Who we are and what we do

Welcome to the Structured Light Laboratory’s home page. We are a small and dynamic group based within the School of Physics at the University of the Witwatersrand in Johannesburg, South Africa. Colloquially called “Wits” (pronounced as “Vits”), the university has produced four Nobel Laureates, many of the world’s top mining CEOs, home to the Cradle of Humankind, and is ranked #1 in South Africa.

Our history traces back to traditional laser beam shaping for commercial applications, then mathematical optics and its applications at the CSIR National Laser Centre, to the new laboratory at Wits, started in 2015. Here we look at Structured Light and its applications. The ability to tailor optical fields is an essential tool in a modern optics laboratory and has come of age with liquid crystal technology, allowing for the digital control of light. By Structured Light we mean the creation of arbitrarily complex light patterns through the control of light’s polarization, amplitude and phase. We used these tools to create accelerating light, non-diffracting light, vector light fields and light carrying optical vortices and orbital angular momentum. We also use these tools to unravel light, what we call modal decomposition, or a “pattern sensitive detector”. We create these fields by a range of techniques, but primarily using digital holograms written to spatial light modulators for the all-digital control of light. We then apply such Structured Light in applications such as optical trapping and tweezing, optical communication and quantum optics, with some recent research highlights listed below:

• A holographic toolkit for creating and detecting spatial modes of light
• Classical entanglement with vector vortex beams
• A new definition for the quality of vector beams
• Real-time quantum error correction using classical light
• Quantum teleportation with orbital angular momentum
• Quantum Key Distribution (QKD) with high-dimensional entangled states
• Entangled Bessel beams and self-healing of quantum states
• High-dimensional quantum state engineering
• A digital laser for on-demand modes from lasers
• A vortex laser for scalar and vector orbital angular momentum modes.

The work is carried out at both the classical and quantum levels and includes topics that range from purely theoretical to purely experimental. Our research builds competency in mathematical algorithms applied in optics, both theoretically and computationally, non-linear optics, diffractive optical elements, micro optics, adaptive optics, refractive beam shapers, digital holograms, spatial light modulators and wavefront sensing.