Brillouin - 100 years
In 2022, we will celebrate the centenary of the founding article by the French physicist Léon Brillouin. He theoretically proposed that scattering of light could be frequency shifted by acoustic waves coming from thermal phonon. At that time, the difficulty to generate intense and coherent light source in a medium limited the possibility to demonstrate this theory. Although Gross’s experiment in1930 was originally set to explore Raman scattering in liquids, it turned out that the observed scattered light did not agree with the expected Raman frequency but agree with the theory proposed by Leon Brillouin. This demonstration started the joint development of Raman and Brillouin spectroscopy method. With the invention of laser in 1960, Brillouin scattering in a solid material could be studied particularly in the stimulated regime, as demonstrated by R. Chiao and C. Townes in 1964. At the same period, the development of optical fiber (1966) has opened new possibility to generate intense nonlinear effect like Brillouin scattering with a very long waveguide and several applications as coherent fiber laser or distributed fiber sensor appeared. Today, the Brillouin scattering speak with opto-mechanics, opto-genetics, biology or quantum optics.This innovative work generated a multitude of scientific works and, 100 years later, this phenomenon is still widely studied (materials, biology, quantum optics, optical fiber) but also used in several industrial fields (laser, sensing, and spectroscopy), these both axes being represented in this school “sound and light”.