Integrated optics play important role in the development for optical network devices, optical processing, instrumentation and quantum information device. Here, multimode interference (MMI) coupler is one of basic comp...
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Integrated optics play important role in the development for optical network devices, optical processing, instrumentation and quantum information device. Here, multimode interference (MMI) coupler is one of basic component preferred for these integrated optic devices in which MMI coupler based on general interference (GIMMI) has been focused for large scale integrated optic devices because of compact size in comparison to MMI coupler based restricted interference (RIMMI). In this paper, we have reviewed different GIMMI structures reported previously. Different waveguide materials are mentioned and compared for fabrication of GIMMI device. The coupling behaviors and modal analysis of GIMMI couplers and their different tapered structures are estimated by using simple model based on sinusoidal modes showing reduced coupling lengths in down tapered structures in comparison to other structures. The excess loss, polarization dependence loss and crosstalk versus fabrication tolerances are obtained to compare their performances revealing almost same losses and fabrication tolerance. The paper reports the use of the GIMMI coupler in wavelength multiplexing, power splitting, switching, optical processing. Finally, Quantum optic application of GIMMI coupler is shown indicating high quantum fidelity of 50:50 coupling ratio.
Anon -uniform distributed silicon optical phased array (OPA) is proposed and numerically demonstrated to realize high directionality and a wide range for beam steering. The OPA is composed of grating antennas with dua...
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Anon -uniform distributed silicon optical phased array (OPA) is proposed and numerically demonstrated to realize high directionality and a wide range for beam steering. The OPA is composed of grating antennas with dual -layer corrugations along silicon strip waveguides, which can achieve a high directionality of 0.96 and a small divergence angle of 0.084 degrees. To reduce the crosstalk between adjacent antennas and realize a wide steering range, the genetic algorithm is improved and utilized to arrange the locations of grating antennas. As a proof of concept, a 32 -channel non -uniform distributed OPA is designed and thoroughly optimized. The simulation results successfully demonstrate a two-dimensional wide steering range of 70 degrees x 18.7 degrees with a side -mode suppression ratio (SMSR) over 10 dB. (c) 2024 Optica Publishing Group
We numerically and experimentally compared rectangular aluminum hollow-core waveguides with and without ridge regarding free-space coupling efficiency, dispersion, attenuation, and single-mode bandwidth for applicatio...
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We numerically and experimentally compared rectangular aluminum hollow-core waveguides with and without ridge regarding free-space coupling efficiency, dispersion, attenuation, and single-mode bandwidth for applications in terahertz technology. The ridge waveguide displays a wider single-mode bandwidth by a factor of 1.46 and reduced dispersion, but suffers from higher loss and attenuation due to increased field confinement. We numerically calculated the modes of both waveguide types and analyzed the electromagnetic properties which are in agreement with the measurement results.
Additive manufacturing (AM) is growing as a key technology for the miniaturization and integration of microwave components. Among several AM processes, laser powder-bed fusion (LPBF) is especially convenient for waveg...
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Additive manufacturing (AM) is growing as a key technology for the miniaturization and integration of microwave components. Among several AM processes, laser powder-bed fusion (LPBF) is especially convenient for waveguides and horns because it allows for 3-D printing of metal-only parts with high accuracy and low surface roughness. During the 3-D printing process, metallic powder materials are selectively consolidated by melting layer by layer together using a heat source, that is, a laser, allowing for adaptation to complex and shaped structures. The present study investigates the feasibility of using LPBF-AM to fabricate waveguides and geodesic H -plane horns in V -band. Geodesic H -plane horns comprise two parallel curved metallic plates to reduce phase errors and achieve high gain and aperture efficiency, and are particularly suited to be fabricated using LPBF. The monolithic waveguides demonstrate significantly better performance than their two-piece counterparts, achieving an average attenuation coefficient of 5.3 dB/m for the straight waveguide and 8 dB/m for the 90 -plane waveguide bend at 50-70 GHz. Similarly, the monolithic geodesic H -plane horn has higher realized gains and radiation efficiencies with only a sixth of the weight compared to the two-piece version at 52-68 GHz. The results demonstrate that the LPBF-AM technique is a promising candidate to produce monolithic metal-only microwave components in V -band.
We studied generalized Bloch boundary conditions and their finite element implementation within the theoretical framework of a symmorphic space group. By combining translation symmetry operations with mirror and rotat...
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We studied generalized Bloch boundary conditions and their finite element implementation within the theoretical framework of a symmorphic space group. By combining translation symmetry operations with mirror and rotational symmetry operations, we developed a procedure for implementing generalized Bloch boundary conditions in the finite element method (FEM) for periodic photonic structures. First, we lay out the theoretical foundation and numerical implementation of generalized Bloch boundary conditions in FEM. We illustrate the proposed method via 2D/3D periodic photonic structures. Without a loss of generality, we calculate the band structures of 2D/3D photonic crystals using our proposed generalized Bloch boundary conditions and benchmark the results against the conventional Bloch boundary conditions. The comparisons show that band structure and eigenmode yield excellent agreement with the results obtained from conventional Bloch boundary conditions. However, our method has improved the computational efficiency by at least twofold. We further elaborate the comparisons with computation errors, memory efficiency, and computation times, all of which show that our proposed method outperforms the conventional one due to careful consideration of the mirror and rotational symmetry operation, apart from the translation symmetry. In addition, our method can easily be extended to other methods such as FDTD and transfer matrix. (c) 2024 Optica Publishing Group
We numerically analyzed the power-coupling characteristics between a high-index-contrast dielectric slot waveguide and a metal-insulator-metal (MIM) plasmonic slot waveguide as functions of structural parameters. Coup...
