Switching Contrast Research Articles

Kidney disease, diabetes, and diameter stenosis predict Rotablation bailout in modified balloon application for severely calcified coronary lesions.

Modified balloon (MB) treatment in severely calcified coronary artery lesions is an established technique. However, some lesions require Rotablation (RA) as bailout strategy. This study aimed to assess predictors of switch from MB to RA and its impact on procedural and midterm outcomes. Four hundred and eighty-three consecutive patients were included undergoing MB treatment (n = 204) with a scoring or cutting balloon, or upfront RA treatment (n = 279) serving as control cohort. Strategy switch from MB to RA was performed in 19 of 204 patients. Procedural success was defined as successful stent implantation and TIMI III flow. In the MB cohort, median age was 72 [63-78] years, 75.5% were male and 42.1% had acute coronary syndrome. Procedure success was achieved in 89.4% of the switch group versus 98.4% of the MB only group (p < 0.001) and in 96.4% of the RA cohort. In the switch group, periprocedural complications (31.6% vs. 8.1% vs. 11.8%, p = 0.007), radiation dose (149 [126-252] vs. 59 [30-97] vs. 102 [59-156] Gcm2; p < 0.001) and contrast volume (250 [190-250] vs. 190 [150-250] vs. 195 [190--250] mL; p < 0.001) were significantly higher. Diabetes (OR 3.8, 95%CI 1.1-13.9, p = 0.042), chronic kidney disease stage 4 or 5 (OR 19.0, 95%CI 3.3-108.6, p < 0.001) and pronounced calcification resulting in higher angiographic diameter stenosis (OR 1.13, 95%CI 1.1-1.2, p = 0.001) independently predicted strategy switch. Midterm results were not affected by strategy switch regarding 1-year target lesion revascularization rates (86% vs. 89% vs. 89%; log-rank p = 0.95). Primary RA strategy might be considered in patients with severely calcified coronary artery lesions with high angiographic diameter stenosis, diabetes or impaired renal function due to increased periprocedural complication rates, radiation dose, and contrast volume following strategy switch.

Topologically-protected optical bistability based on two-dimensional photonic crystal L6 nanocavity dimer array.

We numerically investigate the optical bistability from a two-dimensional photonic crystal L6 nanocavity dimer array structure configured under the Su-Schrieffer-Heeger model. The localized electric field in the topological edge state is highly enhanced, which gives rise to strong nonlinear phenomena such as optical bistability. In comparison, a topologically trivial nanocavity is also designed and its field strength distribution and optical bistable response are also simulated. In order to test the robustness, three types of defects and interferences are introduced in both the topologically non-trivial and trivial cavities. Benefiting from the topological feature, the proposed topological cavity exhibits superior optical bistable performance with low threshold power and high switching contrast compared to that in the trivial cavity. Our work suggests what we believe to be a novel avenue toward the insertion of optical bistable devices with high robustness into future photonic integrated circuits and photonic neural networks.

Electrically Reconfigurable Phase-Change Transmissive Metasurface.

Programmable and reconfigurable optics hold significant potential for transforming a broad spectrum of applications, spanning space explorations to biomedical imaging, gas sensing, and optical cloaking. The ability to adjust the optical properties of components like filters, lenses, and beam steering devices could result in dramatic reductions in size, weight, and power consumption in future optoelectronic devices. Among the potential candidates for reconfigurable optics, chalcogenide-based phase change materials (PCMs) offer great promise due to their non-volatile and analogue switching characteristics. Although PCM have found widespread use in electronic data storage, these memory devices are deeply sub-micron-sized. To incorporate phase change materials into free-space optical components, it is essential to scale them up to beyond several hundreds of microns while maintaining reliable switching characteristics. This study demonstrated a non-mechanical, non-volatile transmissive filter based on low-loss PCMs with a 200 × 200 µm2 switching area. The device/metafilter can be consistently switched between low- and high-transmission states using electrical pulses with a switching contrast ratio of 5.5 dB. The device wasreversibly switched for 1250 cycles before accelerated degradation took place. The work represents an important step toward realizing free-space reconfigurable optics based onPCMs.

