The existing silicon -carbide -on -insulator photonic platform utilizes a thin layer of silicon dioxide under silicon carbide (SiC) to provide optical confinement and mode isolation. Here, we replace the underneath si...
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The existing silicon -carbide -on -insulator photonic platform utilizes a thin layer of silicon dioxide under silicon carbide (SiC) to provide optical confinement and mode isolation. Here, we replace the underneath silicon dioxide layer with 1 - mu m -thick aluminum nitride and demonstrate a 4H -siliconcarbide -on -aluminum -nitride integrated photonic platform for the first time to our knowledge. Efficient grating couplers, low -loss waveguides, and compact microring resonators with intrinsic quality factors up to 210,000 are fabricated. In addition, by undercutting the aluminum nitride layer, the intrinsic quality factor of the silicon carbide microring is improved by nearly one order of magnitude (1.8 million). Finally, an optical pump-probe method is developed to measure the thermal conductivity of the aluminum nitride layer, which is estimated to be over 30 times of that of silicon dioxide. (c) 2024 Optica Publishing Group
A biperiodic nanostructuration consisting of a superperiodicity added to a nanohole lattice of subwavelength pitch is demonstrated to provide both modal confinement and wavelength selectivity within a hybrid III-V on ...
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A biperiodic nanostructuration consisting of a superperiodicity added to a nanohole lattice of subwavelength pitch is demonstrated to provide both modal confinement and wavelength selectivity within a hybrid III-V on a silicon waveguide. The wavelength-selective behavior stems from finely tuned larger holes. Such biperiodic hybrid waveguides have been fabricated by oxide-free bonding III-V material on silicon and display well-defined stop bands. Such nanostructured waveguides offer the versatility for designing advanced optical functions within hybrid devices. Moreover, keeping the silicon waveguide surface planar, such nanostructured waveguides are compatible with electrical operation across the oxide-free hybrid interface. (C) 2015 Optical Society of America
Topological corner states have been used to develop topologically robust Fano-resonant systems immune to structural perturbations while preserving the ultra -sensitive profiles under external factors. In this work, we...
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Topological corner states have been used to develop topologically robust Fano-resonant systems immune to structural perturbations while preserving the ultra -sensitive profiles under external factors. In this work, we have extended the possibility of obtaining Fano-resonant systems by introducing type -II and type -III corner states with a large modal surface to this class of resonance. Through photonic lattices with low symmetry, such as C 2 , it is easy to obtain type -II and type -III corner states due to the tailoring of long-range interactions. Subsequently, one can combine topological cavities of type -II and type -III corner modes with topological waveguides obtained from a first -order topological insulating phase. Our results may pave the way to generate devices suitable for creating non -classical light applicable in quantum computing and ultra -sensitive sensors employing large -area topological states. (c) 2024 Optica Publishing Group
This letter introduces a novel quadruplet structure in waveguide technology, comprising a dual-mode TM cavity within two lambda/4 TE cavities. This structure demonstrates the capability of generating responses with fo...
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This letter introduces a novel quadruplet structure in waveguide technology, comprising a dual-mode TM cavity within two lambda/4 TE cavities. This structure demonstrates the capability of generating responses with four poles and two transmission zeros (TZs). Notably compact, it accommodates both wideband and narrowband responses effectively. The TZs are obtained by exploiting the nonresonating modes within the TM section. The coupling between the resonant mode of the TE section and both resonating and nonresonating modes is achieved by precise positioning of the TE section relative to the TM section. This inherent flexibility in TZ positioning renders the structure highly adaptable. Moreover, this structure can be exploited as building block for the design of higher order filters. Experimental results validate the viability and effectiveness of the proposed structure.
The antenna is an indispensable device in terahertz (THz) wireless communication systems. Owing to the high propagation attenuation of THz waves in atmospheric, THz antennas with high gain and low sidelobe levels (SLL...
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The antenna is an indispensable device in terahertz (THz) wireless communication systems. Owing to the high propagation attenuation of THz waves in atmospheric, THz antennas with high gain and low sidelobe levels (SLLs) are in an urgent need. Here, a metal waveguide transmitarry antenna (MWTA) is proposed to realize high gain and low SLLs at dual THz bands simultaneously. At the frequencies of 0.14 and 0.0972 THz, the peak gains are 32 and 28 dBi, the SLLs are both 21 dB lower than the main lobe, and the 3 dB beamwidths are 4.4(degrees) and 5.7, respectively. As a proof of concept, a prototype with a diameter of 48 mm is fabricated and the measured results are in good agreement with the simulations. The proposed MWTA with high gain and low SLLs at dual THz bands holds great application potential in 6G wireless communication, non-destructive testing, and biomedicine.
