Rubiinalaseja

Rubiinalaseja, or ruby lasers, are a class of solid‑state lasers in which the gain medium is a crystal of aluminum oxide (aluminum oxide, Al2O3) doped with chromium ions (Cr3+). The characteristic output is a narrow red beam with a wavelength of about 694.3 nanometers. Ruby lasers were among the first successful laser systems demonstrated to produce coherent light.

The lasing action begins when the Cr3+ ions embedded in the ruby crystal are optically pumped by intense light, historically from xenon flash lamps and, in later designs, from lamp or diode sources. The chromium ions create a three‑level laser system, with population inversion achieved by promoting ions from the ground state to higher excited states before emission occurs as they relax to a lower energy level. The crystal is placed in an optical resonator, typically a pair of mirrors, to amplify the emitted photons and form a directed laser beam. Ruby lasers are most commonly operated in pulsed mode, using techniques such as Q‑switching to generate short, high‑peak‑power pulses.

Key characteristics include a relatively simple, rugged crystal and a distinct red emission line. They tend to be less efficient and more thermally sensitive than many modern solid‑state lasers, and they require substantial cooling. Consequently, ruby lasers have largely been supplanted by diode‑pumped solid‑state lasers such as Nd:YAG, especially for routine applications. Nevertheless, they remain of historical importance and are still found in some educational settings and niche experiments for their straightforward setup and well‑defined red wavelength.