In an active waveguide in which the refractive index of the inner part is smaller than that of the outer part, there is modal gain if the field-medium gain is higher than a threshold value that is a function of the refractive-index step. The threshold current density is shown to decrease as the refractive-index step increases. This behavior can be explained by considering the interplay between the creation of energy in the medium gain and lateral loss.
© 1990 Optical Society of America
Original Manuscript: January 30, 1989
Manuscript Accepted: July 25, 1989
Published: January 1, 1990
J. Fesquet, "Influence of the refractive-index step on the threshold current density in antiguiding active slabs," J. Opt. Soc. Am. B 7, 134-137 (1990)