Lasers as local oscillators

Conclusions In this survey we have tried to outline the aspects of current laser research and laser technology that are of relevance to heterodyne detection. We have seen that powerful, stable and narrowline sources are available to perform further heterodyne experiments at fixed frequencies. Taking a realistic view, one has to admit, however, that —at least in the far infrared — no really satisfyingtunable source is today available. In the near and the middle infrared, we are confident that further improvements of some of the devices discussed before will allow for true tunable heterodyne observations in the near future.