Researchers have discovered that under specific conditions, a laser beam can cast a visible shadow, challenging the traditional belief that light cannot block light. This phenomenon, demonstrated using ruby crystals and specialized laser settings, opens up possibilities for advanced light control and optical switching technologies. The study, published in Optica, reveals that when a high-power green laser is directed through a ruby cube and illuminated by a blue laser from the side, the interaction increases the optical absorption of the blue light, creating a discernible shadow. Raphael A. Abrahao, the research team leader, explained that this counter-intuitive effect prompts a reevaluation of our understanding of shadows. The research began as a casual conversation about laser physics and culminated in an experiment confirming that a laser can behave like a solid object. The resulting shadow meets all criteria, appearing as a dark region that follows the laser’s contours on the surface it falls upon. The maximum contrast achieved was about 22%, comparable to a tree’s shadow on a sunny day. This breakthrough in light-matter interaction may pave the way for new applications in light technology, enabling one laser beam to control another effectively. Further exploration of different materials and wavelengths is planned.
