We propose silicon nitride (Si3N4) nanowaveguide-based CMOS-compatible integrated sources of spectrally pure visible-telecom photon pairs. Our designs are intrinsically devoid of spectral correlations, eradicating the...
详细信息
We propose silicon nitride (Si3N4) nanowaveguide-based CMOS-compatible integrated sources of spectrally pure visible-telecom photon pairs. Our designs are intrinsically devoid of spectral correlations, eradicating the need for narrow-band filtering that reduces the source brightness. Further, the signal photons lie in the visible–near-infrared (vis-NIR) band, which can provide increased heralding efficiency of the idler photon in the telecom band using high-efficiency single-photon detectors. For example, a rectangular-cross-section silica-clad Si3N4 nanowaveguide with dimensions 680~nm×840~nm and length 7 cm provides a heralded single-photon purity of approximately 91% for a pump wavelength of 956.8 nm and a pump bandwidth of 1200 GHz, with the signal and idler lying in the visible and telecom bands at approximately 701 nm and approximately 1505 nm, respectively, demonstrating a peak spectral brightness of approximately 1.2×104 photon pairs/s/nm/mW2 for a linear propagation loss of 0.5 dB/cm. The effect of propagation losses on the purity is also studied for such source designs. We also propose some designs capable of generating high-purity photon pairs to address various specific vis-NIR quantum memory transitions with telecom-band interfacing for long-distance hybrid quantum networks. Such compact on-chip sources could have potential applications in various quantum technologies, such as sensing, simulation, computing, communication, and networking.
High-efficiency solar cells use waveguides for concentration and higher light harvesting, reducing the area of the solar panels and decreasing their costs. Hence, this work aims to simulate and analyze a solar concent...
详细信息
ISBN:
(数字)9781665452731
ISBN:
(纸本)9781665452731
High-efficiency solar cells use waveguides for concentration and higher light harvesting, reducing the area of the solar panels and decreasing their costs. Hence, this work aims to simulate and analyze a solar concentrator built with three cylindrical lenses and three waveguides. The simulation of the model was conducted using COMSOL Multiphysics software. Results show a maximum optical efficiency of 77% and a concentration ratio of 3.5. The lenses and waveguides sets were developed as a single bulk structure. The model exhibits potential for use in photovoltaics and thermal solar conversion with concentrated radiation.
We consider the propagation of acoustic waves in awaveguide which is unbounded in one direction. We explain how to construct at a given wavenumber penetrable obstacles characterised by a physical coefficient. which ar...
详细信息
We consider the propagation of acoustic waves in awaveguide which is unbounded in one direction. We explain how to construct at a given wavenumber penetrable obstacles characterised by a physical coefficient. which are invisible in various ways. In particular, we focus our attention on invisibility in reflection (the reflection matrix is zero), invisibility in reflection and transmission (the scattering matrix is the same as if there were no obstacle) and relative invisibility (two different obstacles have the same scattering matrix). To study these problems, we use a continuation method which requires to compute the scattering matrix S(rho) as well as its differential with respect to the material index dS(rho). The justification of the method also needs for the proof of abstract results of surjectivity of well-chosen functionals constructed from the terms of dS(rho). We provide a complete proof of the results in monomode regime when the wavenumber is such that only one mode can propagate. And we give all the ingredients to implement the method in multimode regime. We end the article by presenting numerical results to illustrate the analysis.
Accurate and stable frequency sources can be realized by locking lasers to well-known transitions between energy levels in isolated quantum systems such as alkali atoms. Unfortunately, current implementations of such ...
详细信息
Accurate and stable frequency sources can be realized by locking lasers to well-known transitions between energy levels in isolated quantum systems such as alkali atoms. Unfortunately, current implementations of such frequency standards typically involve bulky optical setups and discrete optical components. Furthermore, the common transitions of alkali atoms are in the near-infrared, hindering their use as frequency references in the telecom regime. Our current work is focused on mitigating these deficiencies. In particular, we demonstrate the design, fabrication, and experimental characterization of an on-chip telecom frequency reference that is based on a ladder transition of rubidium atoms integrated with nanoscale optical waveguides. These atomic cladded waveguides are implemented in a serpentine geometry in order to optimize the chip area and maximize the interaction of light with the alkali atoms. Following its fabrication, the device is used to stabilize a telecom laser around a 1.5 mu m wavelength to a precision better than 200 kHz at similar to 250 s. Moreover, in spite of the fact that the natural lifetime of the excited state of the atom corresponding to only a few megahertz line widths, the nanoscale confinement of the optical mode dictates ultrashort interaction times and extreme photonic energy densities allowing us to demonstrate low power and faster (similar to 200 MHz) all-optical modulation of a near-infrared light with a telecom light. The results presented in this paper push forward the efforts toward fully integrated chip-scale stabilization system and provide an extremely efficient link between atomic based devices and silicon photonics platform in the telecom.
The delivery of optical signals from an external light source to a nanoscale waveguide is highly important for the development of nanophotonic circuits. However, the efficient coupling of external light energy into na...
详细信息
The delivery of optical signals from an external light source to a nanoscale waveguide is highly important for the development of nanophotonic circuits. However, the efficient coupling of external light energy into nanophotonic components is difficult and still remains a challenge. Herein, we use an external silica nanofiber to light up an organic- inorganic hybrid nanowaveguide, namely, a system composed of a polymer filament doped with MoS2 quantum dots. Nanofiber-excited nanowaveguides in a crossed geometry are found to asymmetrically couple excitation signals along two opposite directions, with different energy dissipation resulting in different colors of the light emitted by MoS2 quantum dots and collected from the waveguide terminals. Interestingly, rainbow-like light in the hybrid waveguide is achieved by three-in-one mixing of red, green, and blue components. This heterodimensional system of dots in waveguide represents a significant advance toward all-optical routing and full- color display in integrated nanophotonic devices.