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We numerically analyzed the power-coupling characteristics between a high-index-contrast dielectric slot waveguide and a metal-insulator-metal (MIM) plasmonic slot waveguide as functions of structural parameters. Couplings due mainly to the transfer of evanescent components in two waveguides generated high transmission efficiencies of 62% when the slot widths of the two waveguides were the same and 73% when the waveguides were optimized by slightly different widths. The maximum transmission efficiency in the slot-to-slot coupling was about 10% higher than that in the coupling between a normal slab waveguide and an MIM waveguide. Large alignment tolerance of the slot-to-slot coupling was also proved. Moreover, a small gap inserted into the interface between two waveguides effectively enhances the transmission efficiency, as in the case of couplings between a normal slab waveguide and an MIM waveguide. In addition, couplings with very wideband transmissions over a wavelength region of a few hundred nanometers were validated. (C) 2015 Optical Society of America
Silicon-rich nitride films are developed and explored using an inductively coupled plasma chemical vapor deposition system at low temperature of 250 degrees C with an ammonia-free gas chemistry. The refractive index o...
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Silicon-rich nitride films are developed and explored using an inductively coupled plasma chemical vapor deposition system at low temperature of 250 degrees C with an ammonia-free gas chemistry. The refractive index of the developed silicon-rich nitride films can increase from 2.2 to 3.08 at 1550 nm wavelength while retaining a near-zero extinction coefficient when the amount of silane increases. Energy dispersive spectrum analysis gives the silicon to nitrogen ratio in the films. Atomic force microscopy shows a very smooth surface, with a surface roughness rootmean-square of 0.27 nm over a 3 mu m x 3 mu m area of the 300 nm thick film with a refractive index of 3.08. As an application example, the 300 nm thick silicon-rich nitride film is then patterned by electron beam lithography and etched using inductively coupled plasma system to form thin-film micro/nano waveguides, and the waveguide loss is characterized.
We report experimental observation and theoretical explanation of novel propagation regimes for optical beams in an artificial nonlinear material with outstanding photorefractive properties. Nondiffractive beams, whic...
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We report experimental observation and theoretical explanation of novel propagation regimes for optical beams in an artificial nonlinear material with outstanding photorefractive properties. Nondiffractive beams, which keep their shapes invariant in the free space, feature self -splitting from the middle in two separating secondary beams, due to the light -matter interaction. The splitting degree is controlled by means of a phase -pre -modulation method. We propose applications of the self -splitting to the creation of an effectively chiral waveguide and the generation of even -order vortices.
Photonic and plasmonic hybrid nanostructures are the key solution for integratednanophotonic circuits with ultracompact size but relative low loss. However,the poor tunability and modulability of conventional waveguid...
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Photonic and plasmonic hybrid nanostructures are the key solution for integratednanophotonic circuits with ultracompact size but relative low loss. However,the poor tunability and modulability of conventional waveguides makesthem cumbersome for optical multiplexing. Here we make use of twodimensionalmolecular crystal, α-Sb_(2)O_(3) as a dielectric waveguide via totalinternal reflection, which shows polarization-sensitive modulation of the propagatingbeams due to its large polarization mode dispersion. Both experimentsand simulations are performed to verify such concept. These Sb_(2)O_(3) nanoflakescan be coupled with plasmonic nanowires to form nanophotonic beam splittersand routers which can be easily modulated by changing the polarization of theincidence. It thus provides a robust, exploitable and tunable platform for onchipnanophotonics.
On-chip integrated meta-optics hold great promise in creating high-performance and ultracompact optical display devices. Although previous on-chip metasurfaces for meta-display have predominantly enabled binary-image ...
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On-chip integrated meta-optics hold great promise in creating high-performance and ultracompact optical display devices. Although previous on-chip metasurfaces for meta-display have predominantly enabled binary-image near-/far-field exhibition functionalities, this remains a challenge and has not been fully explored to induce multiple intensity levels for meticulous grayscale images in an on-chip integrated scheme. Here, we propose and experimentally demonstrate a practical approach to embed a high-resolution grayscale image display into an on-chip metasurface integrated on a waveguide in the visible regime. By employing the on-chip meta-diatom interference at the nanoscale, continuous intensity levels of the local optical scattering can be modulated for the out-coupling lightwave to create a high-resolution (pixel size of 440 x 440 nm(2)) and broadband meticulous grayscale image display. Moreover, directional-selective dual-channel grayscale displays are further expanded by spatially hybridizing the meta-diatom interferences along both x-/y-directions and jointly storing two grayscale images into a single on-chip metasurface pattern. Owing to the on-chip optical propagation scheme, the captured meticulous grayscale display with high fidelity enjoys a high signal-to-noise ratio and large dynamic range uniquely due to zeroth-order diffraction being interference-free. We envision that the proposed meticulous grayscale meta-display driven by an on-chip guided wave allows for their miniaturized integration and promises high-density information storage/encryption, next-generation high-quality miniature displays, and future virtual/augmented reality functionalities.
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