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In this research, we developed a low-power silicon photonics foundry-fabricated slow-light thermal phase shifter (SLTPS) where the slow-light (SL) effect is achieved using an integrated Bragg grating (BG) waveguide. Heating the grating induces a red shift in the transmission spectrum, leading to an increased group index n g during operation, which facilitates a further reduction in the voltage needed for a π phase shift, i.e., V π. Additionally, we investigated a compact Mach–Zehnder Interferometer (MZI) that incorporates the SLTPS in both arms with a phase shifter length of 50 μ m. A detailed theoretical analysis was conducted to address the non-idealities of the SL-MZI due to uneven optical power splitting and unbalanced loss in the two MZI arms. V π and power consumption for a π phase shift (P π) of the SL-MZI were quantified for operation in the slow-light regime, demonstrating a V π of 1.1 V and a P π of 3.63 mW at an operational wavelength near the photonic band edge. The figure of merit P π × τ is commonly used to assess the performance of thermal optical switches. The SL-MZI in this work has achieved a low P π × τ of 5.1 mW μ s with an insertion loss of 4.4 dB, indicating a trade-off with the V π reduction. [ABSTRACT FROM AUTHOR]

In this paper, we theoretically and numerically demonstrate a tunable and polarization-dependent electromagnetically induced transparency analogy based on graphene terahertz metasurfaces. The unit cell of the metasurface consists of three-layer graphene strips embedded in a silicon grating. The dynamic adjustment of the transparent window can be achieved by changing the coupling distance between the graphene layers and the polarization direction of the incident lights. The operation mechanism behind the phenomenon can be attributed to the near-field interaction and electromagnetic coupling of modes in graphene strips. Furthermore, the full wave electromagnetic simulations obtained by the finite-difference time-domain method agree well with the theoretical fitting results based on the three-harmonic oscillator model. In addition, by changing the Fermi levels, it can not only realize the outstanding slow-light effects with a maximum group index of 3750 but also obtain the four-frequency asynchronous optical switch function in terahertz regions. Therefore, our proposed metamaterial device may have potential applications in image switching, optical switches, slow-light device, optical communication, and optical storage. [ABSTRACT FROM AUTHOR]

We investigate the propagation characteristics of two temporally separated soliton pulses with the same spectra, under the influence of stimulated Raman scattering, within a single-mode optical fiber. This analysis explores the behavior of the interacting solitons while propagating in different chalcogenide materials, exhibiting new features and promising prospects for soliton transmission in optical communication systems. Our study included all the interaction parameters constituting the nonlinear Schrödinger equation (NLSE). We have examined the relationship between the Kerr nonlinearity, interpulse and intrapulse Raman effects, and material-dependent collision length featuring a key aspect in logic design and phase control in mode-locking systems. We have also systematically shown the manifestation of the Raman response function from the Raman gain curve, which our mathematical model (the Lorentzian model) provides, that exhibits a near agreement with experimental data. Our findings reveal significant differences from the typical behavior of two-soliton interaction only due to Kerr nonlinearity. Furthermore, we have investigated the mechanism of the net energy transfer between the interacting solitons as an integral phenomenon involved in multiple soliton propagation. These results provide an insightful understanding of the associated nonlinear effects in high-power soliton transmission systems and are foreseen to possess the potential for designing advanced optical switches and mode-locked lasers. [ABSTRACT FROM AUTHOR]

We report on the observation of longitudinal (in-plane) and transverse (out-of-plane) spin splitting of incident linearly polarized (p and s) light beams reflected at the interface of tungsten di-selenide, a monolayer transition metal dichalcogenide material deposited on a Si/SiO2 substrate, near the Brewster angle of incidence employing the quantum weak measurement technique. The amplified longitudinal and transverse shift values reach up to hundreds of micrometers. The transverse shift value, measured approximately at 400 μm, dominates over the longitudinal shift value at Brewster incidence. In this work, we found positive and negative shift values for the same angle of incidence but distinct polarization states revealing the explicit dependencies upon the angle of incidence and the post-selection angle. The modified weak measurement model provides an excellent interpretation of these experimental findings. This work, thus, provides novel insights into the effects of light–matter interactions and could find important applications in optical switches, nano-photonics, and the non-destructive study of material properties. [ABSTRACT FROM AUTHOR]

In this research, we propose a simple and novel graphene-black phosphorus composite structure. Through the coupling mechanism of bright–bright mode, four layers of graphene and one layer of black phosphorus produce a quadruple plasmon-induced transparency (PIT) effect. The response of the proposed structure to the angle of polarized light is investigated, and it is found that the sensitivities of graphene and black phosphorus to the polarization angle of light are different. In addition, the dynamic regulation of PIT by the Fermi level of graphene and the carrier concentration of black phosphorus are discussed. The modulation depths of the fivefold optical switching are 96%, 99%, 87%, 93%, and 80%, respectively. The quadruple PIT can also be converted into triple PIT, in which single, dual, or triple optical switching are realized, respectively. Finally, with the change in the refractive index of the environment medium, the sensitivity response of the proposed structure is as high as 4.790 THz⋅RIU−1. We believe that this research will contribute to the development of optical switches, modulators, and sensors. [ABSTRACT FROM AUTHOR]

