My watch list
my.chemeurope.com  
Login  

A burst of ”synchronous” light

Sandwich structure of nanocrystals as quantum light source

09-Nov-2018

Empa

Superlattices under the microscope (white light illumination).

Excited photo-emitters can cooperate and radiate simultaneously, a phenomenon called superfluorescence. Researchers from Empa and ETH Zurich, together with colleagues from IBM Research Zurich, have recently been able to create this effect with long-range ordered nanocrystal superlattices. This discovery could enable future developments in LED lighting, quantum sensing, quantum communication and future quantum computing.

Some materials spontaneously emit light if they are excited by an external source, for instance a laser. This phenomenon is known as fluorescence. However, in several gases and quantum systems a much stronger emission of light can occur, when the emitters within an ensemble spontaneously synchronize their quantum mechanical phase with each other and act together when excited. In this way, the resulting light output can be much more intense than the sum of the individual emitters, leading to an ultrafast and bright emission of light – superfluorescence. It only occurs, however, when those emitters fulfill stringent requirements, such as having the same emission energy, high coupling strength to the light field and a long coherence time. As such, they are strongly interacting with each other but at the same time are not easily disturbed by their environment. This has not been possible up to now using technologically relevant materials. Colloidal quantum dots could just be the ticket; they are a proven, commercially appealing solution already employed in the most advanced LCD television displays – and they fulfill all the requirements.

Researchers at Empa and ETH Zurich, led by Maksym Kovalenko, together with colleagues from IBM Research Zurich, have now shown that the most recent generation of quantum dots made of lead halide perovskites offer an elegant and practically convenient path to superfluorescence on-demand. For this, the researchers arranged perovskite quantum dots into a three-dimensional superlattice, which enables the coherent collective emission of photons – thus creating superfluorescence. This provides the basis for sources of entangled multi-photon states, a missing key resource for quantum sensing, quantum imaging and photonic quantum computing.

“Birds of a feather flock together”

A coherent coupling among quantum dots requires, however, that they all have the same size, shape and composition because “birds of a feather flock together” in the quantum universe, too. “Such long-range ordered superlattices could only be obtained from a highly monodisperse solution of quantum dots, the synthesis of which had been carefully optimized over the last few years,” said Maryna Bodnarchuk, a senior scientist at Empa. With such ”uniform” quantum dots of various sizes, the research team could then form superlattices by properly controlling the solvent evaporation.

The final proof of superfluorescence came from optical experiments performed at temperatures of around minus 267 degrees Celsius. The researchers discovered that photons were emitted simultaneously in a bright burst: “This was our ‘Eureka! ‘ moment. The moment we realized that this was a novel quantum light source,” said Gabriele Rainó from ETH Zurich and Empa who was part of the team that carried out the optical experiments.

The researchers consider these experiments as a starting point to further exploit collective quantum phenomena with this unique class of material. “As the properties of the ensemble can be boosted compared to just the sum of its parts, one can go way beyond engineering the individual quantum dots,” added Michael Becker from ETH Zurich and IBM Research. The controlled generation of superfluorescence and the corresponding quantum light could open new possibilities in LED lighting, quantum sensing, quantum-encrypted communication and future quantum computing.

Facts, background information, dossiers
  • perovskites
  • light
  • superlattices
More about Empa
  • News

    A molecular bridge further

    Electronics built from molecules could open up new possibilities in the miniaturization of circuits in the future. Empa researchers, together with partners from Switzerland, the Netherlands, Israel, and  the UK, succeeded in solving a crucial detail in the realization of such circuit elemen ... more

    Self healing robots that "feel pain"

    Over the next three years, researchers from the Vrije Universiteit Brussel, University of Cambridge, École Supérieure de Physique et de Chimie Industrielles de la ville de Paris (ESPCI-Paris) and Empa will be working together with the Dutch Polymer manufacturer SupraPolix on the next genera ... more

    New record for flexible thin-film solar cells

    Flexible solar cell with unprecedented efficiency: The Empa Laboratory for Thin Films and Photovoltaics, headed by Ayodhya N. Tiwari, has broken its own record. The researchers improved the efficiency of energy conversion in CIGS solar cells on flexible polymer substrate to 20.8%. This is 0 ... more

  • Videos

    A water-based, rechargeable battery

    First step to produce a cheap aquous electrolyte for powerful rechargeable batteries: Seven grams of sodium FSI (precise name: sodium bis(fluorosulfonyl)imide) and one gram of water produce a clear saline solution with an electrochemical stability of up to 2.6 volts – twice as much as other ... more

More about ETH Zürich
  • News

    Using industrial waste as insulation for buildings

    ETH spinoff FenX transforms industrial waste into a porous foam suitable for building insulation. Unlike other sustainable materials used for the purpose, this type of insulation is non-flammable and inexpensive to produce. No sooner does one of the four young men come up with the idea than ... more

    Deep learning, prefabricated

    Self-driving cars, the automatic detection of cancer cells, online translation: deep learning makes it all possible. The ETH spin-off Mirage Technologies has developed a deep learning platform that aims to help start-ups and companies more quickly develop and optimise their products. The na ... more

    Mini-spectrometer: Smaller than a coin

    ETH researchers have developed a compact infrared spectrometer. It’s small enough to fit on a computer chip but can still open up interesting possibilities – in space and in everyday life. Nowadays, a mobile phone can do almost anything: take photos or video, send messages, determine its pr ... more

  • Videos

    Oxybromination of methane over vanadium phosphate

    ETH Zurich scientists have discovered a new catalyst that allows the easy conversion of natural gas constituents into precursors for the production of fuels or complex chemicals, such as polymers or pharmaceuticals. The new catalyst is extremely stable and results in fewer unwanted by-produ ... more

Your browser is not current. Microsoft Internet Explorer 6.0 does not support some functions on Chemie.DE