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Broadband Functional Metasurfaces: Achieving Nonlinear Phase Generation toward Achromatic Surface Cloaking and Lensing
摘要： Broadband Functional Metasurfaces: Achieving Nonlinear Phase Generation toward Achromatic Surface Cloaking and Lensing. Generalized law of refraction and reflection has enabled a tremendous amount of degrees of freedom for full vectorial electromagnetic manipulation with metasurfaces. However, owing to the fundamental limitations of bandwidth and efficiency, the implementation of such principle is still far from perfect as truly achromatic efficient wavefront manipulation has not been realized. Here, a design principle based on the generalized Gires–Tournois interference model and catenary electromagnetics theory is proposed that can achieve desired broadband dispersion engineering regardless of the incident polarizations. As a proof of concept, a surface cloak is fabricated and demonstrated with a large fractional bandwidth of more than 40%. An achromatic lens antenna is also designed with focal shift deviation ratio less than 2% across X band to Ku band. Both of the devices show great advances versus traditional approaches by at least one order of magnitude. Besides, this conceptually new design is also applicable to other scenarios, such as beam splitters, vortex beam generators, or metasurface holograms. Considering their compact profiles and simple topologies, it is believed that such functional metasurfaces are promising in practical applications such as beam control, camouflage, and space communications.
关键词： Gires–Tournois interference,achromatic antennas,surface cloaks,functional metasurfaces,broadband dispersion engineering
更新于2025-09-23 15:22:29
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Enhanced Nonlinearity and Engineered Anomalous Dispersion in ${\rm{TeO_{2}}}$-coated ${\rm{Si_{3}N_{4}}}$ Waveguides
摘要： We propose designs of silicon nitride (Si3N4) waveguides with enhanced nonlinear parameter and engineered anomalous group velocity dispersion (GVD) by addition of tellurium oxide (TeO2) top-coating layers of various thicknesses. The proposed waveguides have calculated nonlinear parameters of up to three times that of stoichiometric Si3N4 and exhibit anomalous GVD at near infrared wavelengths. The GVD of such waveguides can be tuned between the normal and anomalous regime with different zero dispersion wavelengths by adjusting the thickness of TeO2 coating. These designs offer promise of higher performance nonlinear devices on a standard low-loss Si3N4 platform with the possibility of integration of active functionalities owing to higher solubility of rare earth dopants in tellurium oxide.
关键词： silicon nitride,dispersion engineering,nonlinear optics,Integrated optics,tellurium oxide
更新于2025-09-16 10:30:52
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[IEEE 2019 United States National Committee of URSI National Radio Science Meeting (USNC-URSI NRSM) - Boulder, CO, USA (2019.1.9-2019.1.12)] 2019 United States National Committee of URSI National Radio Science Meeting (USNC-URSI NRSM) - Frozen-Light Modes in 3-way Coupled Silicon Ridge Waveguides
摘要： Frozen-light modes supported by the stationary inflection point (SIP) within the pass band of 3-way coupled periodic silicon ridge waveguides is demonstrated. Precise tuning of the coupling between forward and backward propagating modes lead to mode degeneracy with vanishing group velocity. The unit cell is tuned to obtain the SIP on the third branch in the dispersion diagram. Subsequently, we demonstrate a finite structure with 23 unit cells to support the frozen mode at the SIP frequency. For this example, the group velocity at the SIP is 385 times slower than speed of light in vacuum. Transmission resonances of the finite structure, as well as the field distribution within the device at the SIP frequency are studied and presented.
关键词： Frozen-light modes,group velocity,dispersion engineering,3-way coupled periodic silicon ridge waveguides,stationary inflection point
更新于2025-09-16 10:30:52
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Ultrafast Pulse Manipulation in Dispersion-Flattened Waveguides With Four Zero-Dispersion Wavelengths
摘要： On-chip formation and manipulation of ultrashort pulses would be of great interest to ultrafast optics and integrated photonics communities. One of key issues is dispersion-assisted nonlinear interactions of broadband frequency components. In this paper, we show for the first time that a bilayer waveguide for quasi-TE mode without using a slot produces a quite flat and saddle-shaped dispersion profile. Different from previously reported TE-mode waveguides with flattened dispersion, the proposed waveguide exhibits a greatly simplified structure with no need for a high-aspect-ratio slot and has quite small group delay difference in a wide spectral range with four zero-dispersion wavelengths (ZDWs). We study supercontinuum generation in hybrid dispersion regime for the first time, in which the broadened spectrum covers a bandwidth with all ZDWs. It is found that one can obtain greatly improved spectral flatness in supercontinuum generation, with a power variation as small as 3 dB over a bandwidth of >500 nm. Moreover, the proposed waveguides are particularly suitable for low-distortion pulse propagation over a long distance, which is important for on-chip ultrashort pulse delivery.
