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[IEEE 2019 Photonics & Electromagnetics Research Symposium - Fall (PIERS - Fall) - Xiamen, China (2019.12.17-2019.12.20)] 2019 Photonics & Electromagnetics Research Symposium - Fall (PIERS - Fall) - Knowledge-aided Color Loading Sparse Recovery STAP Algorithm
摘要： We numerically study the dynamics of supercontinuum generation (SCG) for a variety of possible combinations of photonic crystal fibers (PCFs) and ultrafast fiber laser pulses that the current technologies offer. Three types of PCFs typically used in SCG and four representative types of ultrafast fiber laser pulses are considered for this combinatorial study. We numerically model and qualitatively discuss the nonlinear evolution of the pulses for their whole 12 combinatorial cases. We also quantitatively analyze their output spectra and organize a performance chart for them in terms of spectral bandwidth, flatness, and degree of spectral coherence. Finally, we suggest the most viable combinations among the given PCFs and ultrafast fiber laser pulses in order for generating a target supercontinuum spectrum for various specific cases.
关键词： Optical fiber laser,nonlinear optics,supercontinuum generation,ultrashort pulse
更新于2025-09-23 15:19:57
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Sub-200-kHz single soliton generation in a long ring Er-fiber laser with strict polarization control by using twisted fiber
摘要： In the present work we demonstrate a novel single-soliton ultra-low pulse repetition frequency passively mode-locked erbium-doped fiber laser. We mitigate the residual linear birefringence of fiber by fiber twist to achieve a strict control of polarization. For mode-locking the nonlinear polarization rotation (NPR) was used. Special technique was applied to reduce the overdriving of NPR that allows the generation of single soliton in ultra-long cavity. The strict control of polarization yields a stable relation between the polarization state of the pulses propagating in the cavity and the regimes of generation. A 192.12-kHz train of soliton pulses was obtained with pulse duration of 4.7 ps at 1560.1 nm, the average power was 29 μW and the estimated peak power was ? 30.8 W with an energy of 150.9 pJ.
关键词： Ultra-long laser cavity,Solitons,Nonlinear optics,Overdriving nonlinear effects,Mode-locked fiber lasers
更新于2025-09-23 15:19:57
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Integration of chiral cellulose nanocrystal films in silica optical fibers
摘要： Cellulose nanocrystals have attracted great attention as new “wonder” materials for photonic applications owing to their unique property of spontaneous self-assembly to form chiral nematic films. Here, the incorporation of chiral cellulose nanocrystal films on a photonic waveguide is demonstrated for the first time – in the form of integrated silica optical fibers with a helicoid nanocrystal film on their input facet. In order to achieve repeatable cholesteric ordering across the fiber core modal area, a fabrication method was developed where several optical fiber facets form part of a larger flat surface, which acts as the substrate for the planar anchoring of the cellulose nanocrystals. The resultant optical fibers exhibit significant circular dichroism (almost 40%) in transmission and act as all-fiber spectral filters. The proposed fabrication technique provides a simple, low-cost method for developing chiral silica optical fibers that remain compatible with standard telecommunication fiber technology. It is envisioned that the incorporation of cellulose nanocrystals in other optical fiber types will enable the development of a new class of fiber devices.
关键词： optical films,optical device fabrication,optical materials,optical polarization,fiber optics,optical fibers,optical fiber devices
更新于2025-09-23 15:19:57
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Nonlinear optics with resonant metasurfaces
摘要： The field of nonlinear optics is a well-established discipline that relies on macroscopic media and employs propagation distances longer than a wavelength of light. Recent progress with electromagnetic metamaterials has allowed for the expansion of this field into new directions of new phenomena and novel functionalities. In particular, nonlinear effects in thin, artificially structured materials such as metasurfaces do not rely on phase-matching conditions and symmetry-related selection rules of natural materials; they may be substantially enhanced by strong local and collective resonances of fields inside the metasurface nanostructures. Consequently, nonlinear processes may extend beyond simple harmonic generation and spectral broadening due to electronic nonlinearities. This article provides a brief review of basic concepts and recent results in the field of nonlinear optical metasurfaces.
关键词： frequency conversion,high-harmonic generation,resonances,metasurfaces,nonlinear optics
更新于2025-09-23 15:19:57
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Metasurfaces: Subwavelength nanostructure arrays for ultrathin flat optics and photonics
摘要： Miniaturization is a strong demand of modern scientific technology. However, conventional optical components based on refraction suffer from functional degradation as the device size decreases. Metasurfaces consisting of subwavelength optical antenna arrays have emerged as planar optical devices that enable many promising applications in lenses, holograms, and optical cloaks. During recent decades, metasurfaces have been developed for their specific functionalities by exploiting new materials and design algorithms. In this issue of MRS Bulletin, progress in metasurfaces is discussed to provide a comprehensive understanding of metasurfaces and their novel applications in optics and photonics.
关键词： subwavelength nanostructure arrays,photonics,Metasurfaces,ultrathin flat optics
更新于2025-09-23 15:19:57
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Microcavity Nonlinear Optics with an Organically Functionalized Surface
摘要： We report enhanced optical nonlinear effects at the surface of an ultrahigh-Q silica microcavity functionalized by a thin layer of organic molecules. The maximal conversion efficiency of third harmonic generation reaches ～1680%=W2 and an absolute efficiency of 0.0144% at pump power of ～2.90 mW, which is approximately 4 orders of magnitude higher than that in a reported silica microcavity. Further analysis clarifies the elusive dependence of the third harmonic signal on the pump power in previous literature. Molecule-functionalized microcavities may find promising applications in high-efficiency broadband optical frequency conversion and offer potential in sensitive surface analysis.
