermal mass of the sensor and encapsulation. Here, we fabricate flexible monolayer molybdenum disulfide (MoS2) temperature sensors and arrays, which can detect temperature changes within a few microseconds, over 100× faster than flexible thin-film metal sensors. Thermal simulations indicate the sensors' response time is only limited by the MoS2 interfaces and encapsulation. The sensors also have high temperature coefficient of resistance, ∼1-2%/K and stable operation upon cycling and long-term measurement when they are encapsulated with alumina. These results, together with their biocompatibility, make these devices excellent candidates for biomedical sensor arrays and many other Internet of Things applications.

Observation and simulation of toron polymorphism: Effects of surface anchoring, elasticity and electric field in cholesterics with smectic-A phase beneath

Toron is one of the fundamental chiral topological textures appearing in many spintronic and soft matter systems. Here we report on the observation of torons in cholesteric liquid crystals with positive dielectric anisotropy (Δε > 0). In addition, the materials show smectic-A phase beneath the cholesteric phase, enabling us to see the pretransitional effect on the formation of the torons. In detail, we investigated the relation of toron formability and the external stimuli in terms of temperature and electric field. Importantly, the divergence of the elastic constants (K22 and K33) in the vicinity of the nematic-smectic-A phase transition causes the transition from the toron to the homeotropic alignment. The results reveal that both the homeotropic anchoring strength and the frustrated confinement of the cholesteric helix are important to determine whether the toron texture is selected among other textures like fingers. The confinement ratio, i.e. the ratio of cell thickness to cholesteric pitch, for the incidence of torons was found to be in a wide range of about 0.82 ∼ 1.5. We also show that the torons can be polymer-stabilized so that they retain over a wide temperature window. Even more importantly, the orientational state of the polymer-stabilized toron can be changed by an electric field, realizing fast switching between the dark and bright states. The system may find applications in electric-driven diffraction gratings or privacy protection films with a sub-millisecond response time.

Sub-millisecond switching of multi-level liquid crystal on silicon spatial light modulators for increased information bandwidth.

Sub-millisecond response time with a refresh rate higher than 2000 frames per second (fps) and no degradation of the contrast ratio or diffraction efficiency is demonstrated in working liquid crystal on silicon (LCOS) spatial light modulators (SLMs) with 8-bit grey levels of amplitude and phase modulations. This makes possible to achieve an information bandwidth of about 190 Gb s-1 with a 4k LCOS operating at 10-bit phase modulation levels. The normalised contrast stays at almost the unit level for a frame rate up to 1700 fps and at higher than 0.9 for 2500 fps. The diffraction efficiency stays above -1.0 dB for a frame rate up to 2400 fps. Such a fast response allows us to eliminate image blurring in replaying a fast movie.

Ferroelectric liquid crystal with sub-wavelength helix pitch as an electro-optical medium for high-speed phase spatial light modulators

Deformed-helix ferroelectric liquid crystals (DHFLCs) with sub-wavelength helix pitch usually demonstrate sub-millisecond electro-optical response time, but they cannot provide pure phase modulation. However, here, it is shown experimentally that the planar aligned 50 μm thick layer of ferroelectric liquid crystal (FLC) mixture can be used as an electro-optical medium for the phase spatial light modulators (SLMs) if the mixture exhibits smectic C* phase (SmC*) with the helix pitch around 100 nm or less and operates in DHFLCs electro-optical mode. The electrically controlled spiral phase plate (SPP) was constructed on the base of non-chiral biphenylpyrimidines as liquid crystal smectic C matrix and trifluoromethylalkyl diester of p-terphenyldicarboxylic acid as a non-mesogenic chiral dopant. This SPP is able to form and reconfigure the vortex light fields at the frequency up to 3 kHz that was not yet achieved using known liquid crystal spatial light modulators.

Pupil plane actuated remote focusing for rapid focal depth control.

Laser scanning is widely employed in imaging and material processing. Common laser scanners are often fast for 2D transverse scanning. Rapid focal depth control is highly desired in many applications. Although remote focusing has been developed to achieve fast focal depth control, the implementation is limited by the laser damage to the actuator near laser focus. Here, we present a new method named pupil plane actuated remote focusing, which enables sub-millisecond response time while avoiding laser damage. We demonstrate its application by implementing a dual-plane two-photon laser scanning fluorescence microscope for in vivo recording of calcium transient of neurons in mouse neocortex.

Electrically modulated varifocal metalens combined with twisted nematic liquid crystals.

Focus-tunable lenses are indispensable to optical systems. This paper proposes an electrically modulated varifocal metalens combined with twisted nematic liquid crystals. In our design, a metalens is employed to focus on different points depending on the polarization state of incident light. We demonstrated that the varifocal metalens has a sub-millisecond response time. Furthermore, the numerical aperture of both the first and second focal points can be customized to achieve a wide range of 0.2-0.7. Moreover, the full width at half maximum approached the diffraction limit at multiple focal points. Because of the advantages of our proposed electrically modulated metalens, it has the potential for application in optical technology and biomedical science, both of which require high image quality and a rapid response time.

Phascope: Fine-Grained, Fast, Flexible Motion Profiling based on Phase Offset in Acoustic OFDM Signal

Acoustic Doppler shift estimation is a cost-effective way to implement Human-Computer Interaction applications across existing smart devices such as smart phones and smart spekaers. However, due to the inherent uncertainty principle in the traditional time-frequency analysis, it remains challenging to profile motions accurately and timely. In this paper, phase offset in acoustic OFDM signal is leveraged for developing Phascope, a fine-grained, fast and flexible motion profiling scheme. We evaluate Phascope using simulation and experiment on COTS devices. Sub-millisecond response time is achieved for Phascope in our experiment. Besides, with optimal subcarrier selection and SNR of 30 dB over all subcarriers, Phascope can estimate motion speed of 0.1 m/s with 6.75% root-mean-square error (RMSE) compared to optimized FFT method.

Fast-response Pancharatnam-Berry phase optical elements based on polymer-stabilized liquid crystal.

In this paper we demonstrate fast-response Pancharatnam-Berry (PB) phase optical elements (PBOEs) based on polymer-stabilized liquid crystal (PSLC). First, a non-interferometric photo-alignment technique is employed to generate PB patterns in a dye-doped liquid crystal by green laser light. Then the samples are exposed to UV light to form polymer networks. Due to the greatly increased elastic constant in PSLC, all PBOEs can achieve submillisecond response time, while maintaining high diffraction efficiency (>90%). Furthermore, a varifocus PB lens (PBL) is implemented based on two identical PB lens elements and its application in fatigue free augmented-reality (AR) displays is verified. The fast response PBOEs based on PSLC hold great potential for various display and photonics applications.

Polarization-independent fast optical shutter with high transmission.

In this work, we designed a fast cholesteric shutter by switching the director between homeotropic and transient planar states. It is polarization independent, has sub-millisecond response time, high transmission in homeotropic state, and is highly reflective in the transient planar state. We also developed a driving waveform to achieve a long dark state of the device. The device has potential to be applied in the optics and display industries, for applications that could include augmented reality, head-up displays, transparent OLED displays, and smart windows.