Continuously tunable resonant ruby laser reflector

The general theoretical requirements for making multisurfaced (resonant) reflectors frequency-tunable are described. Specifically, eflectors that can be used to stabilize and control the lasing spectrum of ruby lasers are considered. Fabry-Perot ring analysis showed that a four-surface reflector (two parallel sapphire flats) with a spacer (stellite) having close to the ideal thermal expansion coefficient, for thermal frequency tunability, could be used to continuously tune a ruby laser near 6944 A more than 0.3 A with a spectral width less than +/-0.01 A.