  In this report we study the Vernier effect in coupled laser systems
consisting of two cavities. We show that depending on the nature of their
coupling, not only can the "supermodes" formed at the overlapping resonances of
the coupled cavities have the lowest thresholds and lase first as previously
suggested, leading to a manifestation of the typical Vernier effect now in an
active system; these supermodes can also have increased thresholds and are
hence suppressed, which can be viewed as an inverse Vernier effect. We
attribute this effect to detuning-dependent Q-spoiling, and it can lead to an
increased free spectrum range and possibly single-mode lasing, which may
explain the experimental findings of several previous work. We illustrate this
effect using two coupled micro-ring cavities and a micro-ring cavity coupled to
a slab cavity, and we discuss its relation to the existence of exceptional
points in coupled lasers.
