Fundamental limitations to gain enhancement in periodic media and waveguides.
A common strategy to compensate for losses in optical nanostructures is to add gain material in the system. By exploiting slow-light effects it is expected that the gain may be enhanced beyond its bulk value. Here we show that this route cannot be followed uncritically: inclusion of gain inevitably modifies the underlying dispersion law, and thereby may degrade the slow-light properties underlying the device operation and the anticipated gain enhancement itself. This degradation is generic; we demonstrate it for three different systems of current interest (coupled-resonator optical waveguides, Bragg stacks, and photonic crystal waveguides). Nevertheless, a small amount of added gain may be beneficial.
DTU Fotonik, Department of Photonics Engineering, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark.
Jure
J
Grgić
Johan Raunkjær
JR
Ott
Fengwen
F
Wang
Ole
O
Sigmund
Antti-Pekka
AP
Jauho
Jesper
J
Mørk
N Asger
NA
Mortensen