The photoinduced semiconductor-to-metal transition (PSMT) unveils crucial photodynamic mechanisms and holds great promise for information storage, sensing, optoelectronics, optical switches, etc. All previously reported PSMTs have occurred between two structural phases of the same material, lacking real-space evidence at the atomic or molecular level. Herein, we report atomic-scale observations of a photoinduced 'face changing': light irradiation transforms a semiconductor copper selenide (Cu2Se) surface layer on Cu(111) into a well-defined metallic Cu layer. Se atoms sink to form a new Cu2Se sublayer, while the original subsurface Cu atoms are lifted to the top layer. The Cu2Se-to-Cu transition barrier is significantly lower in the excited state compared to the ground state. Thermoactivation enables the reverse transition. The photoinduced Cu2Se-to-Cu and thermoactivated Cu-to-Cu2Se transitions are highly reversible. This work, which demonstrates PSMT between two distinct materials and photo-driven interlayer atom migration, unlocks an unconventional and intriguing route for PSMT and surface modification technologies. Photoinduced semiconductor-to-metal transitions are usually between different phases of the same material. Here the authors show the transformation of a single layer Cu2Se on Cu(111) into a metallic Cu surface layer and uncover its mechanism. [ABSTRACT FROM AUTHOR]

In this work, we demonstrate the connectivity-dependent optical 'crack resistance' of a doped epsilon-near-zero metamaterial (ENZ), which is distinct from conventional media. The optical transmission performance of the doped ENZ is robust against one or more subwavelength cracks as long as the connectivity of the doped ENZ is not broken by these cracks. As the doped ENZ is cut off by a crack, its transmittance decreases sharply and becomes sensitive to the location of the crack, especially the width of the crack. This unusual optical 'crack resistance' exhibits potential applications in designing ultrasensitive optical devices such as optical switches and displacement sensors. [ABSTRACT FROM AUTHOR]

Direct wide-bandgap III-Ns and II-Os have recently gained considerable attention due to their unique electrical and chemical properties. These novel semiconductors are being explored to design short-wavelength light-emitting diodes, sensors/biosensors, photodetectors for integration into flexible transparent nanoelectronics/photonics to achieve high-power radio-frequency modules, and heat-resistant optical switches for communication networks. Knowledge of the elastic constants structural and mechanical properties has played crucial roles both in the basic understanding and assessing materials' use in thermal management applications. In the absence of experimental structural, elastic constants, and mechanical traits, many theoretical simulations have yielded inconsistent results. This work aims to investigate the basic characteristics of tetrahedrally coordinated, partially ionic BeO, MgO, ZnO, and CdO, and partially covalent BN, AlN, GaN, and InN materials. By incorporating a bond-orbital and a valance force field model, we have reported comparative results of our systematic calculations for the bond length d , bond polarity α P , covalency α C , bulk modulus B , elastic stiffness C (= c 11 − c 12 2 ) , bond-stretching α and bond-bending β force constants, Kleinmann's internal displacement ζ, and Born's transverse effective charge e T * . Correlations between C / B , β / α , c 12 c 11 , ζ,  a n d   α C   revealed valuable trends of structural, elastic, and bonding characteristics. The study noticed AlN and GaN (MgO and ZnO) showing nearly comparable features, while BN (BeO) is much harder compared to InN (CdO) material, with drastically softer bonding. Calculations of microhardness H , shear modulus G , and Young's modulus Y have predicted BN (BeO) satisfying a criterion of super hardness. III-Ns (II-Os) could be vital in electronics, aerospace, defense, nuclear reactors, and automotive industries, providing integrity and performance at high temperature in high-power applications, ranging from heat sinks to electronic substrates to insulators in high-power devices. [ABSTRACT FROM AUTHOR]

NaYF 4 :30%Er-NaYF 4 -NaYF 4 :20%Ho-NaYF 4 core–shell nanocrystals, which exhibit distinct upconversion (UC) luminescence in the green, yellow, and red regions under 1530 nm, 980 nm, and 1150 nm laser excitation, respectively, have been synthesized. These nanocrystals were subsequently encapsulated within a WO 3 hydrogel matrix with photochromic properties. The nanocrystals underwent a color transition to dark blue upon exposure to 365 nm ultraviolet light, a change that is reversible and allows for dynamic modulation of the UC luminescence. The integration of this nanocrystal-hydrogel system with a silicon-based photodetector facilitates a rapid reduction in current, enabling "hard switching" without the need for continuous 365 nm irradiation. Furthermore, irradiation at 365 nm induces a gradual decrease in current, which can slowly recover, thus achieving a "soft switching" effect. [Display omitted] Optical switches are increasingly acknowledged for their potential advantages over mechanical counterparts in various domains. However, research on optical switches remains relatively nascent, primarily focusing on applications like anti-counterfeiting, switching chemical reactions, etc., while neglecting the control of photocurrent switching. Here, we have developed NaYF 4 :30 %Er-NaYF 4 -NaYF 4 :20 %Ho-NaYF 4 core–shell nanocrystals with unique upconversion (UC) multi-color emission properties under 1530 nm, 980 nm and 1150 nm laser excitations. These nanocrystals allow for optical control of circuit switching by modulating photocurrent signals in photosensitive circuits. The UC emission is due to the self-sensitization of rare earth ions in the core and shell. By adjusting the intermediate shell thickness, we have optimized the luminescence and investigated the mechanism. Combining these nanocrystals with a WO 3 quantum dots (QDs) photochromic hydrogel, dynamic variation of UC emissions could be realized. Moreover, by combining with a commercial silicon photodetector, we constructed a photosensitive circuit demonstrating the modulation of photocurrent signal output and realized the "hard switching" of rapid circuit cutoff. Furthermore, by using the photochromic effect of WO 3 QDs, the "soft switching" of slow circuit cutoff and recovery were also achieved. This work has significant implications for the development and application such as energy management system and smart home of optical switches in various fields. [ABSTRACT FROM AUTHOR]

