Suffolk Reporter

Physicists at the University of Ottawa have made a groundbreaking discovery in the field of optics, revealing that light can cast a shadow under certain conditions. This research was led by Jeff Lundeen, an associate professor in the Department of Physics at uOttawa, in collaboration with the Boyd Research Group.

The study challenges conventional understanding as photons typically pass through each other without interaction. However, this experiment demonstrated that "under certain conditions, light can actually block other light, creating a shadow," according to Professor Lundeen. He emphasized that this finding opens new possibilities for controlling and manipulating light.

The experimental setup involved directing a green laser beam through a ruby crystal while simultaneously illuminating it from the side with blue light. This arrangement resulted in a visible shadow on a surface due to reverse saturation of absorption in the ruby crystal. The phenomenon allows the green laser to obstruct blue light passage, forming a dark region that mirrors the laser beam's contours.

Professor Lundeen noted, "What's particularly fascinating is how closely this laser shadow behaves like a traditional shadow." The shadow follows the shape of its source—the laser beam—and adapts to surfaces similarly to natural shadows.

The researchers also developed a theoretical model predicting the contrast of these shadows. Their findings showed that darkness increased with higher power levels of the green laser beam, achieving up to 22% contrast—similar to shadows observed on sunny days.

This discovery not only enhances understanding of light-matter interactions but also suggests potential applications in optical switching, fabrication, and imaging technologies. As Professor Lundeen stated, "We're excited about the possibilities this opens up."