The authors of the article “Photonic Nanojets” (OPN, January 2021, p. 34) apologize for not providing historical context on the concept’s development. In 1998, Kawata et al. observed optical field enhancement from laser irradiation of spherical polystyrene particles of size d ≤ λ on a photosensitive film.1 In 2000, Mosbacher et al. used Mie theory and experiments to show how the enhancement scales with particle size across a wide range (0.4 λ ≤ d ≤ 3.2 λ) and to explain that it is due to focusing.2 In 2004, the Backman–Taflove group at Northwestern University showed that in addition to field enhancement, light generated on the shadow side of a microcylinder can propagate with a sub-diffraction width over a distance of several optical wavelengths, and named the effect a photonic nanojet.3

The authors also regret any confusion caused by the title of the OPN feature, which is the same as a previously published review paper.4

1. Y. Kawata et al. Opt. Commun. 161, 6 (1999).
2. M. Mosbacher et al. Appl Phys A 72, 41 (2001).
3. Z. Chen et al. Opt. Express 12, 1214 (2004).
4. A. Heifetz et al. J. Comp. Theor. Nanosci. 6, 1979 (2009).