Quantum optics breakthrough Chinese scientists achieve room temperature, controlled superfluorescence technology

Researchers hoping to synthesize a brighter, more stable nanoparticle for optical applications have found that their creation instead exhibits an even more surprising property: a burst of superfluorescence (SF) - a unique quantum optical phenomenon - at room temperature, at regular intervals.

The research results were published on August 29 in the journal Nature Photonics under the title "Variable frequency superfluorescence at room temperature" [1]. This technology is expected to be applied to the production of faster microchips, neural sensors or the development of materials for quantum computing applications, as well as some biological research.

It is worth mentioning that two of the corresponding authors of the paper are Chinese scientists.

Shuang Fang Lim, the first author, received his PhD from the University of Cambridge, UK, and is currently a professor at North Carolina State University; his research focuses on synthetic characterization, photophysics, bioconjugation and applications of UCNP

The second author, Gang Han, a professor at the University of Massachusetts, graduated from Nanjing University with both his undergraduate and master's degrees, and his research is at the intersection of nanotechnology, neuroscience, bioimaging and therapeutics; in 2022, he was selected as a member of the College of Fellows by the American Institute for Medical and Biological Engineering (AIMBE), which consists of the top 2% of medical and biological engineers in the United States

Superfluorescence (SF) is a unique quantum optical phenomenon that arises from the assembly of self and cooperatively coupled emitters.

Hyperfluorescence occurs when atoms in a material synchronize and simultaneously emit a brief but intense amount of light. This property is valuable for quantum optics applications, but is extremely difficult to achieve at room temperature and over sufficiently long time intervals.

Lanthanide-doped "upconversion nanoparticles" (UCNP), a material synthesized by the team, were designed to create a brighter optical material - one in which light from one atom stimulates more of the same light from another. They produced hexagonal ceramic crystals ranging in size from 50 nanometers (nm) to 500 nm and began testing their luminescent properties, which led to an impressive breakthrough: they instead discovered hyperfluorescence, where first all the atoms align and then glow together.

The process of achieving hyperfluorescence at room temperature.

When we excited the material with different laser intensities, we found that it emits three pulses of hyperfluorescence at fixed intervals with each excitation," said Shuang Fang Lim, associate professor of physics at North Carolina State University and co-corresponding author of the study. And these pulses do not degrade, with each pulse being 2 nanoseconds in length. Thus, not only does UCNP exhibit hyperfluorescence at room temperature, but it does so in a controlled manner."

Hyperfluorescence at room temperature is difficult to achieve because it is difficult for atoms to glow together without being "kicked" away from their surroundings. However, in UCNP, the light comes from electron orbitals that are "buried" beneath other electrons, which act as a shield and emit hyperfluorescence even at room temperature.

In addition, the hyperfluorescence of UCNP is technically exciting because it is Anti-Stoke's shift, which means that the wavelength of light emitted is shorter and more energetic than the wavelength that initiates the reaction.

This intense and fast Anti-Stoke's shift hyperfluorescence emission is well suited for numerous advanced materials and nanomedicine platforms," said Gang Han, professor of biochemistry and molecular biotechnology at the University of Massachusetts and co-corresponding author of the study. For example, UCNPs have been used in a wide range of biological applications: from background-noise-free biosensing, precision nanomedicine and deep tissue imaging, to cell biology, visual physiology and optogenetics."

"However, a challenge for current UCNP applications is their slow emission, which often makes detection complex and undesirable. But the speed of anti-Stoke shift hyperfluorescence is a complete game changer: 10,000 times faster than current methods. We believe that this hyperfluorescent nanoparticle offers a revolutionary solution for clean, fast and dense light sources for bioimaging and phototherapy."

The unique properties of UCNP may lead to their use in numerous fields.

Lim said, "First, room temperature operation makes applications easier. And 50 nm is the smallest hyperfluorescent medium in existence. With the ability to control the pulses, we can use these crystals as timers, neurosensors or on microchips. Also, larger crystals allow us to have better control over the pulses."

Reference link：

[1]https://wraltechwire.com/2022/08/29/ncsu-research-could-mean-faster-microchips-quantum-computing-applications/

[2]https://www.nature.com/articles/s41566-022-01060-5