Shrink down gold spirals that are as big as a dim by around six million times and you will get nano spirals or the world’s tiniest continuous spirals. These spirals boast unique optical characteristics, counterfeiting that will be almost impossible if they are embedded in objects such as currency, identity cards, etc.
These tiny spirals were fabricated by faculty and students representing the Vanderbilt University. Next, the optical properties of those spirals were illustrated using ultrafast lasers at the Pacific Northwest National Laboratory in Richland and the Vanderbilt University. The results of the study were published online in the May 21 edition of Journal of Nanophotonics.
Roderick Davidson II, a doctoral student at the Vanderbilt University and one of the key members of the research group, said that the nano-spirals are definitely much smaller than any other spiral variety talked about in scientific literature to date.
Here, it must be mentioned that Davidson II was the one who figured out the right method of studying the optical behavior of these nano-spirals. The credit of designing and making the spirals, on the other hand, goes to Jed Zeigler, another doctoral student of the University; Zeigler is currently working at the Naval Research Laboratory.
The majority of the other researchers who studied the unique characteristics of the nano-spirals did so by putting together discrete nano-particles in the spiral pattern. The spirals formed by those researchers resembled the ones drawn on paper using a series of ink dots.
The spirals formed by the research team representing the Vanderbilt University were different due to their solid arms and smaller structures. This description should help you in comprehending how small these nano-spirals are: the width of a square containing hundred nano-spirals on one of its side is less than one-hundredth of a millimeter.
These spirals develop some unique optical properties the moment they are shrunk to form structures smaller than the wavelength of a visible beam of light. For instance, illumination of these nano-spirals by infrared laser light results in the emission of visible blue light.
When the infrared laser beam hits the small spirals, it gets absorbed by electrons present in the spirals’ gold arms. Arms of the nano-spirals are extremely thin; as a result, the electrons automatically move along them. Electrons that reach the spirals’ center absorb the significant amount of energy, which results in the emission of blue light. This blue light’s frequency is two times that of the incoming infrared laser beam.
According to experts, these nano-spirals can be used for protecting us against identity theft. They are saying that if these spirals get embedded in identity cards, credit cards etc., they can be detected by means of a device similar to a barcode reader.