  Theoretical investigations of dynamical behavior in optical parametric
oscillators (OPO) have generally assumed that the cavity detunings of the
interacting fields are controllable parameters. However, OPOs are known to
experience mode hops, where the system jumps to the mode of lowest cavity
detuning. We note that this phenomenon significantly limits the range of
accessible detunings and thus may prevent instabilities predicted to occur
above a minimum detuning from being evidenced experimentally. As a simple
example among a number of instability mechanisms possibly affected by this
limitation, we discuss the Hopf bifurcation leading to periodic behavior in the
monomode mean-field model of a triply resonant OPO and show that it probably
can be observed only in very specific setups.

Optics