The demand for compact and high-performance optical devices in the short-wave infrared (SWIR) region continues to grow, driven by applications ranging from molecular spectroscopy to advanced sensing technologies. Yan He and Adetunmise Dada, from the University of Glasgow, and their colleagues present a new metalens design that addresses key limitations of conventional optics in this crucial spectral band. Their research overcomes the challenges of chromatic aberration and bulky components by utilising subwavelength nanostructures to precisely control light, achieving stable focusing performance across a broad range of wavelengths. This innovative metalens, fabricated on a calcium fluoride substrate, demonstrates effective suppression of chromatic aberration between 1800 and 2300 nanometres, maintaining a remarkably stable focal position and offering a pathway to compact, high-performance infrared optical systems.

Metasurfaces for Achromatic, Broadband Optics
Research into metasurfaces and metalenses is rapidly advancing, particularly in the mid-infrared to visible spectrum. A key focus is achieving specific optical properties, including achromaticity, polarization control, broadband operation, and maximizing light manipulation efficiency. These compact structures promise to revolutionize optical systems. Current research explores various design principles, materials, and fabrication techniques to create high-performance metasurfaces. Scientists are investigating materials like silicon and calcium fluoride, and employing methods such as electron beam lithography and nanopillar fabrication.

Researchers are also exploring how to integrate multiple metalenses to create more complex optical systems. This field is particularly active in the mid-infrared spectrum, driven by applications in sensing, thermal imaging, and spectroscopy. Work also extends to visible and near-infrared wavelengths for imaging and displays, and to the telecom band for optical communication. Advanced concepts include manipulating light dispersion and exploring the potential of metasurfaces for nonlinear optics.

Broadband Achromatic Metalens for SWIR Imaging
Scientists have developed a novel metalens design operating within the short-wave infrared (SWIR) band, specifically between 1800 and 2300 nanometres. Constructed from silicon nanopillars on a calcium fluoride substrate, the device achieves broadband achromaticity, meaning it effectively focuses light across a wide spectrum without the colour distortions common in traditional lenses. By carefully controlling the geometry of these nanostructures, scientists have demonstrated continuous control over the phase of light, enabling stable focusing performance throughout the SWIR range. Simulations reveal that the metalens maintains a stable focal position with variation of only six percent of the focal length across the entire bandwidth, representing a significant advancement in compact optical systems.

Researchers acknowledge a trade-off between transmission efficiency and polarization purity, indicating that maintaining both high transmission and precise polarization control remains a challenge for future optimization. This work establishes valuable design guidelines and a foundation for developing advanced photonic systems requiring spectral manipulation in the SWIR band. The authors highlight the need for experimental validation through fabrication and characterization of the proposed design, and suggest future work could focus on improving polarization control without compromising broadband performance.

Broadband Achromatic Focusing with a Metalens
A breakthrough in short-wavelength infrared (SWIR) optics has been achieved with a metalens capable of broadband achromatic focusing within the 1. 8-2. 3 micrometre range. This device maintains stable focusing performance across this entire bandwidth, with focal position variation limited to only 6% of the focal length. The metalens utilizes a calcium fluoride substrate with silicon nanostructures arranged in a periodic 900-nanometre grid, enabling precise control over both dispersion and phase.

Researchers carefully adjusted the length and width of these nanostructures to simultaneously compensate for dispersion and modulate phase, achieving stable focusing performance. Calculations demonstrate the metalens effectively suppresses chromatic aberration, a common issue in wide-spectrum optics, across the 1800-2300nm range. The design employs a unified phase compensation strategy based on geometric and Pancharatnam-Berry phase tuning, simplifying fabrication and enhancing scalability. This metalens represents the first demonstration of achromatic focusing across the entire 1. 8-2. 3 micrometre range, addressing a significant gap in existing SWIR optical devices. The team’s approach overcomes limitations of previous designs, paving the way for compact, high-performance SWIR systems with applications in sensing, quantum information transmission, and nonlinear optics.

TrendForce 2025 Infrared Sensing Application Market and Branding Strategies
Release: 01 January 2025
Format: PDF / EXCEL
Language: Traditional Chinese / English
Page: 196