Profiling terahertz beam electric fields with a metasurface
Profiling terahertz beam electric fields with a metasurface lead image
Light in the terahertz frequency range can be used to characterize many different materials. But to advance terahertz technology, researchers need better tools to detect and profile terahertz beams. For example, most techniques today cannot measure a terahertz beam’s incident electric field.
Lange et al. developed a scalable, low cost, and fast detection profiling technique that measures the peak electric field distribution and absolute polarity of a terahertz beam in real time. This is faster than standard thermal imaging techniques.
Their method uses a single-layer metallic metasurface. When excited with a terahertz beam, the metasurface emits electrons into a surrounding gas, which in turn is ionized and produces light emission in the ultraviolet-visible range via glow discharge.
This upconversion of the light to the ultraviolet-visible range via lightwave-driven field emission allowed the authors to image the terahertz beam with complementary metal-oxide-semiconductor-based cameras, which are more cost effective than focal plane arrays designed to operate in the terahertz frequency range.
The technique can be scaled from the terahertz frequency range to infrared because it relies solely on the geometry of the metasurface and the electrical conductivity of the metal.
“We believe using electron field emission for detection of terahertz and infrared light is an exciting and fundamentally new technique that can be readily adopted by anyone with access to a basic cleanroom,” said author Simon Lange. “We also believe the technique holds great promise for commercialization due to its scaling ability in frequency and virtually unlimited detection area size.”
Next, the authors plan to enhance the sensitivity of this detection technique by improving the design and lowering manufacturing tolerances.
Source: “Lightwave-driven electron emission for polarity-sensitive terahertz beam profiling,” Simon Jappe Lange, Matthias C. Hoffmann, and Peter Uhd Jepsen, APL Photonics (2023). The article can be accessed at https://doi.org/10.1063/5.0125947 .