The emergence of twisted metamaterials opens up an avenue for research in metamaterials. However, the current emphasis primarily lies in mechanics, rendering it intriguing to explore the application of compression-torsion coupling effect in optics. This present study introduces a thin-walled circular tube (TWCT) structure, characterized by a pronounced twisting angle of up to 59.5°, achieved only through a single-layer TWCT configuration. We demonstrate a significant compression-torsion coupling phenomenon, surpassing the findings of previous research endeavors. TWCT's deformation mechanism is harnessed in optical imaging through the integration of experimental, theoretical, and finite element approaches. The information stored in TWCT can be gradually projected through optical imaging when the elastic strain stimulates TWCT. These findings presented herein introduces a straightforward and valid approach to employ TWCT as a reliable mechanical switch for optical imaging, thereby showcasing its potential in the fields of cryptographic techniques, information storage, and transmission via optical imaging. [ABSTRACT FROM AUTHOR]

Satellite-based quantum communication channels are important for ultra-long distances. Given the short duration of a satellite pass, it can be challenging to efficiently connect multiple users of a city-wide network while the satellite is passing over that area. We propose a network with dual-functionality: during a brief satellite pass, the ground network is configured as a multipoint-to-point topology where all ground nodes establish entanglement with a satellite receiver. During times when this satellite is not available, the satellite up-link is rerouted via a single optical switch to the ground nodes, and the network is configured as a pair-wise ground network. We numerically simulate a pulsed hyper-entangled photon source and study the performance of the proposed network configurations for quantum key distribution. We find favourable scaling in the case that the satellite receiver exploits time-multiplexing whereas the ground nodes utilize frequency-multiplexing. The scalability, simple reconfigurability, and easy integration with fibre networks make this architecture a promising candidate for quantum communication of many ground nodes and a satellite, an important step towards interconnection of ground nodes at a global scale. [ABSTRACT FROM AUTHOR]

A study of multistability, optomechanically induced transparency, and fast to slow light propagation in a hybrid electro-optomechanical system is conducted. This system features one fixed mirror and one movable mirror with a Kerr medium inside the electro-optomechanical cavity. In addition to the linear optomechanical coupling between the mechanical resonator and the radiation pressure of the optomechanical cavity, quadratic optomechanical coupling is also considered. For this hybrid system, the optical switching results demonstrate that, with appropriate system parameters, the behavior of the intracavity mean photon number can be switched among mono-, bi-, and multistability. We also discuss optomechanically induced transparency and tunable fast-to-slow light propagation in the red-resolved sideband regime. The absorption spectra show asymmetric features influenced by nonlinearities such as linear and quadratic optomechanical couplings and the Kerr constant, which impact peak positions and intensities. Additionally, we observe tunable fast-to-slow light transitions by adjusting the linear optomechanical coupling, while negative group delay is seen in the presence of quadratic optomechanical coupling and the Kerr coefficient. This hybrid system holds potential for applications in all-optical switches, tunable optical buffers, and quantum information processing. [ABSTRACT FROM AUTHOR]

The compact and broadband optical switch with a large port count is demanded with the increasing communication capacity. In this article, a universal method for modeling the 1 × N switch using multimode interferometer (MMI) through transmission matrixes is proposed. Herein, the reasons for the narrowing of the operating bandwidth switch are analyzed. As a proof of concept, a wide bandwidth 1 × 4 switch, which has an insertion loss lower than 23.7 dB, and a cross talk better than −10 dB at 1550 nm are simulated, designed, and fabricated. The cross talk throughout the C band is lower than −8.5 dB. According to the experimental result, the 1 × 4 switch with four‐equal‐length modulating arms shows a 32 nm bandwidth for −10 dB cross talk which is 13 times larger than traditional switch. The switch realizes a multi‐port logic optical switch by modulation. The 1 × N switch based on the generalized Mach–Zehnder interferometer (GMZI) structure reduce the footprint significantly compared with the 1 × N switch consisting of a 1 × 2 switch cascade. It is believed that 1 × N switch based on GMZI structures is a promising solution to increase integration density. [ABSTRACT FROM AUTHOR]

The continuous push for high-performance photonic switches is one of the most crucial premises for the sustainable scaling of programmable and reconfigurable photonic circuits for a wide spectrum of applications. Conventional optical switches rely on the perturbative mechanisms of mode coupling or mode interference, resulting in inherent bottlenecks in their switching performance concerning size, power consumption and bandwidth. Here we propose and realize a silicon photonic 2×2 elementary switch based on a split waveguide crossing (SWX) consisting of two halves. The propagation direction of the incident light is manipulated to implement the OFF/ON states by splitting/combining the two halves of the SWX, showing excellent performance with low excess loss and low crosstalk over an ultrawide bandwidth. Both elementary switch and a 64×64 switch array based on Benes topology are fabricated and characterized, demonstrating great potential for practical scenarios such as photonic interconnect/routing, Lidar and spectroscopy, photonic computing, as well as microwave photonics. This work proposes a unique mechanism of manipulating the mode propagation for photonic switching with a brand-new split waveguide crossing, demonstrating great potential for the applications in a wide spectrum of scenarios. [ABSTRACT FROM AUTHOR]

The editorial in Micromachines discusses the advancements in photonic and optoelectronic devices and systems, emphasizing their benefits over traditional electronic devices in terms of speed, efficiency, and energy consumption. The text covers topics such as beam dynamics, sensing technologies, and photonic devices and systems, showcasing innovative research in these areas. The document highlights the growing market demand for photonic devices and the need for continuous research to enhance performance while balancing size, weight, and power constraints. [Extracted from the article]

