Reviewed by Lexie CornerOct 16 2024
Researchers have demonstrated a compact and efficient alternative to conventional infrared cameras using silicon metasurfaces, which convert infrared light into visible light through frequency mixing. This breakthrough could lead to more affordable broadband infrared cameras, overcoming existing challenges and opening up new possibilities for practical applications. The study was published in Light: Science & Applications.
The broadband nonlinear imaging achieved by Si metasurface through FWM processes. a, The schematic diagram of the broadband nonlinear imaging process: an infrared image with a broadband wavelength coverage, referred to as the signal beam, mixes with an additional infrared light known as the pump beam. When both beams pass through the designed metasurface, this induced arrangement facilitates the generation of a visible output based on four-wave mixing (FWM) processes. b, Left: The schematic diagram of Si bi-layer metasurface. Right: Scanning electron microscopy images of the metasurface from the top. c, The measured FWM emission spectra from Si metasurface while tuning the signal wavelength when fixing the pump wavelength at 1130 nm. The tuning ranges of the signal wavelength are from 2300 to 4700 nm. Image Credit: Ze Zheng, Daria Smirnova, Gabriel Sanderson, Cuifeng Ying, Demosthenes C. Koutsogeorgis, Lujun Huang, Zixi Liu, Rupert Oulton, Arman Yousefi, Andrey E. Miroshnichenko, Dragomir N. Neshev, Mary O'Neill, Mohsen Rahmani, and Lei Xu
Infrared imaging is a key technology in various fields, from examining biological specimens and intricate materials to detecting hidden patterns in physical systems. It is particularly useful for sensitive operations, such as firefighting and search and rescue, as infrared light can penetrate smoke and fog. Moreover, infrared imaging can detect heat emissions, making it valuable for security and night vision applications.
Despite these benefits, modern infrared cameras have significant limitations. Their large size and high power consumption often require cooling systems, restricting their practicality. More critically, current cameras rely on semiconductor-based technology that only captures a narrow portion of the infrared spectrum, limiting each camera to specific applications and requiring multiple devices for different uses.
Due to the complications of today's bulky, power-hungry, and expensive infrared imaging technology, we are unlikely to have an infrared camera at home. However, nonlinear frequency conversion, a process that manipulates and translates electromagnetic signals across various frequency regimes, holds a massive potential to revolutionize infrared detection technology.
Mohsen Ramhami, Professor and Leader, UK Research and Innovation Future Leaders Fellow, Nottingham Trent University
“We have demonstrated that arrays of engineered silicon nanoparticles called metasurfaces can convert infrared light into visible light through a frequency mixing process. Such metasurfaces that are integrable to regular cameras offer a promising solution for advanced infrared imaging,” said Ramhami.
The silicon industry is well-established, known for producing small electronic chips and circuits with excellent uniformity and compatibility with complementary metal-oxide-semiconductor (CMOS) packaging methods. While silicon photonics has traditionally focused on telecommunications equipment, fiber optics, and waveguides, the use of silicon nanoparticles and metasurfaces represents a relatively new area of interest.
This emerging field, particularly in the nonlinear domain, facilitates efficient light coupling between integrated circuitry and free-space environments, expanding the potential applications of silicon technology beyond its conventional uses.
Our demonstration benefits from an innovative and meticulous arrangement of silicon metasurface featuring a bi-layer device with silicon nanoparticles on top and silicon thin film underneath. By employing the light-matter interaction with both layers and interference of the resonances generated in both layers, we managed to induce multiple hybrid resonances, which significantly enhance Four-Wave Mixing (FWM) across a broad wavelength range.
Ze Zheng, PhD Candidate and Leading Author, Nottingham Trent University
Zheng said, “This enhancement allows the detection of weak infrared signals, thanks to the quadratic power dependence of the nonlinear emission on the pump beam.”
By measuring the time delays of the mixed infrared photons as they pass through a sample, the team demonstrated that their FWM-based imaging platform can detect sample thicknesses, offering a proof of concept.
Additionally, this method is polarization-selective, which adds extra functionality, such as identifying polarization-sensitive materials and enhancing surface detection sensitivity and resolution.
Our infrared imaging across 1000-4700 nm with one device demonstrates new possibilities for developing broadband and compact devices for infrared imaging. This opens up a new research and development direction to address the current limitations of infrared cameras, such as high cost, complexity, and narrow bandwidth. This is the first step to make the next generation of infrared cameras more accessible and efficient.
Lei Xu, Study Co-Leader and Associate Professor, Nottingham Trent University
Journal Reference:
Zheng, Z., et al. (2024) Broadband infrared imaging governed by guided-mode resonance in dielectric metasurfaces. Light Science & Applications. doi.org/10.1038/s41377-024-01535-w.