Abstract
We report detection and measurement of the millimeter wave difference frequency between two near laser lines at 1.152 μ. The two spectral transitions, separated by 2.26 Å, oscillate in pure neon in a single laser device, producing about 150 μW total power in several longitudinal modes. The many resulting 51.3‐kmc beat frequencies have been studied by optical heterodyne techniques. A type of diode has been found which has enough microwave sensitivity and enough optical sensitivity to combine the optical detector and the microwave heterodyne functions in a single element. The preliminary value for the difference in frequency between the and 2S4 → 2P7 transitions in neon at 150 mtorr is (51,360 ± 150) Mc. This value is not in agreement with the value calculated from Vol. I of Sitterly's Atomic Energy Levels (ref. 12).