Optical Switching Research Articles

Low cross talk, low P π silicon optical switch based on highly balanced couplers and folded phase shifters

The cross talk and power consumption of the 2 × 2 optical switch is a key metric in the design of large-scale photonic integrated circuits (PICs). We build a theoretical model of a 2 × 2 Mach–Zehnder interferometer (MZI) optical switch, taking into account both imbalances in the arm loss and the coupler splitting ratio. The splitting ratio imbalance requirement for a given switch cross talk is summarized, which provides a guideline for the switch design. A 2 × 2 multimode interference (MMI) coupler design with low excess loss (<0.14 dB) and low imbalance (<0.13 dB) over the C-band is given. Its robustness to width variations up to ±40 nm is demonstrated. The 2 × 2 MZI switches with such an MMI are fabricated on a silicon-on-insulator (SOI) substrate using both electron beam (EB) and deep ultraviolet (DUV) lithography. The EB and DUV MMI switches exhibit cross talk of <−35 dB and <−30 dB over 40 nm, respectively. Folded configurations are used for both the silicon waveguides and the metal heaters to increase the power efficiency, resulting in a Pπ of ∼8 mW.

Sensitive Detection of Hg2+ and l-Cysteine through Optical Asymmetry-Tuned Fluorescence Switch Off-On Behavior in N-Doped Chiral Carbon Dot.

Blue-emissive nitrogen-doped chiral carbon dots (d-NCD230 and l-NCD230) exhibiting antipodal chiroptical activity, synthesized from the thermal pyrolysis of citric acid and d/l-aspartic acid in 1:2 molar ratios, have been explored as chirality-based fluorescent turn-off/on probes for the detection of Hg2+ and l-cysteine (l-Cys). Circular dichroism (CD) spectroscopy revealed that the chiroptical activity originates from a synergy among intrinsic chirality, chiral precursors on the NCD surface, and hybridization of lower energy levels within the embedded chiral chromophore. Quantitative analysis of optical asymmetry using the Kuhn asymmetry factor (g) at the CD signal of 312 nm showed a higher value for d-NCD230 (1.03 × 10-4) compared to l-NCD230 (1.13 × 10-5). Moreover, we have demonstrated chirality transfer and chiral inversion phenomena in d/l-NCDs by preparing carbon dots with different precursor ratios at different temperatures and probing them through CD spectroscopy. The NCDs exhibited selective fluorescence quenching in the presence of Hg2+, demonstrating linearity in the Stern-Volmer plot. Limits of detection (LODs) for Hg2+ were calculated to be 129 and 192 nM for d-NCD230 and l-NCD230, respectively, in the 0-150 μM concentration range. The quenching mechanism involves nonradiative electron transfer due to Hg2+ binding to oxygen-rich functional groups on the d/l-NCD230 surface. The slight variation in LOD values between d-NCD230 and l-NCD230 indicates the negligible effect of the chirality on Hg2+ sensing. Notably, the fluorescence intensity of d/l-NCD230 could be restored upon adding l-cysteine, with d-NCD230 showing a more pronounced enhancement than l-NCD230. This differential response is attributed to a preferential stereoselective interaction arising from the homochirality of d-NCD230/Hg2+ and l-cysteine. These findings demonstrate the potential of chiral nitrogen-doped carbon dots as sensitive and selective probes for Hg2+ and l-cysteine, with implications for environmental monitoring and biological sensing applications.

A microring resonator full-duplex 5 × 5 optical routing switch based on ITO material

A microring resonator full-duplex 5 × 5 optical routing switch based on ITO material

Polarization-insensitive ultra-wideband tunable perfect absorber based on a vanadium dioxide metasurface