Shape Shifting and Locking in Mechanically Responsive Organic‐Inorganic Hybrid Materials for Thermoelastic Actuators

AbstractThe construction of mechanically responsive materials with reversible shape‐shifting, shape‐locking, and stretchability holds promise for a wide range of applications in fields such as soft robotics and flexible electronics. Here, we report novel thermoelastic one‐dimensional organic–inorganic hybrids (R/S‐Hmpy)PbI3 (Hmpy=2‐hydroxymethyl‐pyrrolidinium) to show mechanical responses. The single crystals undergo two phase transitions at 310 K and 380 K. When heated to 380 K, they show shape‐shifting and expansion along the b‐axis by about 13.4 %, corresponding to a larger deformation than that of thermally activated shape memory alloys (8.5 %), and exhibit a strong actuation force. During the cooling process, the stretched crystal shape maintains and a shape‐locking phenomenon occurs, which is lifted when the temperature decreases to 305 K. Meanwhile, due to the introduction of chiral ions, the thermal switching shows a 10‐fold second‐order nonlinear switching contrast (common values typically below 3‐fold). This study presents a thermoelastic actuator based on shape‐shifting and ‐locking of organic–inorganic hybrids for the first time. The dielectric and nonlinear optical switching properties of organic–inorganic hybrids broaden the range of applications of mechanically responsive crystals.

Shape Shifting and Locking in Mechanically Responsive Organic-Inorganic Hybrid Materials for Thermoelastic Actuators.

The construction of mechanically responsive materials with reversible shape-shifting, shape-locking, and stretchability holds promise for a wide range of applications in fields such as soft robotics and flexible electronics. Here, we report novel thermoelastic one-dimensional organic-inorganic hybrids (R/S-Hmpy)PbI3 (Hmpy=2-hydroxymethyl-pyrrolidinium) to show mechanical responses. The single crystals undergo two phase transitions at 310 K and 380 K. When heated to 380 K, they show shape-shifting and expansion along the b-axis by about 13.4 %, corresponding to a larger deformation than that of thermally activated shape memory alloys (8.5 %), and exhibit a strong actuation force. During the cooling process, the stretched crystal shape maintains and a shape-locking phenomenon occurs, which is lifted when the temperature decreases to 305 K. Meanwhile, due to the introduction of chiral ions, the thermal switching shows a 10-fold second-order nonlinear switching contrast (common values typically below 3-fold). This study presents a thermoelastic actuator based on shape-shifting and -locking of organic-inorganic hybrids for the first time. The dielectric and nonlinear optical switching properties of organic-inorganic hybrids broaden the range of applications of mechanically responsive crystals.

Post-processing of phase change material in a zero-change commercial silicon photonic process.

Integration of phase change material (PCM) with photonic integrated circuits can transform large-scale photonic systems by providing non-volatile control over phase and amplitude. The next generation of commercial silicon photonic processes can benefit from the addition of PCM to enable ultra-low power, highly reconfigurable, and compact photonic integrated circuits for large-scale applications. Despite all the advantages of PCM-based photonics, today's commercial foundries do not provide them in their silicon photonic processes yet. We demonstrate the first-ever electrically programmable PCM device that is monolithically post-processed in a commercial foundry silicon photonics process using a few fabrication steps and coarse-resolution photolithography. These devices achieved 1.4 dB/μm of amplitude switching contrast using a thin layer of 12.5 nm GeSbTe in this work. We have also characterized the reconfiguration speed as well as repeatability of these devices over 20,000 switching cycles. Our solution enables non-volatile photonic VLSI systems that can be fabricated at low cost and high reliability in a commercial foundry process, paving the way for the development of non-volatile programmable photonic integrated circuits for a variety of emerging applications.

Photonic fan-out and local selectable inversion of the optical hysteresis shape

We demonstrate and elucidate the local selectable inversion of the hysteresis shape of a bistable optical signal after fan-out. This selectability is based on a hysteresis-shape transformation that yields a switching contrast over 20 dB in magnitude for both the inversion clockwise (CW) and the non-inversion counterclockwise (CCW) hysteresis shapes, while maintaining input-switching powers. This behavior leverages an initial signal whose bistability is manifested by its state of polarization; a generalized Malus’ law elucidates how selection is possible by controlling the transmittivity hysteresis through each local polarizer. The concept is demonstrated using a Fabry–Pérot semiconductor optical amplifier to produce the initial bistable polarization-rotating signal, followed by a 1 × 2 fan-out and the realization of all four hysteresis shapes at each location, independent of the other location. This fan-out and selectable inversion behavior is applicable to other nonlinear photonic systems and provides new functionality for parallel optical processing.

Effect of exceptional point on the performance of a bistable all-optical switch.

