Hybrid Nanoantennas for Ultradense Data Recording

Selective laser exposure to create hybrid nanostructures (Source: ITMO)

Selective laser exposure to create hybrid nanostructures (Source: ITMO)

A group of scientists from ITMO Univer­sity in Saint Peters­burg has put forward a new approach to effective manipulation of light at the nanoscale based on hybrid metal-dielectric nano­antennas. The new technology promises to bring about a new platform for ultradense optical data recording and pave the way to high throughput fabrication of a wide range of optical nano­devices capable of localizing, enhancing and mani­pulating light at the nanoscale.

Nanoantenna is a device that converts freely propa­gating light into localized light compressed into several tens of nanometers. The loca­lization enables scientists to effectively control light at the nanoscale. This is one of the reasons why nano­antennas may become the funda­mental building blocks of future optical computers that rely on photons instead of electrons to process and transmit information. This inevitable replacement of the infor­mation carrier is related to the fact that photons surpass electrons by several orders of magnitude in terms of information capacity, require less energy, rule out circuit heating and ensure high velocity data exchange.

Until recently, the production of planar arrays of hybrid nano­antennas for light mani­pulation was considered an extremely painstaking process. A solution to this problem was found by researchers from ITMO University in colla­boration with colleagues from Saint Petersburg Academic University and Joint Institute for High Tempera­tures in Moscow. The research group has for the first time developed a technique for creating such arrays of hybrid nano­antennas and for high-accuracy adjustment of individual nano­antennas within the array. The achievement was made possible by subsequently combining two production stages: lithography and precise exposure of the nano­antenna to a femto­second laser – ultrashort impulse laser.

The practical application of hybrid nano­antennas lies, in particular, within the field of ultradense data recording. Modern optical drives can record information with density around 10 Gbit/inch2, which equals to the size of a single pixel of a few hundred nanometers. Although such dimensions are comparable to the size of the nano­antennas, the scientists propose to additionally control their color in the visible spectrum. This procedure leads to the addition of yet another dimension for data recording, which immediately increases the entire data storage capacity of the system.

Apart from ultradense data recording, the selective modification of hybrid nano­antennas can help create new designs of hybrid meta­surfaces, waveguides and compact sensors for environ­mental monitoring. In the nearest future, the research group plans to focus on the development of such specific applications of their hybrid nanoantennas. The nanoantennas are made of two components: a truncated silicon cone with a thin golden disk located on top. The researchers demonstrated that, thanks to nanoscale laser reshaping, it is possible to precisely modify the shape of the golden particle without affecting the silicon cone. The change in the shape of the golden particle results in changing optical properties of the nano­antenna as a whole due to different degrees of resonance overlap between the silicon and golden nano­particles.

“Our method opens a possi­bility to gradually switch the optical properties of nanoantennas by means of selective laser melting of the golden particles. Depending on the intensity of the laser beam the golden particle will either remain disc-shaped, convert into a cup or become a globe. Such precise manipulation allows us to obtain a functional hybrid nanostructure with desired properties in the flicker of a second,” comments Sergey Makarov, researcher at the Department of Nano­photonics and Meta­materials of ITMO University.

Contrary to conven­tional heat-induced fabrication of nano­antennas, the new method raises the possibility of adjusting individual nanoantennas within the array and exerting precise control over overall optical properties of the hybrid nano­structures. “Our concept of asymmetric hybrid nano­antennas unifies two approaches that were previously thought to be mutually exclusive: plasmonics and all-dielectric nano­photonics. Our hybrid nano­structures inherited the advantages of both approaches – locali­zation and enhancement of light at the nanoscale, low optical losses and the ability to control the scattering power pattern. In turn, the use of laser reshaping helps us precisely and quickly change the optical properties of such structures and perhaps even record infor­mation with extremely high density,” concludes Dmitry Zuev, lead author of the study. (Source: ITMO)

Reference: D. A. Zuevet al.: Fabrication of Hybrid Nanostructures via Nanoscale Laser-Induced Reshaping for Advanced Light Manipulation, Adv. Mat. 28, 3087 (2016); DOI: 10.1002/adma.201505346

Link: Department of Nanophotonics and Metamaterials, ITMO University, Saint Petersburg, Russia

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