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Exceptional Two-Photon Absorption in Alkynylruthenium-Gold Nanoparticle Hybrids
摘要： Ruthenium alkynyl “star” complexes with tri(2-thienyl)-, tris(1,2,3-triazolyl)-, or triphenyl-benzene cores stabilize gold nanoparticles (AuNPs). Cyclic voltammetry, transmission electron microscopy, molecular modeling, dynamic light scattering, X-ray photoelectron spectroscopy, and energy-dispersive X-ray spectroscopy studies are consistent with ca. 5 trithienyl- or triazolyl-benzene-cored star complexes decorating the exterior of each AuNP. The ca. 2.5 nm diameter (by TEM) trithienylbenzene-cored gold nanoparticle hybrids are significantly less absorbing than classical Brust nanoparticles stabilized by 1-dodecanethiol; with femtosecond pulsed radiation, they exhibit exceptionally strong saturable absorption and two-photon absorption across the visible range and into the NIR region (3,000,000 GM at 500 nm, 46,000 GM at 750 nm; 1 GM = 10-50 cm4 s photon-1).
关键词： Gold nanoparticles,nonlinear optics,inorganic materials,metal alkynyl complexes,organometallics.
更新于2025-09-23 15:23:52
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Influence of experimental parameters on linear, nonlinear optical and ultrafast dynamics properties of In doped ZnO nanorods
摘要： In-doped ZnO (IZO) nanorods have been successfully synthesized by chemical vapour deposition method. The structure, morphology and linear optical properties of IZO nanorods have been characterized. The excitation intensity and temperature - dependent the photoluminescence of IZO nanorods were analyzed. The nonlinear optical absorption properties were studied by using the Z-scan technique with same wavelengths at different laser pulses and energies. IZO nanorods showed two-photon absorption (TPA) mechanism at 532 nm. In the low-energy pulse regime, IZO nanorods showed TPA induced ground state saturable absorption (SA). However, with increasing the energy pulse regime, an apparent TPA induced reverse-saturable absorption (RSA) was observed. The ultrafast dynamics properties of IZO nanorods were investigated by the pump-probe technique under different laser parameters. The femtosecond transient absorption spectra show that the few decades picosecond component has been assigned to the shallow donor mixed with donor bound recombination, and the slowed components represent the decay from donor–acceptor pair recombination.
关键词： Zinc oxide,Nonlinear optics properties,Photoluminescence,Chemical vapour deposition
更新于2025-09-23 15:23:52
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Nonlinear Diffraction in Asymmetric Dielectric Metasurfaces
摘要： Metasurfaces provide new and promising mechanisms to control and manipulate light at the nanoscale. While most metasurfaces are designed to operate in the linear regime, it was recently shown that such metasurfaces may also generate nonlinear signal, by manipulating the higher order susceptibility terms. As such, metasurfaces can generate additional harmonics, without the need for light propagation, as typically occur in nonlinear crystals. While such demonstrations typically rely on the nonlinear properties of metals, we hereby report the design, fabrication and experimental characterization of a resonant dielectric metasurface made of amorphous silicon to create and manipulate second harmonic light and control its diffraction patterns. As shown in the paper, the second harmonic generation of light follows selection rules which rely on the asymmetry of the meta-atom. Given the fact that silicon crystals are centrosymmetric, the generation of second harmonic signal in amorphous silicon is intriguing. In fact, second harmonic signal is generated mostly from the surface of the meta atom. It is the use of nanostructures that increases the surface to volume ratio and enables second harmonic generation. Additionally, the meta atom is designed to exploit its spectral resonances in the principal and the second harmonic frequencies for providing electromagnetic field enhancement which assist in boosting up the generation of second harmonic signal.
关键词： Metasurfaces,Nonlinear optics,Dielectric metasurfaces,Phase gradient metasurfaces
更新于2025-09-23 15:23:52
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Optical matching of a multimode gradient fibre and single-mode stepped-index fibre in a photopolymerizable composition
摘要： The opportunity to optically match waveguides characterized by an essentially different field structure in a photopolymerizable medium is investigated. The example of a multimode gradient fibre (core diameter 50 μm) and a single-mode stepped-index fibre SMF-28 (core diameter 8.2 μm) shows that the efficiency of radiation transmission from the wide fibre into the narrow one can reach 60% at a distance between their end faces of about 900 μm.
关键词： nonlinear optics,photopolymer,optical matching of fibres,fibre optics,laser radiation
更新于2025-09-23 15:22:29
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Characterization of Polarization Pulling in Fiber Optical Parametric Amplifiers
摘要： In fiber optical parametric amplifiers (FOPAs), the output states of polarization (SOPs) of both the signal and the idler are affected by the pump SOP through the polarization pulling effect. We proposed a normalized model to characterize the general dynamics of polarization pulling in degenerated pump FOPAs. By using this model, we determined the relationship between the output degree of polarization (DOP) and the gain of the FOPAs over three orders of magnitude changes in polarization-mode dispersion (PMD) coefficient. We demonstrated numerically that when fibers with typical PMD coefficients are used, the output signals of the FOPAs can achieve higher DOP than those of co-propagating fiber Raman amplifiers, which depends on whether the parametric gain is sufficiently large to compensate the PMD-induced phase mismatch. We also found that for FOPAs using different types of fibers with moderate PMD coefficients, this DOP-gain relationship exhibits highly similar behaviors. We thus adopted a set of modified empirical formulas to analyze this relationship. This formula can also describe the relationship between the output DOP and the conversion efficiency of the idler. The results indicate that in all cases studied, FOPAs achieve much stronger polarization pulling to the idlers than the signals.
