Scientists Trap Light in Ultra-Thin 40 Nanometre Layer

In a major breakthrough in photonics, scientists have successfully trapped infrared light within a structure just 40 nanometres thick—over 1,000 times thinner than a human hair. The research, led by teams from the University of Warsaw and other Polish institutions, demonstrates how advanced materials can manipulate light at extremely small scales, opening new possibilities for next-generation technologies.

Breakthrough in Light Confinement

The researchers engineered a nanoscale structure known as a subwavelength grating to confine infrared light. This structure consists of tightly spaced parallel strips that interact with light similarly to a prism. When arranged closer than the wavelength of light, the grating acts like a near-perfect mirror, trapping light within a tiny volume despite being much smaller than the wavelength itself.

Role of Molybdenum Diselenide

A key innovation in the study is the use of molybdenum diselenide (MoSe2), a material with an exceptionally high refractive index. This property slows down light significantly—more than in conventional materials like glass or silicon. As a result, the structure can be drastically thinner while still maintaining strong light confinement. Earlier materials required much thicker layers to achieve similar effects.

Conversion of Infrared to Visible Light

The material also exhibits nonlinear optical behaviour, enabling a process called third harmonic generation. In this process, three infrared photons combine to form a single photon of higher energy, producing visible blue light. The confined structure intensifies this effect, making the conversion over 1,500 times more efficient compared to flat material layers.

Important Facts for Exams

• Infrared light has longer wavelengths than visible light, often extending beyond 700 nanometres.
• Refractive index determines how much light slows down in a material.
• Photonics uses light (photons) instead of electrons for faster data transmission.
• Nonlinear optics involves interactions where light changes frequency or intensity.

Implications for Future Technologies

The study also demonstrated scalable production using molecular beam epitaxy, enabling large-area, ultra-thin films. This makes the technology suitable for real-world applications such as photonic integrated circuits and ultra-compact optical devices. The breakthrough signals a shift towards smaller, faster, and more efficient light-based technologies that could surpass traditional electronic systems.