Microring cavities based on whispering-gallery modes (WGMs) have a very high-quality factor (Q) and a small mode volume, greatly improving the interaction between light and matter, which has attracted great attention in microlaser, nonlinear, and sensing fields. Plasmonics in the microcavity further enhance compression of the optical field. Recently, research on enhanced optical sensing sensitivity and low threshold laser based on exceptional points (EPs) is quite impressive. In this work, we propose a new, to our knowledge, all-optical switch by using the bistable effect under the EP of an ultra-compact plasmonic racetrack resonator and perform numerical simulations using the finite-difference time-domain (FDTD) method. The introduction of EPs further enhances the localization of the light field and thus improves the Kerr nonlinear effect of the microcavity; low threshold optical bistability is achieved. The results show that the device under an EP has a relatively lower threshold (input optical power threshold of 2.2 MW/cm2), shorter switching time (1.725 ps), and significantly improved switching contrast (17.16 dB) compared with those without EP. Our research lays the groundwork for optical switches that are chip-integrated, have low power consumption, and exhibit short switching times.

Room-Temperature Phase Transition Material with Switchable Second-Order Nonlinear Optical Properties.

Phase transition materials with switchable second-order nonlinear optical (NLO) properties have attracted extensive attention because of their great application potential in photoelectric switches, sensors, and modulators, while metal-free organics with NLO switchability near room temperature remain scarce. Herein, we report a hydrogen-bonded metal-free organic crystal, 2-methylpropan-2-aminium 2,2-dimethylpropanoate (1), exhibiting a room-temperature phase transition and favorable NLO switchability. Through investigations on its thermal anomalies, dielectric properties, and crystal structures, we uncover that 1 holds a near-room-temperature phase transition at 303 K from noncentrosymmetric point group C2v to centrosymmetric one D2h, which is attributed to the order-disorder transformations of both tert-butylamine cations and dimethylpropionic acid anions. Accompanied by symmetry change during the phase transition, 1 exhibits reversible and repeatable NLO "on-off" switchability with a desirable switching contrast ratio of ca. 19 between high and low NLO states. This discovery demonstrates a metal-free organic crystal with NLO switching behavior near room temperature, serving as a promising candidate in smart and ecofriendly photoelectric functional materials and devices.

Improved optical contrast of plasmonic phase change memory using a Fabry-Perot cavity

As a promising technology to realize multilevel, non-volatile data storage and information processing, optical phase change technologies have attracted extensive attention in recent years. However, existing phase-change photonic devices face significant challenges such as limited switching contrast and high switching energy. This study introduces an innovative approach to tackle these issues by leveraging Fabry-Perot (F-P) cavity resonance and plasmon resonance techniques to enhance the modulation effect of phase change materials (PCMs) on the light. To the best of our knowledge, a novel device structure is proposed, featuring an elliptic nano-antenna placed on an F-P cavity waveguide composed of symmetric Bragg grating. This design exploits the enhanced electric field to achieve low power consumption and high contrast. The device enables crucial functions, including read, write, and erase operations, under all light conditions. Through the synergistic utilization of plasma and F-P cavity effects, an ultra-high switching contrast of around 70.6% is achieved. By varying the pulse power or duration, the proportion between the crystalline and amorphous states of the PCMs is altered, consequently modifying its refractive index. With its wide range of applications in optical storage and computing, the device holds significant potential for advancing these fields.

High‐Capacity Photochromic Rotary Encoder for Information Encryption and Storage

AbstractPhotochromic materials are widely used in optical data storage, data encryption, and anti‐counterfeiting because of their ability to be written, erased, and read repeatedly. However, conventional information encryption and storage capabilities based on a “matrix” pattern in a 2D plane are limited to fewer storage dimensions, making information less secure. Here, a new concept of expanding the storage dimensions is presented by manipulating the rotation angle in 2D photochromic encoding disks based on the principle of the absolute encoder. For this purpose, a novel photochromic material, NaNbO3:xEu3+ is developed, with highly efficient red emission, a large luminescence switching contrast, and antithermal quenching behavior. The designed photochromic rotary encoder made with the NaNbO3‐based material exhibits higher‐level data encryption than that of conventional encoders and unlimited storage capability. This study presents exciting opportunities for information storage and encryption using luminescent photochromic materials.

The role of the correlated motion(s) of the chromophore in photoswitching of green and red forms of the photoconvertible fluorescent protein mSAASoti

Wild-type SAASoti and its monomeric variant mSAASoti can undergo phototransformations, including reversible photoswitching of the green form to a nonfluorescent state and irreversible green-to-red photoconversion. In this study, we extend the photochemistry of mSAASoti variants to enable reversible photoswitching of the red form. This result is achieved by rational and site-saturated mutagenesis of the M163 and F177 residues. In the case of mSAASoti it is M163T substitution that leads to the fastest switching and the most photostable variant, and reversible photoswitching can be observed for both green and red forms when expressed in eukaryotic cells. We obtained a 13-fold increase in the switching efficiency with the maximum switching contrast of the green form and the appearance of comparable switching of the red form for the C21N/M163T mSAASoti variant. The crystal structure of the C21N mSAASoti in its green on-state was obtained for the first time at 3.0 Å resolution, and it is in good agreement with previously calculated 3D-model. Dynamic network analysis reveals that efficient photoswitching occurs if motions of the 66H residue and phenyl fragment of chromophore are correlated and these moieties belong to the same community.

