Periodic incorporation of quantum wells inside a
one-dimensional Bragg structure is shown to enhance coherent coupling
of excitons to the electromagnetic Bloch waves. We demonstrate strong
coupling of quantum well excitons to photonic crystal Bragg modes at
the edge of the photonic band gap, which gives rise to mixed Bragg
polariton eigenstates. The resulting Bragg polariton branches are in
good agreement with the theory and allow demonstration of Bragg
polariton parametric amplification.

From: A. Askitopoulos, L. Mouchliadis, I. Iorsh, G. Christmann,
J. J. Baumberg, M. A. Kaliteevski, Z. Hatzopoulos and P. G. Savvidis
“Bragg
Polaritons: Strong Coupling and Amplification in an
Unfolded Microcavity“,
Physical Review Letters
106, 076401 (2011).