Abstract

Doppler-free signals have been obtained from three different techniques: degenerate four-wave mixing (D4WM); optogalvanic spectroscopy (OGS); and saturation spectroscopy on the 546.1-nm line, 6³P₂ 7³S, transition of atomic mercury. A saturable absorption provides the nonlinearity for all three dissimilar techniques. The sensitivity is defined as S = 1/(N_m * P_x), where P_x is the total input power at which the SNR is a maximum, and N_m is the minimum density of atoms detectable when the input power equals P_x.

© 1986 Optical Society of America