A simple laser for quantum-like classical light

Tailoring light is much like tailoring cloth, cutting and snipping to turn a bland fabric into one with a desired pattern. In the case of light, the tailoring is usually done in the spatial degrees of freedom, such as its amplitude and phase (the ‘pattern’ of light), and its polarization, while the cutting and snipping might be controlled with spatial light modulators and the like. This burgeoning field is known as structured light, and is pushing the limits in what we can do with light, enabling us to see smaller, focus tighter, image with wider fields of view, probe with fewer photons, and to pack information into light for new high-bandwidth communications. Structured light has also been used to test the classical-quantum boundary, pushing the limits with what classical light can do for quantum processes, and vice versa. This has opened the intriguing possibility of creating classical light that has quantum-like properties—as if it is ‘classically entangled.’ But how to create and control such states of light, and how far can one push the limits?