Artificial Generation of High Harmonics via Nonrelativistic Thomson Scattering in Metamaterial

A universal route to efficient non-linear response via Thomson scattering in linear solids

Non-linear materials are cornerstones of modern optics and electronics. Strong dependence on the intrinsic properties of particular materials, however, inhibits the at-will extension of demanding non-linear effects, especially those second-order ones, to widely adopted centrosymmetric materials (for example, silicon) and technologically important burgeoning spectral domains (for example, terahertz frequencies). Here we introduce a universal route to efficient non-linear responses enabled by exciting non-linear Thomson scattering, a fundamental process in electrodynamics that was known to occur only in relativistic electrons in metamaterial composed of linear materials. Such a mechanism modulates the trajectory of charges, either intrinsically or extrinsically provided in solids, at twice the driving frequency, allowing second-harmonic generation at terahertz frequencies on crystalline silicon with extremely large non-linear susceptibility in our proof-of-concept experiments. By offering a substantially material- and frequency-independent platform, our approach opens new possibilities in the fields of on-demand non-linear optics, terahertz sources, strong field light-solid interactions and integrated photonic circuits.

Research on the reflection-type ELC-based optomechanical metamaterial

In this paper, we propose a new kind of optomechanical metamaterial based on a planar ELC-type absorbing structure fabricated on the low-loss flexible substrate. The nonlinear coupling mechanism and nonlinear response phenomenon of the proposed optomechanical metamaterial driven by electromagnetic induced force are analyzed theoretically. The mechanical deformation/displacement and the mechanical resonance frequency shift of the metamaterial unit deposed on the flexible substrate are also numerically and experimentally demonstrated to reveal the coupling phenomenon of electromagnetic field and mechanical field. These results will help researchers to further understand the multi-physics interactions of optomechanical metamaterials and will promote the developments of new type of metasurface for high-efficiency dynamic electromagnetic wave controlling and formatting.

Broadband second-harmonic generation from artificial optical nonlinearity

In this Letter, we present a mechanism for effectively broadening the bandwidth of second-harmonic generation (SHG) with the metamaterial-based artificial optical nonlinearity. As the nonlinear response of the artificial nonlinearity arising from the magnetoelectric coupling constructed by the meta-molecule (MM) structure, the broadband second-order nonlinearity can be built by simply combining the MMs with different geometrical sizes together. The physical model and the numerical simulation fully support the artificial generation and modulation of the broadband second harmonics. Our work suggests a new route for realizing the on-chip custom-designed nonlinear optical devices with broadband operation.

Chirality Enhancement Using Fabry-Pérot-Like Cavity

Chiral molecules that do not superimpose on their mirror images are the foundation of all life forms on earth. Chiral molecules exhibit chiroptical responses, i.e., they have different electromagnetic responses to light of different circular polarizations. However, chiroptical responses in natural materials, such as circular dichroism and optical rotation dispersion, are intrinsically small because the size of a chiral molecule is significantly shorter than the wavelength of electromagnetic wave. Conventional technology for enhancing chiroptical signal entails demanding requirements on precise alignment of the chiral molecules to certain nanostructures, which however only leads to a limited performance. Herein, we show a new approach towards enhancement of chiroptical effects through a Fabry–Pérot (FP) cavity formed by two handedness-preserving metamirrors operating in the GHz region. We experimentally show that the FP cavity resonator can enhance the optical activity of the chiral molecule by an order of magnitude. Our approach may pave the way towards state-of-the-art chiral sensing applications.

Functional Charge Transfer Plasmon Metadevices

Reducing the capacitive opening between subwavelength metallic objects down to atomic scales or bridging the gap by a conductive path reveals new plasmonic spectral features, known as charge transfer plasmon (CTP). We review the origin, properties, and trending applications of this modes and show how they can be well-understood by classical electrodynamics and quantum mechanics principles. Particularly important is the excitation mechanisms and practical approaches of such a unique resonance in tailoring high-response and efficient extreme-subwavelength hybrid nanophotonic devices. While the quantum tunneling-induced CTP mode possesses the ability to turn on and off the charge transition by varying the intensity of an external light source, the excited CTP in conductively bridged plasmonic systems suffers from the lack of tunability. To address this, the integration of bulk plasmonic nanostructures with optothermally and optoelectronically controllable components has been introduced as promising techniques for developing multifunctional and high-performance CTP-resonant tools. Ultimate tunable plasmonic devices such as metamodulators and metafilters are thus in prospect.