TPU Researchers Design Eco-Friendly Optical Switch For Green Photonics

Researchers from the School of Non-Destructive Testing of Tomsk Polytechnic University have first presented and showcased the concept of a green optical switch. It is based on the property of a freezing water droplet to act as a biocompatible natural microlens capable of forming photonic hooks. The switch functions due to a temperature-induced change in the refractive index inside the water droplet. It is environmentally friendly, simple and low-cost to manufacture, and it can potentially find applications in green sensors, integrated optics and optical computers.

The research findings are published in Nanomaterials (Q1; IF:5,719).

Freezing water droplet is a promising natural object studied by mesotronics (mesoscale photonics). In particular, the droplets can serve as a novel ground for many optical devices due to the fact that the solid and liquid states of water droplets make it possible to create and make use of various optical effects.

Researchers from Tomsk Polytechnic University have designed an optical switch based on a curved light beam of a specific shape, also known as the photonic hook effect. For this purpose, they used a cooled water droplet, placed on a cold superhydrophobic (water-repelling) surface to retain its spherical shape to the maximum. The freezing drop can be used as an optical switch due to its temperature sensitivity and relatively fast switching dynamics.

An optical switch based on the photonic hook effect is a forward-scattering device. That means that the position and shape of the field localization is sensitive to the spatial position and the distance between the droplet and the detectors. Thus, the photonic hooks in this kind of a switch function as switching channels, making it possible to create a two-channel switch based on a freezing water droplet. Whilst microscopic water droplets of about 5-10 microns in size are abundant in fog and clouds.

In addition, the device is temperature sensitive. The unique property of the photonic hook to change its curvature depending on the temperature makes the switch applicable for miniaturized "on-a-chip" devices, in green optoelectronics and mesotronics. In this case, no additional micromechanical devices, electrical signal or multi-wavelength light control are required.