Russian physicists have invented an optical version of a transistor, based on a silicon nanoparticle. The research could lead to optical computers in the future.

Current computers are limited by the time needed to trigger a transistor — usually around 0.1 to 1 nanosecond (10⁻⁹ of a second). An optical transistor could work up to 1000 times faster — at picoseconds (10⁻¹² of a second), the researchers explain.

In the study, a group of Russian scientists from ITMO University, Lebedev Physical Institute and Academic University in Saint Petersburg created a new approach to designing optical transistors, based on a prototype using only one silicon nanoparticle.

They achieved this by irradiating the silicon nanoparticle with an intense, ultrashort laser pulse*, which caused the nanoparticle to switch the direction in which incident light was scattered. The next step is to introduce introduce a signal beam.

The study was published in the scientific journal Nano Letters.

* The laser acts as a control beam, providing ultrafast photoexcitation of dense and rapidly recombining electron-hole plasma whose presence changes the dielectric permittivity of silicon for a few picoseconds. This abrupt change in the optical properties of the nanoparticle allowed for controlling the direction in which incident light was scattered.

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Abstract of Tuning of Magnetic Optical Response in a Dielectric Nanoparticle by Ultrafast Photoexcitation of Dense Electron–Hole Plasma

We propose a novel approach for efficient tuning of optical properties of a high refractive index subwavelength nanoparticle with a magnetic Mie-type resonance by means of femtosecond laser irradiation. This concept is based on ultrafast photoinjection of dense (>10²⁰ cm^–3) electron–hole plasma within such nanoparticle, drastically changing its transient dielectric permittivity. This allows manipulation by both electric and magnetic nanoparticle responses, resulting in dramatic changes of its scattering diagram and scattering cross section. We experimentally demonstrate 20% tuning of reflectance of a single silicon nanoparticle by femtosecond laser pulses with wavelength in the vicinity of the magnetic dipole resonance. Such a single-particle nanodevice enables designing of fast and ultracompact optical switchers and modulators.