Optical feedback in microlasers
Optical feedback is a ubiquitous phenomenon that occurs any time a (small) amount of light is retroreflected into the source. Given the reversibilty of optical paths, it is impossible to avoid its presence. Nefarious effects are known in optical communications, even though only tiny amounts of light are reflected back into the very sensitive semiconductor-based emitter. On the other hand, it is possible to exploit the sensitivity of the device for sensing purposes. Most of the investigations performed up until now have centered on reflections from either mirrors or at least optical smooth surfaces.
The experimental project consists in exploring the effect of light backscattering into a laser due to the presence of "impurities". A liquid sample containing a suspension of scatterers will be employed to reinject a variable amount of radiation into the laser and to study its effect on the laser emission in terms of temporal oscillations, emission wavelength and spectral width..
Interested candidates are kindly asked to contact Gian Luca Lippi (Gian-Luca.Lippi - at - inphyni.cnrs.fr).
Influence of low-level electrical and instrumentation noise on sensitive measurements
Electrical and instrumentation noise is an unavoidable feature of any measurement system. Today's instrumentation is based on the digitization of analog signals for storage and processing. The intrinsic low-level nature of the noise implies a strong discretization of its features, which degenerate its nature from a random gaussian distribution to a small ensemble of levels. This operation may accompany instrument-specific characteristics which modify the distribution of the digitized signal. When small, but identifiable signals are superposed to such noise, they are also strongly discretized. The combination of the two effects results in unexpected modifications of the signal's properties.
The experimental project is centered on the acquisition and analysis of noise from a measurement chain to characterize its properties and connect it to the features of the sampling instrumentation.
Interested candidates are kindly asked to contact Gian Luca Lippi (Gian-Luca.Lippi - at - inphyni.cnrs.fr).