- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Steering Second Harmonic Beam in Nanophotonic Waveguides by Gratings
摘要： Efficient manipulation of the wavefront at the nanoscale is important for optical beaming, signal encoding, and nonlinear phase matching, etc. Diffraction gratings are widely adapted for the control of the wavefront of lightwaves, but predominantly in linear optics. Here, we demonstrated the flexible steering of the second harmonic (SH) beams in nanophotonic waveguides using gratings. The emission angle of the SH signals can be shifted by an amount of 60° from the waveguide axis into the collection cone, allowing the detection of the otherwise undetectable SH from co-propagating waveguide modes in the high-loss waveguides. The SH conversion efficiency (3 × 10?5 W?1) from co-propagating modes contributes up to 26.7% of the total SH signal. As the pump wavelength varies from 770 to 840 nm, the SH beam is swept by up to 22°. This design functions as a nonlinear grating coupler for nanophotonic systems and could be used for efficient nonlinear coherent light generation and integrated nonlinear nanophotonics.
关键词： Fourier imaging,nanophotonics,second harmonic generation,nonlinear grating coupler,beam steering
更新于2025-09-11 14:15:04
-
Enhanced piezoresponse and nonlinear optical properties of fluorinated self-assembled peptide nanotubes
摘要： Self-assembled L,L-diphenylalanine (FF) nanostructures offer an attractive platform for photonics and nonlinear optics. The nonlinear optical (NLO) coefficients of FF nanotubes depend on the diameter of the tube [S. Khanra et al. Phys. Chem. Chem. Phys. 19(4), 3084–3093 (2017)]. To further enhance the NLO properties of FF, we search for structural modifications. Here, we report on the synthesis of fluorinated FF dipeptides by replacing one ortho-hydrogen atom in each of the phenyl groups of FF by a fluorine atom. Density-functional theoretical calculations yield insights into minimum energy conformers of fluorinated FF (Fl-FF). Fl-FF self-assembles akin to FF into micron-length tubes. The effects of fluorination are evaluated on the piezoelectric response and nonlinear optical properties. The piezoelectric d15 coefficient of Fl-FF is found to be more than 10 times higher than that of FF nanotubes, and the intensity of second harmonic generation (SHG) polarimetry from individual Fl-FF nanotubes is more than 20 times that of individual FF nanotubes. Furthermore, we obtain SHG images to compare the intensities of FF and Fl-FF tubes. This work demonstrates the potential of fluorine substitution in other self-assembled biomimetic peptides for enhancing nonlinear optical response and piezoelectricity.
关键词： piezoresponse,density-functional theory,nonlinear optical properties,fluorinated self-assembled peptide nanotubes,second harmonic generation
更新于2025-09-11 14:15:04
-
Vectorial nonlinear optics: Type-II second-harmonic generation driven by spin-orbit-coupled fields
摘要： Vectorial nonlinear optics refers to the investigation of optical processes whose nonlinear polarization (NP) undergoes spin-orbit-coupling (SOC) interactions where, in general, the driving light field or the new field generated by the interaction contains the SOC property. To contribute to fundamental knowledge in this domain, we examine the type-II second-harmonic generation (SHG) induced by vectorial laser modes. First, we provide a general theory to analyze the vectorial SHG process. Second, by using two typical vector modes as examples, we show how the SOC of the pump field dictates nonlinear interaction. Finally, we corroborate our theoretical predictions through experiments to confirm the crucial role of the SOC in nonlinear interactions. These results enhance our fundamental understanding of SOC-mediated nonlinear optics and lay the foundation for further fundamental studies as well as possible applications.