Non-Terrestrial Networks (NTNs) will constitute a cornerstone of the next-to-come Sixth-Generation (6G) technology. Specifically, Low-Earth Orbit (LEO) satellite constellations play a crucial role, either as a stand-alone networking solution or as a complement to terrestrial networks, in providing network access and services anywhere and anytime with lower latency than geostationary satellites. However, LEO’s narrow coverage areas and mobility will likely cause service interruptions whenever the link between the NTN platform and NTN-Gateway (GW) (i.e., the feeder link) becomes unavailable. The Third Generation Partnership Project (3GPP) has defined a set of feeder link switch over procedures, which may lead to a long procedure duration and, hence, long service interruptions, especially in the case of NTN-GWs located far from each other. To cope with the mentioned issues, this paper proposes a novel feeder link switch over procedure, which exploits inter-satellite links (ISLs) to implement, through a chain of LEO satellites, virtual visibility between a LEO satellite and an NTN-GW that are not in direct sight. This aims at reducing the time of feeder link switch over and avoiding service disruptions. The advantages of the proposed ISL-aided feeder link switch over procedure over the one defined by 3GPP are assessed via simulative campaigns. [ABSTRACT FROM AUTHOR]

In this work, a multifunctional metasurface based on vanadium dioxide (VO2) is designed. By inserting a vanadium dioxide layer into the dielectric layer, the wideband absorber and polarization converter can be switched in the terahertz band. When vanadium dioxide is in the metallic phase, the multifunctional metasurface acts as a broadband absorber in the 9.97–23.31 THz range. When the vanadium dioxide is insulating, the metasurface acts as a polarization converter, with a conversion efficiency greater than 90% from linear polarization to cross-polarization in the range of 2.65–8.26 THz. In addition, the effects of incidence and polarization angles on the metasurface properties are also discussed. This study shows that multifunctional metasurfaces have broad application prospects in terahertz optical switches, electromagnetic stealth technology, modulators, and communication systems. [ABSTRACT FROM AUTHOR]

In this paper, we propose an N -bit optical digital-to-analog converter (DAC) by integrating N pairs of 2 × 2 phase change based on-chip photonic switches and 2 × 2 multimode interference (MMI) splitters. An on-chip photonic switch is constructed by integrating a wavelength-selectable racetrack micro-ring resonator with the phase change chalcogenide Ge2Sb2Se4Te (GSST). The GSST-integrated switch utilizes a racetrack resonator configuration for performing the accurate modulation of the resonant wavelength to prevent intercoupling between adjacent units. In order for electrothermal heating of the GSST film to trigger its phase transition for switchable control, an indium tin oxide heater with a bowtie-shaped structure is integrated into the racetrack resonator. Using numerical calculations, we demonstrate that an 8 V voltage pulse at a duration of 300 ns, with an energy consumption of 18.45 nJ, could change the optical state from an OFF state to an ON state. Another 6 V voltage pulse of 250 ns duration, followed by a 4 V pulse of varying duration, with a total energy consumption of 34.78 nJ, can switch the optical state from an ON state to an OFF state. The asymmetric structure of the 2 × 2 MMI shows ultra-high transmittance approaching 50% in the through port (connected to the next order of MMI), enabling the creation of multistage cascaded MMI splitters with an output light power ratio close to 50%. Our results show that this configuration potentially offers a feasible solution for applications of optical DACs. [ABSTRACT FROM AUTHOR]

A contribution of free charge carriers in an ensemble of anisotropic silicon nanocrystals to the optical properties in the infrared region has been numerically analyzed. Utilizing a generalized effective medium model that accounts for the shape anisotropy of silicon nanocrystals and mobile charge carriers the reflectance, absorption, and transmittance were found to be strongly dependent on the concentration of free charge carriers. For charge carrier (hole) concentrations ranging from 10 16 to 10 20 c m - 3 , significant birefringence and linear dichroism (absorption anisotropy) are observed, along with a non-monotonic dependence of the refractive index and transmittance coefficients for perpendicular polarization directions. The simulation results align well with experimentally measured transmittance spectra of in-plain anisotropic porous silicon films prepared electrochemically from heavily boron-doped (110)-oriented crystalline silicon wafers. Furthermore, the obtained results are discussed in view potential applications in all-silicon based optical switches and modulators and other active elements of the silicon photonics. [ABSTRACT FROM AUTHOR]

This paper introduces a new controllable anomalous hollow cosh-Gaussian beam (CAHcGB). Based on the Snyder-Michell model and the ABCD matrix description of strongly nonlocal nonlinear media (SNNM), we investigate the transmission characteristics of CAHcGB. Analytical expressions for the electric field, beam width, wavefront curvature radius, and critical power of CAHcGB in SNNM are derived. The results demonstrate that CAHcGB undergoes periodic evolution during transmission in SNNM, influenced by both the beam parameters and the initial beam power. When the critical power equals the incident power, the beam width remains unchanged throughout transmission, resembling a CAHcGB soliton; otherwise, it periodically changes, akin to a breather. The study also reveals that the on-axis intensity evolution curve can exhibit various shapes such as concave, platform, or Gaussian-like, depending on the input power. The research results hold significant potential for applications in optical fiber communication systems, all-optical networks, and optical switches. [ABSTRACT FROM AUTHOR]

Liquid crystal (LC) droplets are highly attractive for applications in privacy windows, optical switches, optical vortices, optical microresonators, microlenses, and biosensors due to their ease of fabrication and easy alignment at surfaces. This review presents the latest advancements in LC droplets, which have nematic, chiral nematic, and twist–bend nematic and ferroelectric nematic phases, or blue phases. Finally, it discusses the challenges and opportunities for applications based on LC droplets. The main challenges encompass the precise control of internal structures and defects to meet diverse application requirements, enhancing stability and durability across various environments, reducing large-scale production costs to improve commercial feasibility, increasing response speeds to external stimuli to adapt to rapidly changing scenarios, and developing tunable LC droplets to achieve broader functionalities. [ABSTRACT FROM AUTHOR]

