point dipole

Light scattering from three-level systems: The T matrix of a point dipole with gain
T. Savels, A. P. Mosk, and A. Lagendijk
Phys. Rev. A 71, 043814: 1-7 (2005)

Optical emission in periodic dielectrics
R. Sprik, B.A. van Tiggelen, and A. Lagendijk
Europhys. Lett. 35, 265-270 (1996)