关键词： spin-orbit-coupling,Vectorial nonlinear optics,vector modes,type-II second-harmonic generation,nonlinear polarization
更新于2025-09-11 14:15:04
-
[IEEE 2019 21st International Conference on Transparent Optical Networks (ICTON) - Angers, France (2019.7.9-2019.7.13)] 2019 21st International Conference on Transparent Optical Networks (ICTON) - Microcavity-Enhanced Surface Nonlinear Optics
摘要： Confinement and manipulation of photons using microcavities have triggered intense research interest in both fundamental and applied photonics for decades. As a prominent example, whispering-gallery microcavities have ultrahigh Q factors and small mode volumes, making them promising candidates for enhancing light-matter interactions, especially for nonlinear optics. In this work, we report the second-order nonlinear optics induced by symmetry breaking at the surface of an ultrahigh-Q silica microcavity under a sub-milliwatt continuous-wave pump. By dynamically coordinating the double-resonance phase matching, a second harmonic is achieved with a co(cid:81)(cid:89)(cid:72)(cid:85)(cid:86)(cid:76)(cid:82)(cid:81)(cid:3)(cid:72)(cid:73)(cid:73)(cid:76)(cid:70)(cid:76)(cid:72)(cid:81)(cid:70)(cid:92)(cid:3)(cid:82)(cid:73)(cid:3)(cid:19)(cid:17)(cid:19)(cid:23)(cid:28)(cid:8)(cid:3031)(cid:58)-1, 14 orders of magnitude higher than that of the non-enhancement case.
关键词： nonlinear optics,symmetry breaking,microcavity,second harmonic generation,surface
更新于2025-09-11 14:15:04
-
[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) - Impact of Strain on the Second-Harmonic Generation in Transition Metal Dichalcogenide Monolayers
摘要： Second-harmonic generation (SHG) is a powerful measurement technique to analyse the symmetry properties of crystals. Mechanical strain can reduce the symmetry of a crystal and even weak strain can have an immense impact on the SHG intensity along different polarization directions [1]. The impact of strain on the SHG can be modelled with a second-order nonlinear photoelastic tensor [2,3]. We find that the photoelastic tensors depends highly on the excitation wavelength. We investigated the influence of strain on SHG for MoS2, MoSe2, WS2, and WSe2 monolayers. In order to quantify the strain induced anisotropy in the polarization resolved SHG we define two parameters. The Distortion (cid:1830) = (cid:4672), which is the ratio of the minima to the maxima of the envelope function of the polarization resolved SHG and the Intensity (cid:1835) = (cid:2024)((cid:1827)(cid:2870) + (cid:1828)(cid:2870)), which is the integral of the SHG intensity over all polarization directions. Our investigation allows for highly sensitive, non-invasive strain matrix imaging at the submicron scale as well as strain engineering of the conversion efficiency of SHG for all investigated materials.
关键词： Second-harmonic generation,strain,photoelastic tensor,polarization resolved SHG,transition metal dichalcogenide monolayers
更新于2025-09-11 14:15:04
-
Bolted joint integrity monitoring with second harmonic generated by guided waves
摘要： In this study, the second harmonic generation due to the contact nonlinearity caused by bolt loosening is studied experimentally and numerically using three-dimensional explicit finite element simulations. In particular, it is demonstrated that the magnitude of the second harmonic generation normally increases with the loosening of the bolted joint, and there is a reasonable agreement between the numerical simulations and experimental results. The finite element model, which was validated against the experimentally measured data, is further utilized to investigate an important practical situation when a loosened bolt is weakened by fatigue cracks located at the edge of the hole. The numerical case studies show that the contact nonlinearity and the change of the behaviour of the second harmonic generation with the tightening level are very different to the corresponding results with the fatigue cracks. This identified difference in the second harmonic generation behaviour can serve as an indicator of the bolted joint integrity and thus provide early warning for engineers to make decision on the necessity of carrying out further safety inspections. Overall, the findings of this study provide improved physical insights into second harmonic generation for bolt loosening, which can be used to further advance damage detection techniques using nonlinear guided waves.
