nanoemitter

A nanoemitter is a nanoscale light source that emits photons through quantum or excitonic transitions. In nanophotonics, nanoemitters are typically individual quantum emitters capable of on-demand light generation, such as colloidal quantum dots, color centers in diamond (for example, nitrogen-vacancy or silicon-vacancy centers), defect centers in two-dimensional materials like tungsten diselenide, or single organic molecules confined in nanoscale hosts. Nanoemitters are often integrated with photonic structures to improve emission rate, directionality, and collection efficiency.

Key features of nanoemitters include the ability to produce nonclassical light, such as single photons, and tunable spectral properties. Their emission can be characterized by measurements of the second-order correlation function, with g2(0) values less than 0.5 indicating single-photon behavior. Emission properties can be modified by coupling to optical cavities, waveguides, or plasmonic antennas, which enhance the spontaneous emission rate (Purcell effect) and tailor the emission pattern.

Realization and integration methods vary. Colloidal quantum dots are synthesized chemically and positioned on substrates, while diamond-based emitters are created by implantation of defects or growth of nanodiamonds. 2D material emitters arise from localized excitons in monolayers. Deterministic placement remains technically challenging but is crucial for scalable on-chip photonics.

Applications span quantum information processing, secure quantum communication, quantum sensing, and nanoscale imaging. Ongoing research addresses challenges such as spectral diffusion, blinking, stability under operation, and achieving high photon indistinguishability and extraction efficiency.