| dc.description.abstract | Over the last 15 years, wavefront shaping has emerged as a powerful technique to control the propagation of light within scattering media by precisely sculpting the spatial distribution of an electromagnetic field. Today, wavefront shaping is a cornerstone approach to solving many light scattering problems in optics. This technique is being used to see and probe deep into tissue, replace traditional optical components like lenses, and render opaque objects transparent.
Here we explore applications of wavefront shaping to two new problems.
The first of these is wavefront shaping in the face of dynamic media that results in light scattering that fluctuates in time. Existing wavefront shaping applications rely on light scattering from static scattering media -- imagine the constant distortions of sunlight through a frosted glass window. We envisage a scattering scenario wherein
some parts of the medium are static, while others are moving -- like trying to image inside of a living organism with blood vessels flowing through largely static tissue. We demonstrate, numerically and experimentally, a new suite of wavefront shaping tools that determine paths for the light that carefully navigate through static and around dynamic scattering areas. These tools include an assortment of matrices and optimisation algorithms that use information about the time fluctuations of a light field to find such paths. This research opens the door to combining our new techniques with the plethora of existing methods such as the transmission matrix, phase conjugation, and iterative wavefront optimisation to offer expanded applications in the field of wavefront shaping.
The second problem we investigate is in the field of optical tweezing. Optical tweezers, which use the transfer of momentum from a focused laser beam to a micro-scale object, to trap the object and control its motion, have allowed researchers to gain unrivaled access to and control over the mesoscale world. We aim to trap micro-spheres immersed in water more tightly by moulding the spatial distribution of an optical trap. The interaction between the light and the trapped particle is changed by manipulating the incident optical field. We develop new ways to optimise the optical trap shape, both numerically and experimentally, such that our final optimised traps reduce the 3D motion of trapped micro-scale particles in water by orders of magnitude compared to conventional Gaussian traps. These enhanced optical traps hold promise for many applications in the field of micro-manipulation, including trapping of previously un-trappable particles.
Our work demonstrates that wavefront shaping can be applied to dynamic scattering media and optical tweezers, opening avenues to new applications in imaging, optical communications, and optical micro-manipulation. | en_GB |