In the field of modern optical computing and communication, optical bistability plays a crucial role. With a weak third-order nonlinear coefficient, low switch thresholds of optical bistability from Si-based nanophotonic structures remain a challenge. In this work, a metasurface consisting of silicon nanostrip arrays placed on the optically thick silver film is proposed. The light–matter interaction is enhanced by mirror-inducing the magnetic anapole states (MASs) and asymmetrically optimizing its silicon nanostrip. Numerical results show that the average enhancement factor (EF) of an electric field can be greatly enhanced to be 1524.8. Moreover, the optical bistability of the proposed metasurface achieves the thresholds of ION-OFF and IOFF-ON of 8.5 MW/cm2 and 7.1 MW/cm2, respectively, which is the lowest threshold when compared to the previous works based on silicon nanostructures. The angular dependance of the bistability performance is also investigated. This work facilitates the proposed hybrid metasurface in the fields of miniaturized all-optical switches and modulators, which are key components in optical computing and communication. [ABSTRACT FROM AUTHOR]

Electromagnetically induced transparency (EIT), nonlinearity, and optical chirality hold significant applications in many areas such as optical switches, slow-light devices, chiral harmonic conversion, and optical storage. In this work, we theoretically propose an asymmetric all-dielectric metasurface supporting toroidal dipole-quasi-bound states in the continuum (TD-q-BICs). High quality (Q) EIT, strong third harmonic generation (THG), and giant nonlinear chirality are achieved via the extremely enhanced electric field energy localized in the Si plate by the TD-q-BIC. A huge transition from high Q EIT with transmission of ∼0.99 to strong chirality with circular dichroism (CD) of ∼0.9 is realized by tuning the angle and polarization state of incident light. Strong THG with efficiency of 4.5 × 10−3 under linear polarization light is due to the highly localized electric field supported by the TD-q-BIC and perfect nonlinear CD chirality with theoretically value of ∼1 originates from the large discrepancy in electric field distributions under different circularly polarized light. Our work provides an innovative paradigm to construct TD-q-BICs-governed EIT analogs, THG, and nonlinear chirality for the development of multifunction nanophotonic meta-devices. [ABSTRACT FROM AUTHOR]

Mode‐division multiplexing (MDM) introduces a new dimension to on‐chip optical interconnection, where the multimode optical switch is one of the core components. However, researchers are still struggling to reduce the chip size and response time, despite great efforts being made. Here, a compact, scalable, fast‐response multimode 2 × 2 switch supporting four modes is demonstrated based on the specific inverse design. The device consists of two multimode 2 × 2 CB couplers (including mode converters, multimode interference couplers, and crossings) and a thermo‐optic (TO) phase shifter. It achieves extinction ratios exceeding 15 dB for all modes at the central wavelength of 1.55 µm. All the fundamental components are designed by an improved general shape optimization method, realizing a compact size and a larger manufacturing tolerance (±20 nm). Besides, a hydrogen‐doped indium oxide microheater is introduced as a TO phase shifter to achieve a fast response (≈3.5 µs in average) for all modes. This solution provides an effective avenue toward large‐scale multimode optical switch matrices for the future MDM systems. [ABSTRACT FROM AUTHOR]

This article reports opto-electronic switching properties of heterostructure GaN/AlGaN lateral Avalanche Transit Time (ATT) diode oscillator. A novel technique has been adopted for the incorporation of 2DEG effect in two-terminal device. This is achieved through the inherent conduction band offset and subsequent application of Cathode Field Plate (CFP) in combination with lateral orientation. The performance superiority of the proposed electrical and optical switches over conventional silicon devices is evidently established and experimentally verified. Under dark condition, maximum RF power output with and without series resistance has been obtained as, RFP SR ∼ 1.5 × 10 11 W / m 2 and R F P ∼ 2.84 × 10 11 W / m 2 at 0.4THz. Also, the mentioned parasitic series resistance has been obtained to be, R Parasitic ∼ 7 × 10 - 10 Ω / m 2 . Under illumination, output power with and without series resistance, have been deduced to be RFP SR ∼ 1 × 10 11 W / m 2 and R F P ∼ 2 × 10 11 W / m 2 at 0.5THz, for M N = 10 . To the best of authors' knowledge this is the first report on electro-optical performance optimization study in connection with exotic type GaN/AlGaN two-terminal ATT oscillator. A power combining technique is used in designing a 3 × 3 array. For the 3 × 3 array structure, the parasitic series resistance is obtained to be R Parasitic ∼ 8.5 × 10 - 10 Ω / m 2 . Value of the series resistance has increased for such array as compared to a single diode, due to circuit loading. In spite of such increase in series resistance, RF output power increases substantially for the array structure, due to enhanced negative conductance. Under dark condition at 0.4THz, RFP SR ∼ 4 × 10 11 W / m 2 and R F P ∼ 7.7 × 10 11 W / m 2 are the RF power output with and without series resistance. Further, for illuminated array structure, peak RF power output, with and without series resistance, is obtained to be RFP SR ∼ 2.4 × 10 11 W / m 2 and R F P ∼ 5.3 × 10 11 W / m 2 at 0.5THz, for M N = 10 . The reported performance enhancement of the newly designed ATT diode is due to the high mobility 2DEG transport region. Such 2DEG has resulted from the quantum confinement caused by GaN/ AlGaN conduction band offset in conjunction with the unique CFP and lateral orientation of the proposed diode. For the first time, quantum confined high mobility 2DEG transport region has been formed in a two-terminal ATT device. [ABSTRACT FROM AUTHOR]

A wavelength-switchable polarization mode filter (PMF) based on a graphene-coated D-shaped photonic crystal fiber (DPCF) is proposed. Due to the different coupling properties between the two polarized core modes and surface plasmon polariton (SPP) modes, the PMF is designed for y-polarized mode filtering. In order to enhance the interaction between the graphene and fiber, gold is coated on top of graphene. Finite element method is applied to analyze the performance. Results show that the filtering wavelength can be modulated by adjusting the chemical potential (μc) of graphene. Especially, a single-wavelength PMF can be switched to a dual-wavelength or a three-wavelength filter by increasing the value of μc. The extinction ratio is higher than 25 dB with a small device length of 100 μm over the wavelength range of 1.0~1.4 μm. The wavelength-switchable PMF has a great potential in polarization modulation, WDM communication system, and multi-parameter sensing. [ABSTRACT FROM AUTHOR]

