First Optical Microscope Achieves Atomic-Level Imaging

Metaverse Planet July 22, 2025Last Updated: July 22, 2025

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Scientists have developed a new optical imaging system, “ULA-SNOM,” capable of resolving details as small as one nanometer using light, an unprecedented feat for optical microscopy.

For many years, scientists have used microscopes to examine objects on a very small scale, from cells to viruses. However, even the most powerful optical microscopes are fundamentally limited by a physical rule known as the diffraction limit, preventing them from clearly imaging structures smaller than approximately 200 nanometers.

This physical limitation has long prevented the direct observation of how light interacts with a single atom or molecule. Yet, such observations are of paramount importance for materials science, electronics, and quantum technologies.

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Atomic-Level Behavior of Light Can Now Be Observed

Now, an international team of researchers has overcome this challenge. With their newly developed imaging method, “ULA-SNOM” (ultra-low amplitude scattering-type near-field optical microscopy), they have successfully resolved details as small as one nanometer using light. In other words, scientists can now directly observe how light behaves at the atomic scale – an achievement previously thought possible only with electron microscopes.

This breakthrough could revolutionize many fields, from designing solar panels to understanding chemical reactions, by enabling us to examine the fundamental structure of matter.

To achieve this high resolution, the researchers built upon an existing technique called scattering-type scanning near-field optical microscopy (s-SNOM). In this method, a sharp metal tip is illuminated with a laser and scanned across the surface of a material. The light scattered from the surface provides information about nanoscale structures. However, classical s-SNOM systems offer a maximum resolution of 10 to 100 nanometers, which is insufficient for imaging individual atoms.

The New Technique: ULA-SNOM

The researchers’ innovative ULA-SNOM method enabled them to move the tip with an extremely small oscillation, only between 0.5 and 1 nanometer – roughly the width of three atoms. This level of precise movement made it possible to acquire sufficient optical signal while simultaneously resolving atomic-level details. Larger oscillations would decrease resolution, while smaller oscillations would increase signal noise.

The tip itself was crafted from silver, carefully shaped and polished using a focused ion beam. A visible red laser with a wavelength of 633 nanometers and a power of 6 milliwatts was directed at this tip, creating a phenomenon called a “plasmonic cavity.” This cavity allowed light to interact with the material at an atomic scale.

To maintain this delicate setup, the experiment was conducted under ultra-high vacuum and at a very low temperature of −265°C (8 Kelvin). These conditions eliminated vibrations and surface contamination, allowing the tip to be held stably just one nanometer from the surface. Additionally, a special technique called “self-homodyne detection” was used to filter background light and amplify the true signal, resulting in much clearer optical data.

The team tested their system by examining single-atom-thick silicon islands placed on a silver surface. Despite the silicon layers being only one atom high, the microscope could clearly show both the boundary between silicon and silver and how each material responded to light. This demonstrated that the microscope could image not only the shape but also differences in the optical properties of materials at the atomic level.

When researchers compared the spatial resolution with images from a traditional STM (scanning tunneling microscope) – a powerful device used for atomic-scale surface imaging – ULA-SNOM was found to offer the same level of detail with approximately 1 nanometer resolution. This value is very close to the 0.9 nanometer resolution provided by STM.

First-Ever Imaging of How a Single Atom Changes a Material’s Optical Behavior

For the first time, researchers could clearly see how a single atom or defect affects a material’s optical behavior. This development offers immense potential in many areas, such as designing nanostructures, discovering new photonic materials, or producing more efficient solar cells. Furthermore, this technique now makes it possible to examine quantum dots, single-molecule sensors, or biological structures at the atomic level.

Nevertheless, the implementation of ULA-SNOM presents some challenges. The method requires cryogenic cooling, ultra-high vacuum, specially shaped metal tips, and highly precise laser systems. Therefore, for now, it can only be used in advanced research laboratories. Future work is expected to focus on making this method more practical, accessible, and widespread.