Generating ultra-pure radar frequencies with semiconductor lasers

The radar's principle of operation relies on a contrast between an
emitted microwave and the corresponding echo which is
scaterred/reflected back by a given target.
The resolution of a radar is therefore tightly related to the spectral
purity of the emitted microwave, and the generation of ultra-pure
radio-frequencies is still a important challenge in microwave technology.

Few years ago, a new device referred to as "optoelectronic oscillator"
(OEO) was proposed to generate such high spectral purity microwaves, and
it mainly consists on a semiconductor laser whose output light is
subjected to nonlinear modulation and delay. The aim of this talk will
be to present a model which can accurately describe the dynamical
behavior of OEOs. In particular, the model predicts that as the gain of
the oscillator is increased, the ultra-pure single-mode solution becomes
unstable beyond a precise critical value. Experimental measurements
confirm this scenario with an excellent precision, thus validating the
model. An extension to the stochastic and multimode dynamics of the OEO
will also be proposed. At last, the consequences of these nonlinear
phenomena on the performances of OEO-based systems will be discussed.