Large diameter diffractive lens enables detailed imaging in air and space

Many of the world’s largest telescopes — whether on the ground, in the air, or in space — use mirrors as their primary optical element. Mirrors have the advantage of being flat and lightweight, facilitating construction of large reflective surfaces. However, mirrors can also blot or distort parts of the image, introducing imperfections.

In contrast, diffractive lenses can be just as lightweight as mirrors without the downsides. Majumder et al. employed inverse design and grayscale lithography to develop a 100 mm diameter multilevel diffractive lens optimized for the 400 to 800 nm wavelength range.

Traditional lens setups using curved lenses are cheap and easy to make, but difficult to scale to large sizes. While diffractive lenses are in use, they have proven challenging to manufacture in large sizes and covering large wavelength ranges.

“We demonstrated that computational methods could achieve similar results with significant reductions in weight and footprint,” said author Rajesh Menon.

To design this lens, the authors created an efficient computational framework and developed a precise lithography process to manufacture it. They tested their lens by building a custom optical setup and adapting their lens into a telescope format to take photos of the sun and moon. In their tests, the lens was sharp enough to resolve sunspots and lunar features.

The authors hope their design will result in a clearer picture of our world and our universe.

“If successful, these flat lenses could lead to simpler, cheaper airborne and space-based imaging systems for astronomy and Earth observation,” said Menon. “Lighter, cheaper ground-based telescopes would also have many applications, including use by hobbyists.”

Source: “Color astrophotography with a 100mm-diameter f/2 polymer flat lens,” by Apratim Majumder, Monjurul Meem, Alexander Ingold, Paul Ricketts, Tanner Obray, Nicole Brimhall, and Rajesh Menon, Applied Physics Letters (2025). The article can be accessed at https://doi.org/10.1063/5.0242208 .