Zero-crossing technique for clock-transition detection in a Rb frequency standard

A technique for detection of the clock-transition, in an Rb frequency standard, by means of magnetic field modulation is proposed. In this technique the microwave frequency is held constant and the magnetic field is rapidly swept across the zero value. This zero crossing produces a transient in the transmitted light intensity. The amplitude of the transient is strongly dependent on microwave frequency and shows picks corresponding to the Rb hyperfine transitions. The pick which corresponds to the clock transition can be utilized to lock the servo-loop in a rubidium frequency standard. The zero crossing detection technique has the advantage that it has a low sensitivity to a stray magnetic field since the signal is generated when the total magnetic field is nearly zero