Acoustic tweezers use ultrasound for contact-free, bio-compatible, and precise manipulation of particles from millimeter to submicrometer scale. In microfluidics, acoustic tweezers typically use an array of sources to...
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Acoustic tweezers use ultrasound for contact-free, bio-compatible, and precise manipulation of particles from millimeter to submicrometer scale. In microfluidics, acoustic tweezers typically use an array of sources to create standing wave patterns that can trap and move objects in ways constrained by the limited complexity of the acoustic wave field. Here, we demonstrate spatially complex particle trapping and manipulation inside a boundary-free chamber using a single pair of sources and an engineered structure outside the chamber that we call a shadow waveguide. The shadow waveguide creates a tightly confined, spatially complex acoustic field inside the chamber without requiring any interior structure that would interfere with net flow or transport. Altering the input signals to the two sources creates trapped particle motion along an arbitrary path defined by the shadow waveguide. Particle trapping, particle manipulation and transport, and Thouless pumping are experimentally demonstrated.
We analyze the parity-time (PT) symmetric phase in coupled two waveguides with a Kerr-type medium in between. Paying attention to the emitted field from a dipole source inside, we show that when the strength of the di...
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We analyze the parity-time (PT) symmetric phase in coupled two waveguides with a Kerr-type medium in between. Paying attention to the emitted field from a dipole source inside, we show that when the strength of the dipole increases, the optical Kerr effect can render a phase transition from the exact PT phase to the broken PT phase. Furthermore, a salient phenomenon of bistable-like PT phase is observed, in which the emitted field possesses a paradox between the two kinds of PT phases. We show that the physical mechanism of this bistable-like phenomenon is a globally inhomogeneous PT phase, in which different spatial regions of the whole structure can possess different PT phases (broken or exact). This study highlights the potential to manipulate the PT phase transition by using optical non linearity for many interesting applications. (C) 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
Eigenmodes of waveguide EBG channels in an electromagnetic crystal that represents a 2D periodic array of metal cylinders with gaps containing lumped elements (LEs) are studied. The array of cylinders with LEs is inst...
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Eigenmodes of waveguide EBG channels in an electromagnetic crystal that represents a 2D periodic array of metal cylinders with gaps containing lumped elements (LEs) are studied. The array of cylinders with LEs is installed between the screens of a planar waveguide. Control of propagation characteristics of the fundamental mode using variations in the LE capacitance in the cylinders inside the waveguide channel is analyzed. The problem of eigenmodes is solved with the aid of numerical simulation using periodic boundary conditions. A parametric analysis of the central frequency and the band of the single-mode regime is performed for two- and three-row EBG waveguides. It is shown that the highest (with respect to width) odd mode is the dominant factor that limits the working bandwidth.
For guiding light on a chip,it has been pivotal to use materials and process flows that allow low absorption and *** on subwavelength gratings,here,we show that it is possible to create broadband,multimode waveguides ...
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For guiding light on a chip,it has been pivotal to use materials and process flows that allow low absorption and *** on subwavelength gratings,here,we show that it is possible to create broadband,multimode waveguides with very low propagation losses despite using a strongly absorbing *** perform rigorous coupled-wave analysis and finite-difference time-domain simulations of integrated waveguides that consist of pairs of integrated high-index-contrast *** showcase this concept,we demonstrate guiding of visible light in the wavelength range of 550-650 nm with losses down to 6dB/cm using silicon gratings that have a material absorption of 13,000 dB/cm at this wavelength and are fabricated with standard silicon photonics *** approach allows us to overcome traditional limits of the various established photonics technology platforms with respect to their suitable spectral range and,furthermore,to mitigate situations where absorbing materials,such as highly doped semiconductors,cannot be avoided because of the need for electrical driving,for example,for amplifiers,lasers and modulators.
Photonic topological valley kink states have become a significant research frontier with a plethora of applications. Unlike the guided modes with adjustable widths in conventional waveguides, the valley kink states ar...
