A ruby laser was the first laser invented in 1960 by Theodore Maiman. It uses a synthetic ruby crystal as the gain medium and produces red light at 694.3 nm. Ruby lasers were used for early laser experiments including measuring the distance to the moon and producing holograms, though newer laser media have replaced them. The ruby crystal provides population inversion needed for stimulated emission through its chromium dopant atoms.

1. RUBY LASER

9. THE IONS AFTER GIVING A PART OF THEIR ENERGY TO CRYSTAL LATTICE DECAY TO E2 STATE UNDERGOING RADIATION LESS TRANSITION. Metastable state In metastable state , the concentration of ions increases while that of E1 decreases. Hence,population inversion is achieved.

10. A SPONTANEOUS EMISSION PHOTON BY CR3+ ION AT E2 LEVEL INITIATES THE STIMULATED EMISSION BY OTHER CR3+ IONS IN METASTABLE STATE Metastable state 1.79 eV