intensity-dependent refractive index

The intensity-dependent refractive index means that a material's ability to bend light changes depending on how strong the light is. When intense light, like a powerful laser, passes through, it can temporarily alter the material’s structure at a microscopic level, making it more or less resistant to light. This change affects how the light continues to travel, often leading to effects like self-focusing or creating new light patterns. Essentially, the material's optical properties are not fixed but vary with the strength of the light passing through it.