Nanophotonica

Nanophotonica, or nanophotonics, is the study of light-matter interactions at nanometer scales, where the size of structures and their spacing approach the wavelength of light. In this regime, nanostructuring can confine, guide, and manipulate photons beyond the diffraction limit, enabling control of optical fields at subwavelength scales.

The field encompasses several subareas, including plasmonics, dielectric nanophotonics, metamaterials and metasurfaces, photonic crystals, and nanoscale waveguides and resonators. Plasmonics uses collective electron oscillations in metals to concentrate light into nanoscale volumes, often with strong field enhancement but with inherent losses. Dielectric nanophotonics relies on high-index materials to confine light with lower losses. Metasurfaces and metamaterials engineer phase, amplitude, and polarization with subwavelength elements to achieve unusual optical responses.

Quantum nanophotonics studies the interaction of quantum emitters—such as quantum dots or color centers—with nanostructured environments to realize efficient single-photon sources, entangled photons, and enhanced light-matter coupling. Fabrication and integration employ lithography, self-assembly, and chemical synthesis of nanostructures, along with integration with silicon photonics for on-chip functionality.

Applications include chemical and biological sensing, spectroscopy and imaging, on-chip optical communication, nonlinear and quantum information processing, and improvements in photovoltaics and light-emitting devices. Characterization uses near-field techniques (NSOM/s-SNOM), electron energy loss spectroscopy, and cathodoluminescence to map local optical responses and the local density of states.

Key challenges include material losses in metals, fabrication precision and variability, thermal management, device scalability, and integration with existing technologies. Ongoing research aims to enable practical nanophotonic systems with enhanced performance and new functionalities.