- 标题
- 摘要
- 关键词
- 实验方案
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Polarization-Independent, Narrowband, Near-IR Spectral Filters via Guided Mode Resonances in Ultrathin a-Si Nanopillar Arrays
摘要： We report the optical properties obtained through experiments, simulation, and theory, of ultra-thin (<0.1λ), amorphous Si nanopillar arrays embedded in a thin film of SiO2 designed for narrowband filtering for multi- and hyper-spectral imaging in the near-infrared. The fabricated nanopillar arrays are square-packed with subwavelength periodicity, heights of ~100 nm, and a radius-to-spacing ratio, r/a, of ~0.2. Specular reflection measurements at normal incidence demonstrate that these arrays behave as narrow stopband filters in the near-infrared (λ = 1300-1700 nm) and attain ~90% reflectivity in band and a full width at half maximum as low as 20 nm. Using a combination of full wave simulations and theory, we demonstrate that these narrowband filtering properties arise from efficient grating coupling of light into guided modes of the array because the nanopillar arrays serve as photonic crystal slabs. This phenomenon is known as a guided mode resonance. We discover that the spectral location of these resonances is passively tunable by modifying array geometry and is most sensitive to nanopillar spacing. Theoretical photonic crystal slab band diagrams accurately predict the spectral locations of the observed resonance and provide physical insights into and support the guided mode resonance formulation. This work demonstrates that these ultra-thin all-dielectric nanopillar arrays have advantages over existing hyperspectral filter designs because they are polarization independent and do not suffer from material absorption loss and have significant implications for minimizing imaging device size.
关键词： guided mode resonance,nanopillar array,hyperspectral
更新于2025-09-23 15:23:52
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Blu-ray DVD as SERS substrate for reliable detection of albumin, creatinine and urea in urine
摘要： We report here the working of a simple reproducible surface enhanced Raman scattering (SERS) substrate by efficiently guiding localized plasmon resonance (LSPR) field of gold nanoparticles (AuNPs) through trapping it in the nano channels of a blu-ray digital versatile disc (BRDVD). SERS based sensing of the designed substrate has been performed. The trapped AuNPs in the channel of the BRDVD generate guided mode resonance (GMR) field and the photon lifetime of the coupled em field in the channel increases which accounts for overall enhancement of the local field intensity. These two factors are primarily responsible for enhancement of the scattered Raman signal from the substrate. The proposed SERS substrate yields reasonably stable signal intensity over a period of 45 days. With the designed substrate Raman signal intensities of three clinically important chemicals namely albumin, creatinine and urea in urine have been measured and quantified reliably. The minimum concentration of albumin, creatinine and urea which can be measured by Raman spectrometer are 0.1 μg/mL, 0.2 μg/mL and 0.6 μg/mL respectively. These values are well below the normal range and thus meet the requirement of detection and analysis of these chemicals for different clinical purposes.
关键词： SERS,Nanochannel,LSPR,BRDVD,Guided mode resonance,Urine sample
更新于2025-09-23 15:23:52
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Refractive Index Sensor Based on a Gradient Grating Period Guided-Mode Resonance
摘要： In this study, we introduce a novel refractive index sensor based on gradient grating period guided-mode resonance (GGP-GMR). Rather than a constant grating period, as in typical GMR, GGP-GMR comprises a grating period varying in increments of 2 nm. For grating variation from 386 to 392 nm, a detection range of 0.109 RIU with a bulk sensitivity of 1433.7 μm/RIU and theoretical and experimental detection limits of 5.58 × 10?3 and 10?2 RIU, respectively, can be achieved. Several tactics that can be readily adopted are suggested to improve the limit of detection by an order to 10?4 RIU, sufficient for detecting many clinically relevant biomarkers. The readout system requires a narrow band of light and a simple charge-coupled device combined with the compact design of the GGP-GMR sensor, which eases the miniaturization of the system for handheld devices as well as its integration with smartphones.
关键词： Bandstop filter,guided-mode resonance,subwavelength nanostructure.