This paper provides a polarization-insensitive ultra-wideband tunable perfect absorber based on a patterned vanadium dioxide (VO2) metasurface. The absorption bandwidth reaches 18.5 THz, surpassing that of most previous studies, through integrating two distinct region patterns (A and B). The proposed absorber features a three-layer sandwiched structure and a simpler metasurface pattern, demonstrating the advantages of lower manufacturing cost and a simplified photolithography process. In addition, by optimizing geometric parameters and manipulating VO2 conductivity, the absorption spectrum reveals three specific perfect absorption peaks with the absorptance of 99.06%, 99.85%, and 99.85% at 10 THz, 14 THz, and 21.5 THz and shows polarization-insensitive performance due to the C4 rotational symmetry of the metasurface pattern. Furthermore, we illustrate that the intrinsic mechanism of the proposed perfect absorber arises from the lossy localized surface plasmon polarization (LSPP) excited by the incident wave, with the Fabry–Perot (FP) cavity enhancing LSPP absorption. The absorber reveals a good impedance matching with the free space, where the real and imaginary parts are close to 1 and 0, which also explains the perfect absorption from the perspective of the impedance matching theory. The device can transition between perfect absorption mode and total reflection mode, with relative absorptance also adjustable via manipulating the VO2 conductivity. Ultimately, the absorber displays an excellent angle tolerance maintaining absorptance above 90% in the range of 0°–50°. Consequently, the proposed polarization-insensitive ultra-wideband tunable perfect absorber can be applied in optical switching, object cloaking, and wireless communication.

Green Synthesis of Noble Metal Nanoparticles: Nonlinear Optics and Applications

This study presents a green method for synthesising gold nanoparticles (AuNPs) and silver nanoparticles (AgNPs) employing Gum Arabic extract as a reducing and stabilising agent. The synthesised nanoparticles are characterised using UV-Vis absorption spectroscopy and transmission electron microscopy (TEM). The visible colour change and the presence of surface plasmon resonance (SPR) peaks confirmed the formation of silver and gold nanoparticles. The size of the nanoparticles was determined from the UV-Vis spectra data, and the results were compared to sizes measured by TEM. The nonlinear refraction (n2) and nonlinear absorption (b) coefficient of AgNPs and AuNPs at 488 and 514 nm were investigated under continuous wave (CW) mode excitation using the Z-scan technique. By fitting the experimental data to the Z-scan theoretical equations, the nonlinear refraction index and the nonlinear absorption coefficient were found. The origin of the nonlinearities was discussed, and it was proposed to be of thermal effect for the nonlinear refractive index and Reverse Saturation Absorption (RSA) for nonlinear absorption. Optical limiting and switching were demonstrated by taking advantage of the samples' nonlinear optical characteristics.

Tunable bistability, optomechanical and magnomechanically induced transparency in opto-magnomechanical system

We investigate theoretically the optical properties of a hybrid optomechanical system embedded with a yttrium iron garnet (YIG) sphere. It is considered that YIG interacts with a single mode of the microcavity through magnetic dipole coupling. To enhance the magnomechanical coupling, the magnon mode is directly driven by a microwave field. The microcavity is driven by the control and probe field. The study of steady-state dynamics of the system shows bistable behavior. Furthermore, optomechanically induced transparency under the influence of a strong control field in the system is explored. In addition, magnomechanically induced transparency (MMIT) due to the presence of nonlinear magnon–phonon interaction is studied. Fano like shape is observed in MMIT. The impact of different system parameters is studied. Our results will provide a theoretical approach to understand opto-magnomechanical systems. These results may be useful in all optical switching devices and optical transistors.

Dynamically controllable two-color electromagnetically induced grating via spatially modulated inelastic two-wave mixing

A scheme for controlling two-color electromagnetically induced grating (TCEIG) in a coherently prepared cold atomic ensemble with a four-level inverted Y-type configuration is proposed via exploiting inelastic two-wave mixing process. By adding an intensity mask behind the auxiliary control field, the transmission functions of the incident probe field and the generated signal field are modulated periodically, thereby leading to the formation of TCEIG. Using experimentally achievable parameters, both the probe and signal fields with different frequencies can be simultaneously diffracted into high-order diffractions. It is found that the diffraction efficiencies of TCEIG, especially the first-order diffraction efficiency, can be significantly improved via adjusting the detunings of the probe and signal fields. Furthermore, it is also demonstrated that the diffraction of TCEIG can be manipulated via tuning the intensity and detuning of the control field. Finally, we investigate the influence the phase mismatch on the diffraction of TCEIG. It is shown that the diffraction pattern of the probe field is rather robust against the phase mismatch, while the diffraction intensities of the signal field are suppressed by the phase mismatch. Our scheme may provide a possibility for the all-optical control of optical switch and wavelength division multiplexing.

