Compound cavity lasers have very interesting properties due to the interference between modal combs. The so-called Vernier effect may induce either strongly monomode dynamics or high frequency modal beating, see for instance .
This type of dynamics can be studied with Freetwm following a versatile approach: for a low number of intracavity reflectors, one can define several sub-sections, coupled via their respective boundary conditions. However, when the number of intracavity reflector is large, like e.g. to form a rough photonic crystal, this approach is not practical and we provide another method where one can insert directly reflectors inside a single section.
On the left, one can observe the results of this latter approach where harmonic multimode dynamics is induced by placing inside the cavity four 1% intracavity reflectors located at L/2, 5L/8, 3L/4 and 7L/8 within a cavity of length L.
In each subsection, one can notice that the population inversion (D0) evolves around different values due to the compound cavity effect
The four maxima of the intensity within the cavity indicates that the laser operates in a regime where one mode every eigth is active.