更新于2025-09-23 15:22:29
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[IEEE 2018 International conference on Computing, Electronic and Electrical Engineering (ICE Cube) - Quetta, Pakistan (2018.11.12-2018.11.13)] 2018 International Conference on Computing, Electronic and Electrical Engineering (ICE Cube) - Mathematical Modeling of Photonic Crystal based Optical Filters using Machine Learning
摘要： In this paper, we present a new approach to design photonic crystal based optical filters using machine learning based mathematical model. The presented optical filter device finds its application in near infrared spectral range. The design and spectral response of the filter can be predicted using the proposed mathematical model which can considerably reduce simulation time and efforts. The numerical simulation of the optical filter device along with its spectral results and mathematical modeling are described.
关键词： machine learning in optics,machine learning,optical filters,guided-mode resonance,Dielectric photonic crystals,low-index contrast,FDTD
更新于2025-09-23 15:22:29
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Near-field observation of guided-mode resonances on a metasurface via dielectric nanosphere excitation
摘要： We study laser-induced guided-mode resonances on an ultra-thin anisotropic metallic metasurface using direct near-field mapping. Coupling of the incident light to the surface waves is provided by a resonant laser-printed silicon nanosphere placed on the metasurface using nano-manipulation under electron-beam supervision. To visualize the propagation of the guided modes, we employ scattering-type scanning near-field optical microscopy in the near-infrared region (850 nm). The guided-mode resonances excited by the nanosphere demonstrate vanishing anisotropy due to weak confinement at the metasurface/air interface. We also extract the wavenumber of the observed modes through Fourier transformation of the measured near-field maps and find it to be in good agreement with numerical calculations.
关键词： Metasurface,Surface waves,Anisotropy,s-SNOM,Guided-mode resonance,Nano-Optics
更新于2025-09-23 15:21:01
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Resonant modal analysis and dual-mode tailoring in high refractive index contrast two-dimensional nanorod arrays
摘要： Resonant modal analysis and dual-mode tailoring in high refractive index contrast two-dimensional (2-D) nanorod arrays are proposed. The specific modes of the guided mode resonances (GMRs) excited by the 2-D nanorod arrays can be distinguished based on the equivalent medium theory (EMT) and the analysis of the electric/magnetic fields. The broadband reflection and enhanced transmission can be obtained by the tailoring between the resonant dual-mode of the 2-D nanorod arrays. It is shown that the 2-D nanorod arrays can support the excitation of the resonant dual-mode with low-quality factor (low-Q) TM0 and high quality factor (high-Q) TE0 modes on a reflection broadband. The coupling of the edges of the resonant dual-mode can be tailored to create the resonant transmission with polarization independence near 1.31 μm. By merely changing the angle of incidence, one can achieve triple transmission channels due to the interaction of the nondegenerate resonant dual-modes.
关键词： Dual-mode tailoring,Modal analysis,Two-dimensional nanorod arrays,Guided mode resonance
更新于2025-09-23 15:19:57
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Electro-optical Amplitude and Phase Modulators Based on Tunable Guided-Mode Resonance Effect
摘要： Here, electrically tunable amplitude and phase modulators are designed by the hybridization of indium tin oxide (ITO) into a guided-mode resonance mirror (so-called GMRM) which consists of a high-index silicon (Si) nanograting placed on top of a Si guiding core followed by a silicon-dioxide optical buffer layer and a highly reflective substrate. The physical mechanism is based on the intriguing optical characteristics of GMRMs and integration of a dual-gated ITO with the capability of charge carrier modulation into the Si nanograting. A gate-tunable amplitude modulator with a modulation depth as high as ≈0.80 is realized by careful selection of structural parameters, excitation of a strongly coupled guided-mode resonance, and modifying the external bias voltage. This design can also be adjusted only by changing the thickness of its optical buffer layer and moderating the strength of the guided-mode resonance to serve as an efficient active phase modulator. The phase variation of ≈210° and relatively high reflection amplitude in 0.45-0.6 range are accomplished when the applied bias voltage alters from -15 V to +24 V. This reflection phase tuning mainly originates from the carrier depletion and accumulation inside the incorporated 5 nm-thick ITO layer. The accurate modeling and numerical calculation of optical response of the proposed unit cell for different applied external voltages are carried out through linking the electrostatics device physics model and rigorous coupled wave analysis (RCWA) optical simulation. The design rules and physical principles behind the dual-gated ITO-integrated GMRM unit cell are discussed in-depth by investigation of the structural parameters, the nature of supported resonances, and voltage-dependent effects of inhomogeneous carrier distributions in both ITO and Si layers. The electrical addressability and individual control over pixelated subwavelength unit cells provide the opportunity for realizing an actively reconfigurable metasurface with the desired gradient phase delay.