A novel design of ultrahigh efficiency and ultralow threshold energy all-optical switches based on local state transition of complete-connected optical waveguide networks (CCOWNs) is proposed. The generation of the ultra-narrow transmission peak and the ultra-strong photonic localization in network is attributed to the mutation of states, which are significant improvements in the performance of all-optical switch. First, the ultra-strong photonic localization induces the Kerr effect in nonlinear material, which transforms the transmission peaks into a transmission valley and results in the super-high efficiency. The efficiency of switch based on CCOWN with 11 unit cell (UC) and each UC possessing 7 nodes was calculated and found to be approximately 1.38 × 10 39 , which is 13 orders of magnitude better than previously reported. Furthermore, the ultra-strong photonic localization also leads to the ultralow threshold energy. Calculations reveal that the threshold control energy of all-optical switch based on CCOWN only with 7 UC and each UC possessing 5 nodes is about 5.78 × 10 - 30 J, which is 5 orders of magnitude smaller than the best reported results. In addition, fitting formulas for the transmission and switching efficiency with UC number have been derived, and the results show that the switching efficiency increased exponentially with the UC number and nodes. This study not only presents a new model for designing all-optical switch with outstanding performance, but also provides the possibility for further practical use of all-optical switch, while deepening our insight into optical waveguide networks. [ABSTRACT FROM AUTHOR]

With the rapid development of communication networks and computing, optical switches as an important elementary unit are highly needed. In this article, a silicon‐based optical switch with Ge2Sb2Te5 (GST)‐enabled phase‐shifting region is proposed. This optical switch is based on contra‐directional couplers composed of two phase‐shifted Bragg gratings. To minimize the impact of GST absorption loss, GST is only used in the phase‐shifting area, and the switching function is achieved by changing the state of GST. In the results, it is shown that the proposed device has a 3 dB operation bandwidth of about 163.2 GHz (1.394 nm) and an extinction ratio of about 19.06 dB for the drop port and about 20.25 dB for the through port. The loss at the central operational wavelength is about 1.3 and 1.04 dB for the through port and the drop port, respectively, and the largest loss over the entire operation bandwidth for these two ports is 1.66 and 2.35 dB. Furthermore, the optical switch is shown to be bidirectional, achieving similar performance when light propagates in the opposite direction. Compared with previous works, the proposed optical switch realizes wider operation bandwidth, higher extinction ratio, and lower loss.

The compact and broadband optical switch with a large port count is demanded with the increasing communication capacity. In this article, a universal method for modeling the 1 × N switch using multimode interferometer (MMI) through transmission matrixes is proposed. Herein, the reasons for the narrowing of the operating bandwidth switch are analyzed. As a proof of concept, a wide bandwidth 1 × 4 switch, which has an insertion loss lower than 23.7 dB, and a cross talk better than −10 dB at 1550 nm are simulated, designed, and fabricated. The cross talk throughout the C band is lower than −8.5 dB. According to the experimental result, the 1 × 4 switch with four‐equal‐length modulating arms shows a 32 nm bandwidth for −10 dB cross talk which is 13 times larger than traditional switch. The switch realizes a multi‐port logic optical switch by modulation. The 1 × N switch based on the generalized Mach–Zehnder interferometer (GMZI) structure reduce the footprint significantly compared with the 1 × N switch consisting of a 1 × 2 switch cascade. It is believed that 1 × N switch based on GMZI structures is a promising solution to increase integration density.

A hybrid structure composed of a grating coupled graphene structure and two one-dimensional photonic crystals (PhCs) is investigated, where the topological edge state (TES) and the graphene surface plasmon polariton (GSPP) are coupled to generate Fano resonances. The grating coupled graphene structure is used to excite the GSPP and provides a broad resonance. The two PhCs are designed to possess opposite topological properties; thus, the TES appears at the interface and exhibits a narrow resonance. The constructive and destructive interference between the GSPP and the TES results in the Fano resonance. By analyzing the resonant behaviors, it is found that the line shape of Fano resonance can be actively tuned by the graphene Fermi energy. We apply our results to the optical switching, a high-performance optical switch is achieved, and the modulation depth can reach as high as 23.31 dB. In addition, owing to the characteristic of Fano resonance with steep dispersion and asymmetric profile, our designs might offer an alternative strategy to achieve potential applications in sensors, filters, optical switches, and slow-light devices. [ABSTRACT FROM AUTHOR]

In this paper, we theoretically investigate the transmission properties of a structure composed of a topological one-dimensional photonic crystal (1D PhC) heterostructure and a conventional 1D PhC containing indium-antimonide (InSb) as a defect layer using the transfer matrix method. The phenomenon of Fano resonance can be achieved by coupling the defect mode with the topological edge state mode, which is supported by the topological PhC. The numerical results show that a narrow Fano resonance is observed in the transmission spectrum of the structure in the presence of the external magnetic field applied to the InSb defect layer. The optical properties of the InSb defect layer, and, therefore, the Fano resonance, can be dynamically controlled by changing the applied external magnetic field. The results obtained with the proposed structure reveal that the magnetic field has the greatest influence on controlling the optical properties of the Fano resonance. These findings could be beneficial for optical devices such as optical filters, sensors, and optical switches. [ABSTRACT FROM AUTHOR]

