Superfast light source made from quantum dots

April 28, 2016 // By PAUL BUCKLEY
Researchers at the Niels Bohr Institute have shown that light sources can be made much faster
Researchers at the Niels Bohr Institute (København, Denmark) have shown that light sources can be made much faster by using a principle that was predicted theoretically in 1954.

The superfast light sources can be used in laser lights, LED lights and in single-photon light sources for quantum technology.

All light sources work by absorbing energy – for example, from an electric current – and emit energy as light. But the energy can also be lost as heat and it is therefore important that the light sources emit the light as quickly as possible, before the energy is lost as heat.

The researchers at the Niels Bohr Institute worked with quantum dots that can be incorporated into optical chips. In a quantum dot, an electron can be excited (i.e. jump up), for example, by shining a light on it with a laser and the electron leaves a ‘hole’. The stronger the interaction between light and matter, the faster the electron decays back into the hole and the faster the light is emitted.

But the interaction between light and matter is naturally very weak and it makes the light sources very slow to emit light and this can reduce energy efficiency.

Already in 1954, the physicist Robert Dicke predicted that the interaction between light and matter could be increased by having a number of atoms that ‘share’ the excited state in a quantum superposition.

In a quantum dot, there are both negatively charged particles and positively charged particles that are missing electrons (also referred to as holes). The attraction between the electron and hole creates a new quantum state with a very strong light-matter interaction and a corresponding quick release of light.

In a quantum dot, there are both negatively charged particles and positively charged particles that are missing electrons (also referred to as holes). The attraction between the electron and hole creates a new quantum state with a very strong light-matter interaction and a corresponding quick release of light.