Vector inversion generators or spiral generators are compact, high voltage pulse generators consisting of a pair of conducting foils wound in a spiral and a switch. We developed an improved analytical model predicting...
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Vector inversion generators or spiral generators are compact, high voltage pulse generators consisting of a pair of conducting foils wound in a spiral and a switch. We developed an improved analytical model predicting the time evolution of the output voltage of such spiral generators. Our model (i) takes into account that the current in the switch results from the current on active and passive waveguides and (ii) takes into account the losses of the conductor in equations describing the propagation of voltage and current pulses in both waveguides. The model is compared to experimental results involving different input switches and at different temperatures to investigate the influence of resistive losses on the output voltage. The model is further developed to obtain the time evolution of the current in the switch. Our model is then used to predict the amplitude of the first two peaks of the oscillatory response of spiral generators as a function of a set of dimensionless parameters.
2D metal carbides and nitrides (MXene) are promising material platforms for on-chip neural networks owing to their nonlinear saturable absorption effect. The localized surface plasmon resonances in metallic MXene nano...
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2D metal carbides and nitrides (MXene) are promising material platforms for on-chip neural networks owing to their nonlinear saturable absorption effect. The localized surface plasmon resonances in metallic MXene nanoflakes may play an important role in enhancing the electromagnetic absorption;however, their contribution is not determined due to the lack of a precise understanding of its localized surface plasmon behavior. Here, a saturable absorber made of MXene thin film and a silicon waveguide with MXene flakes overlayer are developed to perform neuromorphic tasks. The proposed configurations are reconfigurable and can therefore be adjusted for various applications without the need to modify the physical structure of the proposed MXene-based activator configurations via tuning the wavelength of operation. The capability and feasibility of the obtained results of machine-learning applications are confirmed via handwritten digit classification task, with near 99% accuracy. These findings can guide the design of advanced ultrathin saturable absorption materials on a chip for a broad range of applications.
Physical limitations on the operation speed of electronic devices has motivated the search for alternative ways to process information. The past few years have seen the development of neuromorphic photonicsia branch o...
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Physical limitations on the operation speed of electronic devices has motivated the search for alternative ways to process information. The past few years have seen the development of neuromorphic photonicsia branch of photonics where the physics of optical and optoelectronic devices is combined with mathematical algorithms of artiecial neural networks. Such a symbiosis allows certain classes of computation problems, including some involving artiecial intelligence, to be solved with greater speed and higher energy efeciency than can be reached with electronic devices based on the von Neumann architecture. We review optical analog computing, photonic neural networks, and methods of matrix multiplication by optical means, and discuss the advantages and disadvantages of existing approaches.
To keep up with the growing bandwidth demands, photonic integrated circuits (PICs) have been widely employed in various application scenarios where high capacity and high-bandwidth density interconnects are required. ...
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To keep up with the growing bandwidth demands, photonic integrated circuits (PICs) have been widely employed in various application scenarios where high capacity and high-bandwidth density interconnects are required. However, it is challenging to scale the PICs toward future petabit per second capacity requirements. We study the scalability bottlenecks of PICs in terms of guiding materials, dense integration approaches, wide-band optical sources, and high efficiency tunable and modulation devices. We also look for possible solutions to address these challenges. In the end, we provide a perspective on future PIC development. Moore's law for integrated photonics may last for a much shorter time than that in the microelectronics industry, requiring significant innovations and technological breakthroughs in PIC research.
This work presents a detailed modeling-based analysis of integrated micro-ring resonators used for absorption spectroscopy. Generally, sensors based on micro-ring resonators detect changes in the real part of the sens...
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This work presents a detailed modeling-based analysis of integrated micro-ring resonators used for absorption spectroscopy. Generally, sensors based on micro-ring resonators detect changes in the real part of the sensing medium refractive index, at critical coupling. In absorption spectroscopy, however, micro-ring resonators are used to measure changes in the imaginary part of the index and are most sensitive away from critical coupling, with separate maxima in the under- and over-coupled regimes. In this work, we present a detailed analysis of the under-coupled regime, explaining the relationships between sensitivity, mode confinement, and losses. The analysis is based on reverse-symmetry waveguides to increase the proportion of mode power in the sensing medium and incorporates a realistic model of propagation losses based on experimental measurements of sidewall roughness. The analysis demonstrates that the resonant nature of the sensor is most effective at small radii compared to a non-resonant structure of equal size and shows a behavior of diminishing returns at larger device sizes regarding sensitivity and elevated proportions of mode power in the evanescent field.
A comprehensive theoretical analysis of two-plane waveguide coupler with arbitrary coupling ratios in the H-plane and E-plane directions is provided and a design of the two-plane coupler with 1:2 $\mathbf{1}:\sqrt{\ma...
