Paramagnetic Spectra of Substituted Sapphires--Part I: Ruby

Among the paramagnetic salts t h a t have been used as active materials in three-level solid-state masers ( 3 L S S M ) , 1 ' 2 ' 3 ruby shows rather desirable properties. While maser action of this material has been achieved at microwave signal frequencies of 3 to 10 kmc, 4 it should be possible to cover more than the whole centimeter microwave range. Perhaps even more important from a practical point of view are the bulk physical properties. Extremely good heat conductivity at low temperatures allows handling of relatively high microwave power dissipation. Industrial growth of large single crystals by the flame fusion technique and 111achinability with diamond tools make it possible to fabricate long sections of ruby to very close tolerances, a necessity in travelling-wave maser ( T W M ) development. Also, ruby can be bonded to metals, thus allowing a high degree of versatility in maser structural design. While the use of ruby in 3LSSM, in particular in nonreciprocal T W M , will be described * This work is partially supported bv the Signal Corps under Contract Number DA-36-039 sc-73224. 271