A light beam can now be made to carry a twist that spins microscopic objects like an invisible wrench. This property, called orbital angular momentum (OAM), was only discovered in the 1990s, yet it is already 100 times stronger than the spin from ordinary circularly polarised light. The problem is that fundamental physics questions and technological limits still block its practical use. This research programme will tackle those barriers head-on. If successful, OAM could enable a sharper form of microscopy that reveals details conventional light cannot. It could also underpin fast, secure cryptographic networks where data is encoded in the beam’s twist, making it far harder to intercept. And it could lead to new optical sensors for measuring tiny rotations or forces. The project is largely fundamental science—exploring how OAM behaves in both classical and quantum regimes—but the potential payoffs are concrete. Just as Maxwell’s equations led to radio and lasers, understanding OAM’s hidden momentum could quietly reshape communications, imaging, and sensing technologies that underpin modern infrastructure.
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Stand in the way of a light beam and it could both knock you over and send you in a twirl. Over 100 years ago Maxwell worked out the fundamental equations describing how light propagates through space. Embedded within these equations is that light carries both energy and momentum, but although its energy is apparent in our everyday lives, its momentum is not. However, shine light down a microscope and its momentum can be seen to move, or trap, microscopic objects. Circularly polarized light also carries a Spin Angular Momentum causing the microscopic object to spin. Although the study of light has been central to the development of modern physics, it was not until the 1990's that it was realized that a whole new class of light beam could be created simply in the laboratory. Inserting a modified diffraction grating in the beam from a laser pointer is all that is required to create a light beam carrying Orbital Angular Momentum. The effect of OAM can be 100's time greater than that given by the spin alone - allowing our previous demonstration of the optical rotation of microscopic objects: an optical spanner! Beyond microscopic rotations, Orbital Angular Momentum (OAM) opens new opportunities across optical science.We wish to unlock the potential of OAM in both classical and quantum science. However, fundamental questions remain pertaining both to the underlying physics and technological limitations. This research programme will address these limitations, each a scientific achievement in their own right but together paving the route to:- OAM to enable an improved form of microscopy.- OAM as a secure basis on which to build a fast cryptographic network.- OAM at the heart of new types of optical sensors. We benefit from critical friends and will form an international steering panel to meet annually with the team. We have the agreement of two of the world's leading scientists to serve on this panel. To maximise our wider impact, the panel will also include an industrialist from Scottish Enterprise and be convened by the chair of the Glasgow University KT committee. The panel will agree with the PIs, quantitative targets for high-impact journal publications, invited talks at both academic and industrial events and, most importantly, targets for exploitation (patents, license, consultancy).
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