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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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Plasmonic Metamaterials for Nanochemistry and Sensing
摘要： Plasmonic nanostructures were initially developed for sensing and nanophotonic applications but, recently, have shown great promise in chemistry, optoelectronics, and nonlinear optics. While smooth plasmonic films, supporting surface plasmon polaritons, and individual nanostructures, featuring localized surface plasmons, are easy to fabricate and use, the assemblies of nanostructures in optical antennas and metamaterials provide many additional advantages related to the engineering of the mode structure (and thus, optical resonances in the given spectral range), field enhancement, and local density of optical states required to control electronic and photonic interactions. Focusing on two of the many applications of plasmonic metamaterials, in this Account, we review our work on the sensing and nanochemistry applications of metamaterials based on the assemblies of plasmonic nanorods under optical, as well as electronic interrogation.
关键词： field enhancement,sensing,localized surface plasmons,optical antennas,nanochemistry,optical resonances,electronic interrogation,surface plasmon polaritons,metamaterials,Plasmonic nanostructures
更新于2025-09-12 10:27:22
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Wide-band enhancement of the transverse magneto-optical Kerr effect in magnetite-based plasmonic crystals
摘要： The transverse magneto-optical Kerr effect (TMOKE) in magnetite-based magnetoplasmonic crystals is studied experimentally and theoretically. We analyze angle-resolved TMOKE spectra from two types of structures where noble metallic stripes are incorporated inside a thin magnetite film or located on top of a homogeneous film. A multiple-wide-band enhancement of the TMOKE signal in transmission is demonstrated. The complex dielectric permittivity and gyration are experimentally determined using the ellipsometry technique as well as Faraday rotation and ellipticity measurements. The obtained parameters are used in rigorous coupled-wave analysis (RCWA) calculations for studying the optical resonances. Our RCWA calculations of transmittance and TMOKE are in good agreement with the experimental data. The role of guiding and plasmonic modes in the TMOKE enhancement is revealed. We demonstrate that the TMOKE provides rich information about the studied optical resonances.
关键词： transverse magneto-optical Kerr effect,ellipticity measurements,gyration,magnetoplasmonic crystals,Faraday rotation,dielectric permittivity,optical resonances,RCWA,magnetite,TMOKE
更新于2025-09-12 10:27:22
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Engineering the Enhancement of Nonlinear Optical Properties of 2D Structures
摘要： The challenge of nonlinear optics stems from the negligible interaction among electromagnetic waves in free space, motivating substantial efforts to identify materials with sufficient anharmonic response as to enable optical nonlinearities at low light powers. On the nanoscale, near-field intensity enhancement through optical resonators has been widely explored to design active photonic devices operating on subwavelength scales. Further interest in nanoscale nonlinear optics has arisen with the isolation of graphene and other atomically-thin materials that combine a large electro-optic response with strong intrinsic nonlinearities. Despite their large nonlinear optical susceptibilities, the response of 2D materials is limited by their inherently small volumes. Optical resonances provide a promising way for circumventing this limitation, as they can enhance the driving electric field, thus boosting the effective nonlinear response. In the present work we introduce a figure-of-merit (FoM) that quantifies the enhancement of the nonlinear optical response that can be achieved in 2D materials by means of resonant cavities. As concrete examples, we apply our FoM to explore the extrinsic near-field enhancement provided by (1) localized nanoparticle plasmons acting on a 2D material; (2) the extrinsic enhancement in a 2D material produced by Mie-like resonances in dielectric nanoparticles; (3) the intrinsic enhancement of optical nonlinearity in a dielectric nanoparticle by its supported Mie resonances; (4) the effect of lattice resonances on the nonlinear response for a periodic 2D array of dielectric nanodisks. We focus in particular on the enhancement in second- and third-harmonic generation, as well as the Kerr nonlinearity, quantifying the yield of these nonlinear processes in each of the systems. Our FoM provides an efficient tool to explore the dependence of the nonlinear response enhancement by optical resonances on the size-to-wavelength ratio, composition, and geometry, thus facilitating the design of structures with optimal nonlinear yields.
关键词： Kerr nonlinearity,optical resonances,harmonic generation,nonlinear optics,2D materials,figure-of-merit
更新于2025-09-12 10:27:22
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Femtosecond Laser Assisted Fabrication of Visible Wavelength All-Dielectric Nano-Membrane Metasurfaces
摘要： Metamaterials allow control and tailoring the optical response of natural materials to achieve unprecedented functionalities. These artificial electromagnetic media are engineered by structuring materials on a subwavelength scale. Metamaterials have conventionally been made out of noble plasmonic metals. Intrinsically, plasmonic metamaterials suffer from high energy dissipation due to ohmic losses at ultraviolet to visible spectral frequencies. Therefore, in recent years, all-dielectric resonant metamaterials typically made from high-index dielectrics have been explored widely as they can potentially alleviate such losses, while allowing similar functionalities. One of the factors constraining their widespread use is slow and high-cost production techniques required to achieve nanoscale structures across large areas in reasonable timescales. Here we demonstrate that laser direct writing can be used as a viable alternative to FIB and EBL for implementation of optical metasurfaces. Our proposed approach allows manufacturing all-dielectric metasurfaces with flexible geometry and high uniformity at mm2/min throughput rates. Laser direct writing relies on removing the material via irradiation with an intense light source producing a contaminant free nano-patterned surface. The patterning was performed using femtosecond laser pulses with a bandwidth centred at 515 nm (a second harmonic of the Yb:KGW laser). The laser beam was focused with a 0.6 NA objective lens producing a spot size of 430 nm. Optimized experimental conditions allowed us to fabricate arrays of holes directly in free-standing, 50 nm thick SiN membranes, which exhibit strong optical resonances in the visible spectral range. Each perforation is achieved with a single femtosecond laser pulse, providing for an area of 1×1 mm2 to be patterned within 10 minutes. Our writing technique allowed us to inscribe holes with sub-200 nm in diameter, which is well below the diffraction limit. The periods of arrays ranged from 300 to 1000 nm allowing us to achieve optical resonances in the visible with high resonance quality factors up to 46 (for a metasurface period of 520). Quality factor is defined here as Q = λR/Δλ, where λR is the reflection resonance wavelength and Δλ is the half-maximum linewidth). The asymmetry in the structure, which leads to polarization dependent resonance, stems from a linearly polarized laser beam resulting in asymmetric intensity distribution at the focal point. Although our proof of principle demonstration is limited to dielectric nanomembranes, this technique can be easily extended to fabrication of metasurfaces in semiconductors and metals due to the nonlinear character of femtosecond laser pulse interaction with materials. In conclusion, we have demonstrated feasibility and versatility of femtosecond laser processing for developing scalable optical metasurfaces.
关键词： metasurfaces,all-dielectric,optical resonances,femtosecond laser,metamaterials
更新于2025-09-12 10:27:22