Nei laboratori dell'Università della Pennsylvania nasce il primo circuito in cui all'elettricità è stata sostituita la luce. Nader Engheta, docente di elettronica alla Penn's School of Engineering and Applied Science, ci prova dal 2005, quando con alcuni studenti pubblicò un articolo che conteneva la tracce concettuali di questa interessante innovazione, denominata Metactronics.
Experimental realization of optical lumped nanocircuits at infrared wavelengths Nature Materials 11, 208–212 (2012) Published online 29 January 2012
Yong Sun, Brian Edwards, Andrea Alù and Nader Engheta
The integration of radiofrequency electronic methodologies on micro- as well as nanoscale platforms is crucial for information processing and data-storage technologie. In electronics, radiofrequency signals are controlled and manipulated by ‘lumped’ circuit elements, such as resistors, inductors and capacitors. In earlier work, we theoretically proposed that optical nanostructures, when properly designed and judiciously arranged, could behave as nanoscale lumped circuit elements—but at optical frequencies. Here, for the first time we experimentally demonstrate a two-dimensional optical nanocircuit at mid-infrared wavelengths. With the guidance of circuit theory, we design and fabricate arrays of Si3N4 nanorods with specific deep subwavelength cross-sections, quantitatively evaluate their equivalent impedance as lumped circuit elements in the mid-infrared regime, and by Fourier transform infrared spectroscopy show that these nanostructures can indeed function as two-dimensional optical lumped circuit elements. We further show that the connections among nanocircuit elements, in particular whether they are in series or in parallel combination, can be controlled by the polarization of impinging optical signals, realizing the notion of ‘stereo-circuitry’ in metatronics—metamaterials-inspired optical circuitry.
[Figure: Overall sketch of the cross-section of a typical nanorod array, suspended over a (600 μm×600 μm) window etched in a silicon substrate by KOH]