关键词： Bolt loosening,bolted joint,second harmonic generation,fatigue crack,contact nonlinearity,torque loss,structural health monitoring,guided waves
更新于2025-09-10 09:29:36
-
Nonlinear optical microscopy for label-freely detecting gastric intestinal metaplasia
摘要： Intestinal metaplasia has been widely considered as a precursor of gastric cancer. As a result, early detection and accurate diagnosis will have important clinical significance. Therefore, nonlinear optical microscopy using two-photon excited fluorescence combined with second harmonic generation was used for investigating gastric mucosal intestinal metaplasia in this work. The imaging results showed that this microscope has the ability to directly identify this lesion from normal tissues in the absence of labels, and to further differentiate the subtyping of intestinal metaplasia. Furthermore, nuclear areas from normal gastric mucosa and intestinal metaplasia subtypes were measured, respectively, to show the cell changes while gastric mucosa developed from normal to intestinal metaplasia. This study may provide an approach for further researching these diseases in the future, and highlights the potential of nonlinear optical microscopy as a diagnostic tool for label-free identification of gastric intestinal metaplasia.
关键词： second harmonic generation,gastric intestinal metaplasia,nonlinear optical microscopy,two-photon excited fluorescence
更新于2025-09-10 09:29:36
-
Enhancement of the Second Harmonic Generation from WS <sub/>2</sub> Monolayers by Cooperating with Dielectric Microspheres
摘要： Herein, a 20-fold enhancement of the optical second harmonic generation (SHG) from WS2 monolayers by cooperating with SiO2 dielectric microspheres (MSs) is reported. Detailed experiment and simulation studies indicate that the SHG enhancement is dominantly originated by the enhanced excitation intensity and enlarged collection efficiency produced by the SiO2 MSs. The size effect of the SiO2 MS on the SHG enhancement is also systematically investigated. Moreover, the SHG enhancement is found to be very sensitive to the surrounding refractive index of the SiO2 MS, which advocates great promise for the photonic sensing applications. This work provides a low-cost and efficient approach to enhancing the SHG emission, and demonstrates great potential for functional nanodevices based on hybrid dielectric structures.
关键词： second harmonic generation,nanodevices,WS2 monolayers,nonlinear optics,photonic nanojets
更新于2025-09-10 09:29:36
-
Delocalized Nonlinear Vibrational Modes in Graphene: Second Harmonic Generation and Negative Pressure
摘要： With the help of molecular dynamics simulations, delocalized nonlinear vibrational modes (DNVM) in graphene are analyzed. Such modes are dictated by the lattice symmetry, they are exact solutions to the atomic equations of motion, regardless the employed interatomic potential and for any mode amplitude (though for large amplitudes they are typically unstable). In this study, only one- and two-component DNVM are analyzed, they are reducible to the dynamical systems with one and two degrees of freedom, respectively. There exist 4 one-component and 12 two-component DNVM with in-plane atomic displacements. Any two-component mode includes one of the one-component modes. If the amplitudes of the modes constituting a two-component mode are properly chosen, periodic in time vibrations are observed for the two degrees of freedom at frequencies ω and 2ω, that is, second harmonic generation takes place. For particular DNVM, the higher harmonic can have frequency nearly two times larger than the maximal frequency of the phonon spectrum of graphene. Excitation of some of DNVM results in the appearance of negative in-plane pressure in graphene. This counterintuitive result is explained by the rotational motion of carbon hexagons. Our results contribute to the understanding of nonlinear dynamics of the graphene lattice.
关键词： molecular dynamics,nonlinear dynamics,second harmonic generation,delocalized nonlinear vibrational mode,graphene,negative pressure
更新于2025-09-10 09:29:36
-
[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) - Second-Harmonic Generation by Mie-resonant Nanoparticles with Bulk Quadratic Nonlinearity
摘要： We study resonantly enhanced second-harmonic generation (SHG) by dielectric nanoparticles made of noncentrosymmetric materials with bulk quadratic nonlinearity. By combining analytical and numerical methods, we analyze the multipolar nature of the second-harmonic generated fields in AlGaAs and BaTiO3 nanoparticles optically excited in the vicinity of the low-order Mie resonances, with a particular focus on the magnetic dipole resonance. We derive selection rules for the multipolar composition of the nonlinear radiation depending on the symmetry of the crystalline structure and polarization of the incident light. The developed description can be instructive for design of highly-efficient nonlinear optical nanoantennas with reconfigurable radiation characteristics.
关键词： second-harmonic generation,nonlinear scattering,nanophotonics,Mie resonances,high-index nanoparticles
更新于2025-09-10 09:29:36