关键词： Nonlinear Optics,Microcavity,Third Harmonic Generation,Surface Functionalization,Organic Molecules
更新于2025-09-23 15:19:57
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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) - Hot Electrons Modulation of Third Harmonic Generation in Graphene
摘要： Hot-electrons dominate the ultrafast (～fs-ps) optical and electronic properties of metals and semiconductors and they are exploited in a variety of applications including photovoltaics and photodetection. Here we perform power-dependent third harmonic generation (THG) measurements on gated single layer graphene (SLG) and we show that hot-electrons modulate significantly the power-law dependence of THG, inducing a large deviation from the expected cubic power-law. We use a Chemical Vapor Deposition (CVD) SLG sample transferred on Fused Silica (FS) and gated by ionic liquid (IL), Fig.1(a). We excite the sample with the idler beam of an Optical Parametric Oscillator (OPO, Coherent) at a photon energy of ?ω0=0.69eV. The OPO is seeded by a mode-locked Ti:Sa laser (Coherent) with 150fs pulse duration and 80MHz repetition rate. The OPO idler spot-size is～4.7μm and the pulse duration ～300fs.
关键词： Hot electrons,nonlinear optics,third harmonic generation,graphene
更新于2025-09-23 15:19:57
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Femtosecond-laser direct-writing volume phase gratings inside Gea??Asa??S chalcogenide glass
摘要： In this study, volume-phase gratings (VPGs) were fabricated inside Ge–As–S chalcogenide glasses (ChG) with femtosecond-laser writing technology. VPGs with high thicknesses were obtained through single-step writing by exploiting the self-focusing effect of highly nonlinear ChGs. The clear diffraction patterns and high diffraction efficiency of the prepared gratings indicated their high optical performance. Testing results showed that the diffraction efficiency of VPGs first increased with laser pulse energies and then decreased when the laser damage threshold of the glass reached 9.42 nJ. Grating thickness also exhibited the same trend as laser pulse energies and reached the maximum value of 28 μm at 9.42 nJ. The changes in the refractive indexes of volume gratings fabricated under different laser pulse energies were carefully investigated. The changes in the refractive indexes of the gratings remained at the same level while laser pulse energy was increased. Meanwhile, grating thickness played a key role in diffraction efficiency. The maximum diffraction efficiency of the prepared VPGs reached 50% at 808 nm under optimized laser parameters.
关键词： chalcogenide glass,volume-phase grating,laser direct-writing,nonlinear optics
更新于2025-09-23 15:19:57
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Active control of multiple, simultaneous nonlinear optical processes in plasmonic nanogap cavities
摘要： Plasmonic structures are promising to enhance and control nonlinear optical processes as the subwavelength-scale elements not only increase the local electric field intensities but also result in relaxed phase matching conditions. This opens the possibility to observe and further manipulate multiple nonlinear optical processes simultaneously which would be forbidden in bulk crystals due to incompatible phase matching requirements. Here we enhance and control the relative strength between third harmonic generation (THG), sum frequency generation (SFG) and four wave mixing (FWM) arising from 1-7 nm Al2O3 layers sandwiched between a gold film and silver nanorectangles. We demonstrate that the relative strength of the three, simultaneous nonlinear optical processes can be precisely controlled by either the ratio between the powers of the two excitations or the thickness of the Al2O3 layer. Furthermore, enhancements up to 106-fold for THG and FWM are observed along with 104-fold enhancements for SFG response when the resonance of the transverse and longitudinal mode of the cavity are matched to the two pump excitations. The ability to obtain and control multiple, nonlinear optical processes simultaneously opens new capabilities for advanced on-chip manipulation and processing of optical signals on the deep nanoscale.
关键词： metasurface,frequency conversion,plasmonics,tuning,nonlinear optics
更新于2025-09-23 15:19:57
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Performance of assembled X-ray optics consisted of a polycapillary X-ray optics and a monocapillary X-ray optics for micro X-ray fluorescence spectrometry
摘要： A micro X-ray fluorescence (μ-XRF) spectrometry instrument based on an assembled X-ray optics was constructed in the laboratory. The assembled X-ray optics consisted of a polycapillary slightly focusing X-ray lens and a tapered monocapillary X-ray lens (TMXRL). The output X-ray beam of the polycapillary slightly focusing X-ray lens was focused again by the TMXRL. A TMXRL with output aperture of 12.01 μm was drawn by a nested glass tube. To evaluate the performance of the instrument, a performance comparison between different capillary X-ray optics was conducted. The intensity of the Fe Kα from an iron plate was used to indicate the analysis efficiency of the μ-XRF instrument. The relative gain of the instrument was corrected by comparing the intensity per unit area for a pinhole aperture. Compared with TMXRL single used, the assembled X-ray optics also had a micro focal spot. Furthermore, the relative gain of the assembled X-ray optics and the intensity of the Fe Kα from the iron plate obtained by the assembled X-ray optics were approximately 5 times those of the TMXRL single used. This highly intense micro X-ray beam with several diameters obtained by the assembled X-ray optics will be useful for μ-XRF analysis.
关键词： Capillary X-ray optics,Micro X-ray focusing,Micro X-ray fluorescence,Laboratory X-ray source
更新于2025-09-23 15:19:57