Making Infrared Light Visible: New Equipment Utilizes 2D Materials to Convert Infrared Light

Infrared imaging and sensing technology can be used in various fields, from astronomy to chemistry. For example, when infrared light passes through a gas, sensing changes in light can help scientists identify specific properties of the gas. The use of visible light may not always achieve this sensing.

However, existing infrared sensors are bulky and inefficient. In addition, due to the use of infrared sensors in the field of national defense, they are also subject to export restrictions. Therefore, there is an urgent need to develop localized and efficient equipment.

The method adopted by the IISc team is to feed the input infrared signal and pump beam together into the mirror stack. The nonlinear optical properties of the materials that make up the mirror stack can cause frequency mixing, resulting in an output beam with increased frequency (up conversion), while other characteristics remain unchanged. Using this method, they were able to convert infrared light with a wavelength of approximately 1550 nanometers upwards into visible light with a wavelength of 622 nanometers. The output light waves can be detected using traditional silicon-based cameras.

"This process is coherent - the characteristics of the input beam are preserved at the output end. This means that if a specific pattern is printed on the input infrared frequency, it will automatically transfer to the new output frequency," explained Varun Raghunathan, Associate Professor of Electronic Communication Engineering (ECE) and corresponding author of this research report published in Laser&Photonics Reviews.

The main author Jyothsna KM is calibrating the beam for the upconversion experiment
He added that the advantage of using gallium selenide lies in its high optical nonlinearity, which means that a single photon of infrared light and a single photon of the pump beam can combine to form a single photon with an upconversion frequency.

The research team can even use a thin layer of gallium selenide with a size of only 45 nanometers to achieve up conversion. Compared to traditional devices that use centimeter sized crystals, this small-sized device is more cost-effective. The study also found that its performance can be comparable to the most advanced upconversion imaging systems currently available.

The first author and doctoral student at the European School of Electronic Engineering, Jyothsna K Manattayil, explained that they used particle swarm optimization algorithms to accelerate the calculation of the required correct layer thickness. The wavelength that can be converted upwards through gallium selenide varies depending on the thickness. This means that the material thickness needs to be adjusted according to the application situation.

She said, "In our experiment, we used 1550 nanometers of infrared light and 1040 nanometers of pump beam. However, this does not mean that it cannot be used for other wavelengths. We see that performance does not decrease at various infrared wavelengths ranging from 1400 nanometers to 1700 nanometers."

Looking ahead, researchers plan to expand their work to upconvert longer wavelengths of light. They also attempted to improve the efficiency of the equipment by exploring other stacking geometries.

Raghunathan said, "The world is very interested in conducting infrared imaging without using infrared sensors, and our work may change the game rules of these applications.".

Related links: https://phys.org/news/2024-06-infrared-visible-device-2d-material.html
Paper link: https://dx.doi.org/10.1002/lpor.202400374

Source: Guangxing Tianxia