Australian researchers develop ultrafast nanoscale photonics switch

Australian researchers, in association with Russian scientists, have created an ultrafast all-optical switch on silicon nanostructures. This device may become a platform for future computers and permit the transfer of data at an ultrahigh speed.

The work, by researchers from the Australian National University and the Lomonosov Moscow State University, belongs to the field of photonics — an optics discipline that appeared in the 1960s, simultaneously with the invention of lasers.

Photonics has the same goals as electronics does, but it uses photons — the quanta of light — instead of electrons. The biggest advantage of using photons is the absence of interactions between them. As a consequence, photons address the data transmission problem better than electrons. This property can primarily be used in computing where IPS (instructions per second) is the main attribute to be maximised.

The typical scale of electronic transistors — the basis of contemporary electronic devices — is less than 100 nanometres, where the typical scale of photonic transistors stays on the scale of several micrometres. Nanostructures that are able to compete with the electronic structures — for example, plasmonic nanoparticles — are characterised by low efficiency and significant losses. Therefore, coming up with a compact photonic switch was a very challenging task.

Three years ago several groups of researchers simultaneously discovered an important effect: they found out that silicon nanoparticles exhibit strong resonances in the visible spectrum — the so-called magnetic dipole resonances. This type of resonance is characterised by strong localisation of light waves on subwavelength scales, inside the nanoparticles. This effect turned out to be interesting to researchers but, according to Maxim Shcherbakov, the first author of the article published in Nano Letters, nobody thought that this discovery could create a basis for development of a compact and very rapid photonic switch.

Nanoparticles were fabricated in the Australian National University by e-beam lithography followed by plasma-phase etching. It was done by Alexander Shorokhov, who served an internship in the university as a part of a presidential scholarship for studying abroad. The samples were brought to Moscow, and all the experimental work was carried out at the Faculty of Physics of Lomonosov Moscow State University, in the Laboratory of Nanophotonics and Metamaterials.

“In our experimental research, me and my colleague Polina Vabishchevich from the faculty used a set of nonlinear optics methods that address femtosecond light-matter,” said Maxim Shcherbakov. “We used our femtosecond laser complex acquired as part of the MSU development program.”

Eventually, researchers developed a ‘device’: a disc 250 nm in diameter that is capable of switching optical pulses at femtosecond rates (femtosecond is a one millionth of one billionth of a second). Switching speeds that fast will facilitate creation of data transmission and processing devices that will work at tens and hundreds terabits per second. 

The operation of the all-optical switch created by MSU researchers is based on the interaction between two femtosecond pulses. The interaction becomes possible due to the magnetic resonance of the silicon nanostructures. If the pulses arrive at the nanostructure simultaneously, one of them interacts with the other and dampers it due to the effect of two-photon absorption. If there is a 100 fs delay between the two pulses, the interaction does not occur, and the second pulse goes through the nanostructure without changing.

Our work represents an important step towards novel and efficient active photonic devices — transistors, logic units and others, said said Maxim Shcherbakov. Features of the technology implemented in our work will allow its use in silicon photonics. In the nearest future, we are going to test such nanoparticles in integrated circuits, said Shcherbakov.