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A comprehensive theoretical analysis of two-plane waveguide coupler with arbitrary coupling ratios in the H-plane and E-plane directions is provided and a design of the two-plane coupler with 1:2 $\mathbf{1}:\sqrt{\mathbf{2}}$ coupling ratio in the H-plane direction and 2:1 $\sqrt{\mathbf{2}}:\mathbf{1}$ coupling ratio in the E-plane direction is reported. The analysis of the two-plane waveguide coupler is fully refined and accomplished by the authors. To realise an arbitrary and different coupling ratio in the two directions, it is crucial to specifically constrain the transition phase of the quarter model of the two-plane coupler for different boundaries as necessitated by mode polarity. A prototype of the proposed two-plane coupler is manufactured and measured to verify the concept. Its performance is observed from 27.0 to 29.5 GHz (8.85% fractional bandwidth). The measurement results are basically in accord with the simulation results, demonstrating the reliability of the theoretical analysis. Finally, samples of designed conventional H-plane and E-plane couplers are provided, cascading of which can realise the same functionality as the proposed two-plane coupler. Compared with one-plane couplers, the two-plane coupler reported realises overall miniaturisation rates in terms of length and volume around 58.4% and 50.1%, respectively. According to the demonstration and verification of the two-plane couplers having arbitrary coupling ratios, the employment of the two-plane couplers to replace the conventional one-plane couplers to realise miniaturisation of 2-D beam switching matrices will be promoted in future applications.
We have implemented and verified a parallel-series Iwan-type nonlinear model in a 3D fourth-order staggered-grid velocity-stress finite-difference method. The Masing unloading and reloading behavior is simulated by tr...
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We have implemented and verified a parallel-series Iwan-type nonlinear model in a 3D fourth-order staggered-grid velocity-stress finite-difference method. The Masing unloading and reloading behavior is simulated by tracking an overlay of concentric von Mises yield surfaces. Lame parameters and failure stresses pertaining to each surface are cali-brated to reproduce the stress-strain backbone curve, which is controlled by the reference strain assigned to a given depth level. The implementation is successfully verified against established codes for 1D and 2D SH-wave benchmarks. The capabilities of the method for large-scale nonlinear earthquake modeling are demonstrated for an Mw 7.8 dynamic rup-ture ShakeOut scenario on the southern San Andreas fault. Although ShakeOut simula-tions with a single yield surface reduces long-period ground-motion amplitudes by about 25% inside a waveguide in greater Los Angeles, Iwan nonlinearity further reduces the values by a factor of 2. For example, inside the Whittier Narrows corridor spectral accel-erations at a period of 3 s are reduced from 1g in the linear case to about 0.8 in the bilinear case and to 0.3-0.4g in the multisurface Iwan nonlinear case, depending on the choice of reference strain. Normalized shear modulus reductions reach values of up to 50% in the waveguide and up to 75% in the San Bernardino basin at the San Andreas fault. We expect the implementation to be a valuable tool for future nonlinear 3D dynamic rupture and ground-motion simulations in models with coupled source, path, and site effects.
Integrated quantum photonics (IQP) provides a path to practical, scalable quantum computation, communications and information processing. Realization of an IQP platform requires controlled engineering of many nanophot...
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Integrated quantum photonics (IQP) provides a path to practical, scalable quantum computation, communications and information processing. Realization of an IQP platform requires controlled engineering of many nanophotonic components. However, the range of materials for monolithic platforms is limited by the simultaneous need for high-quality quantum light sources, high optical performance, and availability of scalable nanofabrication techniques. Here, the fabrication of IQP components from the recently emerged material hexagonal boron nitride (hBN), including tapered waveguides, microdisks, and 1D and 2D photonic crystal cavities, is demonstrated. Resonators with quality factors greater than 4000 are achieved, and proof-of-principle complex, free-standing IQP circuitry fabricated from single-crystal hBN is engineered. The results show the potential of hBN for scalable integrated quantum technologies.
The demand for high-speed and low-loss interconnects in modern computer architectures is difficult to satisfy by using traditional Si-based electronics. Although optical interconnects offer a promising solution owing ...
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The demand for high-speed and low-loss interconnects in modern computer architectures is difficult to satisfy by using traditional Si-based electronics. Although optical interconnects offer a promising solution owing to their high bandwidth, low energy dissipation, and high-speed processing, integrating elements such as a light source, detector, and modulator, comprising different materials with optical waveguides, presents many challenges in an integrated platform. Two-dimensional (2D) van der Waals (vdW) semiconductors have attracted considerable attention in vertically stackable optoelectronics and advanced flexible photonics. In this study, optoelectronic components for exciton-based photonic circuits are demonstrated by integrating lithographically patterned poly(methyl methacrylate) (PMMA) waveguides on 2D vdW devices. The excitonic signals generated from the 2D materials by using laser excitation were transmitted through patterned PMMA waveguides. By introducing an external electric field and combining vdW heterostructures, an excitonic switch, phototransistor, and guided-light photovoltaic device on SiO2/Si substrates were demonstrated.
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