2.1.1. General points
In microwave photonic links, the first component to consider is the optical source, which is now always a laser diode.
The history of laser invention is complex and eventful. Although some facts are still disputed [AGR 86; BER 99; TAY 00], the main milestones of this invention can be sketched:
– the first stimulated emission demonstration appears to have been carried out in 1947 by W. E. Lamb and R. C. Retherford [BER 99], and in 1950, A. Kastler proposed an optical pumping method, demonstrated by Brossel, Kastler, and Winter in 1952;
– in 1953, C. H. Townes and his research students, P. Gorgond and H. J. Zeiger, created the first pulsed MASER (Microwave Amplification by Stimulated Emission of Radiation). Independently, N. Basov and A. Prokhorov (USSR) created a CW MASER; Townes, Basov, and Prokhorov got the Nobel Prize in 1964;
– in 1957, A. L. Schalow and C. H. Townes published the principles of an optical MASER;
– the term “laser” (light amplification by stimulated emission of radiation) was introduced in 1959 by G. Gould, who filed a patent the same year. This patent was only recognized by the American patent office after 18 years of proceedings. The authorization to receive royalties on this patent, and the others, required another 10 years of proceedings [TAY 00];
– the first pulsed solid-state laser (a 694 nm emitted wavelength ruby crystal pumped by a flashlamp) was created in 1960 by T. H. ...