Reconfigurable Micro/Nano-Optical Devices Based on Phase Transitions: From Materials, Mechanisms to Applications.

In recent years, numerous efforts have been devoted to exploring innovative micro/nano-optical devices (MNODs) with reconfigurable functionality, which is highly significant because of the progressively increasing requirements for next-generation photonic systems. Fortunately, phase change materials (PCMs) provide an extremely competitive pathway to achieve this goal. The phase transitions induce significant changes to materials in optical, electrical properties or shapes, triggering great research interests in applying PCMs to reconfigurable micro/nano-optical devices (RMNODs). More specifically, the PCMs-based RMNODs can interact with incident light in on-demand or adaptive manners and thus realize unique functions. In this review, RMNODs based on phase transitions are systematically summarized and comprehensively overviewed from materials, phase change mechanisms to applications. The reconfigurable optical devices consisting of three kinds of typical PCMs are emphatically introduced, including chalcogenides, transition metal oxides, and shape memory alloys, highlighting the reversible state switch and dramatic contrast of optical responses along with designated utilities generated by phase transition. Finally, a comprehensive summary of the whole content is given, discussing the challenge and outlooking the potential development of the PCMs-based RMNODs in the future.

Pulsed laser deposition of Sb2S3 films for phase-change tunable nanophotonics

Non-volatile phase-change materials with large optical contrast are essential for future tunable nanophotonic applications. Antimony trisulfide (Sb2S3) has recently gained popularity in this field due to its low absorption in the visible spectral region. Although several Sb2S3 deposition techniques have been reported in the literature, none of them was optimized with respect to stoichiometry, lowest possible absorption, and large refractive index contrast (Δn) upon the phase change. Here we present a comprehensive multi-parameter optimization of pulsed laser deposition of Sb2S3 towards this end. We correlate the specific deposition with the resulting compositional and optical properties and report parameters leading to films with extraordinary qualities (Δn = 1.2 at 633 nm). Additionally, we suggest crystal orientations and vibrational modes associated with the largest change in the refractive index and propose them as useful large-scale indicators of the Sb2S3 switching contrast.

Analysis of high-contrast all-optical dual-wavelength switching in asymmetric dual-core fibers.

We systematically present experimental and theoretical results for the dual-wavelength switching of 1560 nm, 75 fs signal pulses (SPs) driven by 1030 nm, and 270 fs control pulses (CPs) in a dual-core fiber (DCF). We demonstrate a switching contrast of 31.9 dB, corresponding to a propagation distance of 14 mm, achieved by launching temporally synchronized SP-CP pairs into the fast core of the DCF with moderate inter-core asymmetry. Our analysis employs a system of three coupled propagation equations to identify the compensation of the asymmetry by nonlinearity as the physical mechanism behind the efficient switching performance.

Electrically tunable and switchable perfect infrared absorber based on ENZ material

In this paper, a dynamically tunable and switchable perfect infrared absorber is put forward, which is composed of a gold ring array, an indium tin oxide (ITO) layer, an alumina (Al2O3) spacer and a continuous Au film from top to bottom. Epsilon-near-zero (ENZ) mode in ITO layer is excited by localized surface plasmon resonance (LSPR) mode of the gold ring. With the increase of the biasing voltage V, the carrier concentration of ITO material decreases, and the absorption peak caused by ENZ resonance blue shifts obviously. Notice that our infrared absorber can realize bidirectional switching of “ON” and “OFF” states at 1210 nm, with modulation depth of 70 % and switching contrast (SC) of 241 %, manifesting its excellent electrical regulation performance. After verification, the switching performance of our absorption structure has a high precision tolerate of the manufacturing process. A clear Fano type absorption curve appears in the wavelength range 1000 nm–1300 nm, under the biasing voltage V of 3.4 V. Moreover, a series of small absorption peaks are produced by Fabry-Pérot (F–P) resonance in the horizontal plane caused by the standing wave in the ENZ layer, and this phenomenon is unexpected. We propose a theoretical interpretation for the absorption mechanism in both cases based on multiple interference model. It is also proved that the proposed infrared absorber is polarization insensitive and exhibits high absorptance (>90 %) over an incident range of 0 deg–60 deg. The electrically tunable absorption switch function makes our absorber have potential in selective thermal emitters, infrared sensors, infrared stealth, beam focusing and other fields.