To mitigate the temperature sensitivity of photonic devices, materials with a negative thermo-optical coefficient (TOC) are integrated to optical waveguides. However, previously reported waveguides are made athermal a...
详细信息
To mitigate the temperature sensitivity of photonic devices, materials with a negative thermo-optical coefficient (TOC) are integrated to optical waveguides. However, previously reported waveguides are made athermal at only one wavelength. In this paper, we theoretically propose a new broadband athermal waveguide, which consists of TiO2 with a negative TOC and SiC with a positive TOC in its core. This composite core shows a near-zero broadband effective TOC, i.e., +/- 1 x 10(-6)/K over a 780-nm bandwidth from 1280 to 2060 nm. Furthermore, it also has low anomalous dispersion, from 66 to 329 ps/nm/km in the same wavelength range. This new athermal waveguide, when used to form microresonators, enables us to achieve broadband nonlinear applications with negligible intra-cavity thermal dynamics on a chip. We also show that the proposed waveguide can be tightly bent without suffering from a large bending loss/substrate leakage, which is suitable for dense integration.
Bound states in the continuum (BICs) are trapped or guided modes with frequencies in radiation continua. They are associated with high-quality-factor resonances that give rise to strong local field enhancement and rap...
详细信息
Bound states in the continuum (BICs) are trapped or guided modes with frequencies in radiation continua. They are associated with high-quality-factor resonances that give rise to strong local field enhancement and rapid variations in scattering spectra, and have found many valuable applications. A guided mode of an optical waveguide can also be a BIC, if there is a lateral structure supporting compatible waves propagating in the lateral direction;i.e., there is a channel for lateral leakage. A BIC is typically destroyed (becomes a resonant or a leaky mode) if the structure is slightly perturbed, but some BICs are robust with respect to a large family of perturbations. In this paper, we show (analytically and numerically) that a typical BIC in optical waveguides with a left-right mirror symmetry and a single lateral leakage channel is robust with respect to any structural perturbation that preserves the left-right mirror symmetry. Our study improves the theoretical understanding on BICs and can be useful when applications of BICs in optical waveguides are explored. (C) 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
We present a numerical approach to efficiently calculate spin-wave dispersions and spatial mode profiles in magnetic waveguides of arbitrarily shaped cross section with any non-collinear equilibrium magnetization that...
详细信息
We present a numerical approach to efficiently calculate spin-wave dispersions and spatial mode profiles in magnetic waveguides of arbitrarily shaped cross section with any non-collinear equilibrium magnetization that is translationally invariant along the waveguide. Our method is based on the propagating-wave dynamic-matrix approach by Henry et al. (Ref. 19) and extends it to arbitrary cross sections using a finite-element method. We solve the linearized equation of motion of the magnetization only in a single waveguide cross section, which drastically reduces computational effort compared to common three-dimensional micromagnetic simulations. In order to numerically obtain the dipolar potential of individual spin-wave modes, we present a plane-wave version of the hybrid finite-element/boundary-element method by Fredkin and Koehler which we extend to a modified version of the Poisson equation. Our method is applied to several important examples of magnonic waveguides including systems with surface curvature, such as magnetic nanotubes, where the curvature leads to an asymmetric spin-wave dispersion. In all cases, the validity of our approach is confirmed by other methods. Our method is of particular interest for the study of curvature-induced or magnetochiral effects on spin-wave transport and also serves as an efficient tool to investigate standard magnonic problems.& nbsp;(C) 2021 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license(http://***/licenses/by/4.0/).
In this study, dyadic Green's functions (DGFs) for a partially filled rectangular waveguide in the presence of a graphene layer is derived in closed form using the Ohm-Rayleigh method and the method of scattering ...
详细信息
In this study, dyadic Green's functions (DGFs) for a partially filled rectangular waveguide in the presence of a graphene layer is derived in closed form using the Ohm-Rayleigh method and the method of scattering superposition. Having DGFs of a linear medium, the response of the structure to any arbitrary current distribution can be achieved. In this work, after a brief review on governing equations for graphene conductivity, the electric fields of the structure due to infinitesimal electric dipoles are obtained using the proposed DGFs in closed form. To show the efficiency and accuracy of the proposed method, the results are compared with the simulation results of commercial software, where excellent agreement is observed.
Novel rectangular waveguides with graphene inserts biased by light are proposed herein. The graphene films short the conductor plates of waveguides and support the localized transverse-electric modes. Their electric f...
详细信息
Novel rectangular waveguides with graphene inserts biased by light are proposed herein. The graphene films short the conductor plates of waveguides and support the localized transverse-electric modes. Their electric fields are parallel to the wide walls of these waveguides, and the eigenmodes have decreased conductor loss. The designs do not involve the conductor and graphene strips with their sharp edges, and the loss associated with the current crowding effect is excluded. The waveguides are treated in the quasi-linear regime using a rigorous field matching method, and the complex dispersion eigenmodal equation is solved using a validated iteration algorithm. At the terahertz frequencies of amplification, where the real part of graphene conductivity is negative, a gain increase is found with the eigenmodal number. This gain can be tuned by the waveguide geometry, dielectric filling, and the level of quasi-Fermi energy. The ideal waveguide theory is corrected using a perturbation approach and the Drude model of surface resistance of waveguide plates.
暂无评论