Micromanipulation and wave front shaping in disordered media

Abstract

In this thesis we investigate one class of operators that allows us to manipulate a target inside a disordered system. The class of operators used for this task is the generalized Wigner-Smith (GWS) operator [https://doi.org/10.1103/PhysRevLett.119.033903], based on the Wigner-Smith time-delay operator. The GWS-operator depends on one parameter, which we take to be either the position, radius, orientation angle or refractive index of the target. Using an eigenstate of the GWS-operator we can transfer either force, pressure or torque onto the target or control the total intensity inside the target, depending on the choice of parameter. We demonstrate our technique in a two-dimensional waveguide described by the scalar Helmholtz equation. This is, however, just a model system as we believe our approach to be universally applicable because the GWS-operator only depends on the scattering matrix of the system and its derivative with respect to the parameter. We think our procedure is particularly attractive because we have shown, for flux-conserving systems, that we are able to achieve the theoretical maximum of transferred force, pressure or torque onto the target as well as the best focus in the target.