A multi-channel AWG-based FBG interrogation system using a 1 × 4 MEMS optical switch

Fiber Bragg grating (FBG) sensors have been widely used in various fields. In order to further multiplex FBG sensors, multi-channel interrogation systems have been widely studied. In this paper, a multi-channel AWG-based FBG interrogation system using a 1 × 4 MEMS optical switch is proposed. We simulate, design, and fabricate a 32-channel AWG based on silica planar lightwave circuit (PLC), and test the spectrum performance of the AWG. The test results show that the AWG has a good transmission spectrum with an average 3-dB bandwidth of 2.29 nm, an insertion loss of 2.52 dB to 3.95 dB, and a non-adjacent channel crosstalk of –23.06 dB. A temperature experiment is conducted on the multi-channel AWG-based FBG interrogation system. According to the experimental results, the multi-channel FBG AWG-based interrogation system achieves an accuracy within 20 pm, interrogation stability of ±1.07 pm, sensitivity of about 10 pm/°C, a correlation coefficient of about 0.9982 with a deviation within ± 0.002, excellent linearity, and the ability to interrogate 64 FBGs simultaneously.

Cloud data centers and networks: Applications and optimization techniques

As the volume and complexity of big data continue to escalate, optimizing the performance, scalability, and energy efficiency of big data applications within cloud data centers has become increasingly crucial. This journal presents a comprehensive survey of current optimization techniques, focusing on data placement, job scheduling, and network configurations tailored for cloud environments. We explore the impact of various data center topologies on the performance of big data frameworks like Hadoop, emphasizing the trade-offs between performance and energy efficiency. Advanced methodologies, including dynamic data placement strategies, locality-aware scheduling, and innovative reduce task placement techniques, are reviewed in depth. Additionally, we highlight the importance of network power effectiveness (NPE) and examine the role of optical and electronic switching technologies in enhancing data center efficiency. By synthesizing findings from recent studies, this paper provides valuable insights into the optimization of cloud data centers, offering recommendations for improving resource utilization and reducing job completion times while maintaining energy efficiency. The findings contribute to the ongoing efforts to scale and adapt cloud data infrastructures for the rapidly growing demands of big data applications.

Tunable nonlinear optical properties in polyaniline-multiwalled carbon nanotube (PANI-MWCNT) system probed under pulsed Nd:YAG laser

The investigation of the nonlinear optical (NLO) properties of polyaniline (PANI) and polyaniline doped with multi-walled carbon nanotube (PANI-MWCNT) in both solution and film forms was conducted using the open-aperture z-scan approach. A Q-switched resonant Nd: YAG laser with a wavelength of 532nm and two different fluences was utilized in this study. Based on the z-scan experiments, it was observed that the NLO behaviour of PANI and PANI-MWCNT composites exhibited a transition from reverse saturable absorption (RSA) to saturable absorption (SA) when the samples changed from a liquid to a film state. Two photon absorption (TPA) and thermally induced nonlinear scattering are the main mechanisms behind the RSA behaviour of the materials in solution form. The reason for SA behaviour of these materials in film form is attributed as the ground-state free electron bleaching in the conduction band due to the increased laser intensity. Due to increased structural disorder and the defect states or trap levels created by the dopants in the PANI system, the NLO properties of the PANI-MWCNT composite in both solution and film forms have significantly improved compared to those of pure PANI. Urbach tail analysis and carbon cluster determination revealed the presence of defect states in the composites system. The composite between PANI and MWCNT was verified using Fourier transform infrared (FTIR) spectroscopy. The functional elements present in the composites are verified by X-ray photoelectron spectroscopy. The NLO parameters of the samples, viz., the nonlinear absorption coefficient (β), the imaginary part of the nonlinear, and susceptibility χi(3) the figure of merit (FOM) of PANI-MWCNT, exhibited a notable enhancement in their values over PANI. Moreover, the PANI-MWCNT film demonstrated superior SA performance and the PANI-MWCNT solution demonstrated better OL performance compared to that of the PANI film and solution respectively. Also the effects of dopant induced structural modifications and lattice disorder on the NLO behaviour of these materials are correlated with the obtained NLO parameters. The tunable NLO properties accomplished by controlling the structural phase and dopant-induced defects enhance the possibility of these nanostructures for applications in optical limiting, optical switching, optical modulation, optical pulse compression and laser pulse narrowing.