Ultrafast nonlinear absorption in MoTe2 and MoTe2/MoS2 nanocomposite films and its application to all-optical logic gates

We present a detailed theoretical analysis of ultrafast saturable absorption (SA) and reverse SA (RSA) in MoTe2 nano-films with femtosecond (fs) laser pulses at 800 nm. A transition from RSA to SA occurs on increasing the thickness from 30 nm to 80 nm at a constant pump intensity of 141 GW cm−2. On the other hand, a transition from SA to RSA occurs upon increasing the pump intensity in an 80 nm thick MoTe2 nano-film. Theoretical results are in good agreement with reported experimental results. The effect of pump pulse intensity, pulse width, nonlinear absorption coefficient and sample thickness has been studied to optimize the SA ↔ RSA transition. The results for low-power and high contrast all-optical switching in MoTe2 nano-films have been used to design all-optical fs NOT, OR, AND, as well as the universal all-optical NOR and NAND logic gates. The SA behavior of MoTe2/MoS2 nanocomposite films has been used to design all-optical AND and OR logic gates. The nanocomposite films of MoTe2/MoS2 possess a larger nonlinear optical response in comparison to MoTe2 and MoS2 nano-films and, therefore, all-optical logic gates designed using nanocomposite films result in a good switching contrast compared to pure MoTe2 nano-films. Ultrafast operation at relatively low pump intensities demonstrates the applicability of MoTe2 and MoTe2/MoS2 nano-films for ultrafast all-optical information processing.

High optical contrast and multi-level storage of the ultracompact plasmonic device based on phase change materials

The combination of photonic devices and chalcogenide phase change materials (PCMs) provides a potential solution for photonic storage and computing. However, there are still some issues that need to be addressed for currently integrated phase-change photonic memory such as low speed, high energy consumption, and large footprint. To enable stronger interaction between light and PCMs, we utilize the plasmonic enhancement effect to amplify the local electric field, resulting in high energy efficiency in photonic storage and computation. This work proposes a nanoscale elliptical plasmonic nanoantenna that dramatically improves switching speed and energy by placing an Ag elliptical ring wrapped with Ge2Sb2Te5 (GST) on a silicon waveguide. The device exhibits crystalline and amorphous states with insertion losses of 0.3 dB and 1.7 dB, respectively, at a wavelength of 1550 nm. Write and erase operations can be completed by optical pulses of 1.5 ns–1 mW and 3 ns–3 mW, respectively. An ultra-small device volume of only 4.465 × 10−4 (µm3) is capable of achieving a switching contrast ratio of 28.5 %. Moreover, the non-volatile storage of multi-level intermediate states facilitates a wide weight-variation range and allows for precise weight updates, enhancing the overall performance and accuracy of the system. In the handwritten digit recognition task of the three-layer perceptron, the device demonstrates a recognition accuracy rate of 95 %, indicating that our approach can enable a more efficient neuromorphic photonic computing network.

Event-driven adaptive optical neural network.

We present an adaptive optical neural network based on a large-scale event-driven architecture. In addition to changing the synaptic weights (synaptic plasticity), the optical neural network's structure can also be reconfigured enabling various functionalities (structural plasticity). Key building blocks are wavelength-addressable artificial neurons with embedded phase-change materials that implement nonlinear activation functions and nonvolatile memory. Using multimode focusing, the activation function features both excitatory and inhibitory responses and shows a reversible switching contrast of 3.2 decibels. We train the neural network to distinguish between English and German text samples via an evolutionary algorithm. We investigate both the synaptic and structural plasticity during the training process. On the basis of this concept, we realize a large-scale network consisting of 736 subnetworks with 16 phase-change material neurons each. Overall, 8398 neurons are functional, highlighting the scalability of the photonic architecture.

All-optical switching based on coherent control of metasurface

In this paper, we propose a novel method to design ultrafast all-optical switchings based on the coherent perfect absorption principle of metasurface. Using the coherent interaction between two beams of coherent light and the metasurface, the absorption can be modulated between 0.3% and 98. 3%. Since no nonlinear dielectric is used, the ultrafast all-optical switching function can be achieved at arbitrary low intensity conditions. We further studied the mechanism of resonant absorption on metasurface, and analyzed the influence of geometric parameters on resonant absorption. Through time-domain simulation analysis, when the incident laser pulse duration is 40 fs, the switching response time is 82 fs, which provides a switching contrast ratio of more than 108.