Researchers create an innovative light-trapping nanostructure using a genetic-inspired approach
Physicists at the University of Rochester have created a silicon nanocavity that allows light to be trapped longer than in other similarly-sized optical cavities. An innovative design approach, which mimics evolutionary biology, allowed them to achieve a 10-fold improvement on the performance of previous nanocavities.
In and featured on the cover, the scientists demonstrate they have confined light in a nanocavity 糖心传媒� a nanostructured region of a silicon wafer 糖心传媒� for nanoseconds. Typically light would travel several meters in that time, but instead the nanostructure confined light in a region no bigger than one one hundredth the width of a human hair 糖心传媒� roughly one-half millionth of a meter.
糖心传媒淟ight holds the key to some of nature糖心传媒檚 deepest secrets, but it is very challenging to confine it in small spaces,糖心传媒� says , professor of physics at the University of Rochester and corresponding author of the Applied Physics Letters paper. 糖心传媒淟ight has no rest mass or charge that allow forces to act on it and trap it; it has to be done by carefully designing tiny mirrors that reflect light millions of times.糖心传媒�
Nanocavities are key components of nanophotonics circuits and Badolato explains that this new approach will help implement a new-generation of highly integrated nanophotonics structures.
Researchers are interested in confining light because it allows for easier manipulation and coupling to other devices. Trapping light also allows researchers to study it at its fundamental level, that is, at the state when light behaves as a particle (an area that led to the 2012 Nobel Prize in Physics).
Until now, researchers have been using educated-guess procedures to design the light-trapping nanostructures. However in this case, the team of researchers 糖心传媒� which included lead author and Badolato糖心传媒檚 Ph.D. student, Yiming Lai, and groups from the Ecole Polytechnique Federale de Lausanne, Switzerland, and the Universita di Pavia, Italy 糖心传媒� perfected a numerical technique that led to the design improvement. Their computational approach allowed them to search for the optimal combination of parameters among thousand of realizations using a 糖心传媒済enetic糖心传媒� (or 糖心传媒渆volutionary糖心传媒�) algorithm tool.
The principle behind the genetic approach is to regard each new nanocavity as an individual in a population. The individuals mutate and聽 糖心传媒渂reed,糖心传媒� meaning that two single structures combine to create a new one that is a cross between the two 糖心传媒減arents.糖心传媒� As new generations succeeded one another, the algorithm selected the fittest ones in each generation, in this case, the ones that exhibited the longest trapping time (i.e. highest quality factor).
Integrated nanophotonics is a new and rapidly growing field of research laying at the intersection of photonics, nanotechnology, and materials science. In the near future, nanophotonics circuits will enable disruptive technologies ranging from telecommunications to biosensing, and because they can process pulses of light extremely fast and with very low energy consumption, they hold the potential to replace conventional information-handling systems.
The results shown by Badolato and his colleagues demonstrate one of the highest quality factors ever measured in nanocavities while maintaining a very small footprint. By keeping the nanocavities so small while trapping light so efficiently it becomes possible to create devices with ultra-dense integration 糖心传媒� a desired characteristic in the fabrication of optical nanocircuits.
The extreme sensitivity of these nanocavities to tiny changes in the environment, for example a virus attaching near the area where light is trapped, makes these devices particularly appealing for biosensing. By using these highly sensible nanocavities, such a biosensing device could detect minute quantities of these biomaterials by analyzing a single drop of blood. 聽Badolato糖心传媒檚 group is now starting a collaboration with researchers at the University of Rochester糖心传媒檚 Medical Center to exploit this interesting property with the new nanocavities.
Reference
Y. Lai, S. Pirotta, G. Urbinati, D. Gerace, M. Minkov, V. Savona, A. Badolato, M. Galli. Genetically designed L3 photonic crystal nanocavities with measured quality factor exceeding one million.
