We introduce a plasmonic-semiconductor hybrid nanosystem, consisting of a ZnO nanowire coupled to a gold pentamer oligomer by crossing the hot-spot. It is demonstrated that the hybrid system exhibits ...a second harmonic (SH) conversion efficiency of ∼3 × 10–5%, which is among the highest values for a nanoscale object at optical frequencies reported so far. The SH intensity was found to be ∼1700 times larger than that from the same nanowire excited outside the hot-spot. Placing high nonlinear susceptibility materials precisely in plasmonic confined-field regions to enhance SH generation opens new perspectives for highly efficient light frequency up-conversion on the nanoscale.
Nonlinear optical (NLO) materials are of intense academic and technological interest attributable to their ability to generate coherent radiation over a range of different wavelengths. The ...requirements for a viable NLO material are rather strict, and their discovery has mainly been serendipitous. This study reports synthesis, characterization, and, most importantly, growth of large single crystals of a technologically viable NLO material—Rb3Ba3Li2Al4B6O20F. Through the judicious selection of cations, Rb3Ba3Li2Al4B6O20F exhibits a 3D structure that facilitates the growth of large single crystals along the optical axis direction. Measurements on these crystals indicate that Rb3Ba3Li2Al4B6O20F exhibits a moderate birefringence of 0.057 at 1064 nm enabling Type I phase‐matching down to 243 nm. Theoretical calculations indicate the symmetry adapted mode displacement (SAMD) parameter scales with the second‐harmonic generation intensity.
A next‐generation technologically viable nonlinear optical crystal, Rb3Ba3Li2Al4B6O20F, is successfully designed, synthesized, characterized, and grown. This crystal not only solves the layering issue observed in KBe2BO3F and Sr2Be2B2O7, which has hindered their crystal growth, but also does not require the use of toxic BeO in the synthesis. More importantly, it exhibits a moderate birefringence and is nonhygroscopic.
Two new pyrophosphates nonlinear optical (NLO) materials, Rb3PbBi(P2O7)2 (I) and Cs3PbBi(P2O7)2 (II), were successfully designed and synthesized. Both compounds exhibit large NLO effects and ...birefringences. Material I presents the scarce case of possessing the coexistence of large birefringence (0.031 at 1064 nm and 0.037 at 532 nm) and second harmonic generation (SHG) response (2.8× potassium dihydrogen phosphate (KDP)) in ultraviolet NLO phosphates and its SHG is the largest in the phase‐matching (PM) pyrophosphates. Both I and II have three‐dimensional (3D) crystal structures composed of corner‐shared RbO12 (CsO11), RbO10 (CsO10), BiO6, PbO7 (PbO6) and P2O7 groups, in which P2O7 and PbO7 (PbO6) units form an alveolate PbPO∞ skeleton frame. Theoretical calculations reveal that the P−O, Bi−O and Pb−O units are mainly responsible for the moderate birefringence and large SHG efficiency of I.
An ideal balance has been achieved among nonlinear optical (NLO) effect, birefringence and cut‐off edge for Rb3PbBi(P2O7)2 pyrophosphate. Promising UV NLO materials, Rb3PbBi(P2O7)2 and Cs3PbBi(P2O7)2, were obtained in which PbPO∞ layers and BiO6 polyhedra containing two types of lone‐pair cations are present.
Although the cornea is the major refractive element of the eye, the mechanisms controlling corneal shape and hence visual acuity remain unknown. To begin to address this question we have used ...multiphoton, non-linear optical microscopy to image second harmonic generated signals (SHG) from collagen to characterize the evolutionary and structural changes that occur in the collagen architecture of the corneal stroma. Our studies show that there is a progression in complexity of the stromal collagen organization from lower (fish and amphibians) to higher (birds and mammals) vertebrates, leading to increasing tissue stiffness that may control shape. In boney and cartilaginous fish, the cornea is composed of orthogonally arranged, rotating collagen sheets that extend from limbus to limbus with little or no interaction between adjacent sheets, a structural paradigm analogous to 'plywood'. In amphibians and reptiles, these sheets are broken down into broader lamellae that begin to show branching and anastomosing with adjacent lamellae, albeit maintaining their orthogonal, rotational organization. This paradigm is most complex in birds, which show the highest degree of lamellar branching and anastomosing, forming a 'chicken wire' like pattern most prominent in the midstroma. Mammals, on the other hand, diverged from the orthogonal, rotational organization and developed a random lamellar pattern with branching and anastomosing appearing highest in the anterior stroma, associated with higher mechanical stiffness compared to the posterior stroma.
