The solution, created by scientists from the Lodz University of Technology, the Łukasiewicz Institute of Microelectronics and Photonics, the Wrocław University of Science and Technology and the Warsaw University of Technology, achieves up to 94% transmission of infrared radiation while maintaining strong electrical conduction, according to findings published in Light: Science & Applications (doi:10.1038/s41377-026-02270-0).

In many optoelectronic systems, electrodes must simultaneously conduct electricity and allow light to pass through to active components. While this balance is relatively well established in visible-light technologies such as displays and solar cells, it becomes significantly more difficult in the infrared range, where conductive materials tend to strongly absorb or reflect radiation.

“Infrared has a longer wavelength than red light. We cannot see it with the naked eye, but thermal imaging cameras can convert it into an image, and sensors use it to detect heat, the presence of gases, or measure distance,” the article explains.

The researchers say this creates a fundamental trade-off: improving conductivity usually reduces infrared transparency, and vice versa.

To overcome this limitation, the team designed a structured material rather than a conventional thin film. The electrode is based on gallium arsenide and incorporates a precisely arranged microstructure of gold strips embedded within a semiconductor lattice. The design separates functions: metal elements carry electrical current, while the surrounding structure is engineered to transmit infrared radiation with minimal loss.

“This can be compared to an arrangement of two paths on the same surface: current flows through metal paths, and radiation ‘leaks’ through the structure, losing as little energy as possible along the way,” the researchers describe.

The resulting architecture, called metalMHCG (metal-integrated monolithic high-contrast grating), operates at a scale smaller than the infrared wavelength, preventing it from behaving like a conventional diffraction grating. Instead, it acts as a tailored optical surface that controls both electrical and optical behavior.

Researchers report that the structure also reduces reflection at the semiconductor interface, further improving overall transmission. In experiments, the electrode achieved 94% infrared transmission at a wavelength of around 7 micrometres while maintaining a surface resistance of about 2.8 ohms per square, indicating strong conductivity.

The study highlights that this approach breaks the typical trade-off seen in infrared electrode design, where higher conductivity usually comes at the cost of lower transparency. In this case, both properties are improved simultaneously by distributing optical and electrical functions across different elements of the same structure.

The prototype electrodes covered areas larger than 1 cm², which researchers note is a meaningful step toward practical device integration in micro- and nanoelectronics.

Potential applications include infrared detectors, lasers, diodes, thermal imaging systems, gas sensors, optical communication technologies, medical instruments and industrial monitoring devices. Improved infrared transmission could translate into higher sensitivity, lower energy consumption and stronger signal output.

Further work will focus on scaling the technology to full semiconductor wafers and integrating it into functional devices, moving it from laboratory demonstration toward real-world optoelectronic systems. (PAP)

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