Information in Complex Media
Welcome to my personal webpage! I am a post-doctoral researcher studying the propagation of waves in complex scattering media. I am specifically interested in understanding how much information we can extract from these waves.
Detecting hidden objects through disorder
In free space, it is easy to determine whether an object is present or not by measuring the light it scatters. However, whenever this object is surrounded by a complex scattering environment, this task becomes extremely challenging due to the absorption and multiple scattering processes that occur within the system.
In this work, we theoretically and experimentally demonstrate how to detect an object hidden inside a disordered complex system with an exceptionally low photon flux. This is achieved by identifying and generating probe fields that are specifically optimized for this purpose. Light is guided through the disorder in an optimal way, not only to strongly interact with the object, but also to be efficiently detected by the observer. These results allow one to perform minimally-destructive measurements even in complex scattering systems, with potential applications for the metrology of semi-conductor devices and for the characterization of biological tissues.
Original publication: D. Bouchet, L.M. Rachbauer, S. Rotter, A.P. Mosk, and E. Bossy, Phys. Rev. Lett. 127, 253902 (2021)
Optimal information about the invisible
Laser beams can be used to precisely measure an object’s position or velocity. Normally, however, a clear, unobstructed view of this object is required – and this prerequisite is not always satisfied. In biomedicine, for example, structures are examined, which are embedded in an irregular, complicated environment. There, the laser beam is deflected, scattered and refracted, often making it impossible to obtain useful data from the measurement.
However, in collaboration with researchers at Utrecht University (Netherlands) and TU Wien (Vienna, Austria), we have been able to show that meaningful results can be obtained even in such complicated environments. Indeed, there is a way to specifically modify the laser beam so that it delivers exactly the desired information in the complex, disordered environment - and not just approximately, but in a physically optimal way: Nature does not allow for more precision with coherent laser light. The new technology can be used in very different fields of application, even with different types of waves, and has now been presented in the scientific journal "Nature Physics".
Original publication: D. Bouchet, S. Rotter, and A.P. Mosk, Nat. Phys. 17, 564-568 (2021)
Localizing hidden nanoscale particles
Estimating the position of an object from the light it reflects or scatters is common in everyday life. This process is also at the core of modern sensing and imaging techniques, such as the localization of defects in semiconductor chips, or the tracking of nanoscale objects in biological samples. In collaboration with researchers at Utrecht University (Netherlands) and ESPCI Paris (France), we have studied the canonical situation of a nanoscale particle hidden in a disordered scattering medium.
The main result demonstrated in our study is that the information accessible to an observer depends on fundamental quantities characterizing the medium surrounding the particle. To derive this result, a key point was to disentangle the impact of the illumination process from the influence of the local environment of the particle. To this end, we first identified optimal input waves, specifically shaped to localize single particles in complex environments. For such optimal waves, we then proved that the ultimate precision with which the particle can be localized depends on the so-called local density of optical states and dressed polarizability, two fundamental quantities that characterize the optical interaction between the particle and its environment. This result, which was obtained in the context of a research program in which universities collaborate with industry, has now been presented in the scientific journal "Physical Review Letters".
Original publication: D. Bouchet, R. Carminati, and A.P. Mosk, Phys. Rev. Lett. 124, 133903 (2020)