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Photonic topological valley kink states have become a significant research frontier with a plethora of applications. Unlike the guided modes with adjustable widths in conventional waveguides, the valley kink states are usually highly confined around the domain walls. They thus lack the mode width degree of freedom (DOF), posing a serious limitation to potential device applications. Here, by adding a photonic crystal (PhC) featuring Dirac points between two valley PhCs with opposite valley-Chern numbers, we design and experimentally demonstrate topological valley-locked waveguides (TVLWs) with tunable mode widths. The valley-locked waveguide modes are directly visualized via a near-field scan. Moreover, the photonic TVLWs have some unique applications, such as high-energy-capacity topological channel intersections, valley-locked energy concentrators, and topological cavities with designable confinement, as verified numerically and experimentally. The TVLWs with width DOF could be beneficial for interfacing with the existing photonic waveguides and devices, and may serve as a novel platform for practical use of topological lasing, field enhancement, and high-capacity energy transport.
We have successfully fabricated a dispersion engineered ZnSe waveguide. The ZnSe film was deposited on a CaF2 substrate by radio frequency magnetron sputtering, and the waveguide was patterned directly on the ZnSe fil...
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We have successfully fabricated a dispersion engineered ZnSe waveguide. The ZnSe film was deposited on a CaF2 substrate by radio frequency magnetron sputtering, and the waveguide was patterned directly on the ZnSe films by UV lithography and inductively coupled plasma etching. The nonlinear coefficient in the 4-mu m-width waveguide was calculated to be 0.73 w(-1) m(-1) for both TE and TM modes at 1.55 mu m. The loss of the ZnSe rib waveguides was measured to be 4.3 dB/cm at 1550 nm using the cut-back method.
Multi-layer SiN waveguides, also known as Triplex waveguide technology, are a very promising waveguide platform for applications in microwave photonics and quantum photonics due to their low loss and compact circuit f...
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Multi-layer SiN waveguides, also known as Triplex waveguide technology, are a very promising waveguide platform for applications in microwave photonics and quantum photonics due to their low loss and compact circuit footprint. However to date, the Kerr nonlinearity of these multi-layer waveguides, in particular the asymmetric double-stripe (ADS) SiN waveguides, has not been well-investigated. Here, we performed an experimental investigation of the Kerr nonlinearity of ADS SiN waveguides through four-wave mixing (FWM) experiments. We obtained the nonlinear coefficient for this waveguide to be = 0.336 ± 0.023 Wm. When combined with low propagation loss and absence of two-photon absorption, this moderate nonlinearity can be harnessed for chip-based nonlinear signal processing and quantum photonics.
Based on 3D Dirac-semimetal (DSM) modified hybrid waveguides, tunable propagation properties have been investigated, including the effects of Fermi levels, structural parameters, and operation frequency. The results s...
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Based on 3D Dirac-semimetal (DSM) modified hybrid waveguides, tunable propagation properties have been investigated, including the effects of Fermi levels, structural parameters, and operation frequency. The results show that if the operation frequency is smaller (larger) than the transition frequency (hw approximate to 2 vertical bar mu(c)), the proposed hybrid waveguides indicate strong (weak) confinement because the DSM layer manifests a high plasmonic (dielectric low) loss property. The dielectric fiber shape affects the propagation property obviously, as the elliptical parameter decreases, the confinement and figure of merit increase, and the loss reduces. With the increase in Fermi level, the propagation constant increases, and the frequency (amplitude) modulation depth is 32.31% (12.93%) if the Fermi level changes in the range of 0.01-0.15 eV. The results are very helpful in understanding the tunable mechanisms of hybrid wave-guides and designing novel plasmonic devices in the future, e.g., modulators, filters, lasers, and resonators. (C) 2021 Optical Society of America
We show detection of CO2 concentrations as low as 500 ppm using a suspended silicon photonic mid-IR waveguide. The performance is enabled by the low propagation loss (2.35 ±0.25) dB/cm permitting sensing with wav...
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We use asymptotic methods to quantify the properties of topological waveguides and show how these concise results can be used very efficiently to design materials with specific, custom specifications. This work presen...
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