Scientists Develop New Technology to Secure Information by Introducing Chaos

Research aimed at controlling the complex dynamics of optical nonlinearities, such as chaos, with optomechanical crystals, and by altering the excitation laser’s parameters, has been reported by scientists from Institut Català de Nanociència i Nanotecnologia’s (ICN2) Phononic and Photonic Nanostructures (P2N) Group, from the UAB. The finding enables information codification by introducing chaos into the light that carries information.

In the case of modern communications based on optical fiber, light is indispensable. In order to confine photons and mechanical motion to a regular physical volume, optomechanical crystals are developed at nanoscale. Structures like these are being investigated under complex experimental frameworks and may have a positive effect in futuristic telecommunications.

Optical forces initiate the interaction of the mechanical motion and the photons, resulting in a strongly modulated beam of continuous-wave light, after interaction with an optomechanical crystal. In the field of optomechanics, optical nonlinearities are considered to be deleterious, and attempts are underway to reduce their impact.

The research team from ICN2 proposes to apply these nonlinearities to transfer codified information. Strategies like PHENOMEN — which is a European project headed by ICN2 — form the basis for an innovative information technology by integrating radio-frequency (RF) signal processing, photonics, and phononics.

Under the leadership of ICREA Research Professor Dr Clivia Sotomayor-Torres from the ICN2, scientists from the Phononic and Photonic Nanostructures (P2N) Group published an article in the journal Nature Communications. It describes the complex nonlinear dynamics noticed in a silicon optomechanical crystal. The article also explains the way a continuous-wave, low-power laser source gets transformed after traveling via structures that combine mechanical and optical properties of matter and light. The first author of the article is Dr Daniel Navarro-Urrios. The other authors are from Department of Physics, Universidad de La Laguna (Spain) and Nanophotonics Technology Center - Universitat Politècnica de Valencia (Spain).

The article describes the nonlinear dynamics in an optomechanical cavity system. Factors like free-carrier dispersion, thermo-optic effects, and optomechanical coupling have an impact on the stable intensity of a laser beam. The number of photons in the cavity impact and are impacted by such factors, leading to a chaotic outcome. This was modulated by the research team, who smoothly altered the excitation laser’s parameters. The researchers demonstrated precise control for triggering a heterogeneous range of stable dynamical solutions.

The outcome of this research forms the basis of an inexpensive technology, attaining higher security levels in optical communications by means of chaos-based optomechanical cryptographic systems. An optomechanical crystal can be used to introduce dynamical changes in the light beam passing through an optical fiber.

By having in-depth knowledge of the parameters of the optomechanical crystal and the excitation laser that introduce the dynamical changes, original light conditions can be reestablished. When two integrated chips comprising equivalent optomechanical cavities are linked with optical fibers, information can be secured by introducing chaos into the light beam at the emitting end, and curbing it at the reception end.

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