Optical Trapping Takes Shape: The Use of Structured Light Fields

Optical micromanipulation is a powerful and versatile technique based upon the light-matter interaction. Whilst the forces exerted by optical traps are naturally very small, they are sufficient to realize non-invasive mechanical control over mesoscopic particles within atomic, biological and colloidal systems. The inherent compatibility with modern microscopy enhances the reconfigurability of the trap while the accuracy achieved in a calibrated optical trap presents itself as a quantitative force probe. Thus forces can be applied in a controlled manner to biological systems including cells and molecular motors and processes measured with high precision. The impact is not limited to biology. Optical traps have provided seminal studies in colloidal and optical physics including the phase dynamics of thermodynamic systems, Brownian diffusion, aspects of microfluidics, and fundamental issues related to optical angular momentum. This article aims to focus upon the emergent theme of optical trapping with structured light fields. By structured light fields we refer to the generation of multiple arrays of traps and the use of specialist light fields such as Laguerre-Gaussian beams and Bessel beams. Structured light fields are making a major impact on optical trapping and on subsequent applications including those in biomedicine.