关键词： metasurfaces,phase and amplitude modulators,electro-optical materials,silicon,guided-mode resonance,indium tin oxide,All-dielectric
更新于2025-09-23 15:19:57
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Nonlinear Optics in Dielectric Guided-Mode Resonant Structures and Resonant Metasurfaces
摘要： Nonlinear optics is an important area of photonics research for realizing active optical functionalities such as light emission, frequency conversion, and ultrafast optical switching for applications in optical communication, material processing, precision measurements, spectroscopic sensing and label-free biological imaging. An emerging topic in nonlinear optics research is to realize high efficiency optical functionalities in ultra-small, sub-wavelength length scale structures by leveraging interesting optical resonances in surface relief metasurfaces. Such artificial surfaces can be engineered to support high quality factor resonances for enhanced nonlinear optical interaction by leveraging interesting physical mechanisms. The aim of this review article is to give an overview of the emerging field of nonlinear optics in dielectric based sub-wavelength periodic structures to realize efficient harmonic generators, wavelength mixers, optical switches etc. Dielectric metasurfaces support the realization of high quality-factor resonances with electric field concentrated either inside or in the vicinity of the dielectric media, while at the same time operate at high optical intensities without damage. The periodic dielectric structures considered here are broadly classified into guided-mode resonant structures and resonant metasurfaces. The basic physical mechanisms behind guided-mode resonances, electromagnetically-induced transparency like resonances and bound-states in continuum resonances in periodic photonic structures are discussed. Various nonlinear optical processes studied in such structures with example implementations are also reviewed. Finally, some future directions of interest in terms of realizing large-area metasurfaces, techniques for enhancing the efficiency of the nonlinear processes, heterogenous integration, and extension to non-conventional wavelength ranges in the ultra-violet and infrared region are discussed.
关键词： harmonic generation,guided-mode resonance,four-wave mixing,Mie scattering,optical resonances,nonlinear optics,sub-wavelength gratings,Fano resonances,optical switching
更新于2025-09-23 15:19:57
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[IEEE 2018 IEEE CPMT Symposium Japan (ICSJ) - Kyoto, Japan (2018.11.19-2018.11.21)] 2018 IEEE CPMT Symposium Japan (ICSJ) - Wavelength matching of resonance reflection and guided-wave launching for high-performance CRIGF
摘要： Cavity-resonator-integrated guided-mode resonance filter is investigated for an external mirror of laser and a waveguide coupler. Matching wavelengths giving the maximum reflectance and the maximum coupling is theoretically and experimentally investigated.
关键词： Wavelength selective reflectors,Guided-mode resonance,Multi-wavelength light sources
更新于2025-09-19 17:15:36
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[IEEE 2018 20th International Conference on Transparent Optical Networks (ICTON) - Bucharest (2018.7.1-2018.7.5)] 2018 20th International Conference on Transparent Optical Networks (ICTON) - Cavity-Resonator-Integrated Guided-Mode Resonance Filters for Compact WDM Light Source
摘要： A cavity-resonator-integrated guided-mode resonance filter (CRIGF) consists of a grating coupler (GC) integrated in a waveguide cavity resonator on a transparent substrate, and shows a narrowband reflection spectrum for an incident free-space wave of a small diameter. CRIGF of the waveguide cavity formed by two distributed Bragg reflectors (DBRs) of different reflectances is discussed. Such a CRIGF can act as not only a wavelength-selective reflector but also an input waveguide coupler. Integration of such CRIGFs for different wavelengths in a waveguide is proposed to give an array of external mirrors and a wavelength division multiplexer for constructing a compact multi-wavelength light source. Four CRIGFs of 10-μm-size aperture with a wavelength spacing of 15 nm were fabricated and characterized. CRIGF integrated on a reflective layer via an optical buffer layer is also discussed. Optimization of reflective and buffer layers is theoretically investigated to maximize a waveguide-coupled lasing power.
关键词： gratings,waveguides,wavelength multiplexers,external mirrors,guided-mode resonance,waveguide couplers,optical cavities,wavelength filters
更新于2025-09-19 17:15:36