Microwave spectrometer for saturated absorption experiments

A spectrometer has been built to perform Doppler‐free saturated absorption experiments in the millimeter range (30–300 GHz); a plane‐cylindrical resonator between Stark plates has been used. With that device, inverted Lamb‐dips have been observed at 115 GHz with a width 25 times below the Doppler width. However, the essential feature of this apparatus is to allow the application of Stark field typically of 2500 V/cm, leading to such specific uses as the Stark tuned Lamb‐dip, level‐crossing, and mode‐crossing experiments. Typical examples are given and other applications are proposed.