Light is ubiquitous and vital, but also incredibly strange – and it’s possible we’ll never exhaust the opportunities to learn more about it. Case in point: researchers at Harvard have developed a material that can generate and maintain completely new and more complex states of light. It hasn’t even been that long – just 1992, 25 years ago – since light was discovered to have orbital angular momentum. The new tool – a type of metasurface – uses this along with second type of angular momentum called spin angular momentum.
It’s previously been established that a single beam of light can exhibit both types of angular momentum, and that connecting them and using polarisation to control the OAM can result in beams with new and complex shapes, such as the aforementioned corkscrew.
Only certain polarisations could connect to certain OAMs. This is where the new tool comes in – it allows any polarisation to be converted to any OAM, which means it can create spirals and corkscrews and vortices of any size.
“This is a completely new optical component,” said co-first researcher Antonio Ambrosio, Principal Scientist at Harvard Center for Nanoscale Systems.