A REVIEW OF LOCAL-FIELD EFFECTS IN LASING WITHOUT INVERSION

We review the effects of density dependent near dipole-dipole, or loca l field, interactions on lasing without inversion. In particular, we c onsider the nonlinear behaviour of the macroscopic electric susceptibi lity of a dense, coherently prepared, three-level LAMBDA system. For c ertain values of the atomic density, we observe enhancement of the abs orptionless index of refraction and inversionless gain by more than tw o orders of magnitude. We also predict a piezophotonic switching effec t whereby a small change in density induces the system to flip from a strong absorber into a local field enhanced inversionless amplifier.