Synthesis and characterization of piperazine nitrate monochloride semi-organic single crystal for NLO applications

A semiorganic single crystal of piperazine nitrate chloride (PNC) was grown utilising the gradual evaporation solution technique at ambient temperature. The crystal lattice properties and molecular structure of the formed crystal of PNC were identified via X-ray diffraction examination of a single crystal and are consistent with the monoclinic crystal system with space group P21/n. Using Hirshfeld surface analysis, intra and intermolecular interactions were displayed. The FTIR spectrum analysis presented here examines the vibratory patterns of several functional sections found within the PNC crystal. The crystal exhibits a low absorbance throughout the entire visible spectrum according to studies of UV–vis-NIR absorbance and calculated band gap as well as optical constants. TG/DTA analysis was used to identify the stability and breakdown properties. This refractive index was computed using the prism coupling method. At different temperatures studies of the dielectric properties were conducted and the Vickers hardness technique was employed to investigate the mechanical properties. The grown crystal's laser-damaged threshold value was found. The Z-scan method investigates a PNC crystal’s third-order NLO behaviours. This method makes it possible to calculate the material's linear and nonlinear refractive indices. The PNC crystal exhibits strong third-order nonlinear optical properties, crucial for applications in optical switching and NLO devices.

Photon localization transition in a magnetorheological fluid

We investigate photon transport in magnetically tunable fluids, specifically magnetic nanofluids and magnetorheological fluids (MRFs). Our study focuses on the statistical analysis of light transport in these fluids, with a particular focus on earlier theoretical proposals related to the possibility of Anderson localization in these systems. We employ a well-known mesoscopic quantifier, the generalized conductance, to assess the domain of light transport in these systems. Magnetic nanofluids, which contain nanometer-sized magnetite particles, exhibit weak scattering with no substantial consequence on conductance, regardless of the applied magnetic field. In contrast, magnetorheological fluids, a bidispersion of micrometer-sized magnetizable spheres in a magnetic nanofluid, show a decrease in conductance to values below unity as the magnetic field strength increases. This decrease occurs at the magnetic-field-induced photonic bandgap in MRFs, which plays a crucial role in the localization process and is characterized by reduced transmitted intensity, altered speckle patterns, and significant changes in intensity statistics. Our findings also highlight the temporal evolution of field-induced speckles, where the initial high correlation decreases over time, and the correlation width widens indicating that the duration of sustained correlation enhances as the system reaches equilibrium. Consequently, the evolution of field-induced scatterers in MRFs significantly emulates light localization effects as the system attains equilibrium. This study concludes that our system is a prime candidate to observe possible strong localization in a magnetically tunable, dissipative complex system. Such systems hold potential applications in optical switching, adaptive optics, and smart materials design through controlled light manipulation using external magnetic fields.

Controllable switching based on vortex–antivortex pairs in exciton–polariton condensates

Abstract Vortex–antivortex pairs hold significant prospect for applications in high-capacity optical communications, multiparticle manipulations, and data processing systems. In this work, based on vortex–antivortex pairs, we explore a straightforward method to produce a 1–4 optical switch in a polariton condensate with a C-shaped potential. The switch, seeded by a degenerate state containing two vortex–antivortex pairs, can selectively target four objective states: two orthogonal states with a single vortex–antivortex pair and two concentric vortices with opposite circulations. All these topological states are stable states with the application of a single incoherent pump, while the switch is activated by an additional coherent control pulse.

