- To obtain superfluorescence on-demand, researchers used quantum dots made of lead halide perovskites.
- They conducted optical experiments at -267°C, which gave the final evidence of superfluorescence.
A few materials have a tendency to continuously emit light when they are excited by a laser or any other external source. This mechanism is called fluorescence. However, in many quantum systems, the tendency of spontaneously emitting light is much stronger.
When such systems are excited by an external source, they synchronize their quantum mechanical phase with each other, which results in a much more intense output (in the form of light) than the individual emitters combined. This leads to a bright and ultrafast emission of light, i.e. superfluorescence.
However, this only happens when emitters meet specific requirements, for instance, they should have high coupling strength with light field, a larger coherence time, and same emission energy. Also, they must be capable of fully interacting with each other while not being disturbed by their surrounding. So far, scientists haven’t been able to achieve this feat by using thousands of technologically relevant substances.
Recently, researchers at ETH Zurich and Empa created this effect using long-range ordered nanocrystal superlattices. This could pave the way for the development of quantum computing, quantum sensing, quantum-encrypted communication, as well as LED lighting.
Reference: Nature | doi:10.1038/s41586-018-0683-0 | Empa
Colloidal Quantum Dots
To obtain superfluorescence on-demand, the authors used quantum dots made of lead halide perovskites. They organized perovskite quantum dots into a 3D superlattice, enabling coherent collective emission of light (photons), which creates superfluorescence. It’s dynamically red-shifted emission with over 20-fold accelerated radiative decay.
Microscopic view of superlattices (white light illumination) | Credit: Empa
For coherent coupling, the quantum dots must have the same size, shape, and composition. An extremely monodisperse quantum dot solution is required to make long-range ordered superlattices. And such solutions have been thoroughly improved over the last couple of years.
The authors said that by carefully handling the evaporation of the solvent, they could produce superlattices, using uniform quantum dots of varying sizes. Overall, it offers the basis for resources of entangled multi-photon phases – a missing source for photonic quantum computing, quantum imaging, and sensing.
The researchers conducted optical experiments at extremely low temperatures, nearly -267°C, which gave the final evidence of superfluorescence. They found that photons were ejected spontaneously in a bright burst – a novel quantum light source.
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These experiments will help scientists further explore the collective quantum phenomena with lead halide perovskites. Since the properties of this unique type of material can be further enhanced, it’s possible to explore things beyond engineering each quantum dot.
