IISc develops device to convert infrared light to visible, which will have diverse applications in defence and optical communications

IISc develops device to convert infrared light to visible, which will have diverse applications in defence and optical communications


The Indian Institute of Science team has designed a non-linear optical mirror stack using 2D materials, which combines the ability to amplify or convert the frequency of short-wave infrared light into the visible range along with widefield imaging capability.

The Indian Institute of Science team has used 2D materials to create a device they call a non-linear optical mirror stack that amplifies or converts the frequency of short infrared light into the visible range, combined with widefield imaging capability. | Photo credit: File photo

Researchers at the Indian Institute of Science (IISc) have created a device that amplifies or converts the frequency of short infrared light into the visible range. This up-conversion of light has diverse applications, especially in defence and optical communications, IISc said.

“The human eye can see light only at certain frequencies (called the visible spectrum), the lowest frequency of which is red light. Infrared light, which we cannot see, has a frequency even lower than red light. IISc researchers have now created a device that can amplify or convert the frequency of short infrared light into the visible range,” IISc said.

2D materials used

For the first time, the IISc team designed a nonlinear optical mirror stack using a 2D material to achieve this up-conversion, combined with widefield imaging capability, the institute said. The stack consists of multi-layered gallium selenide mounted on top of a gold reflective surface, with a silicon dioxide layer in between.

It said conventional infrared imaging uses exotic low-energy bandgap semiconductors or micro-bolometer arrays, which typically capture heat or absorption signals from the object being studied.

However, the existing infrared sensors are bulky and not very efficient. Their export is also restricted due to their utility in the defence sector. Hence, there is a great need to develop indigenous and efficient equipment.

The method used by the IISc team involves feeding an input infrared signal along with the pump beam onto the mirror stack. The non-linear optical properties of the materials forming the stack result in mixing of frequencies, producing an output beam of increased (up-converted) frequency, but the rest of the properties remain intact. Using this method, they were able to convert infrared light of a wavelength of about 1,550 nm into 622 nm visible light. The output light wave can be detected using conventional silicon-based cameras.

Going forward, the researchers plan to extend their work to up-convert light of longer wavelengths. They are also trying to improve the efficiency of the device by exploring other stack geometries.

Worldwide interest

“There is a lot of interest around the world in doing infrared imaging without using infrared sensors. Our work could be a game-changer for those applications,” said Varun Raghunathan, associate professor in the Department of Electrical Communication Engineering.



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