Multiple stimuli-responsive molecular crystals have gained significant attention recently owing to their wide-range of applications in diverse fields such as optical switches, storage devices, and mechanical actuators. In this study, a nitropentaammine cobalt(III) complex stabilized by 4-nitro cinnamate (C-1) was synthesized and characterized using various spectroscopic and analytical techniques, including singlecrystal X-ray diffraction (SCXRD) study. The complex C-1 exhibits dual-responsive behaviour under UV light (365 nm) and heat, showing bending, cracking, splitting, and displacement. These photo-/thermomechanical responses are attributed to nitro-to-nitrito linkage isomerization within the crystalline phase. The energy optimization of C-1 and its corresponding nitrito isomer through density functional theory (DFT) study reveals that the nitro isomer is energetically more stable than nitrito by 24 kcal mol-1. This indicates that upon irradiation of UV light/heat, the nitro compound gains energy and is converted to the nitrito isomer. The photo-/thermo-mechanical behaviour of C-1 was successfully transferred to a polymer composite, which was fabricated via a solution casting method using C-1 and agarose (1 : 1 weight ratio) and shows actuating behaviour, with the extent of actuation varying for both the external stimuli. [ABSTRACT FROM AUTHOR]

Optical switching technology is emerging as a solution to the limitations of traditional electronic switching. Combining optical switching with mode‐division multiplexing effectively overcomes the limitations of expanding switching capacity solely by increasing the number of ports. This paper introduces a compact four‐mode 2 × 2 optical switch and a four‐mode reconfigurable non‐blocking 4 × 4 optical switch matrix based on the Beneš architecture. The multimode 2 × 2 switch achieves an extinction ratio larger than 15 dB for all modes in the wavelength range of 1530–1590 nm. The multimode 4 × 4 switch matrix has an extinction ratio exceeding 9 dB for all modes and states in the C‐band, with a compact size (1.46 × 0.23 mm2) and low power consumption (0–154 mW). It supports high‐integrity 50 Gbaud PAM4 signal transmission with a bit error rate below the forward error correction limit. These devices pave the way for enhanced integration density and capacity in optical switching systems. [ABSTRACT FROM AUTHOR]

Heat‐activated second harmonic generation (SHG) switching materials are gaining interest for their ability to switch between SHG on and off states, offering potential in optoelectronic applications. The novel nonlinear optical (NLO) switch, (C5H6NO)+(CH3SO3)− (4‐hydroxypyridinium methylsulfonate, 4HPMS), is a near‐room‐temperature thermal driven material with a strong SHG response (3.3 × KDP), making it one of the most potent heat‐stimulated NLO switches. It offers excellent contrast of 13 and a high laser‐induced damage threshold (2.5 × KDP), with reversibility > 5 cycles. At 73 °C, 4HPMS transitions from the noncentrosymmetric Pna21 room temperature phase (RTP) to the centrosymmetric P21/c phase, caused by the rotation of the (C5H6NO)+ and (CH3SO3)− due to partially thermal breaking of intermolecular hydrogen bonds. The reverse phase change exhibits a large 50 °C thermal hysteresis. Density functional theory (DFT) calculations show that (C5H6NO)+ primarily dictates both the SHG coefficient (dij) and birefringence (▵n(Zeiss) = 0.216 vs ▵n(cal.) = 0.202 at 546 nm; Δn(Immersion) = 0.210 vs ▵n(cal.) = 0.198 at 589.3 nm), while the band gap (Eg) is influenced synergistically by (C5H6NO)+ and (CH3SO3)−. Additionally, 4HPMS‐RTP also exhibits mechanochromism upon grinding as well as an aggregation‐enhanced emission in a mixture of acetone and water. [ABSTRACT FROM AUTHOR]

Switching functionality is pivotal in advancing communication systems, serving as a paramount mechanism. Despite numerous innovations in this field, optical switch design, fabrication, and characterization have traditionally followed an iterative approach. Within this paradigm, the designer formulates an informed conjecture regarding the switch's structural configuration and subsequently resolves Maxwell's equations to ascertain its performance. Conversely, the inverse problem, which entails deriving a switch geometry to achieve a targeted electromagnetic response, continues to pose formidable challenges and necessitates substantial time and effort, particularly under the constraints of specific assumptions. In this work, we propose a deep neural network-based method to approximate the spectral transmittance of all-optical switches. The findings substantiate the efficacy of deep learning in the design of all-optical plasmonic switches, which are renowned as the fastest switches at the nanoscale. The nonlinear Kerr effect in square resonators is leveraged to demonstrate the switching performance. Juxtaposed with conventional simulations, the proposed model showcases a remarkable improvement in computational efficiency. Furthermore, deep learning can resolve nanophotonic inverse design problems without reliance on trial-and-error or empirical strategies. Compared to simulations, the mean squared error for both forward and inverse models is meager, with values of around 0.03 and 0.02, respectively. The deep learning-proposed switches exhibit excellent suitability for integration into photonic integrated circuits, substantially influencing the progression of all-optical signal processing. [ABSTRACT FROM AUTHOR]

The document is a contents list for the journal "Chemical Communications" published in 2024. It includes highlights, feature articles, and communications on various topics related to chemistry. The journal is published by The Royal Society of Chemistry, a leading chemistry community. The contents list provides a range of research articles on topics such as catalysts, perovskites, photoluminescence, and electrocatalysis. [Extracted from the article]

The impact of molecular point groups on phase transition materials has been seldom discussed. Two organic cations with different symmetries were incorporated into a [SnCl6]2− framework. By breaking the symmetry of cations, a novel hybrid material with two successive phase transitions featuring a rare "on–off–on" nonlinear optical switch was obtained. [ABSTRACT FROM AUTHOR]

