Seminar 12th May 2010 1 p.m. Building 7, Room 3009
SYMBIOSIS Seminar - Giant amplification of noise
Giampaolo D'Alessandro
University of Southampton
- Categories
- Electromagnetism, Photonics
- Submitter
- Thomas Blumensath
Some dynamical systems display transient growth that may cause an initial perturbation to increase by several order of magnitudes before asymptotically decaying to zero. In particular, in the presence of noise, this transient growth may lead to noise driven chaotic dynamics even in the neighborhood of a linearly stable fixed point.
In this seminar I will give an introduction to the general theory of such dynamical systems and then discuss one specific (optical) device that shows this phenomenon, the synchronously pumped Optical Parametric Oscillator. In optical context transient growth can lead to the amplification of noise up to macroscopic levels even in sub-threshold devices, i.e. in operating conditions where no field would be expected to be emitted. We show that in synchronously pumped optical parametric oscillators noise can be amplified by nine order of magnitudes even below threshold. In these conditions the device emits a non-zero output that is entirely noise driven and that can be used to explore the noise properties of the cavity field.
The theory discussed in this seminar is very general and not limited to an optical context. It would be interesting to see whether there are other applications in biology, engineering and physics where the results presented could be applied.