Researchers at the University of Stuttgart and the Istituto Italiano di Tecnologia have demonstrated a new method for controlling light at the nanoscale. By placing a small gold antenna onto a crystal of molybdenum oxy-dichloride, the team successfully steered infrared light along a precise path without needing any physical waveguides.
Typically, light moves outward in circular waves, which makes directing signals on a microchip difficult. Current solutions require complex manufacturing processes like etching and lithography to create artificial channels for light. This new discovery bypasses those requirements by using the natural properties of the crystal itself.
Molybdenum oxy-dichloride is a biaxial material with different optical behaviors along separate axes. In one direction, it acts as a metal capable of supporting surface plasmons, while in the perpendicular direction, it restricts movement. This anisotropy keeps the optical waves confined within a narrow, invisible route. The team refers to this phenomenon as plasmon canalization.
Experiments show that the behavior of the light is dependent on the infrared wavelength. At 4 micrometers, the light follows a narrow, canalized path. Changing the wavelength shifts the light into circular or hyperbolic forms, giving researchers direct control over how the energy moves through the material. This tunability allows for precise signal routing simply by adjusting the light source.
This finding offers a path toward simpler photonic chip production. By removing the need for labor-intensive structural manufacturing, the approach could lower costs and open new designs for optical communication and quantum technologies. The researchers used specialized equipment from Stuttgart Instruments and attocube systems to map these wave patterns with high accuracy.