Microwave Heterodyne Techniques for Spectroscopic Purposes

Laser-Microwave Heterodyne Techniques for Spectroscopic Purposes 

The combined application of laser light and microwave fields for spectroscopic purposes— not necessarily acting in the same space region or at the same time— normally concerns the irradiation of the two electromagnetic fields independently of each other onto a species. The microwave field thus interacts directly with the species under investigation, and induces transitions, thereby changing level populations. 

However, many cases can be considered where the experimental situation would not allow measuring the energy gap between levels or spectral lines via the absorption or induced emission of a microwave photon. Obvious examples are the isotope shift of a line, or cases where selection rules prevent transitions between the levels. 

Microwave fields are used in many different schemes in order to modify laser light in one or the other way, like side band production, laser pulse shaping, etc. Only a limited selection of the overwhelming number of papers 

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