Abstract
ABSTRACTNear-field optics, with the capability for nanoscale manipulation of photons and enhancement of light-matter interactions, has drawn tremendous attentions in recent years. Compared with traditional noble metals, near-field optics in low-dimensional van der Waals (vdW) materials has revealed various polaritonic modes with gate-tunable competence, high confinement and novel quantum physics. Advanced near-field imaging technique, named scattering-type scanning near-field optical microscopy, allows launching and visualizing the polaritonic waves in both noble metals and vdW materials. In this review, we introduce the fundamental principles of near-field optics and summarize up-to-date near-field studies and related quantum physics in three aspects: (1) In-situ electric field distribution around metallic nanostructures; (2) various polaritons in vdW materials and heterostructures; (3) quantum physical phenomena related to near-field optics in low-dimensional system. Then, we discuss the state-of-the-art near-field optics combing imaging with spectroscopy, transient measurement or Terahertz lasers for revealing new physics. To conclude, we summarize the nowadays challenges and present perspectives in the near-field optics field.
Highlights
0:61λ nsinθ where δ is optical resolution, λ is incident wavelength, n is the refractive index of the medium in which the objective works, θ is the half of aperture angle, and nsinθ is called numerical aperture
The application of scanning near-field optical microscopy (SNOM) has expanded from metallic system to van der Waals materials [27], even quantum materials [28,29] and provided manifold novel and exciting insights into polaritonics, which have not been possible by standard farfield methods and other electronic approaches
We summarize the up-to-date near-field polaritonic studies and related physics in three aspects: (1) In-situ electric field distribution around metallic nanostructures, (2) various polaritons in van der Waals (vdW) materials, (3). quantum physical phenomena related to polaritonics in low-dimensional system
Summary
Optics, focusing on the essence of photons and light-matter interaction, is a key research field with history of centuries. Near-field optics [2] provides us an effective way to break the Rayleigh criterion and improve the spatial resolution up to a few percent of incident wavelength. The Abbe diffraction limit is applicable only in classical optics, while the spatial resolution in near-field optics is determined by the distance between probe and sample and the size of probes [4]. (a) The comparison between far-field and near-field optics. The point spread function in far-field optics is determined by diffraction limit, while the spatial resolution in near-field optics is determined by the size of probe. (b) The explanation of breaking the diffraction limit in near-field optics based on uncertainty principle The point spread function in far-field optics is determined by diffraction limit, while the spatial resolution in near-field optics is determined by the size of probe. (b) The explanation of breaking the diffraction limit in near-field optics based on uncertainty principle
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