A dual optical switch regulated by visible light has been developed through an integrated strategy, including luminescent Pt(II) and photochromic spiropyran (SP) as a triplet-sensitizer and photo-regulator building block, respectively. An efficient Förster resonance energy transfer (FRET) process is achieved, along with apparent and emissive color changes under visible light irradiation and temperature stimuli, which was utilized to develop advanced anti-counterfeiting materials. [ABSTRACT FROM AUTHOR]

Photonics integrated circuits (PICs) can overcome the bottlenecks in communication capacity. 3D PIC technology is an attractive method for increasing density effectively and combining different materials on one chip for functional integration. In this study, a low‐cost and reconfigurable 3D integrated silicon photonics (SiPhs) platform is proposed fabricated by depositing polycrystalline silicon (poly‐Si) on crystalline silicon (c‐Si), which is patterned through deep ultraviolet (DUV) stepper‐based manufacturing process. The high mobility of poly‐Si ensures high‐speed and power‐efficient modulation. Based on the proposed 3D SiPhs platform, an 8 × 8 optical switch whose units are separated in different layers is fabricated and packaged. The switch shows average insertion losses of −13.98 and −15.86 dB, while working in “all‐cross” and “all‐bar” states, respectively. The crosstalk is lower than −19 and −11 dB for “all‐cross” and “all‐bar” states. Additionally, an overlayer switch located on the 1st and 3rd layers is proposed and experimentally demonstrated, which offers overlapping capabilities that are more compact compared with switches in a single‐layer platform. This validates the possibility of the large‐density integration scalability of the platform. [ABSTRACT FROM AUTHOR]

Mode‐division multiplexing (MDM) technology, as a new way to increase the communication capacity of a single wavelength carrier, has attracted increasing attention. As a fundamental building block for MDM communication systems, multimode optical switch is playing an important role for routing the increasingly complex network. However, it is still very challenging to achieve a multimode optical switch with high flexibility and low power‐consumption in a large bandwidth. Here, a 1 × 2 dual‐mode optical switch is proposed and experimentally demonstrated, where the E11 and E21 modes can be switched output from either of the two output ports simultaneously or individually with low power‐consumption. For the proposed dual‐mode optical switch, three asymmetric Y‐junctions are used as mode (de)multiplexers, two Mach–Zehnder interferometers form a single‐mode switch matrix, and a 2 × 2 multimode interferometer is used as the waveguide crossing. The device is fabricated with simple photolithography and wet‐etching methods. The measurement results show that the driving powers of the device are lower than 8.4 mW, and the crosstalks are less than −12.4 dB in the wavelength range of 1500–1600 nm. By implementing the dynamic control of resources between the guided modes, the proposed device can greatly improve the flexibility and efficiency of reconfigurable MDM networks. [ABSTRACT FROM AUTHOR]

Polymer dispersed liquid crystals (PDLC) and polymer stabilised cholesteric liquid crystals (PSCLC) are an indispensable class of electrically switchable materials, which have been widely applied in the fabrication of efficient and systematic smart windows. And doping nanoparticles in PDLC films can greatly improve their properties. In this study, PDLC films doped with zirconia nanoparticles were prepared by polymerisation-induced phase separation (PIPS) method, PSCLC films with nematic liquid crystals as the main part (reflecting wavelengths in the range of 400–600 nm) were prepared by UV curing method, and a novel optical switch was developed by combining these two liquid crystal films. The optimal bilayer sample was developed through a comparative analysis of properties among samples with varying formulations for each liquid crystal layer. This study represents a novel advancement in PSCLC and nanoparticle-doped PDLC bilayer structures, showcasing fully actuatable properties in the visible wavelength range. These structures exhibit excellent electro-optical properties and demonstrate stable, sustainable performance that can be regenerated. The findings underscore the potential of PDLC and PSCLC for applications in smart curtains and flexible materials, opening up new avenues for innovative technological applications. [ABSTRACT FROM AUTHOR]

A novel plasmonic waveguide structure consisting of a rectangular resonator side coupled with a split ring resonator (SRR) and a metal–insulator–metal (MIM) waveguide with metal baffle was proposed. The transmission characteristics of the present structure were simulated by a finite-difference time-domain (FDTD) method. The results show that the structure can realize three typical plasmonically-induced reflection (PIR) windows. Meantime, the PIR window can be tuned vertically and horizontally, respectively, and multiple PIR windows with different wavelength intervals can also be obtained by changing the split position. In addition, the sensitivity of the proposed structure can reach up to 1,075 nm/RIU. Furthermore, a rectangular resonator was added to the other side of the plasmonic waveguide structure for realizing the dual-channel PIR window. Another SRR was added to form a symmetrical structure, which further improved the sensitivity and transmittance. Undoubtedly, the proposed structure will have potential applications in sensor and optical switches. [ABSTRACT FROM AUTHOR]

In optical data center networks, the utilization of several software-defined network controllers has been implemented to enhance scalability and reliability. However, during dynamic variations in network traffic, static controller deployment often leads to load imbalance among the controllers. Previous studies have proposed dynamic switch migration as a solution to realize controller load balancing. However, the effectiveness of existing switch migration methods remains insufficient. The load balancing performance of controllers demonstrates limited enhancement following migration, and the migration operations themselves result in supplementary costs. As a result, the issue of switch migration efficiency remains unresolved. To tackle controller load balancing, this research introduces the intelligent controller load balancing (ICLB). ICLB incorporates multiple load metrics to evaluate controller load and selects the ideal target controller based on available resources, leading to enhanced load balancing effectiveness. Moreover, it selects switches while the minimizing migration process, effectively reducing supplementary expenses. Additionally, ICLB can simultaneously manage the workload of multiple controllers during a switch migration process, resulting in enhanced migration efficiency. The outcomes of simulations provide evidence that ICLB offers substantial improvements in controller load balancing performance, along with reduced migration expenses compared to existing solutions. [ABSTRACT FROM AUTHOR]