Experiments demonstrating continuous operation of a solid-state optical maser are described. A continuous coherent wave at 1.065 μ is obtained from trivalent neodymium in CaW${\mathrm{O}}_4$, operating at about 85°K. At room temperature a continuous wave at 1.058 μ is obtained. Room temperature operation is possible due to the large splitting between the terminal state of the maser transition and the ground state (∼2000 ${\mathrm{cm}}^{-1\mathrm{}}$). Near threshold power output ∼10 mw is observed, using silver coatings only.

• Received 15 December 1961

DOI:https://doi.org/10.1103/PhysRev.126.1406