The nonlinear absorption properties of a germanium-on-silicon waveguide have been characterized across the two-photon absorption (TPA) transmission window. The results show that the TPA parameters in germanium wavegui...
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The nonlinear absorption properties of a germanium-on-silicon waveguide have been characterized across the two-photon absorption (TPA) transmission window. The results show that the TPA parameters in germanium waveguides are much stronger than the peak values in silicon, in good agreement with selected measurements conducted in bulk materials. Exploiting the large nonlinear absorption near the bandedge, efficient all-optical modulation is achieved with a modulation depth of similar to 8 dB and a response time <5 ps. (C) 2015 Optical Society of America
All-optical modulation has been demonstrated in a germanium-on-silicon rib waveguide over the mid-infrared wavelength range of 2-3 mu m using a free-carrier absorption scheme. Transmission measurements have shown the ...
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All-optical modulation has been demonstrated in a germanium-on-silicon rib waveguide over the mid-infrared wavelength range of 2-3 mu m using a free-carrier absorption scheme. Transmission measurements have shown the waveguides to have low propagation losses that are relatively independent of wavelength out to 3.8 mu m, indicating that the modulation could be extended further into the mid-infrared region for applications in sensing and spectroscopy. By monitoring the material recovery, the free-carrier lifetime of the micron-sized waveguides has been estimated to be similar to 18 ns, allowing for modulation speeds within the megahertz regime. (C) 2015 Optical Society of America
Subject of study. The absorption coefficient of a metal-to-metal waveguide in a terahertz quantum cascade laser based on GaAs/AlGaAs heterostructures is studied. Aim of study. A theoretical study is performed to deter...
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Subject of study. The absorption coefficient of a metal-to-metal waveguide in a terahertz quantum cascade laser based on GaAs/AlGaAs heterostructures is studied. Aim of study. A theoretical study is performed to determine whether it is possible to significantly reduce the number of stages (the thickness of the active region) in terahertz quantum cascade lasers based on two previously implemented cascade designs with high-gain GaAs/AlGaAs heterostructures with quantum wells and a metal-to-metal waveguide. Method. The absorption coefficient of the metal-to-metal waveguide is numerically calculated using a transfer-matrix method based on Maxwell's equations. Main results. The absorption coefficient of a metal-to-metal waveguide in a terahertz quantum cascade laser is calculated as a function of the number of stages in the laser. We show that, for a laser with a gain of 200 cm-1 - 1 at a temperature of 100 K, only five stages are required for lasing to occur with a total waveguide thickness of 428 nm. Practical significance. Calculations show that it is possible to significantly reduce the thickness of the active region and the number of stages in a terahertz quantum cascade laser, which should simplify development of such a laser and lead to wider use of such lasers. (c) 2024 Optica Publishing Group
The study of Rossby wave propagation in strong jet stream waveguides is essential, as extreme weather events are associated with persistent atmospheric patterns at the surface which may be favored by quasi stationary ...
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The study of Rossby wave propagation in strong jet stream waveguides is essential, as extreme weather events are associated with persistent atmospheric patterns at the surface which may be favored by quasi stationary Rossby waves in the upper troposphere through these pathways. But so far, all the studies are mostly for winter and summer seasons. Therefore, in the present study, we extended earlier works to the transition seasons. The waveguide patterns in both hemispheres during the spring and autumn transition seasons are explored using numerical simulations from a baroclinic model with six selected forcings in the 1979-2016 period. The results show that stronger subtropical jet streams are found in boreal and austral spring associated with stronger wave propagation. Particularly, stronger eddy kinetic energy and wave activity flux are found in boreal spring from the north of Middle East to eastern North Pacific, associated with stronger subtropical Asian jet, and in austral autumn in western Pacific region, associated with greater extension of polar jet. Interhemispheric propagation is verified in spring season in both hemispheres, through the equatorial eastern Pacific and Atlantic ducts, with a northwest-southeast orientation.
In this paper, the propagation of electromagnetic rays in a tropospheric waveguide and spatial processing using digital antenna arrays are studied. The beam traveling through the layers of the atmosphere depends on th...
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