Demonstration of ultra-compact and low-loss 2 × 2 silicon thermo-optic switches based on a mode-conversion nanobeam cavity

Optical switch is an essential component in integrated photonic circuits. A mode-conversion nanobeam cavity (MCNC) coupled with two waveguides has been employed to realize ultra-compact and low-loss 2 × 2 thermo-optic switches in silicon-on-insulator. This system can exhibit either Fano or Lorentzian lineshape in transmission spectra, dependent on the coupling structure. It has a low dropping loss, and two outputs are in the same direction, owing to the unidirectional coupling between the resonant mode and bus waveguides. Here, we have demonstrated a high-performance 2 × 2 Fano switch with a bandwidth of 5.2 nm and a footprint of only 35.5 × 1 µm2. The insertion loss (IL) and crosstalk (CT) are 0.7 dB and −54.1 dB in the bar state, respectively, while the IL and CT are 0.9 dB and −17.4 dB in the cross-state, respectively. In addition, 2 × 2 optical switches with a Lorentzian transmission lineshape have also been realized and then applied to construct a four-channel reconfigurable optical add-drop multiplexer (ROADM). Through thermal tuning, the ROADM has achieved a channel spacing of 200 GHz or 400 GHz, with an inter-channel CT below −12.3 dB or −17.2 dB, respectively. To our knowledge, we have reported the first demonstrations of 2 × 2 Fano switch and ROADM based on MCNCs. The proposed 2 × 2 switches will find potential applications in advanced photonic integrated circuits.

Enhanced ultrafast nonlinear optical response in Bi-doped ZnO glass-ceramics

Incorporating plasmonic nanocrystals (NCs) into solid-state electronics is an important step toward realizing nanophotonic devices. However, only a few noble metal-based systems can directly precipitate plasmonic NCs in a solid transparent medium. In contrast, plasmonic metal oxide NCs can exhibit a plasmonic response at infrared energies that noble metal-based systems cannot reach due to their high carrier concentration. Here we demonstrate the precipitation of bismuth-doped ZnO (BZO) NCs in an aluminosilicate glass matrix, demonstrating a robust near-infrared (NIR)-localized surface plasmon resonance. Benefited from the strong resonant absorption by the plasmonic BZO NCs, these glass ceramics (GCs) exhibit enhanced ultrafast nonlinear optical (NLO) response across the NIR optical communication bands, which might be promising for applications such as optical limiting, optical switching, optical modulation, and NIR-nanophotonic devices.

Ultracompact Polarization-Insensitive 1 × N Silicon-Based Optical Wavelength-Selective Switch by Leveraging I/O Waveguide Spacing Difference

Ultracompact Polarization-Insensitive 1 × <i>N</i> Silicon-Based Optical Wavelength-Selective Switch by Leveraging I/O Waveguide Spacing Difference

Simultaneous bi-directional all-optical multipoint-to-multipoint switching for free-space optical communication networks

A new, to our knowledge, simultaneous bi-directional all-optical multipoint-to-multipoint switching scheme is proposed and experimentally demonstrated for free-space optical (FSO) communication networks. Through tuning the optical switch at the core node, the communication link between each two arbitrary remote nodes can be established. The multipoint transmission performance is tested in a turbulence-tunable atmospheric cell using a 6.25 Gbit/s quadrature phase-shift keying (QPSK) signal. At the bit error rate (BER) of 1×10−3, the power penalty is &lt;3.5dB with a 250°C temperature difference of the atmospheric cell. Moreover, this scheme is compatible with all-optical wavelength conversion, which can achieve strict transparency for different modulation formats. Our proposed scheme offers the possibility to provide an efficient, low-cost, and high-speed method for simultaneous bi-directional all-optical multipoint-to-multipoint FSO communications.

Silicon‐Based Optical Switch with Ge2Sb2Te5‐Enabled Phase‐Shifting Region

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 (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.

High Q-factor multi-Fano resonances in all-dielectric metasurface for high-performance optical switching and sensors

High Q-factor multi-Fano resonances in all-dielectric metasurface for high-performance optical switching and sensors

Deciphering the Optical Switching Mechanism of CdSe/CdS QDs Luminescence by Diarylethene Molecular Photoswitches: A Stochastic Model Analysis

Deciphering the Optical Switching Mechanism of CdSe/CdS QDs Luminescence by Diarylethene Molecular Photoswitches: A Stochastic Model Analysis