Abstract

Light emitted by an atomic source of radiation appears to travel along a straight line (ray) from the location of the source to the observer in the far field. However, when the energy flow pattern of the radiation is resolved with an accuracy better than an optical wavelength, it turns out that the field lines are usually curved. We consider electric dipole radiation, a prime example of which is the radiation emitted by an atom during an electronic transition, and we show that the field lines of energy flow are in general curves. Near the location of the dipole, the field lines exhibit a vortex structure, and in the far field they approach a straight line. The spatial extension of the vortex in the optical near field is of nanoscale dimension. Due to the rotation of the field lines near the source, the asymptotic limit of a field line is not exactly in the radially outward direction and as a consequence, the image in the far field is slightly shifted. This sub-wavelength displacement of the image of the source should be amenable to experimental observation with contemporary nanoscale-precision techniques.

© 2009 Chinese Optics Letters

Nanoscale shift of the intensity distribution of dipole radiation

Jie Shu, Xin Li, and Henk F. Arnoldus
J. Opt. Soc. Am. A 26(2) 395-402 (2009)

Subwavelength displacement of the far-field image of a radiating dipole

Henk F. Arnoldus, Xin Li, and Jie Shu
Opt. Lett. 33(13) 1446-1448 (2008)

Damping of the dipole vortex

Xin Li, Donna M. Pierce, and Henk F. Arnoldus
J. Opt. Soc. Am. A 28(5) 778-785 (2011)

Propagation of magnetic dipole radiation through a medium

Henk F. Arnoldus and Zhangjin Xu
J. Opt. Soc. Am. A 33(5) 882-886 (2016)

Redistribution of energy flow in a material due to damping

Xin Li, Donna M. Pierce, and Henk F. Arnoldus
Opt. Lett. 36(3) 349-351 (2011)