关键词： Dispersion engineering,pulse compression,waveguide,supercontinuum generation
更新于2025-09-12 10:27:22
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[IEEE 2019 IEEE 32nd International Conference on Micro Electro Mechanical Systems (MEMS) - Seoul, Korea (South) (2019.1.27-2019.1.31)] 2019 IEEE 32nd International Conference on Micro Electro Mechanical Systems (MEMS) - Engineering and Tuning of Slow Light in Mid-Infrared Silicon-on-Insulator Photonic Crystal Waveguides
摘要： We design, fabricate, and characterize slow light devices based on photonic crystal waveguides (PhCWs) in the mid-infrared wavelength range of 3.9-3.98 μm. Lattice shifting and thermo-optic tuning methods are employed to manipulate the slow light region for potential spectroscopy sensing applications. Up to 20 nm wavelength shift of the slow light band edge is demonstrated. Normalized delay-bandwidth products as high as 0.084-0.112 are obtained thanks to dispersion engineering. The slow light enhancement effect of thermo-optic tuning efficiency is verified by the proportional relationship between the phase shift and the group index. This work serves as a proof-of-concept that slow light effect can strengthen light-matter interaction and thereby improve device performance in sensing and nonlinearity applications.
关键词： thermo-optic tuning,slow light,mid-infrared,dispersion engineering,silicon-on-insulator,photonic crystal waveguides
更新于2025-09-12 10:27:22
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Slow-Light Frequency Combs and Dissipative Kerr Solitons in Coupled-Cavity Waveguides
摘要： We study Kerr frequency combs and dissipative Kerr solitons in silicon photonic crystal coupled-cavity waveguides (CCWs) with globally optimized dispersion at telecom wavelengths. The corresponding threshold for comb generation is found to explicitly depend on the main CCW figures of merit, namely, the mode volume, the normal-mode quality factor, and the slow-light group index. Our analysis is carried out by solving the nonlinear dynamics of the CCW Bloch modes in the presence of Kerr nonlinearity and two-photon absorption. Our results open the way to CCW comb generation via dispersion engineering and slow-light enhancement.
关键词： dissipative Kerr solitons,silicon photonic crystal,dispersion engineering,slow-light enhancement,coupled-cavity waveguides,Kerr frequency combs
更新于2025-09-12 10:27:22
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The Role of Particle Size in the Dispersion Engineering of Plasmonic Arrays
摘要： Grazing diffraction orders on metal gratings give rise to peculiar optical effects that were contemplated by Wood, Rayleigh and Fano. With plasmonic nanoparticles as resonant grating elements, the phenomenology of such surface lattice resonances becomes quite rich, including spectrally narrow extinction peaks and optical band gap formation. It has been observed that at perpendicular incidence either the higher or lower energy branch corresponding to the first grazing diffraction orders is bright, i.e., couples strongly to light. Reviewing the literature, it appears that particle size is the factor determining which dispersion branch lights up. However, a consistent explanation for this effect is lacking. After revisiting the effect experimentally and by numerical simulation, we clarify the underlying physics by analyzing nanoparticle gratings in terms of, first, an oscillator model and, second, a photonic crystal description. Both approaches reveal the central role of a particle-size-dependent phase shift in the back-scattering of grazing light fields by the particle grating. This phase shift determines the symmetry of the resulting field profiles corresponding to the dispersion branches and thus their ability to couple to the exciting light. This physical understanding could considerably simplify the dispersion engineering of plasmonic nanoparticle gratings for specific applications as sensing or lasing.
关键词： Surface lattice resonances,Hybrid Materials,Magnetic,Optical,Dispersion engineering,Plasmonics,Plasmonic nanoparticles
更新于2025-09-12 10:27:22
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[IEEE 2019 IEEE Photonics Conference (IPC) - San Antonio, TX, USA (2019.9.29-2019.10.3)] 2019 IEEE Photonics Conference (IPC) - Dispersion Engineered Metasurfaces for Broadband Achromatic Optics
摘要： Chromatic aberrations in lenses are challenging to correct over large bandwidth. We show that dispersion-tailored and polarization-insensitive metasurfaces comprising counterintuitive anisotropic nanofins can correct the chromatic aberrations from simple singlet lenses to sophisticated microscope objectives with unprecedented compactness.
关键词： Nanophotonics,Dispersion engineering,Metasurfaces
更新于2025-09-11 14:15:04