Integrated photonics has been pursued on a large variety of materials and platforms over more than half a century. In recent decades, silicon has emerged as the preferred optical and substrate ...material. However, since many optical functionalities cannot be, inherently or conveniently, implemented on silicon-based devices, heterogeneous integration of other materials has been an inevitable constituent of silicon photonics from its inception. This paper reviews recent progress in the heterogeneous integration of dielectrics and compound semiconductors as the core optical material for ultracompact nonlinear integrated photonics, preferably on silicon substrates. Occasionally, important devices on native substrates of the core nonlinear material are also reviewed. The focus is on ultracompact photonic devices and circuits formed on submicron films of lithium niobate (LiNbO3), and the aluminium-gallium-arsenide (AlGaAs) and aluminium-gallium-nitride (AlGaN) families for second-order nonlinear processes, such as second-harmonic generation, and techniques to address phase-matching in them. Integration of second- and third-order nonlinear devices on the same chip appears to be a future trend, thus the related preliminary results are reviewed. A broader introduction to heterogeneously integrated photonics, shortcomings of conventional silicon photonics for application in nonlinear optics, as well as an overview of modeling second-order nonlinear integrated-waveguide devices are also provided for completeness.
Discovering new deep‐ultraviolet (DUV) nonlinear optical (NLO) materials is currently a great challenge. The reported DUV NLO materials are almost exclusively borates or phosphates. Silicates—the ...largest constituent of the earth's crust—are excluded owing to their weak second harmonic generation (SHG) response. We report a silicate, Li2BaSiO4, with edge‐sharing LiO4–SiO4 tetrahedra that achieves the balance between a short UV absorption edge, below 190 nm, and a large SHG response, 2.8×KDP. The SHG intensity is the largest for silicates without second‐order Jahn–Teller cations, and exceeds that of non‐isomorphic Li2SrSiO4 by more than an order of magnitude. As such Li2BaSiO4 may be seen as a promising DUV‐UV NLO material. This research indicates that edge‐sharing tetrahedra is a new design parameter for discovering new DUV NLO materials.
Meet on the edge: Silicates are not usually deep UV nonlinear optical (DUV NLO) materials owing to their weak second harmonic generation (SHG) response. A silicate, Li2BaSiO4, with edge‐sharing LiO4–SiO4 tetrahedra is now shown to have a large SHG response, 2.8×KDP. As such, Li2BaSiO4 is a promising DUV‐UV NLO material. Edge‐sharing tetrahedra is a new design parameter for discovering new DUV NLO materials.
Abstract
The abundant multipolar resonances in all‐dielectric metasurfaces provide a new paradigm to simultaneously induce strong near‐field confinement in the interior of a nanocavity as well as to ...manipulate the far‐field scattering property, which is beneficial for the enhancement of nonlinear effects. Here, third‐harmonic generation (THG) of all‐dielectric silicon metasurfaces that sustain dominant electric dipole (ED), toroidal dipole (TD), and magnetic dipole (MD) moments in near‐infrared is numerically and experimentally studied. The effect of the interplay of these resonant modes on THG is investigated, and a pronounced THG enhancement is observed when these modes become spectrally overlapped, corresponding to the generalized Kerker condition. The constructive interference of the total electric dipole (refers to the summation of the ED and TD scattered fields) and MD modes results in the suppression of the backward scattering along with a strong local‐field enhancement inside the dielectric resonators. The simulation (experimental) results show a 214‐fold (17‐fold) THG enhancement in the vicinity of the generalized Kerker condition compared with the signals of the spectrally separated TD and MD resonances. The silicon‐based metasurfaces with their simple geometry are facile for large‐area fabrication and open new possibilities for the optimization of upconversion processes to achieve efficient nonlinear devices.
We present a thermal model to describe the interaction between the visible modes in micro-ring resonators from the third harmonic generation (THG) nonlinear process. We demonstrate that the model can ...predict the thermal characteristics of the orthogonal THG modes from the interaction and of the resonance coupling between them in micro-ring resonators having a strong nonlinear thermo-optic coefficient. Furthermore, the model can be used to extract the THG efficiency, the linear and nonlinear thermo-optic coefficients and the polarization dependency of the THG modes from the measurement data.
Strong Mie-type magnetic dipole resonances in all-dielectric nanostructures provide novel opportunities for enhancing nonlinear effects at the nanoscale due to the intense electric and magnetic ...fields trapped within the individual nanoparticles. Here we study third-harmonic generation from quadrumers of silicon nanodisks supporting high-quality collective modes associated with the magnetic Fano resonance. We observe nontrivial wavelength and angular dependencies of the generated harmonic signal featuring a multifold enhancement of the nonlinear response in oligomeric systems.
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