Stabilization of single frequency operation of coupled-cavity lasers

We present a theoretical analysis of cleaved coupled-cavity lasers. Mode selectivity arises from two mechanisms. The first is diffraction loss in the gap between the cleaved sections. The second is based on one section acting as a resonant reflector. Our analysis includes the change of refractive index with carrier density which shifts the cavity resonances and causes mode switching. Above threshold the gains g
1
and g
2
of the two cavities are not pinned, but are related for each mode in the form of a curve in the (
g_{1}, g_{2}
) plane. The separation of mode curves along a 45° line determines the ratio of mode intensities. Single mode operation above threshold is described by zones in the (
C_{1}, C_{2}
) plane where C
1
and C
2
are the currents driving the two cavities. Cases of stable, unstable, and bistable operation are discussed.