A Single MoSe2 Fluffy Nanosphere for Localized Light Confinement

Manipulating and focusing the light in a small sphere has been widely investigated; however, the impact of a special fluffy structure on the optical property still remains unclear. Here, we employ a MoSe2 fluffy nanosphere with feature-shaped edges as a three-dimensional model system to study the localized light confinement effect and analyze the inherent mechanism for strong light absorption properties at a single-particle level. The experimental absorption spectrum displays a stable feature without an obvious band-edge transition in a broad-band range, revealing the broad-band absorption property of MoSe2 fluffy nanospheres. The localized enhancement factor inside a fluffy nanosphere is 90.8, and the surrounding lateral scattering area decreases 59.9% according to optical numerical computation. The formation of localized light confinement could originate from restricted optical propagation, such as multiple light scattering, light wave interference and antireflectance features and from rapid absorption and conversion of the incident photons into various energy forms, such as photoelectrons, phonons, and heat. The results not only reveal the impact of fluffy structure on optical responses but also broaden the potential applications of MoSe2 in optical absorbers and single-photon devices.