Fully-structured light for novel light-matter interactions

Fully-structured light - light that has non-uniform intensity, phase and polarization - lies at the heart of an emerging and extremely promising field of research with applications in high-resolution imaging, optical trapping and manipulation of nanoparticles, and high bandwidth quantum optical communications.
Light with structured intensity has already resulted in a surprisingly large number of applications. The well-established technique of optical tweezing, for example, recently awarded the Nobel prize in Physics 2018, uses the dipole force associated with the intensity gradient of a focused Gaussian beam to trap and manipulate small particles such as dielectric spheres, bacteria, and even strands of DNA, with applications in biological science and microrheology.
Light can also have phase structure, and light with a helical phase structure is known to carry orbital angular momentum (OAM). This can be transferred to a trapped particle causing rotation around the centre of the beam and essentially converting optical tweezers into an optical spanner or wrench. Beams carrying OAM are also of interest as a resource in quantum information, such as in the optical implementation of a qubit in quantum information. OAM, however, is not restricted to two orthogonal states and is of therefore of interest for high capacity secure quantum communication and information systems.
Finally, light can also have polarization structure. The polarization state of light is of fundamental relevance in many applications in optics and structuring the polarization has been shown to result in additional beneficial properties, including tighter focusing of beams for use in high-resolution microscopy and imaging. Together with Robert Boyd's group in Ottawa we have recently demonstrated that these fully-structured light beams can result in more stable nonlinear propagation. Such beams may also be ideal candidates for producing complex yet controllable and accessible chiral forces for use in chemistry (trapping of chiral molecules) and biology (interactions with biological material).

To take full advantage of the rich array of applications offered by fully-structured light, however, a full understanding of its complex behaviour during propagation, both linear and non-linear, is essential. This project focuses on the theory and simulation of the interaction of fully-structured light with a number of different materials, such as cold atoms, ultra-cold gases and nonlinear media, for the above-mentioned applications.