By integrating silver nanocubes on graphene sheets, researchers from the Institute of Photonic Sciences and other international centers successfully constructed the smallest infrared optical cavity. In the fields of biomedicine and biotechnology, this advancement may help to better detect molecular materials that normally respond to this light.
In recent decades, miniaturization They make the unimaginable happen. For example, the transistor has changed from the size of a palm to 14 nanometers in 60 years, which is about 1,000 times smaller than the diameter of a human hair. Smaller and smaller electronic circuits make today’s smart phones, health watches, medical probes and even nanosatellites possible.
Miniaturization opens the door to a new era of optical circuits, but it also brings new challenges and obstacles to overcome.One of them is how to deal with control and Nano-level guided light. New technology seeks to confine light to a very small space, which is a million times smaller than the space achieved so far.
In this case, graphene is a material composed of a single layer of carbon atoms. It has excellent optical and electrical properties and can guide light in the form of plasmons. Electrons are oscillations that strongly interact with light.
This Graphene plasmon They have the natural ability to confine light to a small space. So far, these plasmons can only be restricted to one direction, but the real ability of light to interact with small particles (such as atoms and molecules) lies in the ability to compress or limit the volume of photons. In all three dimensions, this type of confinement is considered an optical cavity.
Now my researchersInstitute of Photonics Science (ICFO)In Barcelona, in collaboration with researchers from the Massachusetts Institute of Technology and Duke University, the University of Saclay in Paris, France, and the University of Dudonijo (Portugal) in France, they successfully established a new type of graphene plasmon cavity. Metal nanocubes are deposited on it. Graphene sheets.
This technology makes it possible to obtain the smallest optical cavity for infrared light in history based on graphene plasmons.
50 nanometer silver block
In their experiments, the scientists used silver cubes with a size of 50 nanometers, which were randomly deposited on graphene plates without a specific pattern or orientation. This allows each nanocube and graphene to act as a single cavity.
Then, the researchers passed infrared light through the device and observed that the plasmon propagated in the space between the metal nanocube and the graphene, only compressed to a very small volume.
When you comment Itai Epstein ICFO, the first author of the study, said: “The main obstacle we encountered is that the wavelength of light in the infrared range is very large, and the cube is very small, about 200 times smaller, so it is difficult to get them to interact with each other.”
In order to overcome this shortcoming, a special phenomenon is used: Magnetic resonance Produced when graphene plasmons interact with nanocubes.
Epstein said: “The unique feature of this kind of MRI is that it can act as an antenna that connects the small size of the nanocube and the large wavelength of light.”
Therefore, the generated resonance allows the plasmon to move between the cube and the graphene keeping a very small volume, which is 10 billion times smaller than the volume of conventional infrared light, which is impossible to achieve in the optical limit.
Light scattering nano antenna
In addition, the research team also discovered that the nanocube-graphene cavity acts as a new type of nanoantenna when interacting with light, which can scatter infrared light very effectively.
According to the authors, the results of this study are very promising for the field of molecular and biological detection, and are very important for medicine, biotechnology, food inspection and even safety, because the technology can significantly enhance the light field to detect molecules. A material that usually responds to infrared light.
As the professor said Frank Cobens This achievement led by the ICFO team is significant because it allows us to adjust the volume of the plasma mode to enhance its interaction with small particles (such as molecules or atoms), and to be able to detect and study them. We know that the infrared and terahertz ranges of the spectrum provide valuable information about molecular vibrational resonance, which opens up possibilities for interaction and detection of molecular materials and their use as promising detection techniques. “
Itai Epstein, David Alcaraz, Huang Zhiqin, Varun-Varma Pusapati, Jean Paul Yugonin, A Avinash Kumar, Xander M. Smith, Frank HL Koppens. “Far-field excitation of a single graphene plasma cavity with an ultra-compressed mode volume“. science 2020.