Ad-hoc control of scattering for adaptive opaque lenses

Abstract

Microscopy and optical imaging are drastically limited by the inhomogeneities encountered by the light while propagating from the object of interest to the detection system. In this context, adaptive optics and wavefront manipulation are able to improve the contrast (visibility) of systems embedded in turbid and noisy environments. By wavefront shaping, the fluence of the light propagating through complex systems can be controlled, thus, confining the light in a defined microscopic region in the volume or at the back of scattering structures. We can imagine to counterintuitively exploit the optical barriers, turning them into scattering lenses. In this Thesis we consider these new generation of lenses: we demonstrate them to be configurable optical devices able to produce tailored light structures, hence resulting extremely advantageous if integrated in optical systems.We have initially studied their focusing spatial resolution at different scattering strengths, thereafter we have developed a method that allows to overcome the present limitations and to scale down their resolution of a factor 3 if compared with the previous standard methods. This result has been obtained selecting transmitting optical modes that are directly responsible for the resolution improvement. Therefore, we show that properly filtering the light transmitted at the back of a scatterer we can also obtain numerous novel optical features. Specifically, we demonstrate the full control of non-diffractive light structures named amorphous speckle patterns. Under wavefrontshaping manipulation those complex interference patterns can be converted to Bessel-like beams. The method discloses the possibility to produce Bessel beams at the selected location at the back of scattering barriers. The results presented have potential for providing arranged structured illumination and for enhancing the penetration depth in microscopy providing optimal imaging resolution of thick samples. Thence, complex scattering systems have been recently used as programmable stand-alone optical devices. We have foreseen their operation in optical circuits, for this reason we designed micro-fabricated scattering systems in the bulk of cover-slip glasses. Our photonic structures are proved to be unreproducible and resistant to the deterioration, hence resulting suitable for authentication control operations. Moreover, fashioning the position and thegeometry of the single scatterers via laser ablation we can engineer the process of multiple scattering in order to produce structured illuminations. In particular, we test an anisotropic geometry for the formation of light sheets. When we compare our system with conventionalcylindrical lenses we observe a significant spatial resolution enhancement in the light sheet generated. In addition, our opaque lenses result fully tunable, a property that can allow forbypassing mechanical adjustment for chromatic correction or axial scanning in selected planeillumination microscopy. Ultimately, we present a lab-on-a-chip: a programmable platformthat can support and inspect biological systems of interest in a controlled environment.