A strongly focused beam of light can be used to trap and move objects ranging in size from tens of nanometers to tens of micrometers. These optical tweezers have become a widely-used tool in biology, physical chemistry, and fundamental physics, and the invention was awarded the 2018 Nobel Prize in Physics. The group have worked in optical trapping for over two decades, and some of our recent research directions are highlighted below.

Optical Binding

Optically mediated interactions between trapped objects can cause attractive and repulsive forces and dramatically influence the way they assemble and organize themselves. This offers routes for self-assembly of crystalline “optical matter”.

Optical Rotation

Anisotropic optically trapped particles can be made to spin by using circularly-polarised light. When this rotation takes place in vacuum, the particle can rotate about its own axis several million times per second, creating a gyroscopic effect which stabilises the particle’s motion and cools the translational energy to 40K. The orbital angular momentum of light can also be used to impart rotational motion on the trapped object. These rotational effects in levitated optomechanics may be of interest in guided matter-wave interferometry of massive particles, and in the hunt for quantum friction.

Unconventional Trapping Materials

An under-explored area of optical trapping is the influence of the material properties of the trapped particle. A careful choice of the properties of the particle in the light can allow significant flexibility in tailoring the optical forces torques, and even the temperature of the particles.