Ruby lasers are a type of solid-state laser that use a synthetic ruby crystal as the gain medium. They emit light in a deep red color, typically at a wavelength of 694.3 nanometers. The laser operates by exciting the chromium ions within the ruby crystal using a flashlamp, which then releases energy in the form of coherent light. These lasers were among the first types of lasers developed and are known for their high peak power and ability to produce short pulses of light. Ruby lasers have applications in various fields, including medicine, industrial cutting, and scientific research.