Russian physicists from ITMO University, together with colleagues from Switzerland and China, have created an ultrathin silicon film capable of changing the properties of light pulses at a frequency of up to a billion times per second. TASS was informed about this by the university's press service.
The developed structure is a metasurface applied to an ultrathin silicon membrane, one micron thick, which hangs freely in the air without a solid substrate. A laser pulse changes the properties of silicon almost instantly, so the switching time was a matter of nanoseconds, and the modulation frequency reached about a gigahertz – comparable to the clock speed of modern processors, only signal processing occurs directly with light.
Optical properties can be controlled by heating with electric current or short laser pulses, which generates free electrons in silicon, reducing transparency. Unlike conventional metasurfaces, whose properties are fixed during production, the new development for the first time allows modulating the signal by external influence in the mid-infrared range. This opens the way for compact spectrometers for chemical composition determination, sensitive elements for thermal imagers, secure optical communication systems, and computing devices with minimal power consumption.