Sound and light trapped by disorder

February 8, 2019, Catalan Institute of Nanoscience and Nanotechnology
Credit: Catalan Institute of Nanoscience and Nanotechnology

Sound and light are crucial for our life and are essential in many energy, communication and information technologies. Their interaction allows many fundamental observations in physics, from the detection of cosmic gravitational waves to the cooling of quantum systems into their quantum ground state. However, their interaction may be subtle and weak. Enhancing their interaction requires confining both waves at the same place which is a considerable technological challenge.

In nanotechnology, this has been solved by creating cavities relying on very carefully fabricated patterns. This approach is demanding and easily disturbed by disorder and defects. In a work recently published in Physical Review Letters a totally different approach is proposed, where symmetry and periodicity are not needed, and disorder is embraced. The work has been done in close collaboration with Dr. Daniel Lanzillotti-Kimura, a researcher at CNRS in France. The first author of the work is Guillermo Arregui and the last one is Dr. Pedro David García, both from the ICN2 Phononic and Photonic Nanostructures Group led by ICREA Prof. Dr. Clivia M. Sotomayor-Torres.

Order, symmetry and periodicity are words that have always thrilled researchers. For physicists, the appeal is that regular systems tend to obey simple (or at least symmetric) laws. Even are simplified in their description, which helps understanding their underlying mechanisms. However, the world is complex. However, understanding the inherent complexity of nature ultimately requires departing from perfect symmetry and periodicity. Remarkably, as the authors show in this work, disorder and complexity can be exploited as a resource instead of being treated just as an unavoidable annoyance. In the recently published work, disorder is used to simultaneously localize and light at the nanoscale.

Researchers from the Institut Català de Nanociència i Nanotecnologia (ICN2) and the Centre de Nanosciences et Nanotechnologies – C2N (CNRS / Université Paris-Sud) propose a random multilayered semiconductor structure were a subtle combination of their material properties force the simultaneous co-localization of sound and light. The equations governing the propagation of light and sound in stacks made of (GaAs) and aluminium arsenide (AlAs) are extremely similar, leading to an Anderson colocalization of both excitations in random lattices. This is due to a surprising matching in the contrast of their indices of refraction and their speeds of sound, respectively, something that does not happen, for example, with other similar materials like Si/Ge or InP/GaP. The colocalization in random lattices induces an enhancement of the interaction between the light and sound fields. This interaction relies on the fact that light carries momentum which can be transferred to an object and move it. As a counterpart, a moving object can shift the frequency of light. In everyday life, this interaction is extremely small resulting in negligible effects.

To enhance these mutual interactions, the approach followed by nanotechnology is to concentrate light in small volumes and make use of small objects for which these effects become observable. Here, we show that no particular design is required to achieve this mutual observable interaction, thus relaxing substantially the fabrication needs. This achievement may be used to exploit the interaction between light and sound in arbitrarily designed structures, thus relaxing the very demanding fabrication requirements currently needed in nanotechnology. The co-localization effect shown in the new work unlocks the access to unexplored localization phenomena and the engineering of -matter interactions mediated by Anderson-localized states.

Explore further: Researchers discover a metamaterial with inherently robust sound transport

More information: G. Arregui et al. Anderson Photon-Phonon Colocalization in Certain Random Superlattices, Physical Review Letters (2019). DOI: 10.1103/PhysRevLett.122.043903

Related Stories

The sound of an atom has been captured

September 11, 2014

Researchers at Chalmers University of Technology are first to show the use of sound to communicate with an artificial atom. They can thereby demonstrate phenomena from quantum physics with sound taking on the role of light. ...

Recommended for you

CMS gets first result using largest-ever LHC data sample

February 15, 2019

Just under three months after the final proton–proton collisions from the Large Hadron Collider (LHC)'s second run (Run 2), the CMS collaboration has submitted its first paper based on the full LHC dataset collected in ...

Gravitational waves will settle cosmic conundrum

February 14, 2019

Measurements of gravitational waves from approximately 50 binary neutron stars over the next decade will definitively resolve an intense debate about how quickly our universe is expanding, according to findings from an international ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.