关键词： Nonlinear optics,parametric oscillators and amplifiers,polarization-selective devices
更新于2025-09-23 15:22:29
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Generation of optical signal and terahertz idler photons by spontaneous parametric down-conversion
摘要： Frequency-angular characteristics of signal and idler photons generated under spontaneous parametric down-conversion are studied in a strongly frequency nondegenerate regime, without paraxial approximation, accounting for possible inherent absorption of idler waves in a nonlinear crystal, classical thermal field fluctuations, and the multimode character of parametric interaction induced by transverse spatial limitation of the pump beam. Spatial limitation is shown to lead to a huge increase in angular divergence of the idler photons generated at terahertz frequencies. General expressions are obtained for the frequency-angular sensitivity function of the nonlinear-optical terahertz wave detector and for power densities of the signal and idler photon fluxes. The absorption-induced difference in the parametric conversion coefficients for the noise and externally incident radiation of the idler frequency is shown to be described by approximately the same loss factor for all active spatial idler modes. Two different parametric contributions of the internal thermal noise to the number of output idler photons were revealed with different dependence on the idler-wave absorption. Expressions for the loss factors, which describe absorption-induced effects in signal and idler channels, are obtained and shown to be turning into one another by changing the sign of the absorption coefficient. Relative contribution of thermal and quantum field fluctuations into the intrinsic radiation of a nonlinear crystal at signal and idler frequencies is analyzed accounting for the crystal absorption properties.
关键词： nonlinear optics,thermal fluctuations,terahertz,quantum fluctuations,absorption,spontaneous parametric down-conversion
更新于2025-09-23 15:22:29
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Ultra-broadband second harmonic generation in ZnO nano-tetrapod with over-one-octave bandwidth
摘要： Broadband nonlinear optical frequency conversion has attracted considerable interest in many applications such as optical communication, frequency comb generation and so on. Here, we report on the ultra-broadband second harmonic generation (SHG) from the Zinc oxide nano-tetrapod with less stringent phase-matching requirement. Using a super-continuum source together with an optical parametric oscillator as the excitation light, a broadband SHG with over-one-octave bandwidth spanning from the ultraviolet to near-infrared (375-1100 nm) is readily obtained. The SHG dependence of pump polarization and pump power is also characterized systematically. This nanoscale ultra-broadband optical converter may open a new way for various applications ranging from imaging to on-chip all-optical signal processing operations.
关键词： Nonlinear optics,Nanostructured materials
更新于2025-09-23 15:22:29
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Donor Impurity States in Semiconductor Zincblende Nitride Quantum Systems as a Source of Nonlinear Optical Response
摘要： The optical absorption and the optical rectification coefficients associated to hydrogenic impurity interstate transitions in zincblende GaN-based nanostructures of the quantum wire type are investigated. The system is assumed to have cylindrical shape and the influence of external tuning probes such as hydrostatic pressure and static electric fields is particularly taken into account. The electron states are obtained within the effective mass approximation, via the exact diagonalization of the donor-impurity Hamiltonian with parabolic confinement. The nonlinear optical coefficients are calculated using a nonperturbative solution of the density-matrix Bloch equation. Our results show that the resonance-related features of the optical response become shifted in the frequency range of the incident radiation due to the effect of the hydrostatic pressure, the strength of the applied field and the change in the impurity center position.
关键词： Quantum Wire,Nonlinear Optics,Hydrostatic Pressure,Zincblende GaN
更新于2025-09-23 15:22:29
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[IEEE 2018 IEEE Research and Applications of Photonics In Defense Conference (RAPID) - Miramar Beach, FL (2018.8.22-2018.8.24)] 2018 IEEE Research and Applications of Photonics In Defense Conference (RAPID) - Optical Parametric Oscillation in Random Polycrystalline χ <sup>(2)</sup> Medium
摘要： We demonstrate the first OPO based on random phase matching. The OPO was based on ZnSe ceramic pumped by 62-fs, λ=2.35-μm Cr:ZnS laser pulses, had 90-mW pump threshold and produced an ultra-broad spectrum spanning 3–7.5 μm.
关键词： parametric processes,Parametric processes,Nonlinear optics
更新于2025-09-23 15:22:29
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Development of highly nonlinear polarization-maintaining fibers with normal dispersion across entire transmission window
摘要： A determined polarization state of light is required in nonlinear optics applications related to ultrashort and single-cycle light pulse generation. Such short timescales require up to one full octave of the spectral width of light. A fiber-based, pulse-preserving and linearly polarized supercontinuum can meet these requirements. We report on the development—from linear simulations of the fiber structure, through fabrication of physical fibers to their versatile characterization—of polarization-maintaining, highly nonlinear photonic crystal fibers, intended for femtosecond pumping at a wavelength of 1560 nm. A full octave of linearly polarized light around this wavelength would enable the covering of amplification bandwidths of the three major fiber amplifiers, from ytterbium-doped systems up to thulium- and holmium-doped fiber amplifiers, with a coherent, linearly polarized seed signal. At the same time, an all-normal chromatic dispersion profile over an entire transmission window, and a small dispersion of nonlinearity in the developed fibers, would facilitate use of commercially available femtosecond fiber lasers as pump sources for the developed fibers.
关键词： normal dispersion,birefringence,fibers,nonlinear optics
更新于2025-09-23 15:22:29