Research scientists and electrical engineers are always trying out new ways to make electrical devices smaller and more compact, be it complex computing systems, LiDAR, consumer electronics, or sensors. To achieve this, it is necessary to make the likes of transistors, lasers, and other components smaller first. Sometimes, newly devised methods work, sometimes, they don’t.
Now, a team of Russian research scientists based at ITMO University have proposed a quick and affordable method for creating optical chips right from within a standard Petri dish.
Devices Based On Optical Chips Growing More Common
Today, electronic devices that are based on optical chips and microscopic lasers are becoming more common. They are used in the production of many common applications and systems such as LiDARs, biosensors, consumer devices and, one day, scientists believe that they will form the basis for so-called optical computers that will use photons to transfer and process information.
Current optical chips operate in the infrared range. However, to make the devices even more compact, we need lasers in the visible range says Sergey Makarov, a chief researcher at ITMO. This is because the size of a chip depends on the wavelength of its emission.
ITMO researchers involved with the study, (from left to right: Pavel Trofimov, Anatoly Pushkarev, Ivan Sinev and Sergey Makaorov). Image Credit: ITMP University.
An optical chip consists of a laser component in conjunction with waveguides, and this is where problems can arise. While creating a source that can emit in the green or red part of the color spectrum is relatively easy, waveguides for these wavelengths can be an issue.
"A microlaser is a source of emission that you need to guide somewhere," comments Ivan Sinev, senior researcher at ITMO's Department of Physics and Engineering, "and this is what waveguides are for. But the standard silicon waveguides that are used in IR optics do not work in the visible range. They transmit the signal no further than several micrometers.”
For an optical chip, tens of micrometers need to be transmitted across with a high localization, so that the wavelength would have a small diameter that the light can pass through with a sufficient distance.
Gallium Phosphide Waveguides
Scientists tried a few ways to replace silicon waveguides, including the use of silver, but the transmission distance in these systems was also insufficient. In the end, they used gallium phosphide as a material for the waveguides because i) it has low losses in the visible band, and ii) the light source can be grown directly on a waveguide in a Petri dish via solution chemistry methods.
This is much cheaper than the comonly used method of nanolithography. What’s more, the size of the new chip’s elements is around three times smaller than its counterparts that work in the infrared spectral range.
"The chip's important property is its ability to tune the emission color from green to red by using a very simple procedure: an anionic exchange between perovskite and hydrogen halides vapor," says Anatoly Pushkarev, senior researcher at ITMO's Department of Physics and Engineering.
The emission color can also be changed and reversed post-production, meaning that it could be used in devices and applications that need to transmit several optical signals at different wavelengths.
Furthermore, because the chip includes an optical perovskite nanoantenna that receives the signal traveling along the waveguide, two chips can be used in a single system.